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|
/*
* ============LICENSE_START=======================================================
* feature-server-pool
* ================================================================================
* Copyright (C) 2020 AT&T Intellectual Property. All rights reserved.
* ================================================================================
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
* ============LICENSE_END=========================================================
*/
package org.onap.policy.drools.serverpool;
import static org.onap.policy.drools.serverpool.ServerPoolProperties.BUCKET_CONFIRMED_TIMEOUT;
import static org.onap.policy.drools.serverpool.ServerPoolProperties.BUCKET_TIME_TO_LIVE;
import static org.onap.policy.drools.serverpool.ServerPoolProperties.BUCKET_UNCONFIRMED_GRACE_PERIOD;
import static org.onap.policy.drools.serverpool.ServerPoolProperties.BUCKET_UNCONFIRMED_TIMEOUT;
import static org.onap.policy.drools.serverpool.ServerPoolProperties.DEFAULT_BUCKET_CONFIRMED_TIMEOUT;
import static org.onap.policy.drools.serverpool.ServerPoolProperties.DEFAULT_BUCKET_TIME_TO_LIVE;
import static org.onap.policy.drools.serverpool.ServerPoolProperties.DEFAULT_BUCKET_UNCONFIRMED_GRACE_PERIOD;
import static org.onap.policy.drools.serverpool.ServerPoolProperties.DEFAULT_BUCKET_UNCONFIRMED_TIMEOUT;
import static org.onap.policy.drools.serverpool.ServerPoolProperties.getProperty;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.PrintStream;
import java.io.Serializable;
import java.net.InetSocketAddress;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Base64;
import java.util.Comparator;
import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Queue;
import java.util.Random;
import java.util.Set;
import java.util.TreeMap;
import java.util.TreeSet;
import java.util.UUID;
import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;
import java.util.concurrent.LinkedTransferQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import javax.ws.rs.client.Entity;
import javax.ws.rs.client.WebTarget;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import lombok.EqualsAndHashCode;
import lombok.Getter;
import lombok.Setter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* The server pool uses an algorithmic way to map things like transactions
* (identified by a 'requestID') and locks (identified by a string key)
* into a server handling that transaction or lock. It does this by mapping
* the string name into one of a set of predefined hash buckets, with each
* bucket being assigned to one of the active servers.
* In other words:
* string key -> hash bucket (fixed mapping, known to all servers)
* hash bucket -> server (assignments may change when servers go up or down,
* but remains fairly static when the system is stable)
* With this approach, there is no global dynamic table that needs to be
* updated as transactions, or other objects come and go.
* Each instance of class 'Bucket' corresponds to one of the hash buckets,
* there are static methods that provide the overall abstraction, as well
* as some supporting classes.
*/
@Getter
@Setter
public class Bucket {
private static Logger logger = LoggerFactory.getLogger(Bucket.class);
/*
* Listener class to handle state changes that may lead to
* reassignments of buckets
*/
private static EventHandler eventHandler = new EventHandler();
// Used to hash keywords into buckets
private static MessageDigest messageDigest;
static {
// register Listener class
Events.register(eventHandler);
// create MD5 MessageDigest -- used to hash keywords
try {
// disabling sonar, as the digest is only used to hash keywords - it isn't
// used for security purposes
messageDigest = MessageDigest.getInstance("MD5"); // NOSONAR
} catch (NoSuchAlgorithmException e) {
throw new ExceptionInInitializerError(e);
}
}
/*
* Values extracted from properties
*/
private static String timeToLive;
private static long confirmedTimeout;
private static long unconfirmedTimeout;
private static long unconfirmedGracePeriod;
/*
* Tags for encoding of bucket data
*/
private static final int END_OF_PARAMETERS_TAG = 0;
private static final int OWNER_UPDATE = 1;
private static final int OWNER_NULL = 2;
private static final int PRIMARY_BACKUP_UPDATE = 3;
private static final int PRIMARY_BACKUP_NULL = 4;
private static final int SECONDARY_BACKUP_UPDATE = 5;
private static final int SECONDARY_BACKUP_NULL = 6;
// This is the table itself -- the current size is fixed at 1024 buckets
public static final int BUCKETCOUNT = 1024;
private static Bucket[] indexToBucket = new Bucket[BUCKETCOUNT];
static {
// create hash bucket entries, but there are no assignments yet
for (int i = 0; i < indexToBucket.length; i += 1) {
Bucket bucket = new Bucket(i);
indexToBucket[i] = bucket;
}
}
// this is a list of all objects registered for the 'Backup' interface
private static List<Backup> backupList = new LinkedList<>();
// 'rebalance' is a non-null value when rebalancing is in progress
private static Object rebalanceLock = new Object();
private static Rebalance rebalance = null;
// bucket number
private volatile int index;
// owner of the bucket -- this is the host where messages should be directed
private volatile Server owner = null;
// this host will take over as the owner if the current owner goes down,
// and may also contain backup data to support persistence
private volatile Server primaryBackup = null;
// this is a secondary backup host, which can be used if both owner and
// primary backup go out in quick succession
private volatile Server secondaryBackup = null;
// when we are in a transient state, certain events are forwarded to
// this object
private volatile State state = null;
// storage for additional data
private Map<Class<?>, Object> adjuncts = new HashMap<>();
// HTTP query parameters
private static final String QP_BUCKET = "bucket";
private static final String QP_KEYWORD = "keyword";
private static final String QP_DEST = "dest";
private static final String QP_TTL = "ttl";
private static final String OWNED_STR = "Owned";
// BACKUP data (only buckets for where we are the owner, or a backup)
// TBD: need fields for outgoing queues for application message transfers
/**
* This method triggers registration of 'eventHandler', and also extracts
* property values.
*/
static void startup() {
int intTimeToLive =
getProperty(BUCKET_TIME_TO_LIVE, DEFAULT_BUCKET_TIME_TO_LIVE);
timeToLive = String.valueOf(intTimeToLive);
confirmedTimeout =
getProperty(BUCKET_CONFIRMED_TIMEOUT, DEFAULT_BUCKET_CONFIRMED_TIMEOUT);
unconfirmedTimeout =
getProperty(BUCKET_UNCONFIRMED_TIMEOUT,
DEFAULT_BUCKET_UNCONFIRMED_TIMEOUT);
unconfirmedGracePeriod =
getProperty(BUCKET_UNCONFIRMED_GRACE_PERIOD,
DEFAULT_BUCKET_UNCONFIRMED_GRACE_PERIOD);
}
/**
* Constructor -- called when building the 'indexToBucket' table.
*
* @param index the bucket number
*/
private Bucket(int index) {
this.index = index;
}
/**
* This method converts a String keyword into the corresponding bucket
* number.
*
* @param value the keyword to be converted
* @return the bucket number
*/
public static int bucketNumber(String value) {
/*
* It would be possible to create a new 'MessageDigest' instance each
* It would be possible to create a new 'MessageDigest' instance each
* time this method is called, and avoid the need for synchronization.
* However, past experience has taught me that this might involve a
* considerable amount of computation, due to internal table
* initialization, so it shouldn't be done this way for performance
* reasons.
* If we start running into blocking issues because there are too many
* simultaneous calls to this method, we can initialize an array of these
* objects, and iterate over them using an AtomicInteger index.
*/
synchronized (messageDigest) {
/*
* Note that we only need the first two bytes of this, even though
* 16 bytes are produced. There may be other operations that can be
* used to more efficiently map keyword -> hash bucket. The only
* issue is the same algorithm must be used on all servers, and it
* should produce a fairly even distribution across all of the buckets.
*/
byte[] digest = messageDigest.digest(value.getBytes());
return ((Byte.toUnsignedInt(digest[0]) << 8)
| Byte.toUnsignedInt(digest[1])) & 0x3ff;
}
}
/**
* Fetch the server associated with a particular bucket number.
*
* @param bucketNumber a bucket number in the range 0-1023
* @return the Server that currently handles the bucket,
* or 'null' if none is currently assigned
*/
public static Server bucketToServer(int bucketNumber) {
Bucket bucket = indexToBucket[bucketNumber];
return bucket.getOwner();
}
/**
* Fetch the bucket object associated with a particular bucket number.
*
* @param bucketNumber a bucket number in the range 0-1023
* @return the Bucket associated with this bucket number
*/
public static Bucket getBucket(int bucketNumber) {
return indexToBucket[bucketNumber];
}
/**
* Fetch the bucket object associated with a particular keyword.
*
* @param value the keyword to be converted
* @return the Bucket associated with this keyword
*/
public static Bucket getBucket(String value) {
return indexToBucket[bucketNumber(value)];
}
/**
* Determine if the associated key is assigned to the current server.
*
* @param key the keyword to be hashed
* @return 'true' if the associated bucket is assigned to this server,
* 'false' if not
*/
public static boolean isKeyOnThisServer(String key) {
int bucketNumber = bucketNumber(key);
Bucket bucket = indexToBucket[bucketNumber];
return bucket.getOwner() == Server.getThisServer();
}
/**
* Handle an incoming /bucket/update REST message.
*
* @param data base64-encoded data, containing all bucket updates
*/
static void updateBucket(byte[] data) {
final byte[] packet = Base64.getDecoder().decode(data);
Runnable task = () -> {
try {
/*
* process the packet, handling any updates
*/
if (updateBucketInternal(packet)) {
/*
* updates have occurred -- forward this packet to
* all servers in the "notify list"
*/
logger.info("One or more bucket updates occurred");
Entity<String> entity =
Entity.entity(new String(data, StandardCharsets.UTF_8),
MediaType.APPLICATION_OCTET_STREAM_TYPE);
for (Server server : Server.getNotifyList()) {
server.post("bucket/update", entity);
}
}
} catch (Exception e) {
logger.error("Exception in Bucket.updateBucket", e);
}
};
MainLoop.queueWork(task);
}
/**
* This method supports the 'updateBucket' method, and runs entirely within
* the 'MainLoop' thread.
*/
private static boolean updateBucketInternal(byte[] packet) throws IOException {
boolean changes = false;
ByteArrayInputStream bis = new ByteArrayInputStream(packet);
DataInputStream dis = new DataInputStream(bis);
// the packet contains a sequence of bucket updates
while (dis.available() != 0) {
// first parameter = bucket number
int index = dis.readUnsignedShort();
// locate the corresponding 'Bucket' object
Bucket bucket = indexToBucket[index];
// indicates whether changes occurred to the bucket
boolean bucketChanges = false;
/*
* the remainder of the information for this bucket consists of
* a sequence of '<tag> [ <associated-data> ]' followed by the tag
* value 'END_OF_PARAMETERS_TAG'.
*/
int tag;
while ((tag = dis.readUnsignedByte()) != END_OF_PARAMETERS_TAG) {
switch (tag) {
case OWNER_UPDATE:
// <OWNER_UPDATE> <owner-uuid> -- owner UUID specified
bucketChanges = updateBucketInternalOwnerUpdate(bucket, dis, index);
break;
case OWNER_NULL:
// <OWNER_NULL> -- owner UUID should be set to 'null'
bucketChanges = nullifyOwner(index, bucket, bucketChanges);
break;
case PRIMARY_BACKUP_UPDATE:
// <PRIMARY_BACKUP_UPDATE> <primary-backup-uuid> --
// primary backup UUID specified
bucketChanges = updatePrimaryBackup(dis, index, bucket, bucketChanges);
break;
case PRIMARY_BACKUP_NULL:
// <PRIMARY_BACKUP_NULL> --
// primary backup should be set to 'null'
bucketChanges = nullifyPrimaryBackup(index, bucket, bucketChanges);
break;
case SECONDARY_BACKUP_UPDATE:
// <SECONDARY_BACKUP_UPDATE> <secondary-backup-uuid> --
// secondary backup UUID specified
bucketChanges = updateSecondaryBackup(dis, index, bucket, bucketChanges);
break;
case SECONDARY_BACKUP_NULL:
// <SECONDARY_BACKUP_NULL> --
// secondary backup should be set to 'null'
bucketChanges = nullifySecondaryBackup(index, bucket, bucketChanges);
break;
default:
logger.error("Illegal tag: {}", tag);
break;
}
}
if (bucketChanges) {
// give audit a chance to run
changes = true;
bucket.stateChanged();
}
}
return changes;
}
private static boolean nullifyOwner(int index, Bucket bucket, boolean bucketChanges) {
if (bucket.getOwner() != null) {
logger.info("Bucket {} owner: {}->null",
index, bucket.getOwner());
bucketChanges = true;
bucket.nullifyOwner();
}
return bucketChanges;
}
private synchronized void nullifyOwner() {
setOwner(null);
setState(null);
}
/**
* Gets the set of backups.
*
* @return the set of backups
*/
public synchronized Set<Server> getBackups() {
/*
* For some reason, the junit tests break if Set.of() is used, so we'll stick with
* the long way for now.
*/
Set<Server> backups = new HashSet<>();
backups.add(getPrimaryBackup());
backups.add(getSecondaryBackup());
return backups;
}
private static boolean updatePrimaryBackup(DataInputStream dis, int index, Bucket bucket, boolean bucketChanges)
throws IOException {
Server newPrimaryBackup =
Server.getServer(Util.readUuid(dis));
if (bucket.primaryBackup != newPrimaryBackup) {
logger.info("Bucket {} primary backup: {}->{}", index,
bucket.primaryBackup, newPrimaryBackup);
bucketChanges = true;
bucket.primaryBackup = newPrimaryBackup;
}
return bucketChanges;
}
private static boolean nullifyPrimaryBackup(int index, Bucket bucket, boolean bucketChanges) {
if (bucket.primaryBackup != null) {
logger.info("Bucket {} primary backup: {}->null",
index, bucket.primaryBackup);
bucketChanges = true;
bucket.primaryBackup = null;
}
return bucketChanges;
}
private static boolean updateSecondaryBackup(DataInputStream dis, int index, Bucket bucket, boolean bucketChanges)
throws IOException {
Server newSecondaryBackup =
Server.getServer(Util.readUuid(dis));
if (bucket.secondaryBackup != newSecondaryBackup) {
logger.info("Bucket {} secondary backup: {}->{}", index,
bucket.secondaryBackup, newSecondaryBackup);
bucketChanges = true;
bucket.secondaryBackup = newSecondaryBackup;
}
return bucketChanges;
}
private static boolean nullifySecondaryBackup(int index, Bucket bucket, boolean bucketChanges) {
if (bucket.secondaryBackup != null) {
logger.info("Bucket {} secondary backup: {}->null",
index, bucket.secondaryBackup);
bucketChanges = true;
bucket.secondaryBackup = null;
}
return bucketChanges;
}
/**
* Update bucket owner information.
*
* @param bucket the bucket in process
* @param dis data input stream contains the update
* @param index the bucket number
* @return a value indicate bucket changes
*/
private static boolean updateBucketInternalOwnerUpdate(Bucket bucket, DataInputStream dis,
int index) throws IOException {
boolean bucketChanges = false;
Server newOwner = Server.getServer(Util.readUuid(dis));
if (bucket.getOwner() != newOwner) {
logger.info("Bucket {} owner: {}->{}",
index, bucket.getOwner(), newOwner);
bucketChanges = true;
Server thisServer = Server.getThisServer();
Server oldOwner = bucket.getOwner();
bucket.setOwner(newOwner);
if (thisServer == oldOwner) {
// the current server is the old owner
if (bucket.getState() == null) {
bucket.state = bucket.new OldOwner(newOwner);
}
} else if (thisServer == newOwner) {
// the current server the new owner
if (bucket.getState() == null) {
bucket.state = bucket.new NewOwner(true, oldOwner);
} else {
// new owner has been confirmed
bucket.state.newOwner();
}
}
}
return bucketChanges;
}
/**
* Forward a message to the specified bucket number. If the bucket is
* in a transient state (the value of 'state' is not 'null'), the handling
* is determined by that state.
*
* @param bucketNumber the bucket number determined by extracting the
* keyword from 'message'
* @param message the message to be forwarded/processed
* @return a value of 'true' indicates the message has been "handled"
* (forwarded or queued), and 'false' indicates it has not, and needs
* to be handled locally.
*/
public static boolean forward(int bucketNumber, Message message) {
Bucket bucket = indexToBucket[bucketNumber];
Server server;
synchronized (bucket) {
if (bucket.state != null) {
// we are in a transient state -- the handling is state-specific
return bucket.state.forward(message);
}
server = bucket.getOwner();
}
if (server == null || server == Server.getThisServer()) {
// this needs to be processed locally
return false;
} else {
// send message to remote server
message.sendToServer(server, bucketNumber);
return true;
}
}
/**
* This is a convenience method, which forwards a message through the
* bucket associated with the specified keyword.
*
* @param keyword the keyword extracted from 'message'
* keyword from 'message'
* @param message the message to be forwarded/processed
* @return a value of 'true' indicates the message has been "handled"
* (forwarded or queued), and 'false' indicates it has not, and needs
* to be handled locally.
*/
public static boolean forward(String keyword, Message message) {
return forward(bucketNumber(keyword), message);
}
/**
* Forward a message to the specified bucket number. If the bucket is
* in a transient state (the value of 'state' is not 'null'), the handling
* is determined by that state. This is a variant of the 'forward' method,
* which handles local processing, instead of just returning 'false'.
*
* @param bucketNumber the bucket number determined by extracting the
* keyword from 'message'
* @param message the message to be forwarded/processed
*/
public static void forwardAndProcess(int bucketNumber, Message message) {
if (!forward(bucketNumber, message)) {
message.process();
}
}
/**
* Forward a message to the specified bucket number. If the bucket is
* in a transient state (the value of 'state' is not 'null'), the handling
* is determined by that state. This is a variant of the 'forward' method,
* which handles local processing, instead of just returning 'false'.
*
* @param keyword the keyword extracted from 'message'
* keyword from 'message'
* @param message the message to be forwarded/processed
*/
public static void forwardAndProcess(String keyword, Message message) {
forwardAndProcess(bucketNumber(keyword), message);
}
/**
* Handle an incoming /cmd/dumpBuckets REST message.
*
* @param out the 'PrintStream' to use for displaying information
*/
public static void dumpBuckets(final PrintStream out) {
/*
* we aren't really doing a 'Rebalance' here, but the 'copyData' method
* is useful for extracting the data, and determining the buckets
* associated with each server.
*/
Rebalance rb = new Rebalance();
rb.copyData();
/*
* this method is not accessing anything in the 'Server' or 'Bucket'
* table, so it doesn't need to run within the 'MainLoop' thread.
*/
rb.dumpBucketsInternal(out);
}
/**
* Handle an incoming /cmd/bucketMessage REST message -- this is only
* used for testing the routing of messages between servers.
*
* @param out the 'PrintStream' to use for displaying information
* @param keyword the keyword that is hashed to select the bucket number
* @param message the message to send to the remote end
* @throws IOException when error occurred
*/
public static void bucketMessage(
final PrintStream out, final String keyword, String message) {
if (keyword == null) {
out.println("'keyword' is mandatory");
return;
}
if (message == null) {
message = "Message generated at " + new Date();
}
final int bucketNumber = bucketNumber(keyword);
Server server = bucketToServer(bucketNumber);
if (server == null) {
/*
* selected bucket has no server assigned -- this should only be a
* transient situation, until 'rebalance' is run.
*/
out.format("Bucket is %d, which has no owner%n", bucketNumber);
} else if (server == Server.getThisServer()) {
/*
* the selected bucket is associated with this particular server --
* no forwarding is needed.
*/
out.format("Bucket is %d, which is owned by this server: %s%n",
bucketNumber, server.getUuid());
} else {
/*
* the selected bucket is assigned to a different server -- forward
* the message.
*/
out.format("Bucket is %d: sending from%n"
+ " %s to%n"
+ " %s%n",
bucketNumber, Server.getThisServer().getUuid(), server.getUuid());
// do a POST call of /bucket/bucketResponse to the remoote server
Entity<String> entity =
Entity.entity(new String(message.getBytes(), StandardCharsets.UTF_8),
MediaType.TEXT_PLAIN);
/*
* the POST itself runs in a server-specific thread, and
* 'responseQueue' is used to pass back the response.
*/
final LinkedTransferQueue<Response> responseQueue =
new LinkedTransferQueue<>();
server.post("bucket/bucketResponse", entity, new Server.PostResponse() {
/**
* {@inheritDoc}
*/
@Override
public WebTarget webTarget(WebTarget webTarget) {
// we need to include the 'bucket' and 'keyword' parameters
// in the POST that we are sending out
return webTarget
.queryParam(QP_BUCKET, bucketNumber)
.queryParam(QP_KEYWORD, keyword);
}
/**
* {@inheritDoc}
*/
@Override
public void response(Response response) {
// this is the POST response --
// pass it back to the calling thread
responseQueue.put(response);
}
});
try {
// this is the calling thread -- wait for the POST response
Response response = responseQueue.poll(60, TimeUnit.SECONDS);
if (response == null) {
out.println("Timed out waiting for a response");
} else {
out.format("Received response code %s%nEntity = %s%n",
response.getStatus(), response.readEntity(String.class));
}
} catch (InterruptedException e) {
out.println(e);
Thread.currentThread().interrupt();
}
}
}
/**
* Handle an incoming /bucket/bucketResponse REST message -- this runs on
* the destination host, and is the continuation of an operation triggered
* by the /cmd/bucketMessage REST message running on the originating host.
*
* @param out the 'PrintStream' to use for passing back information
* in a human-readable form
* @param bucket the bucket number, which should be owned by this host
* if we are in sync with the sending host, and didn't get caught
* in a transient state
* @param keyword the keyword selected on the originating end, which should
* hash to 'bucket'
* @param message the message selected on the originating end
*/
public static void bucketResponse(
final PrintStream out, int bucket, String keyword, byte[] message) {
Server thisServer = Server.getThisServer();
Server server = bucketToServer(bucket);
if (server != thisServer) {
/*
* this isn't expected, and either indicates we are out-of-sync with
* pthe originating server, or this operation was triggered while in
* a transient state.
*/
out.println("ERROR: " + thisServer.toString() + ": bucket " + bucket
+ "is owned by\n " + server);
} else {
/*
* As expected, we are the owner of this bucket. Print out a message,
* which will be returned to the originating host, and displayed.
*/
out.println(thisServer.toString() + ":\n"
+ " bucket = " + bucket
+ "\n keyword = " + keyword
+ "\n message = " + new String(message));
}
}
/**
* Handle an incoming /cmd/moveBucket REST message -- this is only
* used for testing bucket migration. It only works on the lead server.
*
* @param out the 'PrintStream' to use for displaying information
* @param bucketNumber the bucket number to be moved
* @param newHostUuid the UUID of the destination host (if 'null', a
* destination host will be chosen at random)
*/
public static void moveBucket(PrintStream out, int bucketNumber, String newHostUuid) {
Server leader = Leader.getLeader();
if (leader != Server.getThisServer()) {
out.println("This is not the lead server");
return;
}
if (bucketNumber < 0 || bucketNumber >= indexToBucket.length) {
out.println("Bucket number out of range");
return;
}
Rebalance rb = new Rebalance();
rb.copyData();
TestBucket bucket = rb.buckets[bucketNumber];
TestServer oldHost = bucket.owner;
if (oldHost == rb.nullServer) {
out.println("Bucket " + bucketNumber + " is currently unassigned");
return;
}
TestServer newHost = null;
if (newHostUuid != null) {
// the UUID of a destination host has been specified
newHost = rb.testServers.get(UUID.fromString(newHostUuid));
if (newHost == null) {
out.println("Can't locate UUID " + newHostUuid);
return;
}
} else {
/*
* Choose a destination host at random, other than the current owner.
* Step a random count in the range of 1 to (n-1) relative to the
* current host.
*/
UUID key = oldHost.uuid;
/*
* Disabling sonar, because this Random() is not used for security purposes.
*/
int randomStart = new Random().nextInt(rb.testServers.size() - 1); // NOSONAR
for (int count = randomStart; count >= 0; count -= 1) {
key = rb.testServers.higherKey(key);
if (key == null) {
// wrap to the beginning of the list
key = rb.testServers.firstKey();
}
}
newHost = rb.testServers.get(key);
}
out.println("Moving bucket " + bucketNumber + " from "
+ oldHost + " to " + newHost);
updateOwner(out, bucket, oldHost, newHost);
try {
/*
* build a message containing all of the updated bucket
* information, process it internally in this host
* (lead server), and send it out to others in the
* "notify list".
*/
rb.generateBucketMessage();
} catch (IOException e) {
logger.error("Exception in Rebalance.generateBucketMessage",
e);
}
}
private static void updateOwner(PrintStream out, TestBucket bucket, TestServer oldHost, TestServer newHost) {
/*
* update the owner, and ensure that the primary and secondary backup
* remain different from the owner.
*/
bucket.setOwner(newHost);
if (newHost == bucket.primaryBackup) {
out.println("Moving primary back from " + newHost + " to " + oldHost);
bucket.setPrimaryBackup(oldHost);
} else if (newHost == bucket.secondaryBackup) {
out.println("Moving secondary back from " + newHost
+ " to " + oldHost);
bucket.setSecondaryBackup(oldHost);
}
}
/**
* This method is called when an incoming /bucket/sessionData message is
* received from the old owner of the bucket, which presumably means that
* we are the new owner of the bucket.
*
* @param bucketNumber the bucket number
* @param dest the UUID of the intended destination
* @param ttl similar to IP time-to-live -- it controls the number of hops
* the message may take
* @param data serialized data associated with this bucket, encoded using
* base64
*/
static void sessionData(int bucketNumber, UUID dest, int ttl, byte[] data) {
logger.info("Bucket.sessionData: bucket={}, data length={}",
bucketNumber, data.length);
if (dest != null && !dest.equals(Server.getThisServer().getUuid())) {
// the message needs to be forwarded to the intended destination
Server server;
WebTarget webTarget;
ttl -= 1;
if (ttl > 0
&& (server = Server.getServer(dest)) != null
&& (webTarget = server.getWebTarget("bucket/sessionData")) != null) {
logger.info("Forwarding 'bucket/sessionData' to uuid {}",
server.getUuid());
Entity<String> entity =
Entity.entity(new String(data, StandardCharsets.UTF_8),
MediaType.APPLICATION_OCTET_STREAM_TYPE);
Response response =
webTarget
.queryParam(QP_BUCKET, bucketNumber)
.queryParam(QP_DEST, dest)
.queryParam(QP_TTL, String.valueOf(ttl))
.request().post(entity);
logger.info("/bucket/sessionData response code = {}",
response.getStatus());
} else {
logger.error("Couldn't forward 'bucket/sessionData' to uuid {}, ttl={}",
dest, ttl);
}
return;
}
byte[] decodedData = Base64.getDecoder().decode(data);
Bucket bucket = indexToBucket[bucketNumber];
logger.info("Bucket.sessionData: decoded data length = {}",
decodedData.length);
if (bucket.state == null) {
/*
* We received the serialized data prior to being notified
* that we are the owner -- this happens sometimes. Behave as
* though we are the new owner, but intidate it is unconfirmed.
*/
logger.info("Bucket {} session data received unexpectedly",
bucketNumber);
bucket.state = bucket.new NewOwner(false, bucket.getOwner());
}
bucket.state.bulkSerializedData(decodedData);
}
/**
* This method is called whenever the bucket's state has changed in a
* way that it should be audited.
*/
private synchronized void stateChanged() {
if (state != null) {
return;
}
// the audit should be run
Server thisServer = Server.getThisServer();
boolean isOwner = (thisServer == owner);
boolean isBackup = (!isOwner && (thisServer == primaryBackup
|| thisServer == secondaryBackup));
// invoke 'TargetLock' directly
TargetLock.auditBucket(this, isOwner);
for (ServerPoolApi feature : ServerPoolApi.impl.getList()) {
feature.auditBucket(this, isOwner, isBackup);
}
}
/**
* Returns an adjunct of the specified class
* (it is created if it doesn't exist).
*
* @param clazz this is the class of the adjunct
* @return an adjunct of the specified class ('null' may be returned if
* the 'newInstance' method is unable to create the adjunct)
*/
public <T> T getAdjunct(Class<T> clazz) {
Object adj = adjuncts.computeIfAbsent(clazz, key -> {
try {
// create the adjunct, if needed
return clazz.getDeclaredConstructor().newInstance();
} catch (Exception e) {
logger.error("Can't create adjunct of {}", clazz, e);
return null;
}
});
return clazz.cast(adj);
}
/**
* Returns an adjunct of the specified class.
*
* @param clazz this is the class of the adjunct
* @return an adjunct of the specified class, if it exists,
* and 'null' if it does not
*/
public <T> T getAdjunctDontCreate(Class<T> clazz) {
synchronized (adjuncts) {
// look up the adjunct in the table
return clazz.cast(adjuncts.get(clazz));
}
}
/**
* Explicitly create an adjunct -- this is useful when the adjunct
* initialization requires that some parameters be passed.
*
* @param adj this is the adjunct to insert into the table
* @return the previous adjunct of this type ('null' if none)
*/
public Object putAdjunct(Object adj) {
synchronized (adjuncts) {
Class<?> clazz = adj.getClass();
return adjuncts.put(clazz, adj);
}
}
/**
* Remove an adjunct.
*
* @param clazz this is the class of adjuncts to remove
* @return the object, if found, and 'null' if not
*/
public <T> T removeAdjunct(Class<T> clazz) {
synchronized (adjuncts) {
// remove the adjunct in the table
return clazz.cast(adjuncts.remove(clazz));
}
}
/**
* Dump out all buckets with adjuncts.
*
* @param out the 'PrintStream' to use for displaying information
*/
public static void dumpAdjuncts(PrintStream out) {
boolean noneFound = true;
String format = "%6s %s\n";
for (Bucket bucket : indexToBucket) {
synchronized (bucket.adjuncts) {
if (bucket.adjuncts.size() != 0) {
if (noneFound) {
out.printf(format, "Bucket", "Adjunct Classes");
out.printf(format, "------", "---------------");
noneFound = false;
}
boolean first = true;
for (Class<?> clazz : bucket.adjuncts.keySet()) {
if (first) {
out.printf(format, bucket.index, clazz.getName());
first = false;
} else {
out.printf(format, "", clazz.getName());
}
}
}
}
}
}
/* ============================================================ */
/**
* There is a single instance of this class (Bucket.eventHandler), which
* is registered to listen for notifications of state transitions. Note
* that all of these methods are running within the 'MainLoop' thread.
*/
private static class EventHandler extends Events {
/**
* {@inheritDoc}
*/
@Override
public void serverFailed(Server server) {
// remove this server from any bucket where it is referenced
Server thisServer = Server.getThisServer();
for (Bucket bucket : indexToBucket) {
synchronized (bucket) {
boolean changes = false;
if (bucket.getOwner() == server) {
// the failed server owns this bucket --
// move to the primary backup
bucket.setOwner(bucket.getPrimaryBackup());
bucket.primaryBackup = null;
changes = true;
if (bucket.getOwner() == null) {
// bucket owner is still null -- presumably, we had no
// primary backup, so use the secondary backup instead
bucket.setOwner(bucket.getSecondaryBackup());
bucket.setSecondaryBackup(null);
}
}
if (bucket.getPrimaryBackup() == server) {
// the failed server was a primary backup to this bucket --
// mark the entry as 'null'
bucket.setPrimaryBackup(null);
changes = true;
}
if (bucket.getSecondaryBackup() == server) {
// the failed server was a secondary backup to this bucket --
// mark the entry as 'null'
bucket.setSecondaryBackup(null);
changes = true;
}
if (bucket.owner == thisServer && bucket.state == null) {
// the current server is the new owner
bucket.setState(bucket.new NewOwner(false, null));
changes = true;
}
if (changes) {
// may give audits a chance to run
bucket.stateChanged();
}
}
}
// trigger a rebalance (only happens if we are the lead server)
rebalance();
}
/**
* {@inheritDoc}
*/
@Override
public void newLeader(Server server) {
// trigger a rebalance (only happens if we are the new lead server)
rebalance();
}
/**
* {@inheritDoc}
*/
@Override
public void leaderConfirmed(Server server) {
// trigger a rebalance (only happens if we are the lead server)
rebalance();
}
/**
* This method is called to start a 'rebalance' operation in a background
* thread, but it only does this on the lead server. Being balanced means
* the following:
* 1) Each server owns approximately the same number of buckets
* 2) If any server were to fail, and the designated primaries take over
* for all of that server's buckets, all remaining servers would still
* own approximately the same number of buckets.
* 3) If any two servers were to fail, and the designated primaries were
* to take over for the failed server's buckets (secondaries would take
* for buckets where the owner and primary are OOS), all remaining
* servers would still own approximately the same number of buckets.
* 4) Each server should have approximately the same number of
* (primary-backup + secondary-backup) buckets that it is responsible for.
* 5) The primary backup for each bucket must be on the same site as the
* owner, and the secondary backup must be on a different site.
*/
private void rebalance() {
if (Leader.getLeader() == Server.getThisServer()) {
Rebalance rb = new Rebalance();
synchronized (rebalanceLock) {
// the most recent 'Rebalance' instance is the only valid one
rebalance = rb;
}
new Thread("BUCKET REBALANCER") {
@Override
public void run() {
/*
* copy bucket and host data,
* generating a temporary internal table.
*/
rb.copyData();
/*
* allocate owners for all buckets without an owner,
* and rebalance bucket owners, if necessary --
* this takes card of item #1, above.
*/
rb.allocateBuckets();
/*
* make sure that primary backups always have the same site
* as the owner, and secondary backups always have a different
* site -- this takes care of #5, above.
*/
rb.checkSiteValues();
/*
* adjust primary backup lists to take care of item #2, above
* (taking #5 into account).
*/
rb.rebalancePrimaryBackups();
/*
* allocate secondary backups, and take care of items
* #3 and #4, above (taking #5 into account).
*/
rb.rebalanceSecondaryBackups();
try {
synchronized (rebalanceLock) {
/*
* if another 'Rebalance' instance has started in the
* mean time, don't do the update.
*/
if (rebalance == rb) {
/*
* build a message containing all of the updated bucket
* information, process it internally in this host
* (lead server), and send it out to others in the
* "notify list".
*/
rb.generateBucketMessage();
rebalance = null;
}
}
} catch (IOException e) {
logger.error("Exception in Rebalance.generateBucketMessage",
e);
}
}
}.start();
}
}
}
/* ============================================================ */
/**
* Instances of this class are created as part of the 'rebalance'
* operation on the lead server, or as part of a 'dumpBuckets' operation
* on any server.
* Each instance of this class corresponds to a 'Bucket' instance.
*/
@EqualsAndHashCode
private static class TestBucket implements Comparable<TestBucket> {
// bucket number
int index;
// owner of the bucket
TestServer owner;
// primary backup for this bucket
TestServer primaryBackup;
// secondary backup for this bucket
TestServer secondaryBackup;
/**
* Constructor -- initialize the 'TestBucket' instance.
*
* @param index the bucket number
*/
TestBucket(int index) {
this.index = index;
}
/**
* Update the owner of a bucket, which also involves updating the
* backward links in the 'TestServer' instances.
*
* @param newOwner the new owner of the bucket
*/
void setOwner(TestServer newOwner) {
if (owner != newOwner) {
// the 'owner' field does need to be changed
if (owner != null) {
// remove this bucket from the 'buckets' list of the old owner
owner.buckets.remove(this);
}
if (newOwner != null) {
// add this bucket to the 'buckets' list of the new owner
newOwner.buckets.add(this);
}
// update the 'owner' field in the bucket
owner = newOwner;
}
}
/**
* Update the primary backup of a bucket, which also involves updating
* the backward links in the 'TestServer' instances.
*
* @param newPrimaryBackup the new primary of the bucket
*/
void setPrimaryBackup(TestServer newPrimaryBackup) {
if (primaryBackup != newPrimaryBackup) {
// the 'primaryBackup' field does need to be changed
if (primaryBackup != null) {
// remove this bucket from the 'buckets' list of the
// old primary backup
primaryBackup.primaryBackupBuckets.remove(this);
}
if (newPrimaryBackup != null) {
// add this bucket to the 'buckets' list of the
// new primary backup
newPrimaryBackup.primaryBackupBuckets.add(this);
}
// update the 'primaryBackup' field in the bucket
primaryBackup = newPrimaryBackup;
}
}
/**
* Update the secondary backup of a bucket, which also involves updating
* the backward links in the 'TestServer' instances.
*
* @param newSecondaryBackup the new secondary of the bucket
*/
void setSecondaryBackup(TestServer newSecondaryBackup) {
if (secondaryBackup != newSecondaryBackup) {
// the 'secondaryBackup' field does need to be changed
if (secondaryBackup != null) {
// remove this bucket from the 'buckets' list of the
// old secondary backup
secondaryBackup.secondaryBackupBuckets.remove(this);
}
if (newSecondaryBackup != null) {
// add this bucket to the 'buckets' list of the
// new secondary backup
newSecondaryBackup.secondaryBackupBuckets.add(this);
}
// update the 'secondaryBackup' field in the bucket
secondaryBackup = newSecondaryBackup;
}
}
/*==================================*/
/* Comparable<TestBucket> interface */
/*==================================*/
/**
* Compare two 'TestBucket' instances, for use in a 'TreeSet'.
*
* @param other the other 'TestBucket' instance to compare to
*/
@Override
public int compareTo(TestBucket other) {
return index - other.index;
}
/**
* Return a string representation of this 'TestBucket' instance.
*
* @return a string representation of this 'TestBucket' instance
*/
@Override
public String toString() {
return "TestBucket[" + index + "]";
}
}
/* ============================================================ */
/**
* Instances of this class are created as part of the 'rebalance'
* operation on the lead server, or as part of a 'dumpBuckets' operation
* on any server.
* Each instance of this class corresponds to a 'Server' instance.
* Unlike the actual 'Server' instances, each 'TestServer' instance
* contains back links to all of the buckets it is associated with.
*/
private static class TestServer {
// unique id for this server
// (matches the one in the corresponding 'Server' entry)
final UUID uuid;
// site socket information (matches 'Server' entry)
final InetSocketAddress siteSocketAddress;
// the set of all 'TestBucket' instances,
// where this 'TestServer' is listed as 'owner'
final TreeSet<TestBucket> buckets = new TreeSet<>();
// the set of all 'TestBucket' instances,
// where this 'TestServer' is listed as 'primaryBackup'
final TreeSet<TestBucket> primaryBackupBuckets = new TreeSet<>();
// the set of all 'TestBucket' instances,
// where this 'TestServer' is listed as 'secondaryBackup'
final TreeSet<TestBucket> secondaryBackupBuckets = new TreeSet<>();
/**
* Constructor.
*
* @param uuid uuid of this 'TestServer' instance
* @param siteSocketAddress matches the value in the corresponding 'Server'
*/
TestServer(UUID uuid, InetSocketAddress siteSocketAddress) {
this.uuid = uuid;
this.siteSocketAddress = siteSocketAddress;
}
/**
* Return a string representation of this 'TestServer' instance.
*
* @return a string representation of this 'TestServer' instance
*/
@Override
public String toString() {
return "TestServer[" + uuid + "]";
}
}
/* ============================================================ */
/**
* This class supports the 'rebalance' operation. Each instance is a wrapper
* around a 'TestServer' instance, as it would be if another specific
* server failed.
*/
@EqualsAndHashCode
private static class AdjustedTestServer
implements Comparable<AdjustedTestServer> {
TestServer server;
// simulated fail on this server
TestServer failedServer;
// expected bucket count if 'failedServer' fails
int bucketCount;
// total number of primary backup buckets used by this host
int primaryBackupBucketCount;
// total number of secondary backup buckets used by this host
int secondaryBackupBucketCount;
/**
* Constructor.
*
* @param server the server this 'AdjustedTestServer' instance represents
* @param failedServer the server going through a simulated failure --
* the 'bucketCount' value is adjusted based upon this
*/
AdjustedTestServer(TestServer server, TestServer failedServer) {
this.server = server;
this.failedServer = failedServer;
this.bucketCount = server.buckets.size();
this.primaryBackupBucketCount = server.primaryBackupBuckets.size();
this.secondaryBackupBucketCount = server.secondaryBackupBuckets.size();
// need to adjust 'bucketCount' for the case where the current
// host fails
for (TestBucket bucket : server.primaryBackupBuckets) {
if (bucket.owner == failedServer) {
bucketCount += 1;
// TBD: should 'primaryBackupBucketCount' be decremented?
}
}
// need to adjust 'bucketCount' for the case where the current
// host fails
for (TestBucket bucket : server.secondaryBackupBuckets) {
if (bucket.owner == failedServer) {
bucketCount += 1;
// TBD: should 'secondaryBackupBucketCount' be decremented?
}
}
}
/* ****************************************** */
/* Comparable<AdjustedTestServer> interface */
/* ****************************************** */
/**
* {@inheritDoc}
*/
@Override
public int compareTo(AdjustedTestServer other) {
/*
* Comparison order:
* 1) minimal expected bucket count if current host fails
* (differences of 1 are treated as a match)
* 2) minimal backup bucket count
* 3) UUID order
*/
int rval = bucketCount - other.bucketCount;
if (rval <= 1 && rval >= -1) {
rval = (primaryBackupBucketCount + secondaryBackupBucketCount)
- (other.primaryBackupBucketCount
+ other.secondaryBackupBucketCount);
if (rval == 0) {
rval = -Util.uuidComparator.compare(server.uuid, other.server.uuid);
}
}
return rval;
}
}
/* ============================================================ */
/**
* This class is primarily used to do a 'Rebalance' operation on the
* lead server, which is then distributed to all of the other servers.
* Part of it is also useful for implementing the /cmd/dumpBuckets
* REST message handler.
*/
private static class Rebalance {
// this table resembles the 'Bucket.indexToBucket' table
TestBucket[] buckets = new TestBucket[indexToBucket.length];
// this table resembles the 'Server.servers' table
TreeMap<UUID, TestServer> testServers = new TreeMap<>(Util.uuidComparator);
/* this is a special server instance, which is allocated any
* owned, primary, or secondary buckets that haven't been allocated to
* any of the real servers
*/
TestServer nullServer = new TestServer(null, null);
/**
* Copy all of the bucket data in the 'buckets' table, and also return
* a copy of the 'Server.servers' table
*/
void copyData() {
// will contain a copy of the 'Bucket' table
final Bucket[] bucketSnapshot = new Bucket[indexToBucket.length];
/*
* This method is running within the 'MainLoop' thread,
* and builds a copy of the 'Bucket' table, as well as the
* list of active servers -- these can then be examined
* in a different thread, without potentially distrupting
* the 'MainLoop' thread.
*
* @return 0 (the return value is not significant at present)
*/
Callable<Integer> callable = () -> {
// copy the 'Bucket' table
for (int i = 0; i < indexToBucket.length; i += 1) {
// makes a snapshot of the bucket information
Bucket bucket = indexToBucket[i];
Bucket tmpBucket = new Bucket(i);
tmpBucket.setOwner(bucket.getOwner());
tmpBucket.setPrimaryBackup(bucket.getPrimaryBackup());
tmpBucket.setSecondaryBackup(bucket.getSecondaryBackup());
bucketSnapshot[i] = tmpBucket;
}
/*
* At this point, 'bucketSnapshot' and 'servers' should be
* complete. The next step is to create a 'TestServer' entry
* that matches each 'Server' entry.
*/
for (Server server : Server.getServers()) {
UUID uuid = server.getUuid();
testServers.put(uuid, new TestServer(uuid, server.getSiteSocketAddress()));
}
return 0;
};
FutureTask<Integer> ft = new FutureTask<>(callable);
MainLoop.queueWork(ft);
try {
ft.get(60, TimeUnit.SECONDS);
} catch (InterruptedException e) {
logger.error("Interrupted", e);
Thread.currentThread().interrupt();
return;
} catch (ExecutionException | TimeoutException e) {
logger.error("Exception in Rebalance.copyData", e);
return;
}
makeTestBucket(bucketSnapshot);
}
private void makeTestBucket(final Bucket[] bucketSnapshot) {
/*
* Now, create a 'TestBucket' table that mirrors the 'Bucket' table.
* Unlike the standard 'Bucket' and 'Server' tables, the 'TestServer'
* entries contain links referring back to the 'TestBucket' entries.
* This information is useful when rebalancing.
*/
for (Bucket bucket : bucketSnapshot) {
int index = bucket.index;
TestBucket testBucket = new TestBucket(index);
// populate the 'owner' field
if (bucket.getOwner() != null) {
testBucket.setOwner(testServers.get(bucket.getOwner().getUuid()));
} else {
testBucket.setOwner(nullServer);
}
// populate the 'primaryBackup' field
if (bucket.primaryBackup != null) {
testBucket.setPrimaryBackup(
testServers.get(bucket.primaryBackup.getUuid()));
} else {
testBucket.setPrimaryBackup(nullServer);
}
// populate the 'secondaryBackup' field
if (bucket.secondaryBackup != null) {
testBucket.setSecondaryBackup(
testServers.get(bucket.secondaryBackup.getUuid()));
} else {
testBucket.setSecondaryBackup(nullServer);
}
buckets[index] = testBucket;
}
}
/**
* Allocate unowned 'TestBucket' entries across all of the 'TestServer'
* entries. When every 'TestBucket' has an owner, rebalance as needed,
* so the 'TestServer' entry with the most buckets has at most one more
* bucket than the 'TestServer' entry with the least.
*/
void allocateBuckets() {
/*
* the following 'Comparator' is used to control the order of the
* 'needBuckets' TreeSet: those with the fewest buckets allocated are
* at the head of the list.
*/
Comparator<TestServer> bucketCount = (s1, s2) -> {
int rval = s1.buckets.size() - s2.buckets.size();
if (rval == 0) {
rval = Util.uuidComparator.compare(s1.uuid, s2.uuid);
}
return rval;
};
// sort servers according to the order in which they can
// take on ownership of buckets
TreeSet<TestServer> needBuckets = new TreeSet<>(bucketCount);
for (TestServer ts : testServers.values()) {
needBuckets.add(ts);
}
// go through all of the unowned buckets, and allocate them
for (TestBucket bucket : new LinkedList<TestBucket>(nullServer.buckets)) {
// take first entry off of sorted server list
TestServer ts = needBuckets.first();
needBuckets.remove(ts);
// add this bucket to the 'buckets' list
bucket.setOwner(ts);
// place it back in the list, possibly in a new position
// (it's attributes have changed)
needBuckets.add(ts);
}
nullServer.buckets.clear();
// there may still be rebalancing needed -- no host should contain
// 2 or more buckets more than any other host
for ( ; ; ) {
TestServer first = needBuckets.first();
TestServer last = needBuckets.last();
if (last.buckets.size() - first.buckets.size() <= 1) {
// no more rebalancing needed
break;
}
// remove both from sorted list
needBuckets.remove(first);
needBuckets.remove(last);
// take one bucket from 'last', and assign it to 'first'
last.buckets.first().setOwner(first);
// place back in sorted list
needBuckets.add(first);
needBuckets.add(last);
}
}
/**
* Make sure that the primary backups have the same site as the owner,
* and the secondary backups have a different site.
*/
void checkSiteValues() {
for (TestBucket bucket : buckets) {
if (bucket.owner != null) {
InetSocketAddress siteSocketAddress =
bucket.owner.siteSocketAddress;
TestServer primaryBackup = bucket.primaryBackup;
TestServer secondaryBackup = bucket.secondaryBackup;
validateSiteOwner(bucket, siteSocketAddress,
primaryBackup, secondaryBackup);
}
}
}
/**
* Validate primary site owner and secondary site owner are valid.
* @param bucket TestBucket
* @param siteSocketAddress site socket address
* @param primaryBackup primary backups
* @param secondaryBackup secondary backups
*/
private void validateSiteOwner(TestBucket bucket, InetSocketAddress siteSocketAddress,
TestServer primaryBackup, TestServer secondaryBackup) {
if (primaryBackup != null
&& !Objects.equals(siteSocketAddress,
primaryBackup.siteSocketAddress)) {
/*
* primary backup is from the wrong site -- see if we can
* use the secondary.
*/
if (secondaryBackup != null
&& Objects.equals(siteSocketAddress,
secondaryBackup.siteSocketAddress)) {
// swap primary and secondary
bucket.setPrimaryBackup(secondaryBackup);
bucket.setSecondaryBackup(primaryBackup);
} else {
// just invalidate primary backup
bucket.setPrimaryBackup(null);
}
} else if (secondaryBackup != null
&& Objects.equals(siteSocketAddress,
secondaryBackup.siteSocketAddress)) {
// secondary backup is from the wrong site
bucket.setSecondaryBackup(null);
if (primaryBackup == null) {
// we can use this as the primary
bucket.setPrimaryBackup(secondaryBackup);
}
}
}
/**
* Allocate and rebalance the primary backups.
*/
void rebalancePrimaryBackups() {
for (TestServer failedServer : testServers.values()) {
/*
* to allocate primary backups for this server,
* simulate a failure, and balance the backup hosts
*/
// get siteSocketAddress from server
InetSocketAddress siteSocketAddress = failedServer.siteSocketAddress;
// populate a 'TreeSet' of 'AdjustedTestServer' instances based
// the failure of 'failedServer'
TreeSet<AdjustedTestServer> adjustedTestServers = new TreeSet<>();
for (TestServer server : testServers.values()) {
if (server == failedServer
|| !Objects.equals(siteSocketAddress,
server.siteSocketAddress)) {
continue;
}
adjustedTestServers.add(new AdjustedTestServer(server, failedServer));
}
if (adjustedTestServers.isEmpty()) {
// this is presumably the only server -- there is no other server
// to act as primary backup, and no rebalancing can occur
continue;
}
// we need a backup host for each bucket
for (TestBucket bucket : failedServer.buckets) {
if (bucket.primaryBackup == null
|| bucket.primaryBackup == nullServer) {
// need a backup host for this bucket -- remove the first
// entry from 'adjustedTestServers', which is most favored
AdjustedTestServer backupHost = adjustedTestServers.first();
adjustedTestServers.remove(backupHost);
// update add this bucket to the list
bucket.setPrimaryBackup(backupHost.server);
// update counts in 'AdjustedTestServer'
backupHost.bucketCount += 1;
backupHost.primaryBackupBucketCount += 1;
// place it back in the table, possibly in a new position
// (it's attributes have changed)
adjustedTestServers.add(backupHost);
}
}
// TBD: Is additional rebalancing needed?
}
}
/**
* Allocate and rebalance the secondary backups.
*/
void rebalanceSecondaryBackups() {
for (TestServer failedServer : testServers.values()) {
/*
* to allocate secondary backups for this server,
* simulate a failure, and balance the backup hosts
*/
// get siteSocketAddress from server
InetSocketAddress siteSocketAddress = failedServer.siteSocketAddress;
// populate a 'TreeSet' of 'AdjustedTestServer' instances based
// the failure of 'failedServer'
TreeSet<AdjustedTestServer> adjustedTestServers =
new TreeSet<>();
for (TestServer server : testServers.values()) {
if (server == failedServer
|| Objects.equals(siteSocketAddress,
server.siteSocketAddress)) {
continue;
}
adjustedTestServers.add(new AdjustedTestServer(server, failedServer));
}
if (adjustedTestServers.isEmpty()) {
// this is presumably the only server -- there is no other server
// to act as secondary backup, and no rebalancing can occur
continue;
}
// we need a backup host for each bucket
for (TestBucket bucket : failedServer.buckets) {
if (bucket.secondaryBackup == null
|| bucket.secondaryBackup == nullServer) {
// need a backup host for this bucket -- remove the first
// entry from 'adjustedTestServers', which is most favored
AdjustedTestServer backupHost = adjustedTestServers.first();
adjustedTestServers.remove(backupHost);
// update add this bucket to the list
bucket.setSecondaryBackup(backupHost.server);
// update counts in 'AdjustedTestServer'
backupHost.bucketCount += 1;
backupHost.secondaryBackupBucketCount += 1;
// place it back in the table, possibly in a new position
// (it's attributes have changed)
adjustedTestServers.add(backupHost);
}
}
// TBD: Is additional rebalancing needed?
}
}
/**
* Generate a message with all of the bucket updates, process it locally,
* and send it to all servers in the "Notify List".
*/
void generateBucketMessage() throws IOException {
ByteArrayOutputStream bos = new ByteArrayOutputStream();
DataOutputStream dos = new DataOutputStream(bos);
// go through the entire 'buckets' table
for (int i = 0; i < buckets.length; i += 1) {
// fetch the 'TestBucket' associated with index 'i'
TestBucket testBucket = buckets[i];
/*
* Get the UUID of the owner, primary backup, and secondary backup
* for this bucket. If the associated value does not exist, 'null'
* is used.
*/
UUID newOwner = null;
UUID newPrimary = null;
UUID newSecondary = null;
if (testBucket.owner != nullServer && testBucket.owner != null) {
newOwner = testBucket.owner.uuid;
}
if (testBucket.primaryBackup != nullServer
&& testBucket.primaryBackup != null) {
newPrimary = testBucket.primaryBackup.uuid;
}
if (testBucket.secondaryBackup != nullServer
&& testBucket.secondaryBackup != null) {
newSecondary = testBucket.secondaryBackup.uuid;
}
// write bucket number
dos.writeShort(i);
// 'owner' field
writeOwner(dos, newOwner);
// 'primaryBackup' field
writePrimary(dos, newPrimary);
// 'secondaryBackup' field
writeSecondary(dos, newSecondary);
dos.writeByte(END_OF_PARAMETERS_TAG);
}
// get the unencoded 'packet'
final byte[] packet = bos.toByteArray();
// create an 'Entity' containing the encoded packet
final Entity<String> entity =
Entity.entity(new String(Base64.getEncoder().encode(packet),
StandardCharsets.UTF_8), MediaType.APPLICATION_OCTET_STREAM_TYPE);
/*
* This method is running within the 'MainLoop' thread.
*/
Runnable task = () -> {
try {
/*
* update the buckets on this host,
* which is presumably the lead server.
*/
Bucket.updateBucketInternal(packet);
} catch (Exception e) {
logger.error("Exception updating buckets", e);
}
// send a message to all servers on the notify list
for (Server server : Server.getNotifyList()) {
server.post("bucket/update", entity);
}
};
MainLoop.queueWork(task);
}
private void writeOwner(DataOutputStream dos, UUID newOwner) throws IOException {
if (newOwner != null) {
dos.writeByte(OWNER_UPDATE);
Util.writeUuid(dos, newOwner);
} else {
dos.writeByte(OWNER_NULL);
}
}
private void writePrimary(DataOutputStream dos, UUID newPrimary) throws IOException {
if (newPrimary != null) {
dos.writeByte(PRIMARY_BACKUP_UPDATE);
Util.writeUuid(dos, newPrimary);
} else {
dos.writeByte(PRIMARY_BACKUP_NULL);
}
}
private void writeSecondary(DataOutputStream dos, UUID newSecondary) throws IOException {
if (newSecondary != null) {
dos.writeByte(SECONDARY_BACKUP_UPDATE);
Util.writeUuid(dos, newSecondary);
} else {
dos.writeByte(SECONDARY_BACKUP_NULL);
}
}
/**
* Supports the '/cmd/dumpBuckets' REST message -- this isn't part of
* a 'rebalance' operation, but it turned out to be a convenient way
* to dump out the bucket table.
*
* @param out the output stream
*/
private void dumpBucketsInternal(PrintStream out) {
// xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxx *
// UUID Type Buckets
String format = "%-36s %-9s %5s %s\n";
int totalOwner = 0;
int totalPrimary = 0;
int totalSecondary = 0;
out.printf(format, "UUID", "Type", "Count", "Buckets");
out.printf(format, "----", "----", "-----", "-------");
for (TestServer ts : testServers.values()) {
// dump out 'owned' bucket information
if (ts.buckets.isEmpty()) {
// no buckets owned by this server
out.printf(format, ts.uuid, OWNED_STR, 0, "");
} else {
// dump out primary buckets information
totalOwner +=
dumpBucketsSegment(out, format, ts.buckets, ts.uuid.toString(), OWNED_STR);
}
// optionally dump out primary buckets information
totalPrimary +=
dumpBucketsSegment(out, format, ts.primaryBackupBuckets, "", "Primary");
// optionally dump out secondary buckets information
totalSecondary +=
dumpBucketsSegment(out, format, ts.secondaryBackupBuckets, "", "Secondary");
}
if (!nullServer.buckets.isEmpty()
|| !nullServer.primaryBackupBuckets.isEmpty()
|| !nullServer.secondaryBackupBuckets.isEmpty()) {
/*
* There are some owned, primary, or secondary buckets that are
* unassigned. It is displayed in a manner similar to buckets that
* do have a server, but the UUID field is marked as 'UNASSIGNED'
* in the first line of the display.
*/
String uuidField = "UNASSIGNED";
// optionally dump out unassigned owned buckets information
if (dumpBucketsSegment(out, format, nullServer.buckets,
uuidField, OWNED_STR) != 0) {
uuidField = "";
}
// optionally dump out unassigned primary backup buckets information
if (dumpBucketsSegment(out, format, nullServer.primaryBackupBuckets,
uuidField, "Primary") != 0) {
uuidField = "";
}
// optionally dump out unassigned secondary backup buckets information
dumpBucketsSegment(out, format, nullServer.secondaryBackupBuckets,
uuidField, "Secondary");
}
out.println("\nTotal assigned: owner = " + totalOwner
+ ", primary = " + totalPrimary
+ ", secondary = " + totalSecondary);
}
/**
* Supports the 'dumpBucketsInternal' command, and indirectly, the
* '/cmd/dumpBuckets' REST message. It formats one segment of bucket data
* (owned, primary backup, or secondary backup), and dumps out the
* associated bucket data in segments of 8. Note: if the size of 'buckets'
* is 0, nothing is displayed.
*
* @param out the output stream
* @param format the message format string
* @param buckets the entire set of buckets to be displayed
* @param uuid string to display under the 'UUID' header
* @param segmentDescription string to display under the 'Type' header
* @return the size of the 'buckets' set
*/
private static int dumpBucketsSegment(
PrintStream out, String format, TreeSet<TestBucket> buckets,
String uuid, String segmentDescription) {
int size = buckets.size();
if (size != 0) {
// generate a linked list of the bucket data to display
LinkedList<String> data = new LinkedList<>();
StringBuilder sb = new StringBuilder();
int count = 8;
for (TestBucket bucket : buckets) {
if (sb.length() != 0) {
// this is not the first bucket in the line --
// prepend a space
sb.append(' ');
}
// add the bucket number
sb.append(String.format("%4s", bucket.index));
count -= 1;
if (count <= 0) {
// filled up a row --
// add it to the list, and start a new line
data.add(sb.toString());
sb = new StringBuilder();
count = 8;
}
}
if (sb.length() != 0) {
// there is a partial line remaining -- add it to the list
data.add(sb.toString());
}
/*
* The first line displayed includes the UUID and size information,
* and the first line of bucket data (owned, primary, or secondary).
* The remaining lines of bucket data are displayed alone,
* without any UUID or size information.
*/
out.printf(format, uuid, segmentDescription, buckets.size(),
data.removeFirst());
while (!data.isEmpty()) {
out.printf(format, "", "", "", data.removeFirst());
}
}
return size;
}
}
/* ============================================================ */
/**
* This interface is an abstraction for all messages that are routed
* through buckets. It exists, so that messages may be queued while
* bucket migration is taking place, and it makes it possible to support
* multiple types of messages (routed UEB/DMAAP messages, or lock messages)
*/
public static interface Message {
/**
* Process the current message -- this may mean delivering it locally,
* or forwarding it.
*/
public void process();
/**
* Send the message to another host for processing.
*
* @param server the destination host (although it could end up being
* forwarded again)
* @param bucketNumber the bucket number determined by extracting the
* current message's keyword
*/
public void sendToServer(Server server, int bucketNumber);
}
/* ============================================================ */
/**
* This interface implements a type of backup; for example, there is one
* for backing up Drools objects within sessions, and another for
* backing up lock data.
*/
public static interface Backup {
/**
* This method is called to add a 'Backup' instance to the registered list.
*
* @param backup an object implementing the 'Backup' interface
*/
public static void register(Backup backup) {
synchronized (backupList) {
if (!backupList.contains(backup)) {
backupList.add(backup);
}
}
}
/**
* Generate Serializable backup data for the specified bucket.
*
* @param bucketNumber the bucket number to back up
* @return a Serializable object containing backkup data
*/
public Restore generate(int bucketNumber);
}
/* ============================================================ */
/**
* Objects implementing this interface may be serialized, and restored
* on a different host.
*/
public static interface Restore extends Serializable {
/**
* Restore from deserialized data.
*
* @param bucketNumber the bucket number being restored
*/
void restore(int bucketNumber);
}
/* ============================================================ */
/**
* This interface corresponds to a transient state within a Bucket.
*/
private interface State {
/**
* This method allows state-specific handling of the
* 'Bucket.forward()' methods
*
* @param message the message to be forwarded/processed
* @return a value of 'true' indicates the message has been "handled"
* (forwarded or queued), and 'false' indicates it has not, and needs
* to be handled locally.
*/
boolean forward(Message message);
/**
* This method indicates that the current server is the new owner
* of the current bucket.
*/
void newOwner();
/**
* This method indicates that serialized data has been received,
* presumably from the old owner of the bucket. The data could correspond
* to Drools objects within sessions, as well as global locks.
*
* @param data serialized data associated with this bucket (at present,
* this is assumed to be complete, all within a single message)
*/
void bulkSerializedData(byte[] data);
}
/* ============================================================ */
/**
* Each state instance is associated with a bucket, and is used when
* that bucket is in a transient state where it is the new owner of a
* bucket, or is presumed to be the new owner, based upon other events
* that have occurred.
*/
private class NewOwner extends Thread implements State {
/*
* this value is 'true' if we have explicitly received a 'newOwner'
* indication, and 'false' if there was another trigger for entering this
* transient state (e.g. receiving serialized data)
*/
boolean confirmed;
// when 'System.currentTimeMillis()' reaches this value, we time out
long endTime;
// If not 'null', we are queueing messages for this bucket
// otherwise, we are sending them through.
Queue<Message> messages = new ConcurrentLinkedQueue<>();
// this is used to signal the thread that we have data available
CountDownLatch dataAvailable = new CountDownLatch(1);
// this is the data
byte[] data = null;
// this is the old owner of the bucket
Server oldOwner;
/**
* Constructor - a transient state, where we are expecting to receive
* bulk data from the old owner.
*
* @param confirmed 'true' if we were explicitly notified that we
* are the new owner of the bucket, 'false' if not
*/
NewOwner(boolean confirmed, Server oldOwner) {
super("New Owner for Bucket " + index);
this.confirmed = confirmed;
this.oldOwner = oldOwner;
if (oldOwner == null) {
// we aren't expecting any data -- this is indicated by 0-length data
bulkSerializedData(new byte[0]);
}
endTime = System.currentTimeMillis()
+ (confirmed ? confirmedTimeout : unconfirmedTimeout);
start();
}
/**
* Return the 'confirmed' indicator.
*
* @return the 'confirmed' indicator
*/
private boolean getConfirmed() {
synchronized (Bucket.this) {
return confirmed;
}
}
/**
* This returns the timeout delay, which will always be less than or
* equal to 1 second. This allows us to periodically check whether the
* old server is still active.
*
* @return the timeout delay, which is the difference between the
* 'endTime' value and the current time or 1 second
* (whichever is less)
*/
private long getTimeout() {
long lclEndTime;
synchronized (Bucket.this) {
lclEndTime = endTime;
}
return Math.min(lclEndTime - System.currentTimeMillis(), 1000L);
}
/**
* Return the current value of the 'data' field.
*
* @return the current value of the 'data' field
*/
private byte[] getData() {
synchronized (Bucket.this) {
return data;
}
}
/* ******************* */
/* 'State' interface */
/* ******************* */
/**
* {@inheritDoc}
*/
@Override
public boolean forward(Message message) {
// the caller of this method is synchronized on 'Bucket.this'
if (messages != null && Thread.currentThread() != this) {
// just queue the message
messages.add(message);
return true;
} else {
/*
* Either:
*
* 1) We are in a grace period, where 'state' is still set, but
* we are no longer forwarding messages.
* 2) We are calling 'message.process()' from this thread
* in the 'finally' block of 'NewOwner.run()'.
*
* In either case, messages should be processed locally.
*/
return false;
}
}
/**
* {@inheritDoc}
*/
@Override
public void newOwner() {
// the caller of this method is synchronized on 'Bucket.this'
if (!confirmed) {
confirmed = true;
endTime += (confirmedTimeout - unconfirmedTimeout);
}
}
/**
* {@inheritDoc}
*/
@Override
public void bulkSerializedData(byte[] data) {
// the caller of this method is synchronized on 'Bucket.this'
if (this.data == null) {
this.data = data;
dataAvailable.countDown();
}
}
/* ******************** */
/* 'Thread' interface */
/* ******************** */
/**
* {@inheritDoc}
*/
@Override
public void run() {
logger.info("{}: 'run' method invoked", this);
try {
byte[] lclData;
long delay;
while ((lclData = getData()) == null
&& oldOwner.isActive()
&& (delay = getTimeout()) > 0) {
// ignore return value -- 'data' will indicate the result
if (!dataAvailable.await(delay, TimeUnit.MILLISECONDS)) {
logger.error("CountDownLatch await time reached");
}
}
if (lclData == null) {
// no data available -- log an error, and abort
if (getConfirmed()) {
// we never received the data, but we are the new owner
logger.error("{}: never received session data", this);
} else {
/*
* no data received, and it was never confirmed --
* assume that the forwarded message that triggered this was
* erroneus
*/
logger.error("{}: no confirmation or data received -- aborting", this);
return;
}
} else {
logger.info("{}: {} bytes of data available",
this, lclData.length);
}
// if we reach this point, this server is the new owner
if (lclData == null || lclData.length == 0) {
// see if any features can do the restore
for (ServerPoolApi feature : ServerPoolApi.impl.getList()) {
feature.restoreBucket(Bucket.this);
}
} else {
// deserialize data
Object obj = Util.deserialize(lclData);
restoreBucketData(obj);
}
} catch (Exception e) {
logger.error("Exception in {}", this, e);
} finally {
runCleanup();
}
}
private void runCleanup() {
/*
* cleanly leave state -- we want to make sure that messages
* are processed in order, so the queue needs to remain until
* it is empty
*/
logger.info("{}: entering cleanup state", this);
for ( ; ; ) {
Message message = messages.poll();
if (message == null) {
// no messages left, but this could change
synchronized (Bucket.this) {
message = messages.poll();
if (message == null) {
// no messages left
noMoreMessages();
break;
}
}
}
// this doesn't work -- it ends up right back in the queue
// if 'messages' is defined
message.process();
}
if (messages == null) {
// this indicates we need to enter a grace period before cleanup,
sleepBeforeCleanup();
}
logger.info("{}: exiting cleanup state", this);
}
private void noMoreMessages() {
if (state == this) {
if (owner == Server.getThisServer()) {
// we can now exit the state
state = null;
stateChanged();
} else {
/*
* We need a grace period before we can
* remove the 'state' value (this can happen
* if we receive and process the bulk data
* before receiving official confirmation
* that we are owner of the bucket.
*/
messages = null;
}
}
}
private void sleepBeforeCleanup() {
try {
logger.info("{}: entering grace period before terminating",
this);
Thread.sleep(unconfirmedGracePeriod);
} catch (InterruptedException e) {
// we are exiting in any case
Thread.currentThread().interrupt();
} finally {
synchronized (Bucket.this) {
// Do we need to confirm that we really are the owner?
// What does it mean if we are not?
if (state == this) {
state = null;
stateChanged();
}
}
}
}
/**
* Return a useful value to display in log messages.
*
* @return a useful value to display in log messages
*/
public String toString() {
return "Bucket.NewOwner(" + index + ")";
}
/**
* Restore bucket data.
*
* @param obj deserialized bucket data
*/
private void restoreBucketData(Object obj) {
if (obj instanceof List) {
for (Object entry : (List<?>) obj) {
if (entry instanceof Restore) {
// entry-specific 'restore' operation
((Restore) entry).restore(Bucket.this.index);
} else {
logger.error("{}: Expected '{}' but got '{}'",
this, Restore.class.getName(),
entry.getClass().getName());
}
}
} else {
logger.error("{}: expected 'List' but got '{}'",
this, obj.getClass().getName());
}
}
}
/* ============================================================ */
/**
* Each state instance is associated with a bucket, and is used when
* that bucket is in a transient state where it is the old owner of
* a bucket, and the data is being transferred to the new owner.
*/
private class OldOwner extends Thread implements State {
Server newOwner;
OldOwner(Server newOwner) {
super("Old Owner for Bucket " + index);
this.newOwner = newOwner;
start();
}
/* ******************* */
/* 'State' interface */
/* ******************* */
/**
* {@inheritDoc}
*/
@Override
public boolean forward(Message message) {
// forward message to new owner
message.sendToServer(newOwner, index);
return true;
}
/**
* {@inheritDoc}
*/
@Override
public void newOwner() {
// shouldn't happen -- just log an error
logger.error("{}: 'newOwner()' shouldn't be called in this state", this);
}
/**
* {@inheritDoc}
*/
@Override
public void bulkSerializedData(byte[] data) {
// shouldn't happen -- just log an error
logger.error("{}: 'bulkSerializedData()' shouldn't be called in this state", this);
}
/* ******************** */
/* 'Thread' interface */
/* ******************** */
/**
* {@inheritDoc}
*/
@Override
public void run() {
logger.info("{}: 'run' method invoked", this);
try {
// go through all of the entries in the list, collecting restore data
List<Restore> restoreData = new LinkedList<>();
for (Backup backup : backupList) {
Restore restore = backup.generate(index);
if (restore != null) {
restoreData.add(restore);
}
}
// serialize all of the objects,
// and send what we have to the new owner
Entity<String> entity = Entity.entity(
new String(Base64.getEncoder().encode(Util.serialize(restoreData))),
MediaType.APPLICATION_OCTET_STREAM_TYPE);
newOwner.post("bucket/sessionData", entity, new Server.PostResponse() {
@Override
public WebTarget webTarget(WebTarget webTarget) {
return webTarget
.queryParam(QP_BUCKET, index)
.queryParam(QP_DEST, newOwner.getUuid())
.queryParam(QP_TTL, timeToLive);
}
@Override
public void response(Response response) {
logger.info("/bucket/sessionData response code = {}",
response.getStatus());
}
});
} catch (Exception e) {
logger.error("Exception in {}", this, e);
} finally {
synchronized (Bucket.this) {
// restore the state
if (state == this) {
state = null;
stateChanged();
}
}
}
}
/**
* Return a useful value to display in log messages.
*
* @return a useful value to display in log messages
*/
public String toString() {
return "Bucket.OldOwner(" + index + ")";
}
}
}
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