Initial code Import.

Issue-ID: MUSIC-21

Change-Id: I89ceab0891b4b7cb999dab532d6bae9092f027cc
Signed-off-by: arthurdent3 <tn1381@att.com>

1 files changed, 205 insertions, 0 deletions

diff --git a/src/main/java/org/onap/music/lockingservice/ProtocolSupport.java b/src/main/java/org/onap/music/lockingservice/ProtocolSupport.java
new file mode 100644
index 00000000..37ae9e96
--- /dev/null
+++ b/src/main/java/org/onap/music/lockingservice/ProtocolSupport.java
@@ -0,0 +1,205 @@
+/*
+ * ============LICENSE_START==========================================
+ * org.onap.music
+ * ===================================================================
+ *  Copyright (c) 2017 AT&T Intellectual Property
+ * ===================================================================
+ *  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.music.lockingservice;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.apache.zookeeper.CreateMode;
+import org.apache.zookeeper.KeeperException;
+import org.apache.zookeeper.ZooDefs;
+import org.apache.zookeeper.ZooKeeper;
+import org.apache.zookeeper.data.ACL;
+import org.apache.zookeeper.data.Stat;
+import org.onap.music.lockingservice.ZooKeeperOperation;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * A base class for protocol implementations which provides a number of higher level helper methods
+ * for working with ZooKeeper along with retrying synchronous operations if the connection to
+ * ZooKeeper closes such as {@link #retryOperation(ZooKeeperOperation)}
+ *
+ */
+class ProtocolSupport {
+    private static final Logger LOG = LoggerFactory.getLogger(ProtocolSupport.class);
+
+    protected ZooKeeper zookeeper;
+    private AtomicBoolean closed = new AtomicBoolean(false);
+    private long retryDelay = 500L;
+    private int retryCount = 10;
+    private List<ACL> acl = ZooDefs.Ids.OPEN_ACL_UNSAFE;
+
+    // public ProtocolSupport(ZooKeeper zookeeper) {
+    // this.zookeeper = zookeeper;
+    // }
+
+    /**
+     * Closes this strategy and releases any ZooKeeper resources; but keeps the ZooKeeper instance
+     * open
+     */
+    public void close() {
+        if (closed.compareAndSet(false, true)) {
+            doClose();
+        }
+    }
+
+    /**
+     * return zookeeper client instance
+     * 
+     * @return zookeeper client instance
+     */
+    public ZooKeeper getZookeeper() {
+        return zookeeper;
+    }
+
+    /**
+     * return the acl its using
+     * 
+     * @return the acl.
+     */
+    public List<ACL> getAcl() {
+        return acl;
+    }
+
+    /**
+     * set the acl
+     * 
+     * @param acl the acl to set to
+     */
+    public void setAcl(List<ACL> acl) {
+        this.acl = acl;
+    }
+
+    /**
+     * get the retry delay in milliseconds
+     * 
+     * @return the retry delay
+     */
+    public long getRetryDelay() {
+        return retryDelay;
+    }
+
+    /**
+     * Sets the time waited between retry delays
+     * 
+     * @param retryDelay the retry delay
+     */
+    public void setRetryDelay(long retryDelay) {
+        this.retryDelay = retryDelay;
+    }
+
+    /**
+     * Allow derived classes to perform some custom closing operations to release resources
+     */
+    protected void doClose() {}
+
+
+    /**
+     * Perform the given operation, retrying if the connection fails
+     * 
+     * @return object. it needs to be cast to the callee's expected return type.
+     * @param operation FILL IN
+     * @throws KeeperException FILL IN
+     * @throws InterruptedException FILL IN
+     */
+    protected Object retryOperation(ZooKeeperOperation operation)
+                    throws KeeperException, InterruptedException {
+        KeeperException exception = null;
+        for (int i = 0; i < retryCount; i++) {
+            try {
+                return operation.execute();
+            } catch (KeeperException.SessionExpiredException e) {
+                LOG.warn("Session expired for: " + zookeeper + " so reconnecting due to: " + e, e);
+                throw e;
+            } catch (KeeperException.ConnectionLossException e) {
+                if (exception == null) {
+                    exception = e;
+                }
+                LOG.debug("Attempt " + i + " failed with connection loss so "
+                                + "attempting to reconnect: " + e, e);
+                retryDelay(i);
+            }
+        }
+        throw exception;
+    }
+
+    /**
+     * Ensures that the given path exists with no data, the current ACL and no flags
+     * 
+     * @param path the lock path
+     */
+    protected void ensurePathExists(String path) {
+        ensureExists(path, null, acl, CreateMode.PERSISTENT);
+    }
+
+    /**
+     * Ensures that the given path exists with the given data, ACL and flags
+     * 
+     * @param path the lock path
+     * @param data the data
+     * @param acl list of ACLs applying to the path
+     * @param flags create mode flags
+     */
+    protected void ensureExists(final String path, final byte[] data, final List<ACL> acl,
+                    final CreateMode flags) {
+        try {
+            retryOperation(new ZooKeeperOperation() {
+                public boolean execute() throws KeeperException, InterruptedException {
+                    Stat stat = zookeeper.exists(path, false);
+                    if (stat != null) {
+                        return true;
+                    }
+                    zookeeper.create(path, data, acl, flags);
+                    return true;
+                }
+            });
+        } catch (KeeperException e) {
+            LOG.warn("Caught: " + e, e);
+        } catch (InterruptedException e) {
+            LOG.warn("Caught: " + e, e);
+        }
+    }
+
+    /**
+     * Returns true if this protocol has been closed
+     * 
+     * @return true if this protocol is closed
+     */
+    protected boolean isClosed() {
+        return closed.get();
+    }
+
+    /**
+     * Performs a retry delay if this is not the first attempt
+     * 
+     * @param attemptCount the number of the attempts performed so far
+     */
+    protected void retryDelay(int attemptCount) {
+        if (attemptCount > 0) {
+            try {
+                Thread.sleep(attemptCount * retryDelay);
+            } catch (InterruptedException e) {
+                LOG.debug("Failed to sleep: " + e, e);
+            }
+        }
+    }
+}