1 files changed, 198 insertions, 0 deletions
diff --git a/src/main/java/org/onap/dmaap/mr/client/HostSelector.java b/src/main/java/org/onap/dmaap/mr/client/HostSelector.java
new file mode 100644
index 0000000..9bd73f9
--- /dev/null
+++ b/src/main/java/org/onap/dmaap/mr/client/HostSelector.java
@@ -0,0 +1,198 @@
+/*******************************************************************************
+ *  ============LICENSE_START=======================================================
+ *  org.onap.dmaap
+ *  ================================================================================
+ *  Copyright © 2017 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=========================================================
+ *
+ *  ECOMP is a trademark and service mark of AT&T Intellectual Property.
+ *  
+ *******************************************************************************/
+package org.onap.dmaap.mr.client;
+
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.Random;
+import java.util.Set;
+import java.util.TreeSet;
+import java.util.Vector;
+import java.util.concurrent.DelayQueue;
+import java.util.concurrent.Delayed;
+import java.util.concurrent.TimeUnit;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class HostSelector
+{
+  private final TreeSet<String> fBaseHosts;
+  private final DelayQueue<BlacklistEntry> fBlacklist;
+  private String fIdealHost;
+  private String fCurrentHost;
+  private static final Logger log = LoggerFactory.getLogger(HostSelector.class);
+
+  public HostSelector(String hostPart)
+  {
+    this(makeSet(hostPart), null);
+  }
+
+  public HostSelector(Collection<String> baseHosts)
+  {
+    this(baseHosts, null);
+  }
+
+  public HostSelector(Collection<String> baseHosts, String signature)
+  {
+    if (baseHosts.isEmpty())
+    {
+      throw new IllegalArgumentException("At least one host must be provided.");
+    }
+
+    this.fBaseHosts = new TreeSet(baseHosts);
+    this.fBlacklist = new DelayQueue();
+    this.fIdealHost = null;
+
+    if (signature == null) {
+      return;
+    }
+    int index = 0 ;
+    int value = signature.hashCode();
+    if(value!=0) {
+    index = Math.abs(value) % baseHosts.size();
+    }
+    Iterator it = this.fBaseHosts.iterator();
+    while (index-- > 0)
+    {
+      it.next();
+    }
+    this.fIdealHost = ((String)it.next());
+  }
+
+  public String selectBaseHost()
+  {
+    if (this.fCurrentHost == null)
+    {
+      makeSelection();
+    }
+    return this.fCurrentHost;
+  }
+
+  public void reportReachabilityProblem(long blacklistUnit, TimeUnit blacklistTimeUnit)
+  {
+    if (this.fCurrentHost == null)
+    {
+      log.warn("Reporting reachability problem, but no host is currently selected.");
+    }
+
+    if (blacklistUnit > 0L)
+    {
+      for (BlacklistEntry be : this.fBlacklist)
+      {
+        if (be.getHost().equals(this.fCurrentHost))
+        {
+          be.expireNow();
+        }
+      }
+
+      LinkedList devNull = new LinkedList();
+      this.fBlacklist.drainTo(devNull);
+
+      if (this.fCurrentHost != null)
+      {
+        this.fBlacklist.add(new BlacklistEntry(this.fCurrentHost, TimeUnit.MILLISECONDS.convert(blacklistUnit, blacklistTimeUnit)));
+      }
+    }
+    this.fCurrentHost = null;
+  }
+
+  private String makeSelection()
+  {
+    TreeSet workingSet = new TreeSet(this.fBaseHosts);
+
+    LinkedList devNull = new LinkedList();
+    this.fBlacklist.drainTo(devNull);
+    for (BlacklistEntry be : this.fBlacklist)
+    {
+      workingSet.remove(be.getHost());
+    }
+
+    if (workingSet.isEmpty())
+    {
+      log.warn("All hosts were blacklisted; reverting to full set of hosts.");
+      workingSet.addAll(this.fBaseHosts);
+      this.fCurrentHost = null;
+    }
+
+    String selection = null;
+    if ((this.fCurrentHost != null) && (workingSet.contains(this.fCurrentHost)))
+    {
+      selection = this.fCurrentHost;
+    }
+    else if ((this.fIdealHost != null) && (workingSet.contains(this.fIdealHost)))
+    {
+      selection = this.fIdealHost;
+    }
+    else
+    {
+      int index = 0;
+      int value = new Random().nextInt();
+      Vector v = new Vector(workingSet);
+      if(value!=0) {
+      index = Math.abs(value) % workingSet.size();
+      }
+      selection = (String)v.elementAt(index);
+    }
+
+    this.fCurrentHost = selection;
+    return this.fCurrentHost;
+  }
+
+  private static Set<String> makeSet(String s)
+  {
+    TreeSet set = new TreeSet();
+    set.add(s);
+    return set; }
+
+  private static class BlacklistEntry implements Delayed {
+    private final String fHost;
+    private long fExpireAtMs;
+
+    public BlacklistEntry(String host, long delayMs) {
+      this.fHost = host;
+      this.fExpireAtMs = (System.currentTimeMillis() + delayMs);
+    }
+
+    public void expireNow()
+    {
+      this.fExpireAtMs = 0L;
+    }
+
+    public String getHost()
+    {
+      return this.fHost;
+    }
+
+    public int compareTo(Delayed o)
+    {
+      Long thisDelay = Long.valueOf(getDelay(TimeUnit.MILLISECONDS));
+      return thisDelay.compareTo(Long.valueOf(o.getDelay(TimeUnit.MILLISECONDS)));
+    }
+
+    public long getDelay(TimeUnit unit)
+    {
+      long remainingMs = this.fExpireAtMs - System.currentTimeMillis();
+      return unit.convert(remainingMs, TimeUnit.MILLISECONDS);
+    }
+  }
+}