From 9fcb2ae8652d1b1fde12812b769f3797c884337c Mon Sep 17 00:00:00 2001
From: Jean-Daniel Cryans <jdcryans@apache.org>
Date: Tue, 15 Apr 2014 22:46:47 +0000
Subject: [PATCH] HBASE-10312 Flooding the cluster with administrative actions
 leads to collapse

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1587742 13f79535-47bb-0310-9956-ffa450edef68
---
 .../hadoop/hbase/monitoring/TaskMonitor.java  | 23 ++++---------------
 1 file changed, 5 insertions(+), 18 deletions(-)

diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/monitoring/TaskMonitor.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/monitoring/TaskMonitor.java
index 1281613a88f..d51f354cf59 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/monitoring/TaskMonitor.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/monitoring/TaskMonitor.java
@@ -27,6 +27,7 @@ import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
 
+import org.apache.commons.collections.buffer.CircularFifoBuffer;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.classification.InterfaceAudience;
@@ -51,8 +52,7 @@ public class TaskMonitor {
   static final int MAX_TASKS = 1000;
   
   private static TaskMonitor instance;
-  private List<TaskAndWeakRefPair> tasks =
-    Lists.newArrayList();
+  private CircularFifoBuffer tasks = new CircularFifoBuffer(MAX_TASKS);
 
   /**
    * Get singleton instance.
@@ -74,9 +74,6 @@ public class TaskMonitor {
         new PassthroughInvocationHandler<MonitoredTask>(stat));
     TaskAndWeakRefPair pair = new TaskAndWeakRefPair(stat, proxy);
     tasks.add(pair);
-    if (tasks.size() > MAX_TASKS) {
-      purgeExpiredTasks();
-    }
     return proxy;
   }
 
@@ -89,15 +86,10 @@ public class TaskMonitor {
         new PassthroughInvocationHandler<MonitoredRPCHandler>(stat));
     TaskAndWeakRefPair pair = new TaskAndWeakRefPair(stat, proxy);
     tasks.add(pair);
-    if (tasks.size() > MAX_TASKS) {
-      purgeExpiredTasks();
-    }
     return proxy;
   }
 
   private synchronized void purgeExpiredTasks() {
-    int size = 0;
-    
     for (Iterator<TaskAndWeakRefPair> it = tasks.iterator();
          it.hasNext();) {
       TaskAndWeakRefPair pair = it.next();
@@ -114,15 +106,8 @@ public class TaskMonitor {
       
       if (canPurge(stat)) {
         it.remove();
-      } else {
-        size++;
       }
     }
-    
-    if (size > MAX_TASKS) {
-      LOG.warn("Too many actions in action monitor! Purging some.");
-      tasks = tasks.subList(size - MAX_TASKS, size);
-    }
   }
 
   /**
@@ -133,7 +118,9 @@ public class TaskMonitor {
   public synchronized List<MonitoredTask> getTasks() {
     purgeExpiredTasks();
     ArrayList<MonitoredTask> ret = Lists.newArrayListWithCapacity(tasks.size());
-    for (TaskAndWeakRefPair pair : tasks) {
+    for (Iterator<TaskAndWeakRefPair> it = tasks.iterator();
+         it.hasNext();) {
+      TaskAndWeakRefPair pair = it.next();
       MonitoredTask t = pair.get();
       ret.add(t.clone());
     }