[SOLR-5215] Deadlock in Solr Cloud ConnectionManager

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 4.2.1
• Fix Version/s: 4.5, 6.0
• Component/s: clients - java, SolrCloud

Environment

Linux 2.6.18-164.el5 #1 SMP Tue Aug 18 15:51:48 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux

java version "1.6.0_18"
Java(TM) SE Runtime Environment (build 1.6.0_18-b07)
Java HotSpot(TM) 64-Bit Server VM (build 16.0-b13, mixed mode)

• Assignee: Mark Miller
• Reporter: Ricardo Merizalde
• Created: 04/Sep/13 19:06
• Updated: 09/May/16 18:52
• Resolved: 14/Oct/13 09:20

Description

We are constantly seeing a deadlocks in our production application servers.

The problem seems to be that a thread A:

• tries to process an event and acquires the ConnectionManager lock
• the update callback acquires connectionUpdateLock and invokes waitForConnected
• waitForConnected tries to acquire the ConnectionManager lock (which already has)
• waitForConnected calls wait and release the ConnectionManager lock (but still has the connectionUpdateLock)

The a thread B:

• tries to process an event and acquires the ConnectionManager lock
• the update call back tries to acquire connectionUpdateLock but gets blocked holding the ConnectionManager lock and preventing thread A from getting out of the wait state.

Here is part of the thread dump:

"http-0.0.0.0-8080-82-EventThread" daemon prio=10 tid=0x0000000059965800 nid=0x3e81 waiting for monitor entry [0x0000000057169000]
java.lang.Thread.State: BLOCKED (on object monitor)
at org.apache.solr.common.cloud.ConnectionManager.process(ConnectionManager.java:71)

• waiting to lock <0x00002aab1b0e0ce0> (a org.apache.solr.common.cloud.ConnectionManager)
  at org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:519)
  at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:495)

"http-0.0.0.0-8080-82-EventThread" daemon prio=10 tid=0x000000005ad40000 nid=0x3e67 waiting for monitor entry [0x000000004dbd4000]
java.lang.Thread.State: BLOCKED (on object monitor)
at org.apache.solr.common.cloud.ConnectionManager$1.update(ConnectionManager.java:98)

• waiting to lock <0x00002aab1b0e0f78> (a java.lang.Object)
  at org.apache.solr.common.cloud.DefaultConnectionStrategy.reconnect(DefaultConnectionStrategy.java:46)
  at org.apache.solr.common.cloud.ConnectionManager.process(ConnectionManager.java:91)
• locked <0x00002aab1b0e0ce0> (a org.apache.solr.common.cloud.ConnectionManager)
  at org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:519)
  at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:495)

"http-0.0.0.0-8080-82-EventThread" daemon prio=10 tid=0x00002aac4c2f7000 nid=0x3d9a waiting for monitor entry [0x0000000042821000]
java.lang.Thread.State: BLOCKED (on object monitor)
at java.lang.Object.wait(Native Method)

• waiting on <0x00002aab1b0e0ce0> (a org.apache.solr.common.cloud.ConnectionManager)
  at org.apache.solr.common.cloud.ConnectionManager.waitForConnected(ConnectionManager.java:165)
• locked <0x00002aab1b0e0ce0> (a org.apache.solr.common.cloud.ConnectionManager)
  at org.apache.solr.common.cloud.ConnectionManager$1.update(ConnectionManager.java:98)
• locked <0x00002aab1b0e0f78> (a java.lang.Object)
  at org.apache.solr.common.cloud.DefaultConnectionStrategy.reconnect(DefaultConnectionStrategy.java:46)
  at org.apache.solr.common.cloud.ConnectionManager.process(ConnectionManager.java:91)
• locked <0x00002aab1b0e0ce0> (a org.apache.solr.common.cloud.ConnectionManager)
  at org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:519)
  at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:495)

Found one Java-level deadlock:
=============================
"http-0.0.0.0-8080-82-EventThread":
waiting to lock monitor 0x000000005c7694b0 (object 0x00002aab1b0e0ce0, a org.apache.solr.common.cloud.ConnectionManager),
which is held by "http-0.0.0.0-8080-82-EventThread"
"http-0.0.0.0-8080-82-EventThread":
waiting to lock monitor 0x00002aac4c314978 (object 0x00002aab1b0e0f78, a java.lang.Object),
which is held by "http-0.0.0.0-8080-82-EventThread"
"http-0.0.0.0-8080-82-EventThread":
waiting to lock monitor 0x000000005c7694b0 (object 0x00002aab1b0e0ce0, a org.apache.solr.common.cloud.ConnectionManager),
which is held by "http-0.0.0.0-8080-82-EventThread"

Java stack information for the threads listed above:
===================================================
"http-0.0.0.0-8080-82-EventThread":
at org.apache.solr.common.cloud.ConnectionManager.process(ConnectionManager.java:71)

• waiting to lock <0x00002aab1b0e0ce0> (a org.apache.solr.common.cloud.ConnectionManager)
  at org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:519)
  at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:495)
  "http-0.0.0.0-8080-82-EventThread":
  at org.apache.solr.common.cloud.ConnectionManager$1.update(ConnectionManager.java:98)
• waiting to lock <0x00002aab1b0e0f78> (a java.lang.Object)
  at org.apache.solr.common.cloud.DefaultConnectionStrategy.reconnect(DefaultConnectionStrategy.java:46)
  at org.apache.solr.common.cloud.ConnectionManager.process(ConnectionManager.java:91)
• locked <0x00002aab1b0e0ce0> (a org.apache.solr.common.cloud.ConnectionManager)
  at org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:519)
  at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:495)
  "http-0.0.0.0-8080-82-EventThread":
  at java.lang.Object.wait(Native Method)
• waiting on <0x00002aab1b0e0ce0> (a org.apache.solr.common.cloud.ConnectionManager)
  at org.apache.solr.common.cloud.ConnectionManager.waitForConnected(ConnectionManager.java:165)
• locked <0x00002aab1b0e0ce0> (a org.apache.solr.common.cloud.ConnectionManager)
  at org.apache.solr.common.cloud.ConnectionManager$1.update(ConnectionManager.java:98)
• locked <0x00002aab1b0e0f78> (a java.lang.Object)
  at org.apache.solr.common.cloud.DefaultConnectionStrategy.reconnect(DefaultConnectionStrategy.java:46)
  at org.apache.solr.common.cloud.ConnectionManager.process(ConnectionManager.java:91)
• locked <0x00002aab1b0e0ce0> (a org.apache.solr.common.cloud.ConnectionManager)
  at org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:519)
  at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:495)