The agent is overloaded [current requests: 128]

Java layer deadlock —“Dead Lock detected!!”, bounce the agent, and then everything is working fine.

SITUATION

The following alerts are received from racnode1 -“The agent is overloaded [current requests: 128]”

From: oracle 
Sent: Friday, 4 August 2017 7:07 PM
Cc: 
Subject: EM Event: Warning: racnode1 - Agent Unreachable (REASON = The agent is overloaded [current requests: 128]). Host is reachable.

...
..
.
Categories=Availability 
Message=Agent Unreachable (REASON = The agent is overloaded [current requests: 128]). Host is reachable. 
Severity=Warning 
Event reported time=Aug 4, 2017 7:06:27 PM AEST
...
..
.

INVESTIGATING

1)   Check agent status

Agent is running
Agent upload is not working
Agent reload is not working
OMS heartbeat is not working

$ emctl status agent
Oracle Enterprise Manager Cloud Control 12c Release 5
Copyright (c) 1996, 2015 Oracle Corporation. All rights reserved.
---------------------------------------------------------------
Agent Version : 12.1.0.5.0
OMS Version : 13.2.0.0.0
Protocol Version : 12.1.0.1.0
..
.
Last Reload : 2017-08-04 11:28:59
Last successful upload : 2017-08-04 14:51:03  <--- 5 hours ago
Last attempted upload : 2017-08-04 14:51:03
..
.
Last attempted heartbeat to OMS : 2017-08-04 14:50:23
Last successful heartbeat to OMS : 2017-08-04 14:50:23
Next scheduled heartbeat to OMS : 2017-08-04 14:51:23

2) Upload agent
$ emctl upload agent
Oracle Enterprise Manager Cloud Control 12c Release 5
Copyright (c) 1996, 2015 Oracle Corporation. All rights reserved.
---------------------------------------------------------------
EMD upload error:The agent is overloaded [current requests: 128]
3) Reload agent
$ emctl reload agent
Oracle Enterprise Manager Cloud Control 12c Release 5
Copyright (c) 1996, 2015 Oracle Corporation. All rights reserved.
---------------------------------------------------------------
EMD reload error:The agent is overloaded [current requests: 128]
4) “emagent_perl.trc” file has no information updated since agent restarted
5) Check “gcagent.log”

Java layer deadlock —“Dead Lock detected!!”

2017-08-04 19:28:59,071 [43:GCThread-13] ERROR -
Dead Lock detected!!
Participating threads:Thread Info Dump:
=================
"HTTP Listener-3592 - /emd/main/ (~Task-free~ OMS.pbs@16398@omsnode=>[150183756670001])" tid=3592 WAITING
 > Accumulated wait time (msec): 1372208 (1 times)

"HTTP Listener-2141 - /emd/main/ (~Task-free~ OMS.pbs@13103@omsnode=>[150182243190001])" tid=2141 BLOCKED
 > Accumulated wait time (msec): 11036289 (76 times)
 > Accumulated blocked time (msec): 16506994 (4 times)

"oracle.dfw.impl.incident.DiagnosticsDataExtractorImpl - Incident Dump Executor (created: Fri Aug 04 14:51:06 EST 2017)" tid=3088 BLOCKED
 > Accumulated blocked time (msec): 16672145 (7 times)

"HTTP Listener-1022 - /emd/main/ (~Task-free~ OMS.pbs@16398@omsnode=>[150181021899001])" tid=1022 WAITING
 > Accumulated wait time (msec): 28746227 (37 times)
 > Accumulated blocked time (msec): 133 (12 times)

"HTTP Listener-1078 - /emd/main/ (DispatchRequests OMS.console@16398@omsnode=>[150181015881006])" tid=1078 WAITING
 > Accumulated wait time (msec): 28719225 (44 times)

=================
Thread Info Dump:
=================
"HTTP Listener-3592 - /emd/main/ (~Task-free~ OMS.pbs@16398@omsnode=>[150183756670001])" tid=3592 WAITING
 sun.misc.Unsafe.park(Native Method)
 - waiting on <0x149717ec> (a java.util.concurrent.locks.ReentrantLock$NonfairSync), which is owned by "HTTP Listener-2141 - /emd/main/ (~Task-free~ OMS.pbs@13103@omsnode=>[150182243190001])" (tid=2141)
 java.util.concurrent.locks.LockSupport.park(LockSupport.java:156)
 java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:811)
 java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:842)
 java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1178)
 java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:186)
...
..
.

SOLUTION

1) Stop agent
$ emctl stop agent
Oracle Enterprise Manager Cloud Control 12c Release 5
Copyright (c) 1996, 2015 Oracle Corporation. All rights reserved.
Stopping agent ...
 stopped.
2) Start agent
$ emctl start agent
Oracle Enterprise Manager Cloud Control 12c Release 5
Copyright (c) 1996, 2015 Oracle Corporation. All rights reserved.
Starting agent ............................................ started.
3) Upload agent successfully
$ emctl upload agent
Oracle Enterprise Manager Cloud Control 12c Release 5
Copyright (c) 1996, 2015 Oracle Corporation. All rights reserved.
---------------------------------------------------------------
EMD upload completed successfully
4) Reload agent successfully
$ emctl reload agent
Oracle Enterprise Manager Cloud Control 12c Release 5
Copyright (c) 1996, 2015 Oracle Corporation. All rights reserved.
---------------------------------------------------------------
EMD reload completed successfully
5)Check agent status successfully
$ emctl status agent
...
..
Last attempted heartbeat to  OMS : 2017-08-04 19:53:31
Last successful heartbeat to OMS : 2017-08-04 19:53:31
Next scheduled heartbeat to  OMS : 2017-08-04 19:54:32

---------------------------------------------------------------
Agent is Running and Ready

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