Liferay clustering with jGroups has been bound to HTTP thread and can cause severe cluster instability

• Type: Bug
• Status: Open
• Resolution: Unresolved
• Affects Version/s: 6.2.10 EE GA1, 7.2.0 GA1, 7.2.10 DXP GA1
• Fix Version/s: None
• Component/s: Fault Tolerance > Clustering Framework
• Labels: None

Overview

Liferay clustering jGroups communication problems can cause significant slowdown the application server HTTP thread, which can lead up situation that cluster is not responding.

My customer's huge Liferay cluster did slow down so much that it is none of the nodes were responding for traffic. On this case one of the nodes where the root cause and when that node was killed then cluster did heal itself. Still, meanwhile, our site wasn't able to serve any traffic for a significant period of time.

By examining thread dumps from that period, the situation was tracked down to jGroups.send(..) and that method was called from the thread that was responding the user Http request.

This ticket describes how to simulate this kind of situation:

Prepare for the simulated test

Create a Liferay DXP 7.2 ( or EE 6.2 clustered fixpack -69 ) environment with Tomcat. (EE 6.2 might require little changes on Byteman script)

Install byteman: https://byteman.jboss.org/downloads.html under `<tomcat>/byteman` directory

Modify <tomcat>/bin/setenv.sh script and add following there at end:

if [ -f "${CATALINA_HOME}/byteman/lib/byteman.jar" ]; then
	BYTEMAN_HOME="${CATALINA_HOME}/byteman"

	CATALINA_OPTS="${CATALINA_OPTS} -Dorg.jboss.byteman.transform.all"
	CATALINA_OPTS="${CATALINA_OPTS} -Dorg.jboss.byteman.allow.config.updates"

	if [ -f "${CATALINA_HOME}/default.btm" ]; then
		echo "Byteman Found with script ${CATALINA_HOME}/default.btm"
		CATALINA_OPTS="${CATALINA_OPTS} -javaagent:${BYTEMAN_HOME}/lib/byteman.jar=script:${CATALINA_HOME}/default.btm,boot:${BYTEMAN_HOME}/lib/byteman.jar,listener:true"
	else
		echo "Byteman Found"
		CATALINA_OPTS="${CATALINA_OPTS} -javaagent:${BYTEMAN_HOME}/lib/byteman.jar=sys:${BYTEMAN_HOME}/lib/byteman.jar,listener:true"
	fi
else
	echo "Booting without ${CATALINA_HOME}/byteman"
fi

With DXP 7.2 / CE 7.2 add to portal-ext.properties (if that exist then make sure to add org.jboss.byteman.* to last.

module.framework.properties.org.osgi.framework.bootdelegation=\
    __redirected,\
    com.liferay.aspectj,\
    com.liferay.aspectj.*,\
    com.liferay.expando.kernel.model,\
    com.liferay.portal.servlet.delegate,\
    com.liferay.portal.servlet.delegate*,\
    com.sun.ccpp,\
    com.sun.ccpp.*,\
    com.sun.crypto.*,\
    com.sun.image.*,\
    com.sun.jmx.*,\
    com.sun.jna,\
    com.sun.jndi.*,\
    com.sun.mail.*,\
    com.sun.management.*,\
    com.sun.media.*,\
    com.sun.msv.*,\
    com.sun.org.*,\
    com.sun.syndication,\
    com.sun.tools.*,\
    com.sun.xml.*,\
    com.yourkit.*,\
    javax.validation,\
    javax.validation.*,\
    jdk.*,\
    sun.*,\
    weblogic.jndi,\
    weblogic.jndi.*,\
    org.jboss.byteman.*

Create Byteman rule file <tomcat>/default.btm file with content of following (File is created for 7.2 so it might vary for other versions).

# Prints log entry when JChannel.close is called
RULE org.jgroups.JChannel.close
CLASS org.jgroups.JChannel
METHOD close
AT ENTRY
BIND
channel:org.jgroups.JChannel = $0;
IF true
DO
#We open trace every time just in case. It won't re-open it.
traceOpen("jgroups_log","jgroups.log");
traceln("jgroups_log","Closing JChannel: " + channel.cluster_name);
ENDRULE

# Prints log entry when JChannel.connect(String) is called
RULE org.jgroups.JChannel.connect
CLASS org.jgroups.JChannel
METHOD connect(String)
AT ENTRY
BIND
threadId = ""+Thread.currentThread().getId() + "/" + Thread.currentThread().getName();
IF true
DO
# We open trace every time just in case. It won't re-open it.
traceOpen("jgroups_log","jgroups.log");
traceln("jgroups_log", threadId + "\t" + new java.util.Date() + "\tConnect JChannel: " + $1);
ENDRULE

# Prints log entry when JChannel.send(org.jgroups.Message) is called
RULE org.jgroups.JChannel.send
CLASS org.jgroups.JChannel
METHOD send(org.jgroups.Message)
AT ENTRY
BIND
threadId = ""+Thread.currentThread().getId() + "/" + Thread.currentThread().getName();
channelName = $0.cluster_name + "";
# Tap rule only to Http thread (Sleep also 5000 ms)
IF formatStack().indexOf("com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain") > 0 
DO Thread.sleep(5000);
traceln("jgroups_log", threadId + "\t" + new java.util.Date() + "\t" + channelName + "\nSend:\nSTACKTRACE\n" + formatStack());
ENDRULE

Test

1. Start the portal

2. Add user and when you save the user information you notice that it is slow and take around 15 seconds (due to the Thread.sleep at Byteman script).

3. If you add a role to user that is taking around 5+ seconds due to the same reason.

4. You can see from <liferay-home>/jgroups.log places at the code where this has been called. Adding user is blocking 3 times and updating role once.

Summary

Cluster communication should be isolated from HTTP thread to increase Liferay's stability on exceptional cases when jGroups is slowing down.