Blog - Page 3 of 4

June 6 2012

Why is my java process taking more memory than I gave it?

Mika Koivisto General heap, java, jvm, memory 0

It seems to be quite common misconseption that the memory you give to java process with -Xmx and -Xms command line arguments is the amount of memory the process will consume but in fact that is only the amount of memory your java object heap will have. The heap is just one factor in how much memory the java process will consume. To better understand how much memory your java application will consume from the system you need to understand all the factors that account for the memory usage. Those factors are:

Objects
Classes
Threads
Native data structures
Native code

The memory consumption associated with each item varies across applications, runtime environments and platforms. So how do you calculate the total memory? Well, it’s not really all that easy to get accurate number because you have little control over the native part. The only parts you can really control is the amount of heap -Xmx, memory consumed by classes -XX:MaxPermSize and thread stack -Xss which controls the amount of memory each thread takes. Be careful when adjusting stack size as too low size will cause StackOverflow exceptions and your application won’t work correctly. So the formula is:

(-Xmx) + (-XX:MaxPermSize) + numberofthreads * (-Xss) + Other mem

The other mem part depends on how much native code is used like NIO, socket buffers, JNI etc. It’s anywhere from 5% of total jvm memory and up. So assume we have following JVM arguments and 100 threads

-Xmx1024m -XX:MaxPermSize=256m -Xss512k

That would mean that the jvm process would take at least: 1024m + 256m + 100*512k + (0.05 * 1330m) = 1396.5m.

I usually use a quick approximation rule of 1.5 * max heap to be the minimum amont of RAM a tomcat process will require. This can be higher if you have large application that requires you to increase MaxPermSize beyond 256m. If you use this to size how much memory your system will require remember that you need to leave memory for the OS and other applications running on the system otherwise you might end up using a lot of virtual memory that will affect your application performance negatively.

May 29 2012

What to Do When You Get “Error listerStart” with Tomcat

Mika Koivisto Howto debugging, tomcat 1

I’m sure many people other than me have banged their head in the wall trying to figure out an error like this:

SEVERE: Error listenerStart 
26-May-2012 13:44:27 org.apache.catalina.core.StandardContext startInternal 
SEVERE: Context [] startup failed due to previous errors

That basically means that tomcat failed to start the webapp because there was an error with some listener, quite often Spring context listener. The really annoying part is that it doesn’t actually show you what went wrong. There’s actually pretty simple way to get tomcat to log the actual error. You just need to create a logging.properties in WEB-INF/classes of the failing webapp and add following lines to it:

org.apache.catalina.core.ContainerBase.[Catalina].level = INFO
org.apache.catalina.core.ContainerBase.[Catalina].handlers = java.util.logging.ConsoleHandler

Then just reload the webapp to see the error in tomcat console log. I hope this tip saves you a lot of hasle from trying to figure out the root cause of the problem.

May 28 2012

How to Create a Consistent Liferay Backup

Mika Koivisto Howto backup, liferay 0

This is a question I’ve gotten asked in nearly all the Liferay System Administrator trainings I’ve given. Most people will just backup their database and Liferay data directory separately but any competent system admin will tell you that it’s not guaranteed to be consistent because someone could upload or delete files between the time you took the database dump and the time you copied the data directory. Now I’m assuming that you are storing your document library binaries to filesystem instead of database.

Now to achieve a consistent backup with minimal interruption to your portal what you need to do is get a read lock on all your Liferay tables. This will prevent writes to the database. Then you dump the database to file with a tool like mysqldump and then you take a quick snapshot of the filesystem before you unlock the tables. You need to keep the connection that locked the tables open until this whole process is done. Once you have the database dump and filesystem snapshot ready only then you can release the lock and then you can backup the data directory using what ever method you would normally use.

For the PoC I’m using MySQL and my filesystem is on Linux LVM volume which supports taking snapshots. I’ve written a Perl script to execute all the commands. I’m sharing the script under GPL and it’s available in Github. Feel free to fork it and modify it to suit your needs and if you have good ideas send me a pull request.

The way the script works is you pass in bunch of parameters like database details, lvm volume location, source and target directories. Here’s an example:

backup_liferay.pl -u dba-backup -p mypassword -d lportal -h localhost \
--lvm-volume-path /dev/vg0/opt --lvm-snapshot-volume-path /dev/vg0/opt-snapshot \
--lvm-snapshot-volume-name opt-snapshot --lvm-snapshot-volume-size 50G \
--snapshot-mount-path /backups/snapshot \
--source-path /liferay-portal-6.1.0/data/document_library \
--db-target-path /backups/mysql/lportal.sql.gz \
--data-target-path /backups/liferay --compress

Now even if that doesn’t exactly match your system I hope it gives you an idea how to roll your own Liferay backup.

May 27 2012

Debugging Maven Plugins

Mika Koivisto Howto debugging, maven 0

When developing maven plugins things don’t always work the way you expect so you need to debug the Mojo to see what’s really going on. I had a weird case where my plugin worked when I ran it independently but when I ran it with mvn clean package it always failed. First thing you can do is run in debug mode which produces a lot more output and shows all the plugin execution configuration. You can enable it with -X argument like this:

mvn -X clean package

Now that didn’t quite help with my case so next thing I did was to run it with remote debugger. That way I could step through the code line by line and inspect all the variables. To do that you just modify the MAVEN_OPTS environment variable in the shell where you are executing you maven plugin and add java debugger agentlib config like this:

MAVEN_OPTS="-agentlib:jdwp=transport=dt_socket,address=8000,server=y,suspend=y"

I used suspend=y so that it would wait for my debugger to attach before continuing the execution. Then you just add some breakpoints in you IDE and remote debug it like any java application. That by the way solved my issue as I realized each of my Liferay maven plugins were initialing Liferay configuration but since they were all run after each other in the same context only the first one mattered.

March 16 2012

Creating Liferay Themes with Maven

Mika Koivisto Liferay liferay, maven

Some time ago I posted on how you can get started creating portlets with Liferay Maven SDK now I’m going to show how you can add themes to your project. If you need a refresher on how to get started check out this post. More

February 28 2012

Getting started with Liferay SAML 2.0 Identity Provider

Mika Koivisto Liferay liferay, salesforce, saml

Liferay 6.1 EE comes with SAML 2.0 Identity Provider and Service

Provider support via SAML plugin. If you are not familiar with SAML
check out my Introduction to SAML presentation slides.

In this post we will configure Liferay to be SAML Identity Provider
and configure Salesforce to be a Service Provider. After we are done
we have a user that can move from Liferay to Salesforce without
requiring to authenticate on Salesforce. More

February 22 2012

Deploying Liferay artifacts to your own maven repository

Mika Koivisto Liferay liferay, maven

As part of Liferay 6.1 release we’ve created a new package that has a convenient script to install Liferay artifacts to your local repository or to a remote repository. This package is provide for both CE and EE releases but it is more useful for EE users because we don’t release EE versions of the artifacts to Maven Central repository. More

February 2 2012

Getting started with Liferay Maven SDK

Mika Koivisto Liferay liferay, maven

This will be the first in series of posts on how to develop Liferay plugins with Maven. In this post we’ll start by creating a new parent project for your plugins and add a portlet project to it. You need to have your maven environment setup with maven and java installed. If you don’t know how to do it I would recommend reading Maven: The Complete Reference from Sonatype, Inc. The chapter 2 has good instructions on how to install maven.

January 10 2012

Liferay 6.1 GA1 Maven artifacts released

Mika Koivisto Liferay liferay, maven

I’m glad to announce that we have released Liferay maven artifacts to 6.1 GA1.

All the artifacts will be pushed into the central repository through http://oss.sonatype.org where they are already available. More

January 18 2011

Overriding and adding struts actions from hook plugins

Mika Koivisto Liferay hook, liferay, struts

This is a new cool feature I worked on with Brian and it’s coming on 6.1 as well as 6.0 EE SP2 and 5.2 EE SP6. With this feature you can add new struts actions to portal from a hook plugin and you can override any existing action with it.

There are two interfaces com.liferay.portal.kernel.struts.StrutsAction and com.liferay.portal.kernel.struts.StrutsPortletAction. The StrutsAction is used for regular struts actions like /c/portal/update_password and StrutsPortletAction is used for those that are used from portlets. More

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