Tuning Tomcat for APEX/ORDS in Production

Introduction

In a previous post Tuning GlassFish for APEX/ORDS in Production I described the steps to configure ORDS and GlassFish for production use. In this post, I will turn my attention to Tomcat and see what needs to be done to get Tomcat production ready for ORDS and APEX. I will focus purely on the Tomcat configurations as I already covered the ORDS side in the previous post.

Like GlassFish, out of the box, Tomcat comes configured for use in a development environment. You will see many of the same limitations as Glassfish when considering production use:

• Tomcat will be running in development mode (which incurs an overhead in checking to see if code has changed)
• If you have more than 1 CPU, you will not be taking advantage of it
• Tomcat will only assign 512m of ram to the JVM (and ORDS), even if you have more available
• Logging will be set to FINE and INFO, adding a logging burden to Tomcat
• You are in danger of timing out on large file uploads

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Setting the Scene

I will use the same example as I did previously. I am going to assume an actively used system with 250 users and an anticipated peak load of 50 sessions. We are assuming that only 50 of these 250 users could be clicking on an APEX button (or making and Ajax request) at exactly the same time requiring all 50 JDBC connections. We are assuming a normal load of 20 concurrently active users. I am going to assume we have a dedicated web server running ORDS and Tomcat with 4GB RAM and 1 Quadcore CPU. The configurations discussed here assume Tomcat version 8.5.6.

Tomcat Configurations

Follow your normal routine for downloading and installing the JDK and Tomcat. I will be calling out the name of the configuration file that needs to be created/changed as well as the setting within the file. I will assume $CATALINA_HOME refers to the root of your Tomcat install folder. So if you installed Tomcat at /opt/tomcat you would see sub-directories of bin, conf, logs etc. making $CATALINA_HOME = /opt/tomcat

Logging
Configuration File: $CATALINA_HOME/conf/logging.properties
Change all occurrences of FINE and INFO to SEVERE

JVM Options
To pass JVM options to Tomcat on startup, you should create a new file called $CATALINA_HOME/bin/setenv.sh

Add the following values:
export CATALINA_OPTS="$CATALINA_OPTS -Xms1536m"
export CATALINA_OPTS="$CATALINA_OPTS -Xmx1536m"
export CATALINA_OPTS="$CATALINA_OPTS -server"
Note: If you are running JDK7, you can also set PermSize and MaxPermSize. Note: PermSize and MaxPermSize not applicable for Java 8.
export CATALINA_OPTS="$CATALINA_OPTS -XX:PermSize=256m"
export CATALINA_OPTS="$CATALINA_OPTS -XX:MaxPermSize=256m"

Main Tomcat Server Configurations
We are going to be configuring Tomcat on Port 8080.
Configuration File: $CATALINA_HOME/conf/server.xml

Add the following under the Catalina Service:

Notes:

• acceptorThreadCount - The number of threads to be used to accept connections. Increase this value on a multi CPU Core machine.
• acceptCount - The maximum queue length for incoming connection requests when all possible request processing threads are in use. Any requests received when the queue is full will be refused. Set to 10 to protect server from getting overloaded.
• maxConnections - The maximum number of connections that the server will accept at any given time. When this number has been reached, the server will accept, but not process, one further connection. Connections are passed on to available threads to perform the actual work.
• maxThreads - The maximum number of request processing threads to be created by a connector, which therefore determines the maximum number of simultaneous requests that can be handled.
• minSpareThreads - The minimum number of threads always kept running waiting for new requests.
• connectionTimeout - The number of milliseconds a connector will wait, after accepting a connection, for the request URI line to be presented.
• disableUploadTimeout - Set to false and use the value in connectionUploadTimeout as the upload timeout.
• connectionUploadTimeout - Specifies the timeout, in milliseconds, to use while a data upload is in progress. This only takes effect ifdisableUploadTimeout is set to false.

Note: The threads described above do not impact JDBC connection pooling, which ORDS is handling for us. ORDS is protecting (or throttling) the JDBC connections Tomcat is organizing the web connections. If we assume the MaxLimit JDBC connection setting in ORDS is 50 then we have a healthy overhead of connections over to queue any users we have over 50.

Conclusion

The above settings are a guideline for configuring Tomcat to run ORDS in a fictitious production environment. As with all things performance, you will still need to go through the exercise of adding load to your system and finding the right settings for your hardware, users, data etc. The good news is, you now know which levers to pull!