Tomcat 7 request processing threading architecture and performance tuning

Tomcat has many parameters for performance tuning (see http://tomcat.apache.org/tomcat-7.0-doc/config/http.html), but for some attribute descriptions it is not a 100% clear how some properties affect each other.

A pretty good explanation regarding acceptCount and maxThreads can be found here: http://techblog.netflix.com/2015/07/tuning-tomcat-for-high-throughput-fail.html 
But that article is missing a ... picture! That's what I tried to create here, with the numbers 1-5 indicating the steps described in the above article:

Just in case should the Netflix URL ever get lost and for easy reference, here's the 5 steps:

The Tomcat attribute maxThreads worked best in my case with value 50, as it won't saturate the machine/CPU. (due to too many workerthreads, many context-switches)


To set maxThreads when using Spring Boot + embedded Tomcat: http://stackoverflow.com/questions/31432514/how-to-modify-tomcat8-acceptcount-in-spring-boot

Other remarks

• Could not get acceptCount set via Spring Boot + embedded tomcat.... Tried by configuring my own embedded Tomcat container (e.g as in here  and here):
  
  connector.setAttribute("acceptCount", acceptCount);
  


• This was for a pure Tomcat setup, no Apache webserver in front of it.
  


• Special care when providing your own executor, see a.o: https://www.packtpub.com/books/content/overview-tomcat-6-servlet-container-part-2
  


• Performance monitoring & profiling was done with tools like: JVisualVm, Java Mission Control (JMC + Java Flight Recorder), JProfiler.

Referenced material

• http://tomcat.10.x6.nabble.com/Tomcat-does-not-honor-acceptCount-configuration-variable-td2159508.html
  


• https://www.packtpub.com/books/content/overview-tomcat-6-servlet-container-part-1
  


• https://www.mulesoft.com/tcat/tomcat-connectors
  


• https://javamaster.wordpress.com/2013/03/13/apache-tomcat-tuning-guide/
  


• https://papweb.wordpress.com/2010/10/30/understanding-tomcat-executor-thread-pooling/
  


• Useful calculation that also shows just increasing maxThreads doesn't mean performance will get better: http://stackoverflow.com/questions/12600826/increase-number-of-concurrent-connections-in-tomcat-7
  


• Some more tuning tips: http://www.genericarticles.com/mediawiki/index.php?title=How_to_optimize_tomcat_performance_in_production
  


• Extra explanation of the attributes, also why certain NIO/BIO settings are recommended: http://stackoverflow.com/questions/25356703/tomcat-connector-architecture-thread-pools-and-async-servlets
  


• To disable/replace the default connector: http://stackoverflow.com/questions/28050354/spring-boot-replace-default-embedded-tomcat-connector
  


• Did not find the thread architecture at this obvious place, or any other search: http://tomcat.apache.org/tomcat-7.0-doc/architecture/requestProcess.html
  


• Similar diagram but for a webserver; none-the-less interesting diagram: http://www3.nd.edu/~dthain/courses/cse30341/spring2009/project4/pool.gif