Passa ai contenuti principali

Tomcat maxThreads configuration

Tomcat maxThreads represents the maximum number of request
processing threads to be created by the HTTPConnector.

<Connector port="8443" protocol="org.apache.coyote.http11.Http11Protocol"
           maxThreads="250" SSLEnabled="true" scheme="https" secure="true"
           clientAuth="false" sslProtocol="TLS" connectiontimeout="20000"/>

This determines the maximum number of simultaneous requests that can be handled. If not specified, this attribute is set to the default value of 200.

How the process works:
  • At server startup, the HTTP Connector will create a number of processing threads based on the value configured for the minSpareThreads attribute.
  • Each incoming request requires a thread for the duration of that request.
  • If the number of simultaneous requests cannot be handled by the currently available request processing threads, additional threads will be created up to the configured maximum (the value of the maxThreads attribute).
  • If still more simultaneous requests are received, they are stacked up up to the configured maximum (the value of the acceptCount attribute).
  • Any further simultaneous requests will receive "connection refused" errors, until resources are available to process them.
Guidelines for maxThreads:
maxThreads is an important tuning parameter, however if you are reaching an error like:
org.apache.tomcat.util.threads.ThreadPool logFull SEVERE: All threads (150) are
currently busy, waiting. Increase maxThreads (150) or check the servlet status
you should at first investigate if it's rather a problem of individual requests taking too long: are your threads returning to the pool? if, for example, database connections are not released, threads pile up waiting to obtain a database connection thereby making it impossible to process additional requests. This is a problem in your webapp. Take a thread dump to find out where they're stuck.
Increasing too much maxThreads will lead to :
  • Consume a good chunk of memory.
  • Your system will spend too much time context switching
So once you have already optimized your application try raising you maxThread attribute up to 500-750. I wouldn't advice to create larger Connectors, rather if 750 Connections are not enough create a Cluster configuration with several Tomcat instances. For example 2 instances of tomcat each one with maxThreads=500 instead of a single Tomcat with maxThreads=1000

Monitoring Tomcat maxThreads

You can monitor Tomcat maxThreads by logging into the Manager Web application which is available at: http://localhost:8080/manager

Once logged into the Manager application (See this tutorial to learn how to create un user for the Manager application), click on the Server Status link. At the bottom of the Server status link you will see this information:


There you can gather important information such as:
  • The number of Max threads 
  • The current thread count 
  • The current thread busy 
  • The Max processing time 
  • The Request count 
  • The Error count   
  • The Bytes received  
  • The Bytes sent 

If you want to learn more about JDK tuning read this tutorial which contains many tips valid also for Tomcat:JBoss Performance Tuning

Commenti

Post popolari in questo blog

Tomcat Websocket example

A WebSocket is a full-duplex communication mechanism that allows both textual and binary messages to be sent between clients and servers, without the HTTP request/response life cycle. WebSockets allow either the client or the server to send a message at any time, providing an asynchronous solution for working with data while the user is performing a task.
Websockets API are included in Tomcat 7 Web server distribution so you don't have to download any extra library:

In this tutorial we will show how to create a WebSocket example using Apache Tomcat and Eclipse.
Start by creating on Eclipse a new Dynamic project named websocket-example:
We will now create a server side class named WebSocketDemo that is going to echo messages from a Javascript client:
package com.sample;import java.io.IOException;import java.nio.ByteBuffer;import javax.websocket.OnMessage;import javax.websocket.Session;import javax.websocket.server.ServerEndpoint; @ServerEndpoint("/echo") publicclass WebSoc…

Tomcat Thread Pool configuration

In order to accept incoming requests, Tomcat uses a Thread pool. You can configure two types of Thread Pools: Shared Pool and Dedicated Pool.
A Shared pool as the name inplies, can be shared among various components in Tomcat. So, for example if you have three connectors in your configuration, then you can use a single shared pool to serve requests for all of them. Here is how to configure a shared thread pool:

Open Tomcat's server.xml file and include the Executor definition:

namePrefix="catalina-exec-" maxThreads="150" minSpareThreads="4"/>
Once you have added the shared thread pool, you need to reference it in your Connector configuration as follows:
namePrefix="catalina-exec-" maxThreads="200" minSpareThreads="4"/>
A Dedicated threadpool is a thread pool which is dedicated to only one connector definition. You can use it in a scenario when you are expecting a peak of connections and you want to have ful…