Agenda

Tomcat Versions Troubleshooting management Tomcat Connectors HTTP Protocal and Performance Log Tuning JVM Tuning Load balancing Tomcat

Tomcat Performance Tuning

Tomcat Versions

Application/System Monitoring

Setup a system to monitor performance over time,

Need a baseline to compare normal from abnormal performance

Espcially true as dev/test is never a true copy of prod

Caveats - typical web server requests spends 80% of its time in application code – so most likely area for optimisation.

Tomcat Performance Tuning

Servelt 3.0 Spec (Dec 2009) Tomcat 7.0.6 Stable support (Jan 2011) Asynchronous servlets

Before only synchronous servlets – servlet thread has to wait for any background process to finish before being returned to pool.

Now servlet can returnt the thread to the pool while background process is running

Tomcat Config

Tomcat Connectors

Most tweaking in Tomcat done with connector parameters.

Two connector types Protocol = determines connector type if not

specified default to HTTP Connector HTTP connector AJP connector – used when tomcat is behind

a web server Server Shutdown – 8005 (not a connector)

HTTP Connector

HTTP Connector – 8080 org.apache.coyote.http11.Http11Protocol

(java BIO) org.apache.coyote.http11.Http11NioProtocol

(java NBIO) – unstable? org.apache.coyote.http11.Http11AprProtocol

(native connector)

Connector protocol attribute: HTTP/1.1 – uses coyote http 1.1

HTTP Connector Comparison

Comparison Table

AJP Connector

AJP (Apache JServe Protocol) Connector – 8009

org.apache.coyote.ajp.AjpProtocol org.apache.coyote.ajp.AjpNioProtocol

(experimental) org.apache.coyote.ajp.AjpAprProtocol

Connector protocol attribute: HTTP/1.1 – uses coyote http 1.1

AJP Connector

AJP (Apache JServe Protocol) Connector – 8009

org.apache.coyote.ajp.AjpProtocol org.apache.coyote.ajp.AjpNioProtocol

(experimental) org.apache.coyote.ajp.AjpAprProtocol

Connector protocol attribute: AJP – Uses coyote.ajp.AjpProtocol

AJP Connector Comparison Comparison Table

Apache – mod_proxy

Pros No need for a separate module compilation

and maintenance. mod_proxy, mod_proxy_http, mod_proxy_ajp and mod_proxy_balancer comes as part of standard Apache 2.2+ distribution

Ability to use http https or AJP protocols, even within the same balancer.

* thanks to blogs.jboss.org

Apache – mod_proxy

Cons: mod_proxy_ajp does not support large 8K+

packet sizes. Basic load balancer Does not support Domain model clustering

Apache - mod_jk

mod_jk - Pros: Advanced load balancer Advanced node failure detection Support for large AJP packet sizes up to 64K

Cons: Need to build and maintain a separate module

– (not really an issue for most Linux distributions)

HTTP KeepAlive

HTTP persistent connection, also called HTTP keep-alive, or HTTP connection reuse, is the idea of using the same TCP connection to send and receive multiple HTTP requests/responses, as opposed to opening a new connection for every single request/response pair – Wikipedia.

HTTP KeepAlive Advantages – The good:

Less CPU and memory usage (because fewer connections are open simultaneously)

Enables HTTP pipelining of requests and responses

Reduced network congestion (fewer TCP connections)

Reduced latency in subsequent requests (no handshaking)

Errors can be reported without the penalty of closing the TCP connection

Disadvantages – The bad

Wasted server resources, thread idle while others waiting to be serviced,

HTTP KeepAlive Advantages – The good:

Less CPU and memory usage (because fewer connections are open simultaneously)

Enables HTTP pipelining of requests and responses

Reduced network congestion (fewer TCP connections)

Reduced latency in subsequent requests (no handshaking)

Errors can be reported without the penalty of closing the TCP connection

Disadvantages – The bad

Wasted server resources, thread idle while others waiting to be serviced,

HTTP KeepAlive

Was a good idea a few years ago. Web 2.0/Ajax – maybe not a good idea

Connectors and KeepAlive KeepAlive – 2 parameters

MaxKeepAliveRequests – max number of requests to serve before closing,

ConnectionTimeOut – max time to keep thread open

MaxKeepAliveRequests Set to 1 for high concurrency, not using SSL,

(disables keep alive) Set to >1 for SSL, low concurrency

Connectors and KeepAlive

ConnectionTimeout - Default = 20 seconds! ConnectionTimeout="20000" too high turn

down to +/- 3000 – 3 seconds If using Apache HTTP – set to disable, let

apache http handle keep-alive, also do SSL on Apache

Which HTTP Connector To Use? BIO use when:

Stablity is important, Keep alive not a limiting factor, Content is dynamic,

APR – use when: (Almost always) faster, especially for SSL, not an issue if

using SSL on Apache http, Lots of static content (sendfile) Keep alive NB factor

Which AJP Connector To Use?

Usually Apache and Tomcat are on the same server or at least on the same LAN.

TCP handshake setup not a limiting factor Let Apache do the SSL and keepAlive

management Use APR unless there is stability issues

Tomcat Load Balancing/Clustering

Difference between load balancing/clustering (Layer 7)

Session replication, Server affinity

Load Balancing/Clustering Options Typical Setup

Apache mod_proxy, mod_jk Tomcat Clustering

Host or Engine level,

Thread Executors

Share Thread Pool between applications, new in Tomcat 6

More efficient use of resources by applications

Must be setuo before connector in server.xml

Thread Executors

Executor Example

Tomcat Caching Static Content

BIO blocks when sending static content, APR uses SEND_FILE, - frees worker

thread <Context cacheMaxSize=”5120”

cacheTTL=”60000”cachingAllowed=”true”> Set cache size to 50MB, default 10MB and

ttl on cache to 60 seconds, default is 5 seconds

JVM Tweaking

Make sure JVM is in server mode, Set -Xms/-Xmx to approrpiate levels. Not to

high or too low, Check cause of out of memory errors – if

permgen space increase heap will make it worse – -XX:PermSize, - XX:MaxPermSize

Change gcc algorithms

JVM Tweaking

Serial: -XX:+UseSerialGC Parallel: -XX:+UseParallelGC (aka

Throughput collector) Parallel Old: -XX:+UseParallelOldGC(aka

Parallel Compacting Collector) Concurrency Collector: -XX:

+UseConcMarkSweepGC aka (CMS or low-latency collector)

JVM Tweaking

Weak generational hypothesis most objects die young. faster GC collection in Eden

JVM Tweaking

-XX:NewRatio=N - Ratio of new gen to old gen

-XX:NewSize=N - Default new gen size

-XX:MaxNewSize=N - Max for new gen size

Tomcat Logging

Logging.properties – Uses customised logger based on apache.commons.logging

Root logger had two handlers defiend – a file handler and console handler but in most Linux distributions this is redirected to a file – disable one for speed improvement

.handlers = 1catalina.org.apache.juli.FileHandler, java.util.logging.ConsoleHandler.handlers = 1catalina.org.apache.juli.FileHandler

Out of Memory

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