tomcat architecture training ver 1.5

Tomcat Architecture & Features

Ravi Saraswathi

August 25, 2009

What we will cover

Tomcat Architecture Server topology Service Engine Connectors HTTP & AJP (and NIO) Host Valves Jasper Life Cycle Events Basic Administration Tomcat Listeners

Java Memory management

JVM Parameters and guidelines Performance tuning strategies with examples JVM Utilities

What we will cover (Continue..)

Tomcat Connectors HTTP, AJP Connector Options Load Balancing mod_JK & mod_proxy

JSP and Servlet Servlet Life Cycle Context Events & Filter

Tomcat Configuration Files Server.Xml Context.xml

Class Loaders and Class path Bootstrap System Common & Shared , WebappX

Web application structure and configuration Web apps directory structure Deployment descriptors (Web.XML)

What we will cover (Continue)

Integration of Tomcat and Apache mod_jk mod_proxy

JNDI

JNDI API & SPI LDAP and Initial Context

System Architecture Non-Dynapub Web application architecture Apache-Tomcat connection (Active-Active, Active-Passive)

Tomcat Architecture

Basics

Tomcat is a Web container from Apache open source foundation.

It implements Servlet and JSP specification from Sun Micro system

Tomcat is made up of pluggable components that fit together in a nested manner.

Tomcat Server Topology

Tomcat The Server

Services

Engine (Catalina)

Context

JSPs Servlets

Valves

AJP Connector8009

SSL Connector

8443

8080HTTP Connector

Hosts Realm

Valves

Valves

Architecture Basics

One Server - One JVM

Service/Engine/Host/Context All are Containers All implement Lifecycle Listeners

Lifecycle Events

How objects get initialized, started & stopped

Object relationships are established during creation (digester parsing)

Digester : XML-to-Java-object mapping

XML Representationof Tomcat Containers

Overview of the major Tomcat componentsService represents grouping of connectors

Connector for protocol handling

Engine for request processing

Host for virtual host handling

Context for web application execution

Tomcat Server Architecture

Source: http://www.vsj.co.uk/java/display.asp?id=319

Server Configuration File

Server.xml Main configuration file Builds server on the fly Parsed using commons-digester Tomcat has hard coded rule sets for the parsing Every element/component is swappable Define Server and Shutdown port Define Connectors Setup Virtual hosts Cannot be reloaded without restarting Tomcat

Entire server.xml parsed based on rules. Look for these rules:

Catalina.java org/apache/catalina/startup/

web.xml also is parsed using the digester

Relationship between the components

UML Associations:

1..* One or more0..1 Zero or one1 One only0..* Zero or more

Realm

For Container Managed Security for Web apps ( elements, and a element in web.xml)

Database of username, Passwords & Roles

Realm can be defined in Engine, Host or Context

JDBCRealm DataSourceRealm JNDIRealm MemoryRealm (tomcat-users.xml) JAASRealm UserDatabaseRealm

Architecture Basics

Copied from the book "Professional Apache Tomcat 5"

context.xml

The Context element represents a web application

Process each HTTP request based on the context path

Each Context MUST have a unique context path.

META-INF/context.xml has all the resources E.g.. Database

Can use for configuring web application class loader, session manager or Realm (database of users & roles).

Tomcat API (http://tomcat.apache.org/tomcat-5.5-doc/catalina/docs/api/index.html)


Tomcat The Server

Services

Engine (Catalina)

Context

JSPs Servlets

Valves

AJP Connector8009

SSL Connector

8443

8080HTTP Connector

Hosts Realm

Valves

Valves

Architecture Basics - Valve

Valve allows you to associate an instance of a Javaclass with a Engine/Host/Context container

Component that can be inserted into the request processing pipeline

Will preprocess all requests received by the connectors Similar concept to Servlet filter Interceptor Pattern Request processing pipeline Configured using a element in the server.xml file

Architecture Basics - Valve

Can be associated with a Tomcat Engine, Host, or Context container

From book Professional Apache Tomcat 6 l

Architecture Basics Valve classes

Access Log Valve It creates log files to track server access

The Remote Dump Filter Dump the HTTP headers and cookies associated with the specified request

Architecture Basics Valve classes

The Remote Host Filter Compare the remote host address of the client

Custom Valve

Create custom valve Extends Valvebase or Implements Valve Interface

Register in Server.xml

Tomcat Listeners

Tomcat Listeners

Java Code modules that Performs actions when events occur

Just before startup

During startup

Just after startup

Just before stop

During stop

Just after stop

Can be configured for a Server, Engine, Host or Context. Defined in Server.xml

Tomcat Default Listeners

APR Lifecycle Listener

Checks for the presence of the APR/native library and loads the library if it is present

Jasper Listener

Initializes the Jasper 2 JSP engine before any web applications that may use it are loaded

Tomcat Default Listeners

Server Lifecycle Listener Initializes the MBeanServer for the MBeans that may be used to manage Tomcat via JMX.

Global Resources Lifecycle Listener Initializes the Global JNDI resources defined in server.xml as part of the Global Resource element

Custom Listeners

Best way to add code/functionality to Tomcat

Register listener in Server.xml

JVM

Tomcat produces very little GC !

Log files messages

-verbose:gc, XX:+PrintGC, XX:+PrintGCDetails,XX:+PrintGCTimeStamps, -XX:+HeapDumpOnOutOfMemoryError

Java VisualVM

Available from JDK 6. Federates several existing tools, including JConsole, jstat, jinfo, jstack, and jmap

Other Tools

Argus, Jprobe, Jconsole, HPROF - Heap Profiler, Eclipse Memory Analyzer, IBM Heap & thread analyzer

JVM Utilities

Jps, Jmap, Jinfo, Jhat, Jstack

Unix Tools Top, vmstat, ulimit a , sar r , mpstat, netstat

Resources for JVM trouble shooting

GC

Young generation New space, when you create an object memory here is allocated.

Tenured generation If it last longer than a while it is moved here

Permanent generation Hold data needed by VM to describe objects (describing classes & Methods)

Java objects

Minor GC

Long Live objects

Full GC

Typical JVM Parameters -Xms1024m \ - Minimum Heap -Xmx1024m \ - Maximum Heap -Xss512k \ - Set maximum native stack size for any thread -XX:+UseConcMarkSweepGC

-XX:GCTimeRatio=99 \ - The ratio of GC time to application time -XX:MaxGCPauseMillis=20 \ - Pause times of 20ms desired.

-XX:PermSize=512m \ - Permanent Size -XX:MaxPermSize=512m \

-XX:NewSize=384m \ - Minor GC (Young Generation)-XX:MaxNewSize=384m \

-XX:SurvivorRatio=6 \

Java Virtual Machine and Memory issues

JVM Parameters Guidelines

-XX:NewSize=128m (Young Generation -Min) High means - Less

often Minor collection occur

Set -XX:NewSize to be one-fourth the size of the max heap size.

Larger Young Generation means smaller Tenured

-XX:MaxNewSize=128m (Young Generation-Max)

-Xms512m & -Xmx512m 60 % of available memory

Set min heap (-Xms) equal to the max heap size (-Xmx) to minimize garbage collections.

Very High Heap size Full GC is slower & GC Occurs less frequently.

Setting too high can cause wasted memory.32-bit OS cap the heap size at between 1.5 and 2.5GB

Mark and sweep Minimizes pause times, avoid "stopping the world Collect the tenured generation concurrently with the execution of the

application Start VM - mark each object Remove -XX:+UseConcMarkSweepGC

Throughput collector Parallel Collector

Distributes GC load across CPUs. Maximize throughput XX:+UseParallelGC Can be used for Multiprocessor Machines (with four or more

processors)

Collectors

JVM Tuning (-verbosegc -XX:+PrintGCDetails)Young generations is too small (Adjust NewSize and MaxNewSize)

[GC [DefNew: 4032K->64K(4032K), 0.0429742 secs] 9350K->7748K(32704K), 0.0431096 secs]

This indicates that only about 40% objects in the young generation were garbage and the rest survive the collection and are being promoted into the old generation.

With an 8 Mbyte size, most of young generation is garbage at the time of the minor collection.

[GC [DefNew: : 8128K->64K(8128K), 0.0453670 secs] 13000K->7427K(32704K), 0.0454906 secs]

Good: - Young Generation Decreased by 3968KNot Good: - Entire heap Decreased only by 1602k

Good: - Young Generation Decreased 8064k

Good: - Total heap is decreased by 5573k

With an 8 Byte Young Generation size, most of young generation is garbage at the time of the minor collection

JVM Trouble Shooting

Connectors


Tomcat The Server

Services

Engine (Catalina)

Context

JSPs Servlets

Valves

AJP Connector8009

SSL Connector

8443

8080HTTP Connector

Hosts Realm

Valves

Valves

Tomcat Connector Architecture

Catalina

webapp

Servlet

Servlet

webapp

Servlet

Servlet

CoyoteHTTP Connector

CoyoteAJP Connector

Apachehttpd

contextwar fileseparate class loader

A particular instance of this component listens for connections on a specific TCP port number on the server.

Load Balancing With mod_jk

round-robin, or weighted round-robin

Connectors

CoyoteAdapter.java - Creates Request/Response objects

HTTP Connector protocol= o.a.coyote.http11.Http11Protocol o.a.coyote.http11.Http11AprProtocol o.a.coyote.http11.Http11NioProtocol HTTP/1.1 aliased to Http11 and Http11Apr

AJP Connector mod_jk (Apache Jserv Protocol)

org.apache.jk.server.JkCoyoteHandler org.apache.coyote.ajp.AjpAprProtocol AJP/1.3 aliased to the two above

Connectors

NIO Allows a Servlet to process I/O asynchronously

Available on Tomcat6 (Current Standard is Tomcat 5.5.27)

NIO can be used to keep a connection open without wasting waiting threads.

Tomcat 6 provide CometProcessor API to facilitate event-based model.

Communication between Connector and Apache modules

From Book Apache Tomcat Professional

ApacheHost -1

ApacheHost -2

TomcatHost -3

TomcatHost -4

Database

Configure mod_proxy

1. Add mod_proxy modules

2. Add ProxyPass Tomcat URL

Define Connector options

Httpd.conf

Server.xml

Consumer

ApacheHost -1

ApacheHost -2

TomcatHost -3

TomcatHost -4

Database

Configure mod_jk

1. Add mod_jk modules

2. Add workers. properties

3. Add the URL pattern (JkMount /myproject/* worker name

Define Connector options

Httpd.conf

Server.xml

Consumer

Mod_JK vs Mod_Proxy

Mod_JK = AJP Connector

Web server plug-in/ Tomcat Redirector

Supports load balancing

Native mod_jk download available for different OS.

Very Fast

Complex Configuration

Let Apache serve static pages

Connectors available for FTP, HTTP, AJP or HTTPS

mod_proxy, mod_proxy_balancer, mod_proxy_http, and mod_proxy_ajp

Easy to Configure

Mod_proxy modules comes as part of apache

Lacks sticky session load balancing. mod_proxy_ajp supports load balancing

Mod_jk Mod_Proxy

HTTP Connector Options

MaxThreads Maximum number of simultaneous requestsTo Increase CPU usage Increase (from 150) MinSpareThreads

Number of threads created at start time

MaxSpareThreads Unused threads allowed to exist

HTTP Connector Options

AcceptCount Max incoming connections Increase to avoid connection refused errors

Connectiontimeout Number of milliseconds wait for the request URL to be presented

Tomcat: The Definitive Guide, Jason Brittain (OReilley 2007)

Class loaders

Class loaders

Find Class files

Parent Child relation ship

Delegate the request to parent class loader

Class loaders

Tomcat 5.5 Tomcat 6.0

Class loaders

1. Bootstrap JVM Run time classes

2. System Load classes to initialize Tomcat - $CATALINA_HOME/bin

3. Common $CATALINA_HOME/lib, as well as classes and resources in JAR files.Preferably no Application Classes

Class loaders

4. Catalina Tomcat classes $CATALINA_HOME/server/classes & lib

5. Shared Put classes and resources that you wish to share across ALL web applications - $CATALINA_BASE/shared

6. WebAppX/WEB-INF/classes and /WEB-INF/lib

Deployment

Tomcat Directory Structure - Basics

Web Application Deployment - Options

HCM Console

Copy the files to webapps folder

HCM Composition Packages From ADM Host - ssh root@ hcmbcs --sync --profile=)

Use Maven or Ant

Copy to a Shortcut or Symbolic Link (webapps)

Use the -d Option of javac or IDE

Web apps - Deployment Sequence

Any Context Descriptors will be deployed first.

Exploded web applications

.war files will be deployed

/ROOT is hardcoded for path=

Runtime deployment triggered by Lifecycle Event

Main programs are HostConfig.java & StandardHost.java

Web Application Structure - Basics

Deployment Descriptor

ROOT: The welcome screen application.

Location webapps/WEB-INF/web.xml Ignore conf/web.xml !! (Tomcat internal specific)

Tomcat monitor web.xml and reload webapps when web.xml changed

Deployment Descriptor Web.xml

Maven

Maven manage a project's build, reporting and documentation

All the information required for the build is contained in a single POM, Project Object Model, XML file

The developer provides information about what is being built and not how

The POM contains detailed METADATA information about the project: Versioning and configuration management Dependencies Project structure Application and testing resources

Maven - POM

Apache Tomcat

ApacheHost -1

ApacheHost -1

TomcatHost -1

TomcatHost -2

Database

Apache- Tomcat Architecture Scenarios Non DynapubLoad balancing for non-clustered applications. No failover strategy. Application may not be available incase of one Tomcat server down

Apache &

TomcatHost -1

Apache &

TomcatHost -2

Database

Apache & Tomcat installed in Same Server

Apache Tomcat Architecture Scenarios Non Dynapub

ApacheHost -1

ApacheHost -2

TomcatHost -1

Tomcat Host -2

Database

ApacheHost -2

ApacheHost -1

TomcatHost -1

TomcatHost -2

Database

Consumer

Consumer

Apache - Tomcat Architecture Scenarios: Non-Dynapub Systems

Tomca

tHost -1

Tomca

tHost -2

Tomca

tHost -4

Apache

Host -3

Apache

Host -4http / ajp13 / https

Apache

Host -1

Apache

Host 2

Tomca

tHost -3

http / ajp13 / https

LB

LB

LB

JDBC

GSLB

JSP/Servlets

Database

JDBC

Tomcat JNDI

JNDI Java Naming and Directory Interface

Provide access to naming and directory service (LDAP) from JAVA Classes

SPI describes how to JNDI enable any naming and directory service


Resources stored in hierarchical order (Various Contexts)

Common Services are LDAP DNS Filesystems NIS etc

Operations Track Ver. 3/Course Title Ver.# /AOL LLC Privileged and Confidential


Copied from book Professional Apache Tomcat 5


Tomcat intercepts the JNDI requests from Webapps.

The GlobalNamingResources element - defines the global JNDI resources for the Server

Per-web-application Initial Context can be configured in context.xml (META-INF)

Reference the JNDI resources in web.xml


Servlet

Servlet - Basics

Servlet is a program that generates a response upon a HTTP request

Multi-threaded means that one Servlet is capable of handling many requests

Servlet containers usually manage concurrent requests by creating a new Java thread for each request.

By using Servlets (Basics)

JspServlet.java - handles all JSP files

Request response model

Read form data

Read HTTP request headers

Set HTTP Status codes and response headers

Use cookies and session tracking

Share data among Servlets.

Servlet Life Cycle - Basics

Servlet methods - Basics

Init Servlet loaded in to memory using the init call

Service

For each incoming request a service() is called

Destroy Called once Servlet is garbage collected from the memory


Servlet Life Cycle - Basics


Deployment Descriptor Web.xml

context-param - Servlet context initialization parameters. and . Access in code using javax.servlet.ServletContext.

getInitParameter() Environment details specified for entire web app

Filter Change client request/response before/after it goes to Servlet. Within filter-mapping Element define the

Listener

Servlet Context events get notified when web apps deployed /shutdown etc

HTTP Session Events get notified with session got activated etc


Deployment Descriptor Web.xml Init-parm

Contains a name/value pair as an initialization parameter of the servlet Access these parameters with the javax.servlet.ServletConfig.

getInitParameter() method.

Defines the access privileges to a collection of resources defined by the

element.

configure how the user is authenticated; the realm name that should be

used for this application; and the attributes that are needed by the form login mechanism

web-resource-collection - The can refer to a directory or filename


JMX

MBeans Usage

Get and set applications configuration (Pull)

Collect statistics (Pull) Performance Resources usage Problems

Notify events (Push)

Faults State changes

JMX Architecture

What are JMX and MBeans

Components: Managed (Instrumented) Resources Agents (and their services) Connectors / Adapters

Goals: Instrument Java Code Create Smart Java Agents Implement Management Middleware Integrate with Industry Standard Management Platforms

What are JMX and MBeans

AOL JMX tool ARGUS Config

MBeans can be interacted with programmatically or via JConsole/VisualVM

MBeans have: Attributes that you can get or set Operations that you can invoke


Questions ?

tomcat architecture training ver 1.5

Documents

integration of tomcat

tomcat entire

tomcat server topologytomcat

tomcat connectors http

commonsdigester tomcat

major tomcat componentsservice

web container

context element