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Version 10.1 by Quinton Dolan on 2007/07/14 21:13
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1 This article was written by Andrew Lindesay ([[http://www.lindesay.co.nz]]) around May 2005. It first appeared as LaTeX PDF and has been transcribed into this Wiki. You use the information contained in this document at your own risk. Please contact the author if you feel there may have been an error in the conversion to Wiki markup.
2
3 |=Contents
4 |
5
6 {{toc style="disc"}}{{/toc}}
7
8 = Abstract =
9
10 From WebObjects 5.2, it has been possible to derive a build product from a WebObjects application project that can be deployed into a J2EE servlet container. This article shows how it is possible to
11 deploy a WebObjects 5.2 application into a Tomcat environment and achieve a very similar topology to the "native" WebObjects deploy.
12
13 = Introduction =
14
15 This document was originally written assuming a Tomcat 5 deployment, but after some difficulties with web services and AXIS, I have modified this document to also cater for a Tomcat 3 deployment. This document covers both circumstances.
16
17 = Assumptions =
18
19 This article assumes the following:
20
21 * WebObjects 5.2 (likely to work fine with newer versions)
22 * Java 1.4
23 * Latest Tomcat release of version 5 (5.5.12 at the time of writing) or 3 (3.3.2 at the time of writing)
24 * Some sort of UNIX deployment.
25 * The reader has some conception of the concepts behind servlet technology.
26 * The reader is familiar with a standard WebObjects deployment topology which will be referred to as //wotaskd// deployment.
27
28 For the purposes of this document, it is assumed that Tomcat has been installed at a directory on the local disc called ##$TOMCATDIR##. It is also assumed that you will have another directory with the files required to configure and run an instance called ##$INSTDIR##. It is assumed also that you will have a directory called ##$JKDIR## with the Tomcat apache adaptor in it. In this article, some configuration files require the paths to be shown and these are tabulated below.
29
30 | ##$TOMCATDIR## | ##/opt/tomcat##
31 | ##$INSTDIR## | ##/opt/fooapp##
32 | ##$JKDIR## | ##/opt/modjk##
33
34 In reality, these directories could be located anywhere.
35
36 == Objective ==
37
38 The objective of this article is to show that a WebObjects application can be deployed into a servlet container and keep some of the desirable attributes of a WebObjects deployment topology. Some of these traits are itemised below.
39
40 * Clustering over a number of hardware nodes to prevent system downtime from a single hardware failure incident.
41 * Clustering over a number of virtual machine //instances// on each hardware node to avoid downtime from a single software failure incident.
42 * Ability to make efficient use of lower cost server hardware rather than encouraging use of large, expensive servers.
43 * Make maximum use of memory availabile in each virtual machine as cache to minimise database traffic and lower stress on the database server.
44 * Ability to make sessions "sticky" to a given virtual machine //instance//, whilst being multiplexed through a single web server front-end adaptor.
45 * Ability to load-balance requests to instances which are operational.
46
47 A standard WebObjects deployment topology is shown in the figure below alongside what is to be achieved with Tomcat. A typical J2EE deployment may have a different topology from this.
48
49 [[image:wo-tomcat-deploy-topology.gif]]
50
51 = Servlet Build Products =
52
53 Creating a servlet build product from a WebObjects application project is covered in some depth by documentation that is supplied by Apple for WebObjects. This is not going to be repeated here, but here is a brief overview of the process.
54
55 * Include the ##JavaWOJSPServlet.framework## framework into your project.
56 * In the build settings, set the ##SERVLET//SINGLE//DIR//DEPLOY//##// value to ##YES## to create the most trouble-free form of deployment servlet.//
57 * Edit the ##SERVLET//DEPLOY//LICENSE## to contain your valid deployment license key if you need one for the version of WebObjects you are using.
58 * Edit the ##SERVLET//WEBAPPS//DIR## to point to ##$INSTDIR/webapps/## or some place where you want the build product to go.
59
60 Now when you choose a //Deployment// build, you will also get the servlet assembled. The end result is a directory structure similar to that shown in the figure below.
61
62 [[image:wo-tomcat-ssd-filelayout-3.gif]]
63
64 = Removing the DOCTYPE from .plist Files =
65
66 Many property-list files (often called plist files) have a document type at the top. This can refer to files on a MacOS-X machine or to files on Apple servers. In either case this can cause problems with deployments which are not on MacOS-X servers. The following script can be run with the argument of the ##WEB-INF## folder to remove these. The WebObjects application runs fine without this information in the plist files. This script can easily be incorporated one way or another as a step in the build process for your WebObjects project.
67
68 {{code}}
69
70 # [apl 3.may.2006]
71 # This will remove any DOCTYPE's from the top of plists so that
72 # they do not attempt to validate the DTD which is either
73 # extracted from /System or the internet over HTTP.
74
75 if [ -z $1 ]; then
76 echo "syntax: stripdocype.sh <directory>"
77 exit 1
78 fi
79
80 for PLISTFILE in `find $1 -name *.plist`
81 do
82 sed \
83 '/<!DOCTYPE [^>]*>/s/.*//' \
84 $PLISTFILE \
85 > /tmp/remove-plist-temp
86
87 cp /tmp/remove-plist-temp $PLISTFILE
88 done
89
90 {{/code}}
91
92 = Application Configuration with Tomcat =
93
94 A WebObjects project with servlet support has a file called ##web.xml.template## in it. By default, this is located in ##/Resources/Servlet Resources/WEB-INF## in your project. The ##web.xml.template## file is used as a template for creating ##web.xml## which is also known as the ##servlet deployment descriptor##. This deployment descriptor is used as the means of communicating settings to the application as well as the servlet container in which the application runs. This section covers some common changes to that file as well as a discussion around a means of general configuration of the application when it is running inside a servlet container.
95
96 == Data Source for Model Database Configuration ==
97
98 Some WebObjects engineers use the ##setConnectionDictionary(...)## method on a model to set the JDBC database connection parameters for the model. However, the servlet container has it's own ##data source## mechanism for supplying database information which will override any connection dictionary information which is set into the model. If you don't want this to happen, and you want your ##setConnectionDictionary(...)## to take effect, comment out the ##resource-ref## item with the title ##jdbc/DefaultDataSource## in the ##web.xml.template## file.
99
100 == Serving WebServerResources ==
101
102 To stop the web server resources (images, CSS files and other static data) from being served out of the java environment, you need to configure the ##context-param## with the name ##WOAppMode## to be ##Deployment## in the ##web.xml.template## file.
103
104 == Application Specific Configuration ==
105
106 This area of configuration covers items such as the following ficticious examples;
107
108 1. Email address of person to contact when system fails.
109 1. Frequency of polling some resource.
110 1. Optional connection information for databases.
111 1. GST rate for New Zealand.
112
113 In other words, these are application-specific configuration values. One way to configure your application specific parameters in a servlet container is to load your config into ##env-entry##s in your ##web.xml## file. Here is such an example of one such entry;
114
115 {{code value="xml"}}
116
117 <env-entry>
118 <env-entry-name>foo/nz.co.foo.FooAppMailFrom</env-entry-name>
119 <env-entry-value>bar@foo.co.nz</env-entry-value>
120 <env-entry-type>java.lang.String</env-entry-type>
121 </env-entry>
122
123 {{/code}}
124
125 You can retrieve these value inside the application with some code as shown below. See the LEConfig class from LEWOStuff, the WebObjects framework from Lindesay Electric for an example. LEWOStuff also comes with a tool to help load standard java properties files into the servlet deployment descriptor.
126
127 {{code}}
128
129 import javax.naming.*;
130
131 // ...later in the same class...
132
133 Object valueO = null;
134
135 try
136 {
137 InitialContext context = new InitialContext();
138 valueO = context.lookup("java:comp/env/foo/nz.co.foo.FooAppMailFrom");
139 }
140 catch(javax.naming.NamingException ne)
141 { /* handle gracefully */ }
142
143 {{/code}}
144
145 It is probably easiest to apply these settings in some automated fashion to the ##web.xml## file as part of a further automated build or deploy process.
146
147 == Application Binary ==
148
149 Put your application servlet build product at ##$INSTDIR## such that the following path exists.
150
151 {{noformat}}
152
153 $INSTDIR/webapps/FooApp/WEB-INF
154
155 {{/noformat}}
156
157 == Tomcat Server Configuration Files ==
158
159 You need to create a tomcat configuration file for each of the instances that you would like to have. The pattern is followed here of having an instance number proceeded by the lower case letter "i". Put the first server configuration file at the following location.
160
161 {{noformat}}
162
163 $INSTDIR/server_i1.xml
164
165 {{/noformat}}
166
167 Here is an example of how this file might look. There is no coverage of the individual settings here as the reader is expected to review the tomcat documentation to discover the specific meanings of these settings.
168
169 === Tomcat 5 ===
170
171 {{code value="xml"}}
172
173 <Server port="7071" shutdown="SHUTDOWN">
174 <Service name="Catalina">
175 <Connector port="8081" maxHttpHeaderSize="8192"
176 maxThreads="150" minSpareThreads="25" maxSpareThreads="75"
177 enableLookups="false" acceptCount="100"
178 connectionTimeout="20000" disableUploadTimeout="true" />
179
180 <Connector port="9091" enableLookups="false" protocol="AJP/1.3" />
181
182 <Engine name="i1" defaultHost="appserver1.foo.co.nz" jvmRoute="i1">
183 <Host name="appserver1.foo.co.nz"
184 appBase="/home/fooapp/webapps"
185 unpackWARs="true" autoDeploy="false"
186 xmlValidation="false" xmlNamespaceAware="false">
187 <Context cookies="false" docBase="FooApp"
188 path="FooApp" reloadable="false">
189 <Manager distributable="false" />
190 </Context>
191 </Host>
192 </Engine>
193
194 </Service>
195 </Server>
196
197 {{/code}}
198
199 === Tomcat 3 ===
200
201 {{code value="xml"}}
202
203 <?xml version="1.0" encoding="ISO-8859-1"?>
204
205 <Server>
206 <ContextManager workDir="work">
207
208 <LoaderInterceptor11 useApplicationLoader="true" />
209
210 <AutoDeploy source="modules" target="modules" redeploy="true" />
211 <AutoWebApp dir="modules" host="DEFAULT" trusted="true"/>
212 <AutoWebApp dir="/home/fooapp/webapps" trusted="true" reloadable="false" />
213
214 <SimpleMapper1 />
215
216 <SessionExpirer checkInterval="60" />
217 <SessionIdGenerator randomClass="java.security.SecureRandom" />
218
219 <WebXmlReader validate="false" />
220 <ErrorHandler showDebugInfo="true" />
221
222 <Jdk12Interceptor />
223 <LoadOnStartupInterceptor />
224 <Servlet22Interceptor />
225
226 <SessionId cookiesFirst="false" noCookies="true" />
227 <SimpleSessionStore maxActiveSessions="256" />
228
229 <Http10Connector port="8081" secure="false" />
230 <Ajp13Connector port="9091" tomcatAuthentication="false" shutdownEnable="true" />
231
232 </ContextManager>
233 </Server>
234
235 {{/code}}
236
237 Assuming that there will be three instances in this example deploy, this entire file should be replicated and modified twice for the other two instances. For the other instances' server configuration files, change the "i1" (Tomcat 5 only) by modifying the numerical component and change the port numbers by making the last digit the instance number. For example, the ports ##7071##, ##8081## and ##9091## are used here. For "i2", use ##7072##, ##8082## and ##9092##.
238
239 You should have three files now present called ##server//i1.xml//##//, ##server##//##i2.xml## and ##server//i3.xml//##// in the directory ##$INSTDIR##.//
240
241 == Startup An Instance ==
242
243 To startup an instance, issue a command as follows. You should issue this command for each of the server configuration files. The ##$JAVA//HOME//##// shell environment variable should have been setup correctly before launching an instance.//
244
245 |=Tomcat 5|##$TOMCATDIR/bin/startup.sh --config $INSTDIR/server//i1.xml//--##--////--
246 |=Tomcat 3|##$TOMCATDIR/bin/startup --config $INSTDIR/server//i1.xml //--//home $TOMCATDIR//##////
247
248 === Tomcat 3 Environment Variables ===
249
250 To pass java environment variables to your application, set the ##TOMCAT//OPTS//##// shell environment variable before starting up the Tomcat 3 environment. An example of this would be as follows;//
251
252 {{noformat}}
253
254 TOMCAT_OPTS=-Dabc=xyz
255 export TOMCAT_OPTS
256
257 {{/noformat}}
258
259 == Check Availability ==
260
261 You can now see if your instance is up using the following URL.
262
263 {{noformat}}
264
265 http://appserver1.foo.co.nz:8081/FooApp/WebObjects/FooApp.woa
266
267 {{/noformat}}
268
269 Note that both the AJP (This is the protocol between the apache adaptor and the individual Tomcat instances.) and the regular HTTP engines are accessing the same running application. This means that a test straight onto the application via HTTP is actually testing the application that is being accessed via AJP. This behaviour provides an opportunity to be able to monitor specific instances of Tomcat over direct HTTP.
270
271 Check each of your instances.
272
273 == Problems ==
274
275 Under Tomcat 5, check the log file at ##$TOMCATHOME/logs/catalina.out## if you are unable to access your instance.
276
277 == Shutdown An Instance ==
278
279 To shutdown an instance, issue a command as follows.
280
281 === Tomcat 5 ===
282
283 {{noformat}}
284
285 $TOMCATDIR/bin/shutdown.sh -config $INSTDIR/server_i1.xml
286
287 {{/noformat}}
288
289 It is also possible to use the UNIX ##telnet## command to connect to the port described in the server configuration file's ##Server## tag and type the word supplied in the ##shutdown## attribute to take out the Tomcat instance.
290
291 === Tomcat 3 ===
292
293 {{noformat}}
294
295 TOMCATDIR/bin/shutdown -ajp13 -port 9091
296
297 {{/noformat}}
298
299 = Apache Adaptor Setup =
300
301 A final deployment usually involves apache feeding inbound requests to instances and handling situations where an instance has gone down and balancing load over the instances that are currently running. This job is undertaken by ##mod//jk//##// which is a module for apache written by the Tomcat group. This module communicates with the tomcat instances using a protocol called ##AJP##. This protocol carries all the information required to check instances are operational as well as relaying requests to the instances. It is assumed that the configuration as well as binaries for the ##mod##//##jk## apache module will be located at ##$JKDIR##.
302
303 == Compiling and Installing ==
304
305 Instructions for downloading and installing ##mod//jk//##// can be obtained from the Tomcat website. The ##mod##//##jk.so## binary should be located at the following path.
306
307 {{noformat}}
308
309 $JKDIR/mod_jk.so
310
311 {{/noformat}}
312
313 Add a line to your system's apache httpd configuration file like this:
314
315 {{noformat}}
316
317 Include /opt/modjk/apache.conf
318
319 {{/noformat}}
320
321 Edit this file to look like this:
322
323 {{noformat}}
324
325 LoadModule jk_module /opt/modjk/mod_jk.so
326 AddModule mod_jk.c
327
328 JkLogFile /opt/modjk/mod_jk.log
329 JkLogLevel info
330
331 JkWorkerProperty worker.list=i1,i2,i3,loadbalancer
332 JkWorkerProperty worker.i1.type=ajp13
333 JkWorkerProperty worker.i1.port=9091
334 JkWorkerProperty worker.i1.host=appserver1.foo.co.nz
335 JkWorkerProperty worker.i1.lbfactor=1
336 JkWorkerProperty worker.i2.type=ajp13
337 JkWorkerProperty worker.i2.port=9092
338 JkWorkerProperty worker.i2.host=appserver1.foo.co.nz
339 JkWorkerProperty worker.i2.lbfactor=1
340 JkWorkerProperty worker.i3.type=ajp13
341 JkWorkerProperty worker.i3.port=9093
342 JkWorkerProperty worker.i3.host=appserver1.foo.co.nz
343 JkWorkerProperty worker.i3.lbfactor=1
344 JkWorkerProperty worker.loadbalancer.type=lb
345 JkWorkerProperty worker.loadbalancer.sticky_session=1
346 JkWorkerProperty worker.loadbalancer.local_worker_only=1
347 JkWorkerProperty worker.loadbalancer.balance_workers=i1,i2,i3
348
349 JkMount /FooApp/* loadbalancer
350
351 {{/noformat}}
352
353 Again, the details of the exact settings will not be covered in this article, but this should provide a simple guide to setting up this file to provide for a multi-instance deploy under Tomcat.
354
355 == Restart Apache ==
356
357 Now restart apache with the following command:
358
359 {{noformat}}
360
361 sudo apachectl restart
362
363 {{/noformat}}
364
365 == Test Application ==
366
367 Now you can test your application using a URL such as this one.
368
369 {{noformat}}
370
371 http://www.foo.co.nz/FooApp/WebObjects/FooApp.woa
372
373 {{/noformat}}
374
375 All three instances that you have setup should take some of the inbound requests.
376
377 == Choosing the Right Instance ==
378
379 ##mod//jk//##// ensures that requests that have started a session will be directed to the correct instance where the session originated. This behaviour is known as sticky sessions. It does not appear to be possible to nominate the instance from the servlet container in another way.//