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Version 7.1 by smmccraw on 2007/07/08 10:33
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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 = Abstract =
4
5 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
6 deploy a WebObjects 5.2 application into a Tomcat environment and achieve a very similar topology to the "native" WebObjects deploy.
7
8 = Introduction =
9
10 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.
11
12 = Assumptions =
13
14 This article assumes the following:
15
16 * WebObjects 5.2 (likely to work fine with newer versions)
17 * Java 1.4
18 * Latest Tomcat release of version 5 (5.5.12 at the time of writing) or 3 (3.3.2 at the time of writing)
19 * Some sort of UNIX deployment.
20 * The reader has some conception of the concepts behind servlet technology.
21 * The reader is familiar with a standard WebObjects deployment topology which will be referred to as //wotaskd// deployment.
22
23 For the purposes of this document, it is assumed that Tomcat has been installed at a directory on the local disc called ##computer code|$TOMCATDIR##. It is also assumed that you will have another directory with the files required to configure and run an instance called ##computer code|$INSTDIR##. It is assumed also that you will have a directory called ##computer code|$JKDIR## with the Tomcat apache adaptor in it. In this article, some configuration files require the paths to be shown and these are tabulated below.
24
25 <center>
26
27 | ##computer code##|$TOMCATDIR
28 | ##computer code##|/opt/tomcat
29 |(((
30 *
31 )))
32 | ##computer code##|$INSTDIR
33 | ##computer code##|/opt/fooapp
34 |
35 | ##computer code##|$JKDIR
36 | ##computer code##|/opt/modjk
37
38 </center>
39
40 In reality, these directories could be located anywhere.
41
42 == Objective ==
43
44 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.
45
46 * Clustering over a number of hardware nodes to prevent system downtime from a single hardware failure incident.
47 * Clustering over a number of virtual machine //instances// on each hardware node to avoid downtime from a single software failure incident.
48 * Ability to make efficient use of lower cost server hardware rather than encouraging use of large, expensive servers.
49 * Make maximum use of memory availabile in each virtual machine as cache to minimise database traffic and lower stress on the database server.
50 * Ability to make sessions "sticky" to a given virtual machine //instance//, whilst being multiplexed through a single web server front-end adaptor.
51 * Ability to load-balance requests to instances which are operational.
52
53 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.
54
55 [[image:wo-tomcat-deploy-topology.gif]]
56
57 = Servlet Build Products =
58
59 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.
60
61 * Include the ##computer code|JavaWOJSPServlet.framework## framework into your project.
62 * In the build settings, set the ##computer code|SERVLET//SINGLE//DIR//DEPLOY//##// value to ##computer code|YES## to create the most trouble-free form of deployment servlet.//
63 * Edit the ##computer code|SERVLET//DEPLOY//LICENSE## to contain your valid deployment license key if you need one for the version of WebObjects you are using.
64 * Edit the ##computer code|SERVLET//WEBAPPS//DIR## to point to ##computer code|$INSTDIR/webapps/## or some place where you want the build product to go.
65
66 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.
67
68 [[image:wo-tomcat-ssd-filelayout-3.gif]]
69
70 = Removing the DOCTYPE from .plist Files =
71
72 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 ##computer code|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.
73
74 {{code}}
75
76 # [apl 3.may.2006]
77 # This will remove any DOCTYPE's from the top of plists so that
78 # they do not attempt to validate the DTD which is either
79 # extracted from /System or the internet over HTTP.
80
81 if [ -z $1 ]; then
82 {panel}
83 echo "syntax: stripdocype.sh <directory>"
84 exit 1
85 {panel}
86 fi
87
88 for PLISTFILE in `find $1 -name *.plist`
89 do
90 {panel}
91 sed \
92 '/<!DOCTYPE [^>]*>/s/.*//' \
93 $PLISTFILE \
94 > /tmp/remove-plist-temp
95 {panel}
96
97 cp /tmp/remove-plist-temp $PLISTFILE
98 done
99
100 {{/code}}
101
102 = Application Configuration with Tomcat =
103
104 A WebObjects project with servlet support has a file called ##computer code|web.xml.template## in it. By default, this is located in ##computer code|/Resources/Servlet Resources/WEB-INF## in your project. The ##computer code|web.xml.template## file is used as a template for creating ##computer code|web.xml## which is also known as the ##computer code|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.
105
106 == Data Source for Model Database Configuration ==
107
108 Some WebObjects engineers use the ##computer code|setConnectionDictionary(...)## method on a model to set the JDBC database connection parameters for the model. However, the servlet container has it's own ##computer code|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 ##computer code|setConnectionDictionary(...)## to take effect, comment out the ##computer code|resource-ref## item with the title ##computer code|jdbc/DefaultDataSource## in the ##computer code|web.xml.template## file.
109
110 == Serving WebServerResources ==
111
112 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 ##computer code|context-param## with the name ##computer code|WOAppMode## to be ##computer code|Deployment## in the ##computer code|web.xml.template## file.
113
114 == Application Specific Configuration ==
115
116 This area of configuration covers items such as the following ficticious examples;
117
118 1. Email address of person to contact when system fails.
119 1. Frequency of polling some resource.
120 1. Optional connection information for databases.
121 1. GST rate for New Zealand.
122
123 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 ##computer code|env-entry##-s in your ##computer code|web.xml## file. Here is such an example of one such entry;
124
125 {{code}}
126
127 <env-entry>
128 <env-entry-name>foo/nz.co.foo.FooAppMailFrom</env-entry-name>
129 <env-entry-value>bar@foo.co.nz</env-entry-value>
130 <env-entry-type>java.lang.String</env-entry-type>
131 </env-entry>
132
133 {{/code}}
134
135 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.
136
137 {{code}}
138
139 import javax.naming.*;
140
141 // ...later in the same class...
142
143 Object valueO = null;
144
145 try
146 {
147 {panel}
148 InitialContext context = new InitialContext();
149 valueO = context.lookup("java:comp/env/foo/nz.co.foo.FooAppMailFrom");
150 {panel}
151 }
152 catch(javax.naming.NamingException ne)
153 { /* handle gracefully */ }
154
155 {{/code}}
156
157 It is probably easiest to apply these settings in some automated fashion to the ##computer code|web.xml## file as part of a further automated build or deploy process.
158
159 == Application Binary ==
160
161 Put your application servlet build product at ##computer code|$INSTDIR## such that the following path exists.
162
163 {{code}}
164
165 $INSTDIR/webapps/FooApp/WEB-INF
166
167 {{/code}}
168
169 == Tomcat Server Configuration Files ==
170
171 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.
172
173 {{code}}
174
175 $INSTDIR/server_i1.xml
176
177 {{/code}}
178
179 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.
180
181 === Tomcat 5 ===
182
183 {{code}}
184
185 <Server port="7071" shutdown="SHUTDOWN">
186 {panel}
187 <Service name="Catalina">
188 <Connector port="8081" maxHttpHeaderSize="8192"
189 maxThreads="150" minSpareThreads="25" maxSpareThreads="75"
190 enableLookups="false" acceptCount="100"
191 connectionTimeout="20000" disableUploadTimeout="true" />
192 {panel}
193
194 <Connector port="9091" enableLookups="false" protocol="AJP/1.3" />
195
196 {panel}
197 <Engine name="i1" defaultHost="appserver1.foo.co.nz" jvmRoute="i1">
198 <Host name="appserver1.foo.co.nz"
199 appBase="/home/fooapp/webapps"
200 unpackWARs="true" autoDeploy="false"
201 xmlValidation="false" xmlNamespaceAware="false">
202 <Context cookies="false" docBase="FooApp"
203 path="FooApp" reloadable="false">
204 <Manager distributable="false" />
205 </Context>
206 </Host>
207 </Engine>
208 {panel}
209
210 </Service>
211 </Server>
212
213 {{/code}}
214
215 === Tomcat 3 ===
216
217 {{code}}
218
219 <?xml version="1.0" encoding="ISO-8859-1"?>
220
221 <Server>
222 <ContextManager workDir="work">
223
224 <LoaderInterceptor11 useApplicationLoader="true" />
225
226 <AutoDeploy source="modules" target="modules" redeploy="true" />
227 <AutoWebApp dir="modules" host="DEFAULT" trusted="true"/>
228 <AutoWebApp dir="/home/fooapp/webapps" trusted="true" reloadable="false" />
229
230 <SimpleMapper1 />
231
232 <SessionExpirer checkInterval="60" />
233 <SessionIdGenerator randomClass="java.security.SecureRandom" />
234
235 <WebXmlReader validate="false" />
236 <ErrorHandler showDebugInfo="true" />
237
238 <Jdk12Interceptor />
239 <LoadOnStartupInterceptor />
240 <Servlet22Interceptor />
241
242 <SessionId cookiesFirst="false" noCookies="true" />
243 <SimpleSessionStore maxActiveSessions="256" />
244
245 <Http10Connector port="8081" secure="false" />
246 <Ajp13Connector port="9091" tomcatAuthentication="false" shutdownEnable="true" />
247
248 </ContextManager>
249 </Server>
250
251 {{/code}}
252
253 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 ##computer code|7071##, ##computer code|8081## and ##computer code|9091## are used here. For "i2", use ##computer code|7072##, ##computer code|8082## and ##computer code|9092##.
254
255 You should have three files now present called ##computer code|server//i1.xml//##//, ##computer code|server##//##i2.xml## and ##computer code|server//i3.xml//##// in the directory ##computer code|$INSTDIR##.//
256
257 == Startup An Instance ==
258
259 To startup an instance, issue a command as follows. You should issue this command for each of the server configuration files. The ##computer code|$JAVA//HOME//##// shell environment variable should have been setup correctly before launching an instance.//
260
261 === Tomcat 5 ===
262
263 {{code}}
264
265 $TOMCATDIR/bin/startup.sh -config $INSTDIR/server_i1.xml
266
267 {{/code}}
268
269 === Tomcat 3 ===
270
271 {{code}}
272
273 $TOMCATDIR/bin/startup -config $INSTDIR/server_i1.xml -home $TOMCATDIR
274
275 {{/code}}
276
277 === Tomcat 3 Environment Variables ===
278
279 To pass java environment variables to your application, set the ##computer code|TOMCAT//OPTS//##// shell environment variable before starting up the Tomcat 3 environment. An example of this would be as follows;//
280
281 {{code}}
282
283 TOMCAT_OPTS=-Dabc=xyz
284 export TOMCAT_OPTS
285
286 {{/code}}
287
288 == Check Availability ==
289
290 You can now see if your instance is up using the following URL.
291
292 {{code}}
293
294 http://appserver1.foo.co.nz:8081/FooApp/WebObjects/FooApp.woa
295
296 {{/code}}
297
298 Note that both the AJP (This is the protocol between the apache adaptor and the individual Tomcat instances.) and the regular HTTP engines are accessing the same running application. This means that a test straight onto the application via HTTP is actually testing the application that is being accessed via AJP. This behaviour provides an opportunity to be able to monitor specific instances of Tomcat over direct HTTP.
299
300 Check each of your instances.
301
302 == Problems ==
303
304 Under Tomcat 5, check the log file at ##computer code|$TOMCATHOME/logs/catalina.out## if you are unable to access your instance.
305
306 == Shutdown An Instance ==
307
308 To shutdown an instance, issue a command as follows.
309
310 === Tomcat 5 ===
311
312 {{code}}
313
314 $TOMCATDIR/bin/shutdown.sh -config $INSTDIR/server_i1.xml
315
316 {{/code}}
317
318 It is also possible to use the UNIX ##computer code|telnet## command to connect to the port described in the server configuration file's ##computer code|Server## tag and type the word supplied in the ##computer code|shutdown## attribute to take out the Tomcat instance.
319
320 === Tomcat 3 ===
321
322 {{code}}
323
324 TOMCATDIR/bin/shutdown -ajp13 -port 9091
325
326 {{/code}}
327
328 = Apache Adaptor Setup =
329
330 A final deployment usually involves apache feeding inbound requests to instances and handling situations where an instance has gone down and balancing load over the instances that are currently running. This job is undertaken by ##computer code|mod//jk//##// which is a module for apache written by the Tomcat group. This module communicates with the tomcat instances using a protocol called ##computer code|AJP##. This protocol carries all the information required to check instances are operational as well as relaying requests to the instances. It is assumed that the configuration as well as binaries for the ##computer code|mod##//##jk## apache module will be located at ##computer code|$JKDIR##.
331
332 == Compiling and Installing ==
333
334 Instructions for downloading and installing ##computer code|mod//jk//##// can be obtained from the Tomcat website. The ##computer code|mod##//##jk.so## binary should be located at the following path.
335
336 {{code}}
337
338 $JKDIR/mod_jk.so
339
340 {{/code}}
341
342 Add a line to your system's apache httpd configuration file like this:
343
344 {{code}}
345
346 Include /opt/modjk/apache.conf
347
348 {{/code}}
349
350 Edit this file to look like this:
351
352 {{code}}
353
354 LoadModule jk_module /opt/modjk/mod_jk.so
355 AddModule mod_jk.c
356
357 JkLogFile /opt/modjk/mod_jk.log
358 JkLogLevel info
359
360 JkWorkerProperty worker.list=i1,i2,i3,loadbalancer
361 JkWorkerProperty worker.i1.type=ajp13
362 JkWorkerProperty worker.i1.port=9091
363 JkWorkerProperty worker.i1.host=appserver1.foo.co.nz
364 JkWorkerProperty worker.i1.lbfactor=1
365 JkWorkerProperty worker.i2.type=ajp13
366 JkWorkerProperty worker.i2.port=9092
367 JkWorkerProperty worker.i2.host=appserver1.foo.co.nz
368 JkWorkerProperty worker.i2.lbfactor=1
369 JkWorkerProperty worker.i3.type=ajp13
370 JkWorkerProperty worker.i3.port=9093
371 JkWorkerProperty worker.i3.host=appserver1.foo.co.nz
372 JkWorkerProperty worker.i3.lbfactor=1
373 JkWorkerProperty worker.loadbalancer.type=lb
374 JkWorkerProperty worker.loadbalancer.sticky_session=1
375 JkWorkerProperty worker.loadbalancer.local_worker_only=1
376 JkWorkerProperty worker.loadbalancer.balance_workers=i1,i2,i3
377
378 JkMount /FooApp/* loadbalancer
379
380 {{/code}}
381
382 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.
383
384 == Restart Apache ==
385
386 Now restart apache with the following command:
387
388 {{code}}
389
390 sudo apachectl restart
391
392 {{/code}}
393
394 == Test Application ==
395
396 Now you can test your application using a URL such as this one.
397
398 {{code}}
399
400 http://www.foo.co.nz/FooApp/WebObjects/FooApp.woa
401
402 {{/code}}
403
404 All three instances that you have setup should take some of the inbound requests.
405
406 == Choosing the Right Instance ==
407
408 ##computer code|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 {t sticky sessions}. It does not appear to be possible to nominate the instance from the servlet container in another way.//