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Version 12.1 by Quinton Dolan on 2007/07/08 20:41
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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 {{toc}}{{/toc}}
4
5 = Abstract =
6
7 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
8 deploy a WebObjects 5.2 application into a Tomcat environment and achieve a very similar topology to the "native" WebObjects deploy.
9
10 = Introduction =
11
12 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.
13
14 = Assumptions =
15
16 This article assumes the following:
17
18 * WebObjects 5.2 (likely to work fine with newer versions)
19 * Java 1.4
20 * Latest Tomcat release of version 5 (5.5.12 at the time of writing) or 3 (3.3.2 at the time of writing)
21 * Some sort of UNIX deployment.
22 * The reader has some conception of the concepts behind servlet technology.
23 * The reader is familiar with a standard WebObjects deployment topology which will be referred to as //wotaskd// deployment.
24
25 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 ##$JKDIR## with the Tomcat apache adaptor in it. In this article, some configuration files require the paths to be shown and these are tabulated below.
26
27 | ##$TOMCATDIR## | ##/opt/tomcat##
28 | ##$INSTDIR## | ##/opt/fooapp##
29 | ##$JKDIR## | ##/opt/modjk##
30
31 In reality, these directories could be located anywhere.
32
33 == Objective ==
34
35 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.
36
37 * Clustering over a number of hardware nodes to prevent system downtime from a single hardware failure incident.
38 * Clustering over a number of virtual machine //instances// on each hardware node to avoid downtime from a single software failure incident.
39 * Ability to make efficient use of lower cost server hardware rather than encouraging use of large, expensive servers.
40 * Make maximum use of memory availabile in each virtual machine as cache to minimise database traffic and lower stress on the database server.
41 * Ability to make sessions "sticky" to a given virtual machine //instance//, whilst being multiplexed through a single web server front-end adaptor.
42 * Ability to load-balance requests to instances which are operational.
43
44 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.
45
46 [[image:wo-tomcat-deploy-topology.gif]]
47
48 = Servlet Build Products =
49
50 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.
51
52 * Include the ##JavaWOJSPServlet.framework## framework into your project.
53 * In the build settings, set the ##SERVLET//SINGLE//DIR//DEPLOY//##// value to ##YES## to create the most trouble-free form of deployment servlet.//
54 * Edit the ##SERVLET//DEPLOY//LICENSE## to contain your valid deployment license key if you need one for the version of WebObjects you are using.
55 * Edit the ##SERVLET//WEBAPPS//DIR## to point to ##$INSTDIR/webapps/## or some place where you want the build product to go.
56
57 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.
58
59 [[image:wo-tomcat-ssd-filelayout-3.gif]]
60
61 = Removing the DOCTYPE from .plist Files =
62
63 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.
64
65 {{code}}
66
67 # [apl 3.may.2006]
68 # This will remove any DOCTYPE's from the top of plists so that
69 # they do not attempt to validate the DTD which is either
70 # extracted from /System or the internet over HTTP.
71
72 if [ -z $1 ]; then
73 echo "syntax: stripdocype.sh <directory>"
74 exit 1
75 fi
76
77 for PLISTFILE in `find $1 -name *.plist`
78 do
79 sed \
80 '/<!DOCTYPE [^>]*>/s/.*//' \
81 $PLISTFILE \
82 > /tmp/remove-plist-temp
83
84 cp /tmp/remove-plist-temp $PLISTFILE
85 done
86
87 {{/code}}
88
89 = Application Configuration with Tomcat =
90
91 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.
92
93 == Data Source for Model Database Configuration ==
94
95 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.
96
97 == Serving WebServerResources ==
98
99 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.
100
101 == Application Specific Configuration ==
102
103 This area of configuration covers items such as the following ficticious examples;
104
105 1. Email address of person to contact when system fails.
106 1. Frequency of polling some resource.
107 1. Optional connection information for databases.
108 1. GST rate for New Zealand.
109
110 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;
111
112 {{code value="xml"}}
113
114 <env-entry>
115 <env-entry-name>foo/nz.co.foo.FooAppMailFrom</env-entry-name>
116 <env-entry-value>bar@foo.co.nz</env-entry-value>
117 <env-entry-type>java.lang.String</env-entry-type>
118 </env-entry>
119
120 {{/code}}
121
122 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.
123
124 {{code}}
125
126 import javax.naming.*;
127
128 // ...later in the same class...
129
130 Object valueO = null;
131
132 try
133 {
134 InitialContext context = new InitialContext();
135 valueO = context.lookup("java:comp/env/foo/nz.co.foo.FooAppMailFrom");
136 }
137 catch(javax.naming.NamingException ne)
138 { /* handle gracefully */ }
139
140 {{/code}}
141
142 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.
143
144 == Application Binary ==
145
146 Put your application servlet build product at ##$INSTDIR## such that the following path exists.
147
148 {{noformat}}
149
150 $INSTDIR/webapps/FooApp/WEB-INF
151
152 {{/noformat}}
153
154 == Tomcat Server Configuration Files ==
155
156 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.
157
158 {{noformat}}
159
160 $INSTDIR/server_i1.xml
161
162 {{/noformat}}
163
164 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.
165
166 === Tomcat 5 ===
167
168 {{code value="xml"}}
169
170 <Server port="7071" shutdown="SHUTDOWN">
171 <Service name="Catalina">
172 <Connector port="8081" maxHttpHeaderSize="8192"
173 maxThreads="150" minSpareThreads="25" maxSpareThreads="75"
174 enableLookups="false" acceptCount="100"
175 connectionTimeout="20000" disableUploadTimeout="true" />
176
177 <Connector port="9091" enableLookups="false" protocol="AJP/1.3" />
178
179 <Engine name="i1" defaultHost="appserver1.foo.co.nz" jvmRoute="i1">
180 <Host name="appserver1.foo.co.nz"
181 appBase="/home/fooapp/webapps"
182 unpackWARs="true" autoDeploy="false"
183 xmlValidation="false" xmlNamespaceAware="false">
184 <Context cookies="false" docBase="FooApp"
185 path="FooApp" reloadable="false">
186 <Manager distributable="false" />
187 </Context>
188 </Host>
189 </Engine>
190
191 </Service>
192 </Server>
193
194 {{/code}}
195
196 === Tomcat 3 ===
197
198 {{code value="xml"}}
199
200 <?xml version="1.0" encoding="ISO-8859-1"?>
201
202 <Server>
203 <ContextManager workDir="work">
204
205 <LoaderInterceptor11 useApplicationLoader="true" />
206
207 <AutoDeploy source="modules" target="modules" redeploy="true" />
208 <AutoWebApp dir="modules" host="DEFAULT" trusted="true"/>
209 <AutoWebApp dir="/home/fooapp/webapps" trusted="true" reloadable="false" />
210
211 <SimpleMapper1 />
212
213 <SessionExpirer checkInterval="60" />
214 <SessionIdGenerator randomClass="java.security.SecureRandom" />
215
216 <WebXmlReader validate="false" />
217 <ErrorHandler showDebugInfo="true" />
218
219 <Jdk12Interceptor />
220 <LoadOnStartupInterceptor />
221 <Servlet22Interceptor />
222
223 <SessionId cookiesFirst="false" noCookies="true" />
224 <SimpleSessionStore maxActiveSessions="256" />
225
226 <Http10Connector port="8081" secure="false" />
227 <Ajp13Connector port="9091" tomcatAuthentication="false" shutdownEnable="true" />
228
229 </ContextManager>
230 </Server>
231
232 {{/code}}
233
234 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##.
235
236 You should have three files now present called ##server//i1.xml//##//, ##server##//##i2.xml## and ##server//i3.xml//##// in the directory ##$INSTDIR##.//
237
238 == Startup An Instance ==
239
240 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.//
241
242 === Tomcat 5 ===
243
244 {{noformat}}
245
246 $TOMCATDIR/bin/startup.sh -config $INSTDIR/server_i1.xml
247
248 {{/noformat}}
249
250 === Tomcat 3 ===
251
252 {{noformat}}
253
254 $TOMCATDIR/bin/startup -config $INSTDIR/server_i1.xml -home $TOMCATDIR
255
256 {{/noformat}}
257
258 === Tomcat 3 Environment Variables ===
259
260 To pass java environment variables to your application, set the ##TOMCAT//OPTS//##// shell environment variable before starting up the Tomcat 3 environment. An example of this would be as follows;//
261
262 {{noformat}}
263
264 TOMCAT_OPTS=-Dabc=xyz
265 export TOMCAT_OPTS
266
267 {{/noformat}}
268
269 == Check Availability ==
270
271 You can now see if your instance is up using the following URL.
272
273 {{noformat}}
274
275 http://appserver1.foo.co.nz:8081/FooApp/WebObjects/FooApp.woa
276
277 {{/noformat}}
278
279 Note that both the AJP (This is the protocol between the apache adaptor and the individual Tomcat instances.) and the regular HTTP engines are accessing the same running application. This means that a test straight onto the application via HTTP is actually testing the application that is being accessed via AJP. This behaviour provides an opportunity to be able to monitor specific instances of Tomcat over direct HTTP.
280
281 Check each of your instances.
282
283 == Problems ==
284
285 Under Tomcat 5, check the log file at ##$TOMCATHOME/logs/catalina.out## if you are unable to access your instance.
286
287 == Shutdown An Instance ==
288
289 To shutdown an instance, issue a command as follows.
290
291 === Tomcat 5 ===
292
293 {{noformat}}
294
295 $TOMCATDIR/bin/shutdown.sh -config $INSTDIR/server_i1.xml
296
297 {{/noformat}}
298
299 It is also possible to use the UNIX ##telnet## command to connect to the port described in the server configuration file's ##Server## tag and type the word supplied in the ##shutdown## attribute to take out the Tomcat instance.
300
301 === Tomcat 3 ===
302
303 {{noformat}}
304
305 TOMCATDIR/bin/shutdown -ajp13 -port 9091
306
307 {{/noformat}}
308
309 = Apache Adaptor Setup =
310
311 A final deployment usually involves apache feeding inbound requests to instances and handling situations where an instance has gone down and balancing load over the instances that are currently running. This job is undertaken by ##mod//jk//##// which is a module for apache written by the Tomcat group. This module communicates with the tomcat instances using a protocol called ##AJP##. This protocol carries all the information required to check instances are operational as well as relaying requests to the instances. It is assumed that the configuration as well as binaries for the ##mod##//##jk## apache module will be located at ##$JKDIR##.
312
313 == Compiling and Installing ==
314
315 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.
316
317 {{noformat}}
318
319 $JKDIR/mod_jk.so
320
321 {{/noformat}}
322
323 Add a line to your system's apache httpd configuration file like this:
324
325 {{noformat}}
326
327 Include /opt/modjk/apache.conf
328
329 {{/noformat}}
330
331 Edit this file to look like this:
332
333 {{noformat}}
334
335 LoadModule jk_module /opt/modjk/mod_jk.so
336 AddModule mod_jk.c
337
338 JkLogFile /opt/modjk/mod_jk.log
339 JkLogLevel info
340
341 JkWorkerProperty worker.list=i1,i2,i3,loadbalancer
342 JkWorkerProperty worker.i1.type=ajp13
343 JkWorkerProperty worker.i1.port=9091
344 JkWorkerProperty worker.i1.host=appserver1.foo.co.nz
345 JkWorkerProperty worker.i1.lbfactor=1
346 JkWorkerProperty worker.i2.type=ajp13
347 JkWorkerProperty worker.i2.port=9092
348 JkWorkerProperty worker.i2.host=appserver1.foo.co.nz
349 JkWorkerProperty worker.i2.lbfactor=1
350 JkWorkerProperty worker.i3.type=ajp13
351 JkWorkerProperty worker.i3.port=9093
352 JkWorkerProperty worker.i3.host=appserver1.foo.co.nz
353 JkWorkerProperty worker.i3.lbfactor=1
354 JkWorkerProperty worker.loadbalancer.type=lb
355 JkWorkerProperty worker.loadbalancer.sticky_session=1
356 JkWorkerProperty worker.loadbalancer.local_worker_only=1
357 JkWorkerProperty worker.loadbalancer.balance_workers=i1,i2,i3
358
359 JkMount /FooApp/* loadbalancer
360
361 {{/noformat}}
362
363 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.
364
365 == Restart Apache ==
366
367 Now restart apache with the following command:
368
369 {{noformat}}
370
371 sudo apachectl restart
372
373 {{/noformat}}
374
375 == Test Application ==
376
377 Now you can test your application using a URL such as this one.
378
379 {{noformat}}
380
381 http://www.foo.co.nz/FooApp/WebObjects/FooApp.woa
382
383 {{/noformat}}
384
385 All three instances that you have setup should take some of the inbound requests.
386
387 == Choosing the Right Instance ==
388
389 ##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.//