Transcript CIS6930: CGI and Servlets

CIS 5930-04 – Spring 2001
Special Topic: Apache and Tomcat
http://aspen.csit.fsu.edu/it1spring01
Instructors: Geoffrey Fox , Bryan Carpenter
Computational Science and Information Technology
Florida State University
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1
The Apache Project
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The Apache Project is a collaborative software
development effort.
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Its goal is to produce a robust, commercial-grade, free
HTTP server.
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The project is run by volunteers—the Apache Group—
communicating and planning through the Internet.
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Organizational support is provided by the Apache
Software Foundation.
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Home page:
http://apache.org
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2
Foundation Myths
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Long ago, when the Web was young, the most famous
Web server in the World was called the NCSA server.
It was developed by Rob McCool at the National Center
for Supercomputing Applications.
McCool left NCSA in 1994, and development of the
public-domain NCSA server temporarily faltered.
At that time, a group of eight powerful Webmasters had
developed their own extensions and bug-fixes for the
NCSA server.
The founding Webmasters—brought together by email—
pooled their updates.
“Apache” came into being early in 1995. It was a series
of “patches” to the NCSA code.
A year later, Apache was the most popular Web server.
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3
Apache and Tomcat
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This “lecture” is mainly a how-to guide to installing the
Apache server and integrating it with the current version
of Tomcat.
This allows a site primarily served by Apache to
seamlessly make servlet and JSP content available.
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4
Obtaining Apache for Linux
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Go to httpd.apache.org and follow the “download” link.
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Negotiate folders through to binaries/linux.
– Or go directly to httpd.apache.org/dist/binaries/linux
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At the time of writing, the relevant file was
apache_1.3.14-i686-whatever-linux2.tar.gz
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5
Installing the Apache Server
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Unpack the distribution:
gunzip -c apache_1.3.14-i686-whatever-linux2.tar.gz | tar
xvf – You can do this step anywhere, e.g. in the /tmp directory.
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Go into the created apache_1.3.4 directory and run
./install-bindist.sh
– I will assume you are logged in as root.
– It should be straightforward to install as an ordinary user, but
you need to ensure the Apache home directory is set to
somewhere in your own home directory. Read the
INSTALL.bindist file.
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6
The Installation Script

If successful, you will probably see a message something
like:
Installing binary distribution for platform i686-whatever-linux2
into directory /usr/local/apache ...
Ready.
+--------------------------------------------------------+
| You now have successfully installed the Apache 1.3.14 |
| HTTP server. To verify that Apache actually works
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| correctly you should first check the (initially
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| created or preserved) configuration files:
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/usr/local/apache/conf/httpd.conf
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| You should then be able to immediately fire up
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| Apache the first time by running:
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/usr/local/apache/bin/apachectl start
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| Thanks for using Apache.
The Apache Group
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http://www.apache.org/ |
+--------------------------------------------------------+
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Customize the Configuration File
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If you wish, edit the file
/usr/local/apache/conf/httpd.conf
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The most likely changes you will need to make at this
stage are to the document root.
For example I changed the lines:
DocumentRoot “/usr/local/apache/htdocs”
to
and
to
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DocumentRoot “/home/httpd/html”
<Directory “/usr/local/apache/htdocs”>
<Directory “/home/httpd/html”>
If you are not installing as root, you will also need to
change the line “Port 80” to specify a port above 1024.
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8
Starting and Stopping the Server
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As the installation script said, you can start the httpd
server program by the command:
/usr/local/apache/bin/apachectl start
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Logically enough, you can stop it by:
/usr/local/apache/bin/apachectl stop
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9
Tomcat vs. Apache
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The Apache Web server
–
–
–
–
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is faster than Tomcat when it comes to static pages,
is more configurable than Tomcat,
is more robust than Tomcat, and
it supports CGI scripts, Server API modules, Perl, PHP, etc.
Hence for real world sites, Apache would generally be a
better choice than Tomcat, except that. . .
– In itself, Apache doesn’t support Servlets or JavaServer Pages!
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10
Integrating Apache and Tomcat
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The solution, of course, is to allow the two Web servers
to work together.
The Apache server will be the principal server, dealing
with static documents.
– Or dynamic documents generated by any of the other
technologies mentioned in the previous slide.
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Apache will forward requests for Servlets or JavaServer
Pages to Tomcat.
The approach we describe here is what was called the
“out-of-process servlet container” the lectures on
Servlets.
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Out-of-Process Servlet Container
Servlet
Request
Browser
80
Apache
Servlet
Request
AJP
HTTP
Client
Tomcat
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8007
Server
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The Adapter
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For Apache to communicate with Tomcat, and forward
requests as necessary, it needs some extra software—
an “adapter”.
An adapter will be implemented as an Apache module.
– An Apache module is a piece of code that can be optionally
linked in to (or left out of) the main server code.
– Non-standard, plug-in, modules will typically be shared-object
libraries (DLLs under Windows).
– These live in a directory called /usr/local/apache/libexec.
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Apache modules generally have names of the form
mod_XXXX
– For example, mod_perl.
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There are two Tomcat adapter modules in common use:
mod_jserv and mod_jk.
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13
mod_jk
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mod_jk is a new Tomcat-Apache plug-in that handles
communication between Tomcat and Apache.
– It replaces the older mod_jserv.
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For more information, see the file doc/mod_jk-howto.html
in the Tomcat release, which is also online at
jakarta.apache.org/tomcat/jakarta-tomcat/src/doc/mod_jkhowto.html
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For now the only way to obtain the mod_jk library for Linux
seems to be to build it yourself. The sources are included
in the source release of Tomcat.
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14
Obtaining mod_jk for Linux

Go to jakarta.apache.org and follow the “Source Code”
link.
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Get the release build of Tomcat (currently 3.2). At the
time of writing, the relevant file is
jakarta-tomcat-3.2-src.tar.gz
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Unpack the distribution:
gunzip -c jakarta-tomcat-3.2-src.tar.gz | tar xvf – You can do this anywhere, e.g. in /tmp.
– I do not particularly recommend you try to rebuild the Tomcat
server itself from this release: it is much easier just to download
the compiled, “binary” version of the server, as described in the
lectures on Servlets.
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15
Building mod_jk
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Go to the directory
jakarta-tomcat-3.2-src/src/native/apache1.3
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If necessary, edit the definition of the macro APXS in
Makefile.linux so that it refers to the apxs command in
the Apache release, probably
/usr/local/apache/bin/apxs.
Build the library:
make -f Makefile.linux
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Install the plug-in in the Apache libexec/ directory, e.g.:
cp mod_jk.so /usr/local/apache/libexec
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16
Updating the Apache Configuration
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In the first instance (until you need to do something
clever) this is very easy, because whenever the Tomcat
server is run, it generates a self-describing “include” file.
– This file contains a series of Apache configuration-file commands.
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The include file is in
jakarta-tomcat-X.X/conf/mod_jk.conf-auto
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In my case I added the line
include /home/users/dbc/jakarta-tomcat-3.2/conf/mod_jk.confauto
to the end of the file /usr/local/apache/conf/httpd.conf.
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17
Fragment of the File mod_jk.conf-auto
#########################################################
# Auto configuration for the /dbc context starts.
#########################################################
# The following line makes apache aware of the location of the /dbc
context
Alias /dbc "/home/users/dbc/jakarta-tomcat-3.2/webapps/dbc"
<Directory "/home/users/dbc/jakarta-tomcat-3.2/webapps/dbc">
Options Indexes FollowSymLinks
</Directory>
# The following line mounts all JSP files and the /servlet/ uri to tomcat
JkMount /dbc/servlet/* ajp12
JkMount /dbc/*.jsp ajp12
# The following line prohibits users from directly accessing WEB-INF
<Location "/dbc/WEB-INF/">
AllowOverride None
deny from all
</Location>
# The following line prohibits users from directly accessing META-INF
<Location "/dbc/META-INF/">
AllowOverride None
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deny from all
</Location>
Remarks
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Recall these are commands that Tomcat generates to
configure Apache.
As the first comments indicates, these commands relate
to the servlet context called dbc/.
The Alias command causes Apache to generally look in
the Tomcat document directory for URLs with paths that
start /dbc.
– This is needed for static documents in the Tomcat directory.
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The first JkMount command causes URLs with paths
that match the pattern /dbc/servlet/* to be redirected to
the AJP module (hence the Tomcat server).
The second JkMount command causes URLs with
paths that match the pattern /dbc/*.jsp to be similarly
redirected Tomcat server.
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19
Configuring “Workers”
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In Tomcat 3.2, the generated include file, jakarta-tomcatX.X/conf/mod_jk.conf-auto has a reference to the file
workers.properties in the same directory. You will probably
have to manually edit this file.
Enclosed comments are fairly self-explanatory. If necessary
change the Java home directory and the path-component
separator (to / rather than \ for Linux).
You may also need to choose one or the other of ajp12 and
ajp13, and comment out references to the other.
– I went with ajp12. ajp13 is supposed to be an improved protocol, but
I know and love ajp12.
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Set the port number for your AJP connector, as specified in
server.xml.
See jakarta-tomcat-X.X/doc/Tomcat-WorkersHowTo.html.
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20
Start the Apache Server. . .
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In principle, we are done. Restart the Apache server.
With the default configuration, URLs with paths in
Tomcat servlet contexts that start /servlet or end with
.jsp are redirected to Tomcat.
– Note Apache will directly serve static .html pages, even if they
are in the Tomcat document directory.
– Because Apache (unlike Tomcat) runs as user nobody by
default, such files now need to be world readable.

(Apparently) things continue to work across multiple
restarts of Tomcat, even without restarting Apache.
– We note however that, according to the FAQ, this is not the case
with AJP13. . .
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