[LINUX] Integrate Apache and Tomcat

Introduction

As a continuation of Tomcat installation and auto-start settings, I summarized the settings to throw the HTTP request received on the Apache side to Tomcat.

Environment used

• OS
• CentOS 7.7（1908）
• Java（Amazon Corretto）
• Java 1.8.0_242
• Apache
• Apache-2.4.6
• Tomcat
• Tomcat-9.0.30

Apache installation

• After installing with the yum command, display the version information to confirm that it was installed correctly.

[root@akagi ~]# yum install -y httpd
[root@akagi ~]# httpd -v
Server version: Apache/2.4.6 (CentOS)
Server built:   Aug  8 2019 11:41:18

Apache autostart settings

• Set the automatic start with systemctl enable ..., and then check the automatic start setting.

[root@akagi ~]# systemctl enable httpd
Created symlink from /etc/systemd/system/multi-user.target.wants/httpd.service to /usr/lib/systemd/system/httpd.service.
[root@akagi ~]# systemctl list-unit-files -t service | grep httpd
httpd.service                                 enabled 

Edit configuration file

• Here, edit httpd.conf and set to make a request from Apache to Tomcat with a reverse proxy.

Check /etc/httpd/conf.modules.d/00-proxy.conf

• /etc/httpd/conf.modules.d/00-proxy.conf describes the settings of the modules used for the reverse proxy.
• Make sure that mod_proxy.so and mod_proxy_ajp.so are listed and not in the comment line.
• If the beginning of the line is #, it will be a comment line.
• mod_proxy_ajp allows you to communicate with Tomcat using a protocol called AJP, which is more efficient than HTTP.
• I think I used the modules mod_jk and mod_jk2 a long time ago, but before I knew it, the module I used changed ...

00-proxy.conf

# This file configures all the proxy modules:
LoadModule proxy_module modules/mod_proxy.so
...
LoadModule proxy_ajp_module modules/mod_proxy_ajp.so
...

Backup of httpd.conf

• Before editing httpd.conf, back up httpd.conf in its original state.

[root@akagi ~]# cd /etc/httpd/conf/
[root@akagi conf]# cp -a httpd.conf httpd.conf.org

Reverse proxy settings

• Set ProxyPass and ProxyPassReverse as follows.
• ProxyPass {request pass} ajp: // localhost: 8009 / {Java app context name}
• ProxyPassReverse {request path} ajp: // localhost: 8009 / {Java application context name}
• Both ProxyPass and ProxyPassReverse have the role of "forwarding the request that came to the request path to the application server (* Tomcat in this case)", but if you want to use redirect, you need to set ProxyPassReverse.
• In the following example, if the request matches http: // {server IP} / tomcat9 /, the context name on port 8009 of the local host (localhost)/(* Tomcat management screen) It is set to transfer.
• Reference URL: Reintroduction to mod_proxy – ProxyPass and ProxyPass Reverse

/etc/httpd/conf/httpd.conf

#Add the following to the end of the file
ProxyPass /tomcat9/ ajp://localhost:8009/
ProxyPassReverse /tomcat9/ ajp://localhost:8009/

• For example, if you want to set a reverse proxy for an app whose context name is test running on Tomcat, the settings will be as follows.
• You can replace the part marked with tomcat9 with any character string.

/etc/httpd/conf/httpd.conf

#Add the following to the end of the file
ProxyPass /tomcat9/ ajp://localhost:8009/test/
ProxyPassReverse /tomcat9/ ajp://localhost:8009/test/

Reflection of settings

• In CentOS 5 series and CentOS 6 series, service httpd graceful is executed, instead of forcibly restarting Apache, only the setting value is reflected, but in CentOS 7 series Apache, graceful Cannot be used.
• According to this article, running systemctl reload httpd with reload has the same effect as the traditional graceful. It seems that you can get it.

[root@akagi ~]# systemctl reload httpd

Confirmation of operation

• Finally, go to http: // {server IP} / tomcat9 / and check that you can see the management screen of Tomcat.

Related work

• Block Tomcat port 8080