Appendix H: Using the MS4W Apache http server as a reverse proxy to Tomcat
To serve a OneGeology WMS through the portal that service must be served using port 80; the default port for any http web service. If you are already serving another web service on port 80 on the same server (such as a GeoNetwork spatial data metadata catalogue for example), then you will need to use a different port number for the existing service. In itself this shouldn’t be too difficult to do, however this might cause problems for your customers due to restrictive firewall rules that prevent them consuming any web service not served on the standard web port number. One way around this is to merge the services together; another possibility (as detailed below) is to use the Apache HTTP web server as a reverse proxy, that is, to handle all requests to the second service as if that service was coming from the MS4W Apache service. The user is thus unaware that there is more than one web service. Each service proxied in this way runs on a separate port number, and may still be accessed directly on that port (depending on your configuration), but it is also available as if it were running on port 80.
The first step is to change the port numbers on which your other web servers work; in this example we have two other web services (a Tomcat based web service which we will run on port 8080, and a jetty based web service which we will run on port 8008). Note that both these ports are recognized alternate ports for http traffic but they may not be open to such traffic in your corporate firewall.
Now we need to edit the Apache HTTP server httpd.conf file. If you have installed the MS4W apache http server as part of the ms4w-and-exemplar-data.zip download this would be located at: c:\ms4w\Apache\conf\httpd.conf.
Check that the following modules are uncommented (by removing the # sign from the line start).
#LoadModule proxy_module modules/mod_proxy.so
#LoadModule proxy_ajp_module modules/mod_proxy_ajp.so
#LoadModule proxy_http_module modules/mod_proxy_http.so
LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_ajp_module modules/mod_proxy_ajp.so
LoadModule proxy_http_module modules/mod_proxy_http.so
Note, we have used mod_proxy here as it is included with the Apache HTTP Server binaries, but you could use other proxy modules such as mod_jk if desired.
Now you need to add or uncomment the following directives (as appropriate for your configuration file); we suggest adding these directives at the end of the file for clarity.
#Important for security!!
#This sets up the reverse proxy, if ‘ ProxyRequests On’ is set you have a forward proxy.
Now for each service (or set of pages within a service) that you wish to proxy you need to add the following set of directives:
A <Proxy> or a <ProxyMatch> block to restrict access to your resources, a ProxyPass directive (to map that web service into the local server URL space), and a ProxyPassReverse directive (which lets Apache adjust the URL in the Location, Content-Location and URI headers on HTTP redirect responses).
- Adding a reverse proxy to the BRGM OneGeology Europe connector for WP6 WMS. This connector runs on the Tomcat server running on port 8080, but will appear to be running as part of the Apache http service running on port 80.
Allow from all
ProxyPass /1GEconnector http://localhost:8080/1GEconnector
ProxyPassReverse /1GEconnector http://localhost:8080/1GEconnector
- Adding a reverse proxy to our Jetty web service which is running a GeoNetwork catalogue. The Jetty service is running on port 8008 but will appear to be running as part of the Apache http service running on port 80. You would normally be able to use ‘ localhost’ or ‘ 127.0.0.1’ to specify a web service running on the same physical server as your Apache web server, but in this instance Jetty has been configured to only accept requests from the server IP (22.214.171.124).
Allow from all
ProxyPass /geonetwork http://126.96.36.199:8008/geonetwork
ProxyPassReverse /geonetwork http://188.8.131.52:8008/geonetwork
- Adding a reverse proxy to our Jetty web service which is running an Intermap mapping client (used by the GeoNetwork catalogue). The Jetty service is running on port 8008 but will appear to be running as part of the Apache http service running on port 80.
Allow from all
ProxyPass /intermap http://184.108.40.206:8008/intermap
ProxyPassReverse /intermap http://220.127.116.11:8008/intermap
- Adding a reverse proxy to our cocoon service, which we need to run our WFS. The cocoon service runs on the Tomcat server running on port 8080, but will appear to be running as part of the Apache http service running on port 80. In this example we are using a ProxyMatch block, which allows us to use a regular expression to map the allowable paths to cocoon.
Allow from 127.0.0.1
ProxyPass /cocoon http://127.0.0.1:8080/cocoon/
ProxyPassReverse /cocoon http://127.0.0.1:8080/cocoon/
That’s it as far as the Apache http server is concerned, but you may also wish to configure your other web servers so that they always proxy their http content through Apache
To do this in Tomcat, you need to modify a Connector block in the server.xml configuration file as below:
ProxyName: is the domain name or IP of the standard (Apache HTTP Server) web service and can be omitted if you are running your Tomcat service on the same server as the http service.
To do this in Jetty you need to make a similar change in the jetty.xml file
Section last modified : 19 June 2011.