The control flow module is an official GeoServer extension. Installation, as usual, is quite easy. You may find the package listed among the other extension downloads on the GeoServer download page (http://geoserver.org/download/). In order to avoid compatibility issues, please ensure that you download a version of the extension exactly matching the GeoServer version you are using.
- Download the ZIP archive. Please verify that the version number in the filename is the same as the GeoServer WAR file you installed. For the 2.5.2 release, the link is as follows:
- Stop your GeoServer instance and then extract the contents of the ZIP archive into the
/WEB-INF/lib/directory in the GeoServer webapp. For example, if you have deployed the GeoServer WAR file, you should place the control flow module's JAR file inCATALINA_HOME/webapps/geoserver/WEB-INF/lib/. - After extracting the extension, restart GeoServer in order for the changes to take effect. In this case, the installation does not cause any change on the web interface that you can look for to check whether the installation was successful.
- Open your favorite text editor, create a new file, and insert following line:
ip.blacklist=127.0.0.1
- Now save the file with the name
controlflow.propertiesinside the<GEOSERVER_DATA_DIR>folder. - Restart GeoServer to have your configuration reloaded.
- Point your browser to the following URL:
http://localhost:8080/geoserver/web - You should see an error page similar to the one shown in the following screenshot:
The control flow module, as its name clearly explains, controls the flow of requests to your GeoServer. That is, every request coming to GeoServer is filtered by the module and then submitted, queued, or rejected.
In this recipe, you inserted the loopback address of your machine in the blacklist, so you can no longer use GeoServer. Of course, this is a very unlikely situation; just useful to demonstrate that the module is working properly.
A more common use of the extension is to limit the concurrent requests from the same user or a service to avoid an overwhelming amount of load that can block your GeoServer.