Add your own services to ESP's Node Controller

Background

Integrating our own custom services with Fast ESP’s Node Controller provides us with several benefits:

• Administrators without in-depth ESP knowledge can easily control services (e.g. start, stop, configure parameters)
• Services can be started at boot time with the rest of ESP
• espdeploy can be used to install our services in a multi-node cluster

The components required for this system are:

1. The ESP Node Controller (with config file NodeConf.xml)
2. The 3rd-party service (like a CherryPy server, log parser, etc.)
3. A wrapper script (see below)

Steps for Integration

1. Define the service you would like to integrate. It can be any script or binary that can be executed on the system. For example, the service might be a python script that takes command-line arguments and continues running itself (as is the case with a webserver).
2. Create the wrapper script that sets up the proper environment and runs/stops the service properly. The wrapper script should be put in the $FASTSEARCH/bin directory (with executable permissions). Additionally, the wrapper script should pass $@ to your actual script so any/all arguments defined in $FASTSEARCH/etc/NodeConf.xml will be passed along properly from the Node Controller to your service. The following is an example of a wrapper script:

   #!/bin/sh
   
   # export the proper python path
   export PYTHONPATH=":/path/to/python"
   
   # run the script (backgrounded)
   python $FASTSEARCH/lib/python2.6/yourmodule/yourservice.py $@ &
   
   # determine the process id of the python script
   SCRIPT_PID="$!"
   
   # upon receiving a SIGTERM, forward it to the process
   trap "kill -TERM $SCRIPT_PID" SIGTERM
   
   # wait for SIGTERM from nctrl
   wait

3. Define the service in $FASTSEARCH/etc/NodeConf.xml
   Add the following to the end of the <startorder> tag:

   <proc>servicename</proc>

   Add the following to the end of the <node> tag, customizing as appropriate:

   <!-- My Custom Service -->
   <process name="servicename" description="My Custom Service">
           <start>
                   <executable>binaryname</executable>
                   <parameters>-p 16940 -v</parameters>
                   <port base="4004"/>
           </start>
           <outfile>servicename.scrap</outfile>
   </process>

4. Reload the Node Controller configuration with the following:

   nctrl reloadcfg

And that’s it!  Now you should be able to start, stop, configure, and deploy your services using Fast ESP tools.  Enjoy!