We need to create a configuration file for Supervisor. A sample configuration is given in this recipe. In this example, we define the Unix HTTP server socket and a few other parameters. Note the rpcinterface:supervisor section where rpcinterface_factory is defined to communicate with clients.

Using Supervisor, we configure a simple server program in the program: 17_2_multithreaded_multicall_xmlrpc_server.py section by specifying the command and some other parameters.

Listing 7.1a gives the code for a minimal Supervisor configuration, as shown:

[unix_http_server] 
file=/tmp/supervisor.sock   ; (the path to the socket file) 
chmod=0700                 ; socket file mode (default 0700) 
 
[supervisord] 
logfile=/tmp/supervisord.log  
loglevel=info                 
pidfile=/tmp/supervisord.pid  
nodaemon=true                
 
[rpcinterface:supervisor] 
supervisor.rpcinterface_factory = supervisor.rpcinterface:make_main_rpcinterface 
 
[program:17_2_multithreaded_multicall_xmlrpc_server.py] 
command=python 17_2_multithreaded_multicall_xmlrpc_server.py ; the  
program (relative uses PATH, can take args) 
process_name=%(program_name)s ; process_name expr (default  
%(program_name)s) 

If you create the preceding Supervisor configuration file in your favorite editor, you can run Supervisor by simply calling it.

Now, we can code an XML-RPC client that can act as a Supervisor proxy and give us the information about the running processes.

Listing 7.1b gives the code for querying a local XML-RPC server, as shown:

#!/usr/bin/env python 
# Python Network Programming Cookbook, Second Edition -- Chapter - 7 
# This program is optimized for Python 2.7.12. 
# Supervisor requires Python 2.x, and does not run on Python 3.x. 
 
 
import supervisor.xmlrpc 
import xmlrpclib 
 
def query_supervisr(sock): 
    transport = supervisor.xmlrpc.SupervisorTransport(None, None, 
                'unix://%s' %sock) 
    proxy = xmlrpclib.ServerProxy('http://127.0.0.1', 
            transport=transport) 
    print ("Getting info about all running processes
             via Supervisord...") 
    print (proxy.supervisor.getAllProcessInfo()) 
 
if __name__ == '__main__': 
    query_supervisr(sock='/tmp/supervisor.sock') 
     

If you run the Supervisor daemon, it will show output similar to the following:

$ supervisord
2013-09-27 16:40:56,861 INFO RPC interface 'supervisor' initialized
2013-09-27 16:40:56,861 CRIT Server 'unix_http_server' running 
without any HTTP authentication checking
2013-09-27 16:40:56,861 INFO supervisord started with pid 27436
2013-09-27 16:40:57,864 INFO spawned: 
'17_2_multithreaded_multicall_xmlrpc_server.py' with pid 27439
2013-09-27 16:40:58,940 INFO success: 
17_2_multithreaded_multicall_xmlrpc_server.py entered RUNNING state, 
process has stayed up for > than 1 seconds (startsecs)
  

Note that our child process, 17_2_multithreaded_multicall_xmlrpc_server.py, has been launched.

Now, if you run the client code, it will query the XML-RPC server interface of Supervisor and list the running processes, as shown:

$ python 17_1_query_xmlrpc_server.py 
Getting info about all running processes via Supervisord...
[{'now': 1380296807, 'group': 
'17_2_multithreaded_multicall_xmlrpc_server.py', 'description': 'pid 
27439, uptime 0:05:50', 'pid': 27439, 'stderr_logfile': 
'/tmp/17_2_multithreaded_multicall_xmlrpc_server.py-stderr---
supervisor-i_VmKz.log', 'stop': 0, 'statename': 'RUNNING', 'start': 
1380296457, 'state': 20, 'stdout_logfile': 
'/tmp/17_2_multithreaded_multicall_xmlrpc_server.py-stdout---
supervisor-eMuJqk.log', 'logfile': 
'/tmp/17_2_multithreaded_multicall_xmlrpc_server.py-stdout---
supervisor-eMuJqk.log', 'exitstatus': 0, 'spawnerr': '', 'name': 
'17_2_multithreaded_multicall_xmlrpc_server.py'}]