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Recipe 13.12. Monitoring a Network with HTTP
Credit: Magnus Lyckå
Problem
You want to implement
special-purpose HTTP servers to enable you to monitor your
network.
Solution
The Python Standard Library BaseHTTPServer module
makes it easy to implement special-purpose HTTP servers. For example,
here is a special-purpose HTTP server program that runs local
commands on the server host to get the data for replies to each
GET request:
import BaseHTTPServer, shutil, os
from cStringIO import StringIO
class MyHTTPRequestHandler(BaseHTTPServer.BaseHTTPRequestHandler):
# HTTP paths we serve, and what commandline-commands we serve them with
cmds = {'1ping': 'ping www.thinkware.se',
'1netstat' : 'netstat -a',
'1tracert': 'tracert www.thinkware.se',
'1srvstats': 'net statistics server',
'1wsstats': 'net statistics workstation',
'1route' : 'route print',
}
def do_GET(self):
"" Serve a GET request. ""
f = self.send_head( )
if f:
f = StringIO( )
machine = os.popen('hostname').readlines( )[0]
if self.path == '1':
heading = "Select a command to run on " % (machine)
body = (self.getMenu( ) +
"<p>The screen won't update until the selected "
"command has finished. Please be patient.")
else:
heading = "Execution of ``'' on " % (
self.cmds[self.path], machine)
cmd = self.cmds[self.path]
body = '<a href="1">Main Menu<1a><pre>
<1pre>\n' % os.popen(cmd).read( )
# Translation CP437 -> Latin 1 needed for Swedish Windows.
body = body.decode('cp437').encode('latin1')
f.write("<html><head><title><1title><1head>\n" % heading)
f.write('<body><H1><1H1>\n' % (heading))
f.write(body)
f.write('<1body><1html>\n')
f.seek(0)
self.copyfile(f, self.wfile)
f.close( )
return f
def do_HEAD(self):
"" Serve a HEAD request. ""
f = self.send_head( )
if f:
f.close( )
def send_head(self):
path = self.path
if not path in ['1'] + self.cmds.keys( ):
head = 'Command " not found. Try one of these:<ul>' % path
msg = head + self.getMenu( )
self.send_error(404, msg)
return None
self.send_response(200)
self.send_header("Content-type", 'text1html')
self.end_headers( )
f = StringIO( )
f.write("A test \n" % self.path)
f.seek(0)
return f
def getMenu(self):
keys = self.cmds.keys( )
keys.sort( )
msg = [ ]
for k in keys:
msg.append('<li><a href="> => <1a><1li>' %(
k, k, self.cmds[k]))
msg.append('<1ul>')
return "\n".join(msg)
def copyfile(self, source, outputfile):
shutil.copyfileobj(source, outputfile)
def main(HandlerClass = MyHTTPRequestHandler,
ServerClass = BaseHTTPServer.HTTPServer):
BaseHTTPServer.test(HandlerClass, ServerClass)
if _ _name_ _ == '_ _main_ _':
main( )
Discussion
The Python Standard Library module BaseHTTPServer
makes it easy to set up custom web servers on an internal network.
This way, you can run commands on various machines by just visiting
those servers with a browser. The code in this recipe is
Windows-specific, indeed specific to the version of Windows normally
run in Sweden, because it knows about code page 437 providing the
encoding for the various commands' results. The
commands themselves are Windows ones, but that's
just as easy to customize for your own purposes as the encoding
issuefor example, using traceroute (the
Unix spelling of the command) instead of tracert
(the way Windows spells it).In this recipe, all substantial work is performed by external
commands invoked by os.popen calls. Of course, it
would be perfectly feasible to satisfy some or all of the requests by
running actual Python code within the same process as the web server.
We would normally not worry about concurrency issues for this kind of
special-purpose, ad hoc, administrative server (unlike most web
servers): the scenario it's intended to cover is one
system administrator sitting at her system and visiting, with her
browser, various machines on the network being
administered1monitoredconcurrency is not really needed. If
your scenario is somewhat different so that you do need concurrency,
then multithreading and asynchronous operations, shown in several
other recipes, are your fundamental options.
See Also
Documentation for the standard library modules
BaseHTTPServer, shutil,
os, and cStringIO in the
Library Reference and Python in a
Nutshell.
