[Xen-devel] [PATCH 0/3] python: Add non-blocking Xenstore watch bindings

[Euan Harris <euan.harris@xxxxxxxxxx>]

Expose xs_fileno() and xs_check_watch() to Python.   These functions
make it posible to write event-driven Xenstore clients in Python:

  #!/usr/bin/env python
  
  import xen.lowlevel.xs
  
  import sys
  import errno
  from select import select
  import time
  
  # Connect to XenStore and set watch
  xsh = xen.lowlevel.xs.xs()
  xsh.watch("/foo", "footoken")
  xsh.watch("/bar", "bartoken")
  
  # Start polling loop
  xsfd = xsh.fileno()
  while True:
     readable, writable, exceptional = select([xsfd], [], [xsfd], 1.0)
     print "%d tick" % time.time()
  
     if readable:
         while True:
             watch = xsh.check_watch()
             if not watch:
                 break
             path, token = watch
             print "%d watch fired: path=%s, token=%s" % (time.time(), 
                                                          path, token)
             value = xsh.read("", path)
             print "%d read %s = %s" % (time.time(), path, value)
  
     if exceptional:
         print "select error"
  
The polling loop can be simplified further by wrapping the call to
xsh.check_watch() in a generator, but this is easier to do in Python
than in the C bindings.


Euan Harris (3):
  python: Add wrapper for xs_fileno()
  python: Extract registered watch search logic from  xspy_read_watch()
  python: Add binding for non-blocking xs_check_watch()

 tools/python/xen/lowlevel/xs/xs.c | 109 ++++++++++++++++++++++++++++++--------
 1 file changed, 86 insertions(+), 23 deletions(-)

-- 
1.8.3.1


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