Following this post, I've written a modification so now the listener is working in multiprocessing.
#!/usr/bin/python
# A code to stream file as it grows
# by Ran Novitsky Nof Oct 25, 2012
import os,time
from multiprocessing import Process,Pipe
# change this file name
FileName = 'stream.txt'
# adapted from http://www.valuedlessons.com/2008/04/events-in-python.html
# the Event class take care of adding, removing and executing the functions
class Event:
def __init__(self):
self.handlers = set()
def handle(self, handler):
self.handlers.add(handler)
return self
def unhandle(self, handler):
try:
self.handlers.remove(handler)
except:
raise ValueError("Handler is not handling this event, so cannot unhandle it.")
return self
def fire(self, *args, **kargs):
for handler in self.handlers:
handler(*args, **kargs)
def getHandlerCount(self):
return len(self.handlers)
__iadd__ = handle
__isub__ = unhandle
__call__ = fire
__len__ = getHandlerCount
# the stream class takes care of the
# function to fire in case of an event
class Stream:
def __init__(self,fname):
self.fname = fname
self.fd = open(fname,'r')
self.get_stream()
def get_stream(self):
# this is the actual function to fire
print self.fd.read(),
def restart(self):
self.fd.seek(0)
# the MockFileWatcher creats the multiprocessing deamon to alert on file change
class MockFileWatcher:
def __init__(self,source_path,sleeptime=0.1):
self.fileChanged = Event()
self.source_path = source_path
self.running=False
self.deamon=False
self.fd = None
self.sleep = sleeptime
# the next two lines can be set outside the class
self.stream = Stream(source_path)
self.fileChanged += self.stream.get_stream # add event handler
def watchFiles(self):
# open the file in non-blocking read mode
self.fd = os.open(self.source_path,os.O_RDONLY | os.O_NONBLOCK)
# go to the end
os.lseek(self.fd,0,2)
self.running=True
self.deamon=False
while self.running:
# try to read
if os.read(self.fd,1)!='':
# New data was added
os.lseek(self.fd,0,2) # go to the end of file
self.fileChanged() # fire the event
# see if the parent process has a message
if self.chiled_conn.poll():
# execute the message
eval(self.chiled_conn.recv())
# sleep for a while
time.sleep(self.sleep)
def watchFilesDeamon(self):
# start the deamon
self.parent_conn,self.chiled_conn = Pipe()
p = Process(target=self.watchFiles)
p.start()
self.p = p
self.deamon=True
return p
def stop(self):
# stop deamon/process
if self.deamon:
self.parent_conn.send('self.stop()')
print "Hold while stopping child process..."
# hold depends on the sleeping time
if self.parent_conn.recv():
pass
#print "chiled is stopped"
self.p.terminate() # terminate multiprocessing
self.deamon=False
# stop process
self.running=False
self.fd=None
# if this is the process make sure parent know we are done
if not self.deamon: self.chiled_conn.send(True)
return True
if __name__=='__main__':
watcher = MockFileWatcher(FileName)
p = watcher.watchFilesDeamon()
print 'from this point the listner is running at the background'
print 'add more code here so you can see how it works.'
# A code to stream file as it grows
# by Ran Novitsky Nof Oct 25, 2012
import os,time
from multiprocessing import Process,Pipe
# change this file name
FileName = 'stream.txt'
# adapted from http://www.valuedlessons.com/2008/04/events-in-python.html
# the Event class take care of adding, removing and executing the functions
class Event:
def __init__(self):
self.handlers = set()
def handle(self, handler):
self.handlers.add(handler)
return self
def unhandle(self, handler):
try:
self.handlers.remove(handler)
except:
raise ValueError("Handler is not handling this event, so cannot unhandle it.")
return self
def fire(self, *args, **kargs):
for handler in self.handlers:
handler(*args, **kargs)
def getHandlerCount(self):
return len(self.handlers)
__iadd__ = handle
__isub__ = unhandle
__call__ = fire
__len__ = getHandlerCount
# the stream class takes care of the
# function to fire in case of an event
class Stream:
def __init__(self,fname):
self.fname = fname
self.fd = open(fname,'r')
self.get_stream()
def get_stream(self):
# this is the actual function to fire
print self.fd.read(),
def restart(self):
self.fd.seek(0)
# the MockFileWatcher creats the multiprocessing deamon to alert on file change
class MockFileWatcher:
def __init__(self,source_path,sleeptime=0.1):
self.fileChanged = Event()
self.source_path = source_path
self.running=False
self.deamon=False
self.fd = None
self.sleep = sleeptime
# the next two lines can be set outside the class
self.stream = Stream(source_path)
self.fileChanged += self.stream.get_stream # add event handler
def watchFiles(self):
# open the file in non-blocking read mode
self.fd = os.open(self.source_path,os.O_RDONLY | os.O_NONBLOCK)
# go to the end
os.lseek(self.fd,0,2)
self.running=True
self.deamon=False
while self.running:
# try to read
if os.read(self.fd,1)!='':
# New data was added
os.lseek(self.fd,0,2) # go to the end of file
self.fileChanged() # fire the event
# see if the parent process has a message
if self.chiled_conn.poll():
# execute the message
eval(self.chiled_conn.recv())
# sleep for a while
time.sleep(self.sleep)
def watchFilesDeamon(self):
# start the deamon
self.parent_conn,self.chiled_conn = Pipe()
p = Process(target=self.watchFiles)
p.start()
self.p = p
self.deamon=True
return p
def stop(self):
# stop deamon/process
if self.deamon:
self.parent_conn.send('self.stop()')
print "Hold while stopping child process..."
# hold depends on the sleeping time
if self.parent_conn.recv():
pass
#print "chiled is stopped"
self.p.terminate() # terminate multiprocessing
self.deamon=False
# stop process
self.running=False
self.fd=None
# if this is the process make sure parent know we are done
if not self.deamon: self.chiled_conn.send(True)
return True
if __name__=='__main__':
watcher = MockFileWatcher(FileName)
p = watcher.watchFilesDeamon()
print 'from this point the listner is running at the background'
print 'add more code here so you can see how it works.'
Try this by changing the file name at the top and run it. then add new lines to the file.
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