BackgroundTaskQueue

This engine plugin allows you to run tasks in response to a request without tying up the request thread.


{{{
#!python
import Queue
import threading


class BackgroundTaskQueue(SimplePlugin):
    
    thread = None
    
    def __init__(self, bus, qsize=100, qwait=2, safe_stop=True):
        SimplePlugin.__init__(self, bus)
        self.q = Queue.Queue(qsize)
        self.qwait = qwait
        self.safe_stop = safe_stop
    
    def start(self):
        self.running = True
        if not self.thread:
            self.thread = threading.Thread(target=self.run)
            self.thread.start()
    
    def stop(self):
        if self.safe_stop:
            self.running = "draining"
        else:
            self.running = False
        
        if self.thread:
            self.thread.join()
            self.thread = None
        self.running = False
    
    def run(self):
        while self.running:
            try:
                try:
                    func, args, kwargs = self.q.get(block=True, timeout=self.qwait)
                except Queue.Empty:
                    if self.running == "draining":
                        return
                    continue
                else:
                    func(*args, **kwargs)
                    if hasattr(self.q, 'task_done'):
                        self.q.task_done()
            except:
                self.bus.log("Error in BackgroundTaskQueue %r." % self,
                             level=40, traceback=True)
    
    def put(self, func, *args, **kwargs):
        """Schedule the given func to be run."""
        self.q.put((func, args, kwargs))
}}}

Use it like this:

{{{
#!python
import cherrypy
from complicated_logging import log

bgtask = BackgroundTaskQueue(cherrypy.engine)
bgtask.subscribe()

class Root(object):
    
    def index(self):
        bgtask.put(log, "index was called", ip=cherrypy.request.remote.ip))
        return "Hello, world!"
    index.exposed = True
}}}


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Another interesting feature for tasks: [IsClientConnected]