[Twisted-Python] Automatic reconnection

Andrew Bennetts andrew-twisted at puzzling.org
Mon Mar 11 20:54:59 EST 2002

Hi all,

I need a tcp.Client that can automatically reconnect when disconnected.

I've written the following class, and it seems to work, but...
  * It doesn't handle unix sockets (that's ok for me, I'm using Windows, so I
    never had them in the first place)
  * I'm not sure what the "connector" is, and thus I suspect it won't for 
    Clients that use it.
  * It's only lightly tested

Is there a better way to do this (i.e. is there a way to do this already in 
Twisted, and I just haven't found it yet)?

Otherwise, I'd be interested in knowing if anyone else would find this useful,
or if maybe it should be included in Twisted.  I suspect I'm not the only
person who wants to be able to write a server which automatically tries to
recover from "upstream" problems.


class ReconnectingClient(tcp.Client):
    """A tcp.Client that automatically reconnects when disconnected
    Overrideable attributes:
        * reconnectionDelay -- number of seconds to wait before reconnecting
        * maxReconnects -- maximum number of reconnects before giving up.  The
          reconnection counter is reset after a successfull reconnection.  Set
          this to None to keep retrying indefinitely.

    The protocol will have connectionLost called as normal when disconnected,
    but may get reconnected after that -- so if you need to reset anything in
    your protocol after a disconnection, do it in Protocol.connectionLost.
    reconnectionDelay = 3.0
    maxReconnects = 5

    def __init__(self, host, port, protocol, timeout=None, connector=None):
        tcp.Client.__init__(self, host, port, protocol, timeout, connector)
        self.reconnectAttempts = 0
        self.reconnectProtocol = protocol

    def connectionLost(self):
        # Disconnect as normal
        # Then schedule a reconnect
        if main.running:        # FIXME: Is this test necessary?
            print 'Lost connection, reconnecting...'
            main.addTimeout(self.reconnect, self.reconnectionDelay)

    def reconnect(self):
        if not self.connected:
            if (self.maxReconnects is None or 
                self.reconnectAttempts < self.maxReconnects):
                    self.reconnectAttempts += 1
                    tcp.Connection.__init__(self, self.createInternetSocket(), 
                    main.addTimeout(self.reconnect, self.reconnectionDelay)
                print 'Reconnection failed after %d attempts.  Giving up.' \
                      % (self.reconnectAttempts,)
            # Reset the reconnect counter if we're connected.
            self.reconnectAttempts = 0

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