Paul Winkler wrote at 2005-11-28 15:37 -0500:
> ...
>> We had to implement a keep alive mechanism to prevent our firewall
>> from behaving in this nasty way.
>
>OK. Can you give a high-level summary of what you did?  I thought of
>using heartbeat to detect loss of connection, but I'm not sure what I
>could do on failure short of restarting Zope.

We knew that our firewall shuts down connections with a timeout
of 30 min. Thus, we have send our ZEO a keep alive message
every 20 min. The code roughly looks like this:

KeepPeriod= int(environ.get('ZEO_KEEP_ALIVE')) * 60

Storage = getConfiguration().dbtab.getDatabase('/')._storage

def keepAlive():
    LOG("CustomZODB",INFO,"Keep alive thread started")
    while 1:
        sleep(KeepPeriod)
        if Storage._ready.isSet():
            LOG("CustomZODB",INFO,"Sending keep alive message")
            Storage._load_lock.acquire()
            try:
                try:
                    Storage._server.get_info()
                    LOG("CustomZODB",INFO,"Sent keep alive message")
                except:
                    LOG("CustomZODB",ERROR,".... failed", error=exc_info())
            finally: Storage._load_lock.release()
        else:
            LOG("CustomZODB",PROBLEM,"Connection is down")
start_new_thread(keepAlive,())


-- 
Dieter
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