We have a setup with a ZEO server and 4 ZEO clients.

During the last weeks we have seen almost daily deadlocks in some of the ZEO clients. I've tried to wait for up to 30 minutes before restarting a client.

I could need an advice on how to debug this.

With DeadlockDebugger I see the same pattern each time:

One thread is hanging:

File "/usr/local/www/zope-2.9.6/lib/python/ZODB/Connection.py", line 732, in setstate
File "/usr/local/www/zope-2.9.6/lib/python/ZODB/Connection.py", line 768, in _setstate
    p, serial = self._storage.load(obj._p_oid, self._version)
File "/usr/local/www/zope-2.9.6/lib/python/ZEO/ClientStorage.py", line 746, in load
    return self.loadEx(oid, version)[:2]
File "/usr/local/www/zope-2.9.6/lib/python/ZEO/ClientStorage.py", line 769, in loadEx
    data, tid, ver = self._server.loadEx(oid, version)
File "/usr/local/www/zope-2.9.6/lib/python/ZEO/ServerStub.py", line 192, in loadEx
    return self.rpc.call("loadEx", oid, version)
File "/usr/local/www/zope-2.9.6/lib/python/ZEO/zrpc/connection.py", line 531, in call
    r_flags, r_args = self.wait(msgid)
File "/usr/local/www/zope-2.9.6/lib/python/ZEO/zrpc/connection.py", line 638, in wait
    asyncore.poll(delay, self._singleton)
  File "/usr/local/lib/python2.4/asyncore.py", line 122, in poll
    r, w, e = select.select(r, w, e, timeout)

The other threads of the ZEO client are waiting for the hanging thread to release the storage lock so that they can acquire it:

File "/usr/local/www/zope-2.9.6/lib/python/ZEO/ClientStorage.py", line 760, in loadEx

When I connect to the ZEO server monitor I can see an increasing number of reads (probably from the other ZEO Clients).

I've set transaction-timeout 15.

How to I dig further to resolve this?

zeo.conf partly below:

  address 8200
  read-only false
  invalidation-queue-size 100
  # pid-filename $INSTANCE/var/ZEO.pid
  monitor-address 8201
  transaction-timeout 15

<filestorage 1>
  path $INSTANCE/var/Data.fs

%import tempstorage
<temporarystorage temp>
  name temporary storage for sessioning


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