Ldap proxy Connection lost

Dear all,
we configured two ldap proxies on a Ubuntu 18.04.4 LTS. It is a test enviroment. After start of the application and the ldap proxies everything works fine but after a couple of minutes the proxy lost the connection to his backend.

Start of proxy:

2020-05-15T09:51:09+0200 [-] ProxyServerFactory starting on 1389

Lost of connection:

2020-05-15T10:56:40+0200 [pi_ldapproxy.proxy#info] BindRequest for 'wasldap', passing through ...

2020-05-15T10:56:40+0200 [twisted.internet.defer#critical] Unhandled error in Deferred:
2020-05-15T10:56:40+0200 [twisted.internet.defer#critical]
        Traceback (most recent call last):
          File "/opt/ldapproxy/buildenv/lib/python2.7/site-packages/twisted/internet/defer.py", line 651, in _runCallbacks
            current.result = callback(current.result, *args, **kw)
          File "/opt/ldapproxy/buildenv/lib/python2.7/site-packages/ldaptor/protocols/ldap/proxybase.py", line 132, in _forwardRequestToProxiedServer
            d.addCallback(forwardit, reply)
          File "/opt/ldapproxy/buildenv/lib/python2.7/site-packages/twisted/internet/defer.py", line 319, in addCallback
          File "/opt/ldapproxy/buildenv/lib/python2.7/site-packages/twisted/internet/defer.py", line 308, in addCallbacks
        --- <exception caught here> ---
          File "/opt/ldapproxy/buildenv/lib/python2.7/site-packages/twisted/internet/defer.py", line 651, in _runCallbacks
            current.result = callback(current.result, *args, **kw)
          File "/opt/ldapproxy/buildenv/lib/python2.7/site-packages/ldaptor/protocols/ldap/proxybase.py", line 126, in forwardit
          File "/opt/ldapproxy/buildenv/lib/python2.7/site-packages/ldaptor/protocols/ldap/ldapclient.py", line 129, in send_multiResponse
            msg = self._send(op)
          File "/opt/ldapproxy/buildenv/lib/python2.7/site-packages/ldaptor/protocols/ldap/ldapclient.py", line 77, in _send
            raise LDAPClientConnectionLostException()
        ldaptor.protocols.ldap.ldapclient.LDAPClientConnectionLostException: Connection lost

2020-05-15T10:57:00+0200 [pi_ldapproxy.proxy#info] 'LDAPAbandonRequest' received, rejecting.

You see the request and after 20sec the application reach her timeout and gives up.
After restart of the proxy every work fine again.
As further info: between proxy and backend is a firewall.

I hope someone can help.
Regards Jörg

Hi @trebra,

if you suspect the firewall to cause this problem: did you check the firewall log? Did you try to place all components in some subnet without firewall in-between?

Best regards,

Henning Hollermann