Re: [External] Re: "Session detached by peer" when trying to re-establish lost connection

[Toralf Lund <to...@pgs.com>]

On 01/04/2019 22:33, Gordon Sim wrote:
> On 01/04/2019 12:54 pm, Toralf Lund wrote:
>> On 28/03/2019 15:56, Toralf Lund wrote:
>>>
>>> Hi,
>>>
>>> I have another question related to my recent post about trying to 
>>> re-establish lost connections. Recall that my system is set up 
>>> without automatic reconnect, but may do a "manual reconnect" via
>>>
>>>   qpid::Messaging connection(url);
>>>
>>>   ...
>>>
>>>   if(!connection.isOpen()) {
>>>     connection.open();
>>>   }
>>>
>>> and that this is sometimes triggered by an "internal disconnect" 
>>> accompanied by an exception with message "Failed to connect 
>>> (reconnect disabled)".
>>>
>>> Now, I just found that some of the reconnects are accompanied by a 
>>> "Session detached by peer" exception. I'm struggling a bit to find 
>>> out what exactly triggers this; the problems occur once every few 
>>> hours at a remote site, and I can't just start or stop or update the 
>>> software at any old time, so it's a bit hard to debug...
>>>
>> I just noticed that the broker log has something like
>>
>>     2019-04-01 11:11:42 [Broker] error Channel exception: session-busy:
>>     Session already attached:
>>     anonymous.c9a1f4cf-7427-4e77-8870-e118b099c6da
>> (/work/build/rpmbuild/BUILD/msat-qpid-cpp-1.36/msat-qpid-cpp-1.36.0/src/qpid/broker/SessionManager.cpp:55) 
>>
>>     2019-04-01 11:11:46 [Protocol] error Connection
>>     qpid.10.31.193.215:5672-10.31.192.61:35954 timed out: closing
>>
>> for most or all the reconnects. The first time-stamp seems to 
>> correspond to the connection open and "Session detached by peer" 
>> exception.
>>
>> Perhaps this means the broker still thinks the old connection is 
>> open, even though the client considers it as lost? And maybe the 
>> attempt to re-establish/re-use the old session with the new 
>> connection fails as a result of that?
>
> Correct. Does the broker log the loss of the connection, e.g. a timed 
> out notice? If so how does the time of that compare to the 
> session-busy error and to the client detecting the failed connection?

The broker also has a message saying "Connection ... timed out: 
closing". This occurs 4-5 seconds after the session-busy error, 
according to the timestamps.

- Toralf


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Re: Re: "Session detached by peer" when trying to re-establish lost connection

[Toralf Lund <to...@pgs.com>]

On 03/04/2019 09:32, Gordon Sim wrote:
> On 03/04/2019 7:32 am, Toralf Lund wrote:
>> The broker also has a message saying "Connection ... timed out: 
>> closing". This occurs 4-5 seconds after the session-busy error, 
>> according to the timestamps.
>
> So for some reason, the broker is deciding the connection is dead 4-5 
> seconds after the client has reconnected... what caused the client to 
> reconnect? Was there a timed out notice there as well?

The direct reason for the reconnect is that "connection::isOpen()" 
returns false on a connection that was successfully opened some time in 
the past. The connection status is checked periodically. The "reconnect" 
option is not set on the connection. Prior to getting a "false" 
isOpen(), an exception with message "Failed to connect (reconnect 
disabled)" is caught, typically while waiting for incoming messages. 
session::nextReceiver() is used for that purpose.

The broker log does not seem to have any messages related to the 
original issue.

- Toralf



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Re: [External] Re: "Session detached by peer" when trying to re-establish lost connection

[Gordon Sim <gs...@redhat.com>]

On 03/04/2019 7:32 am, Toralf Lund wrote:
> The broker also has a message saying "Connection ... timed out: 
> closing". This occurs 4-5 seconds after the session-busy error, 
> according to the timestamps.

So for some reason, the broker is deciding the connection is dead 4-5 
seconds after the client has reconnected... what caused the client to 
reconnect? Was there a timed out notice there as well?

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