[zeromq-dev] epgm debugging help

[Steven McCoy]

On 28 April 2011 01:13, Tom Wilberding <tom at wilberding.com> wrote:

> Any suggestions on how to diagnose this further? Especially any tips for
> being able to log or inspect state within the ZMQ layer? Is there known
> behavior that would explain why ZMQ might "give up" and stop delivering
> to an epgm/SUB client.
>
>
You can perform a lot of tracing at the PGM layer if it helps.  The major
problem scenario is upon unrecoverable data loss, which the raising of
depends upon the PGM parameters which in ZeroMQ are quite relaxed.  Upon
unrecoverable data loss ZeroMQ will close and recycle the PGM socket similar
to a broken TCP ZeroMQ socket.

Tools available for debugging include Wireshark and tcpdump, the former can
decode PGM/UDP packets when configured appropriately.  There are also many
network monitoring systems like Rai Insight, other tools are available, that
provide passive analysis of reliable multicast traffic.  There is a pgmdump
utility within OpenPGM which mimics the PGM support in tcpdump but it is
very limited and only supports PGM/IP.

Other avenues of investigation include:

Enabling logging at the PGM layer and examining the trace ourput:

http://code.google.com/p/openpgm/wiki/OpenPgm5CReferenceErrorHandling

Running passive or active parallel subscribers to the traffic stream and
monitoring their state of the transport.  You can configure a PGM socket to
passively join a transport and not send NAKs or communicate in any manner.

Update ZeroMQ to send PGM logging to the ZeroMQ IPC logging socket and
monitor that.

Update ZeroMQ to monitor PGM state and report ala SNMP but via ZeroMQ
sockets.

Custom build ZeroMQ to enable the SNMP or HTTP monitoring interface inside
OpenPGM to monitor PGM state.

http://code.google.com/p/openpgm/wiki/OpenPgm5CReferenceMonitoringAndAdministration

-- 
Steve-o
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