Unfortunately, it's really hard to say. Possibilities include resource
contention, such as CPU or networking, anything in the middle, such as
load balancers, firewalls, etc., network or system configuration. I
heard of one a while back that ended up being connected to IP table
definition. Can't remember if that was related to docker containers or
full VMs. I've heard that there have been some common problems in some
VM environments, but I don't know what environments or issues
specifically. Maybe VMotion. Maybe the network gets overloaded,
especially between VMs. Or interactions between loads on different VMs.
I'm not as familiar with the current state, but in the past in other
environments I have seen more interference between VMs than expected.
It comes down to standard troubleshooting sorts of behavior. Try to
catch the problem. Gather information about different occurrences. Try
to isolate any commonalities. Isolate a system for reproduction.
You could try a different type of agent, such as an SSH Agent. The
behavior might be different. I've heard recently that Microsoft's SSHD
implementation works well.
Good luck on troubleshooting
Jeff
On 4/14/20 8:31 AM, 'monger_39' via Jenkins Users wrote:
Hi Jeff,
thx. Last week I disabled the ping-thread on master and slaves by
setting the interval to '-1'.
Unfortunately, over the weekend, again one of the slaves (even though
the jobs kept on running),
went into 'offline' mode. It seems indeed that this does not solve
the issue. Or, iow I think it means
that the disconnect was not caused by the ping-thread(s) timing out.
Which puts me to the challenge to figure out what could be this
'external someting' that you mention
that would break the remoting. And I honestly have no idea how to
tackle that yet.
The master, as well as the slave are Windows server VM's running 6
executor slots each. The
tests we are running heavily use TCP communication.
Any idea how to tackle this ?
thx, M.
On Thursday, April 9, 2020, 10:53:48 PM GMT+2, Jeff Thompson
<jthomp...@cloudbees.com> wrote:
On 4/7/20 11:46 PM, 'monger_39' via Jenkins Users wrote:
Hi,
in my Jenkins I am regularly facing master/slave connection drops with a
message like:
hudson.remoting.ChannelClosedException: Channel "unknown": Remote
call on JNLP4-connect connection from IP/IP:58344 failed.
The channel is closing down or has closed down.
Usually these are caused by something external to the Remoting
communication protocol. Most often by something in the system or
networking environment. Sometimes by some bad interaction between
plugins that ends up impacting the channel.
Your best approach is to figure out where these disconnects originate
and resolve the issue.
I have seen a lot of bug-reports on this. For most, a workaround is
advised by disabling the Ping-Thread through setting:
You should be cautious about changing the ping settings or disabling
it entirely. It can cause some weird and unexpected behaviors. If you
do change the settings, I recommend you change one thing at a time and
evaluate the results. If it doesn't make any difference, restore it to
its default setting.
And, is there also a slave setting for the timeoutvalue?
It depends on how you launch the agent. Remoting system properties are
described at
https://github.com/jenkinsci/remoting/blob/master/docs/configuration.md
(naming for all these settings does not look to be very consistent...)
Unfortunately, that's the case.
Jeff Thompson
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