MID server unable to subscribe to AMB channel

[mark69]

We use a MID server, but the MID server log keeps giving these warnings:

ECCQueueMonitor.40 WARNING *** WARNING *** Reconnecting AMB channel..

ECCQueueMonitor.40 WARNING *** WARNING *** Unable to subscribe to AMB channel: /mid/server/77a7ba104fed1200b92af1728110c7dd

From the documentation I can understand the function of the AMB channel, but I cannot find any info on what could be causing connection to the channel to fail.

We use another MID server connected to a customers instance, and this one does not produce these warnings.

Both are hosted from the same machine, so the problem seems to be instance related.

Also, the MID server producing these warnings has a memory leak, and will eventually die with an out of memory message even though it is not actively used.

The other MID server has no memory leakage problems.

Both are fresh installs.

Any ideas?

The instances are different versions by the way. Helsinki for the one producing the warnings, Fuji for the other one.

[klopmas]

Hello Mark,

Here is the Problem that was open by Support for those facing this issue ::

PRB717454 ::"HttpClient" threads count growing on MID Server after AMB subscription failures; started after upgrading to Helsinki

Sam

[kclark1]

Hi Sam and everyone.

This thread is matching some symptoms we are seeing with a Linux MID server behind a proxy (lots of failed subscription messages followed by growing numbers of threads until the server falls over).   Any idea what the root cause might be? Is it caused by proxy traffic being blocked for the AMB subscription channel?

Any Insights would be helpful.

Cheers,

Kevin

[klopmas]

Hello Kevin,

I do not believe there is anything you can change in your proxy to help AMB establish the subscription.

This is a bug in ServiceNow AMB Client Java code as described by Problem PRB717454.

PRB717454   ::   After Helsinki upgrade, "OutOfMemoryError" occurs, and SCCM jobs are not being processed.   The fixed will be in Istanbul Patch 1 and Helsinki Patch 7.

You may want to open a ticket with SNOW Support and have them associate it with the problem.

You can also see this issue if the MID Server user has "Web service access only" checked on the sys_user record.

Sam

[kclark1]

Hi Sam,

Is this something that happens for every MID Server customer in Helsinki?   This is a pretty fresh Helsinki Instance and a brand new MID server that's never been set up before.   It would surprise me if MID Servers just don't work wholesale in Helsinki - I would imagine this would be a pretty major problem for ServiceNow, so there must be something unique to our configuration that is causing it not to work - otherwise no customers needing MID servers would be on Helsinki!

Cheers,

Kevin

[klopmas]

It seems to be happening to some MIDs that are configured to use a proxy on newer instances that are using the AMB client.

Sam