AMB Disconnecting After Connecting Error

[J Benson]

Hello Experts, 

I have a MID Server that is still listed as 'up' but is repeatedly spawning the error 'AMB Disconnecting After Connecting'. I've already followed the proposed fixes in this post.  

Can anyone shed some light on possible causes?

Regards,

James B

[HeyMarkWarmack]

Subscribed to follow.  WashDC patch4-hotfix1b MID servers, half of DEV MID Servers with the same issue, half are good. Not happening in Test or Prod, weird.  Tried Reboot, tried invalidate/validate and rekey.  I didn't check if there were Unresolved Issues before installing the 'Agent Client Collector Framework' in DEV, but would like to resolve.

[HeyMarkWarmack]

Did your AMB error clear?  I recently have two MIDs that got this 'error', but MIDs are Up.  Can't tell if this is a temporary communication issue or if I should address right away?  

Anyone know?

[saint]

Did you find any solution on it?

[AJ-TechTrek]

Hi @J Benson ,

Here’s a complete, ServiceNow-specific troubleshooting + solution guide for your MID Server shows as ‘up’ but throws repeated AMB Disconnecting After Connecting errors issue.
These steps are based on practical field experience and best practices, beyond what’s typically listed in docs or community posts.
 
1.Validate MID Server’s network connectivity
* Make sure the MID Server host can reach your ServiceNow instance over:
* HTTPS (default: https://INSTANCE.service-now.com)
* WebSocket ports (used by AMB: port 443 over HTTPS)
* Check firewall or proxy logs to see if connections are being intermittently dropped or refused.

2.Check for multiple MID Servers with same name or credentials
* Go to MID Servers > Servers in ServiceNow and ensure no duplicate entries.
* Make sure only one MID Server is using that name + same service account.
* Duplicate MIDs can fight over the AMB channel and force repeated disconnects.

3.Confirm correct MID Server version & compatibility
* MID Server and instance must be on compatible family releases (e.g., Vancouver MID must connect to Vancouver instance).
* Upgrade the MID Server if your instance was upgraded recently.

4.Review MID Server logs in detail
* On the MID host, look at:
* agent.log
* wrapper.log
* Search for:
AMBClient - Disconnecting after connecting
* Check if the disconnect is immediately followed by reconnect, or happens after a fixed period (might indicate network idle timeout or reverse proxy).

5.Validate AMB (Asynchronous Message Bus) settings
* Properties to check in ServiceNow:
* glide.amb.websocket.enabled – Should be true (default)
* glide.amb.message_bus – Should be set to websocket (default)
* Restart MID after changing any property.

6. Proxy & SSL
If the MID connects through a proxy:
* Validate the proxy allows WebSocket upgrade headers (Connection: Upgrade and Upgrade: websocket).
* Confirm correct configuration in config.xml or MID Server settings.
* Ensure valid SSL certificates; self-signed or expired certs often cause AMB to drop connections.

7. Check system properties related to clustering / AMB
* Go to sys_properties.list and search for:
* glide.amb.client.heartbeat.interval
* glide.amb.client.heartbeat.timeout
* These control heartbeat frequency; defaults usually work, but in heavily firewalled or high latency environments, these may need tuning.

8.Check for JVM memory or CPU issues
* If the MID Server runs on an overloaded host or under-sized VM, the Java process can drop AMB connections under load.
* Monitor CPU & memory usage, especially during discovery or large scheduled jobs.

Restart the MID Server cleanly
* Sometimes stale sessions cause repeated disconnects:
* Stop the MID Server service.
* Clear work/ and logs/ folders (optional but helps remove corrupted cache).
* Start service again.

9.🛠 If problem persists:
* Enable debug logging in MID Server (agent log level to DEBUG in config.xml).
* Collect:
* agent.log
* wrapper.log
* Open a HI case with ServiceNow support, attach logs, and explain what you've tried.

 
Please appreciate the efforts of community contributors by marking appropriate response as Mark my Answer Helpful or Accept Solution this may help other community users to follow correct solution in future.
 


Thank You
AJ - TechTrek with AJ
LinkedIn:- https://www.linkedin.com/in/ajay-kumar-66a91385/
YouTube:- https://www.youtube.com/@learnitomwithaj
ServiceNow Community MVP 2025