MSMQ worker issue

Hi VGuo,

The worker exhaustion you are experiencing daily is typically driven by application-level behaviors rather than file system restrictions, and I strongly advise against altering default access control lists on core operating system folders to try and resolve this. Modifying permissions within the System32 directory introduces unnecessary security risks to your infrastructure and should be reverted to baseline. The specific error indicating no workers are available, especially with a defined pool of five processes, heavily points to Windows Process Activation Service handling your MSMQ requests via IIS application pools.

When all five configured worker processes become unavailable, they are likely hanging due to unhandled application exceptions, thread deadlocks in your worker code, or entering a poison message loop where faulty messages are continually read and rejected but never cleared. You should inspect the Windows Event Viewer under the System logs for WAS-related Event ID 5002, which indicates an application pool is being automatically disabled due to rapid failures. To properly diagnose the internal thread state, generate a memory dump of the associated w3wp.exe process when the issue is actively occurring.

While investigating the worker process health, you can also monitor the default MSMQ storage directory located at C:\Windows\System32\msmq\storage to ensure the default one-gigabyte quota limit is not compounding the message processing failures. Utilize Performance Monitor alongside your application event logs to trace exactly where your code is hanging under load. Finally, ensuring your environment is running the latest Cumulative Update for Windows Server 2016 Datacenter build 14393 remains a necessary step to eliminate any patched regressions regarding the Net.Msmq listener adapter.

Hope this answer brought you some useful information. Should you have any questions, feel free to leave a comment.

On Windows Server 2016 Datacenter (build 14393), MSMQ “no worker available” or queues becoming inactive can be related to known MSMQ issues introduced by recent security updates.

For this OS, the December 2025 security update KB5071543 (OS Build 14393.8688) introduced changes to the MSMQ security model and NTFS permissions on C:\Windows\System32\MSMQ\storage. After that change, MSMQ users must have write access to this folder. If the MSMQ worker processes (or the account under which they run) do not have sufficient permissions, MSMQ operations can fail under load, leading to symptoms such as:

1. MSMQ queues becoming inactive.
2. Applications unable to write to queues.
3. Errors like “Insufficient resources to perform operation” or message file creation failures.

In a multi-worker configuration, this can surface as “no worker available” because MSMQ cannot create or write message files in the storage folder, so workers effectively cannot process messages.

To address this on Windows Server 2016:

1. Ensure the server is updated with the out-of-band fix released on or after December 18, 2025 (for example, KB5074974). This update resolves the MSMQ permission issue introduced by KB5071543.
2. After installing the latest cumulative update that includes this fix, reboot the server.
3. If the issue persists, verify that the service account(s) used by the MSMQ worker processes have the required NTFS write permissions to C:\Windows\System32\MSMQ\storage.

This combination (installing the post-December 2025 fix and ensuring correct folder permissions) is the supported way to resolve MSMQ worker/queue inactivity issues caused by the security model change.

References:

• December 9, 2025—KB5071543 (OS Build 14393.8688)
• Resolved issues in Windows 10, version 1607 and Windows Server 2016