What are Hung Threads and why is the StreamProcess terminating?
Article ID: CTX233590
Updated On:
Description
On PVS Servers StreamProcess Hung Threads can lead to poor performance, constant target re-connections and even full outages.
These Hung Threads are usually detected by looking at the Windows Application Event logs.
The following Events will be recorded:
| Level | Source | Id | Text |
| Error | StreamProcess | 11 | Detected one or more hung threads. |
| Error | StreamProcess | 11 | Terminating StreamProcess. |
| Information | StreamProcess | 10 | Stream Process Stopped |
What are StreamProcess Threads?
The StreamProcess executable handles all communication between the PVS Server and the Target Devices.
According to the "Threads per Port" configuration on the PVS Server, multiple Threads are created from the StreamProcess executable.
These threads handle the communication with the Target Devices.
These threads handle the communication with the Target Devices.
What exactly are Hung Threads?
A Hung Thread is a thread of the StreamProcess executable that is waiting on a resource to be available to continue its work with the Target Device
There are two resources that, when not available, will hang the thread
There are two resources that, when not available, will hang the thread
vDisk access: If there are any kind of Storage issues, such as communication with storage, permissions, Operating System problems, etc..., the Thread will hang waiting for the vDisk data to be available
Database access: Problems with the SQL Server or Network communication with the SQL Server will cause the Thread to hang while waiting for Database access
Database access: Problems with the SQL Server or Network communication with the SQL Server will cause the Thread to hang while waiting for Database access
Why and how is the StreamProcess terminated?
The StreamProcess Threads routinely notify of their health and what actions they are performing.
If StreamProcess detects that a Thread has not notified of its status for a long time, that Thread is deemed as possibly hung.
When StreamProcess detects there are a high number of Threads hung, the StreamProcess will terminate itself to force the Target Devices to reconnect to other PVS Servers.
If StreamProcess detects that a Thread has not notified of its status for a long time, that Thread is deemed as possibly hung.
When StreamProcess detects there are a high number of Threads hung, the StreamProcess will terminate itself to force the Target Devices to reconnect to other PVS Servers.
It's important to note that this action is performed to actually protect the stability of the Target Devices.
If StreamProcess is not terminated, and the Target Devices are not forced to reconnect to other PVS Servers, then the Target Devices will potentially hang causing an interruption in service.
If StreamProcess is not terminated, and the Target Devices are not forced to reconnect to other PVS Servers, then the Target Devices will potentially hang causing an interruption in service.
The StreamService will then detect that the StreamProcess has terminated and it will proceed to start the StreamProcess again.
What to do if you encounter Events in the Windows Event Logs identifying Hung Thread:
There are a few basic reasons for a StreamProcess Thread to become hung.
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Inability to access the vDisk or the Storage
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Inability to access the PVS Database
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PVS Database may be out of space
Engage the Storage, Network and DBA teams to check the health of those system and resource availability
You can check TCP/IP connectivity to SQL Server by using telnet.
Note that SQL database does not grow slowly, but expands by a pre-configured amount. Inspect the Files property of the PVS database to find the location of the database file and the 'Autogrowth/Maxsize' value.
Confirm all the Anti Virus Exclusions are configured as per the following Citrix Article: https://support.citrix.com/article/CTX124185
Check if there's a pattern to the occurrence of the Events in the Event Logs. For example if there are Hung Threads every night at the same time, check if there are Backup processes that might impact Storage Access or Maintenance procedures
To eliminate the possibility of issues with the Operating System, reboot the PVS Servers
If the issue persists, contact Citrix Support to capture diagnostic data and further narrow down the actual root cause of the issue.
You can check TCP/IP connectivity to SQL Server by using telnet.
Note that SQL database does not grow slowly, but expands by a pre-configured amount. Inspect the Files property of the PVS database to find the location of the database file and the 'Autogrowth/Maxsize' value.
Confirm all the Anti Virus Exclusions are configured as per the following Citrix Article: https://support.citrix.com/article/CTX124185
Check if there's a pattern to the occurrence of the Events in the Event Logs. For example if there are Hung Threads every night at the same time, check if there are Backup processes that might impact Storage Access or Maintenance procedures
To eliminate the possibility of issues with the Operating System, reboot the PVS Servers
If the issue persists, contact Citrix Support to capture diagnostic data and further narrow down the actual root cause of the issue.
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