Symptoms
Session hosts that are placed into Drain mode continue to receive user connections from the load balancer.
As a result:
Users are redirected to a session host that cannot accept new sessions.
New sessions fail to be created. Operations and end‑user access are disrupted.
This behavior is observed when sessions are reported in a Down (WTSDown) state but are still considered eligible targets by the load balancer.
Cause
By default, sessions that are in the Down (WTSDown) state are ignored and not reported to the Connection Broker.
When a host is in Drain mode, this can lead to an inconsistent view of session availability, allowing the load balancer to redirect users to a session host that is no longer able to accept connections.
Resolution
A workaround is available to control how sessions in the Down (WTSDown) state are handled until a permanent feature is implemented in a future version.
Configure the following registry key on the session host:
Path: HKLM\Software\WoW6432Node\Parallels\TSAgent\
Value ExcludeWTSDown (DWORD)
| Value | Behavior |
0 (Default) |
Maintains existing behavior. Sessions in the Down state are ignored and are not reported to the Connection Broker. |
| 1 |
Sessions in state down will be Removed (Not shown in the console but still visible by the qwinsta tool). |
| 2 |
Sessions in state down are shown in console but marked with state Down. Nothing will work on these sessions. |
After changing the value, restart the agent for the setting to take effect.
You can confirm that the setting was applied by locating a log entry similar to the following:
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