Symptoms

On attempt to disable webspace in POA in task manager task fails with the following error:

Task ID 
6280497
Queue name  
domain_service14110
Task name   
Stop virtual web server 1234 on host 'WINWEB01.domain.tld' (host_id=123, sub_id=1009995, domain=d1009995.domain.tld, w_id=102416).
Task description    
Stop virtual web server 8515 on host 'WINWEB01.domain.tld' (host_id=123, sub_id=1009995, domain=d1009995.domain.tld, w_id=102416).
Subscription ID 
1009995
Queue status    
Failed
Start not earlier than  
May-26-2014 08:17
Method name 
taskSetWebSiteState on OBJREF:iis:0:getDomainService:14110
Last execution output   
Destination host 'WINWEB01.domain.tld' (#123), IP '10.8.9.41' : Provisioning request failed. An attempt was made to load a program with an incorrect format. 

<response><errorContext description="Could not load file or assembly 'System.Transactions.dll' or one of its dependencies. An attempt was made to load a program with an incorrect format." code="0x8007000b" executeSeqNo="1"><errorSource namespace="SynchronizationProvider" procedure="LockHostOperations"/></errorContext></response

Cause

Actually, assembly can not be loaded on MPS server where corresponding request should be executed. Some services may have locked assembly.

Resolution

  1. find which exact MPS server is used by checking poa.log file on WINWEB server. Example: 

    May 26 15:21:00 WINWEB01 : INF [task:6280497:25527 457:2444:af8 pleskd]: [task:6280497 Plesk::MPFClient::MPFClientImpl::processRequest] MPF request executed via legacy mode on node 'MPS01'
May 26 15:21:00 WINWEB01 : INF [task:6280497:25527 457:2444:af8 pleskd]: [task:6280497 Plesk::MPFClient::MPFClientImpl::runRequest] MPF request will be executed on node 'MPS01'
May 26 15:21:00 WINWEB01 : DBG [task:6280497:25527 457:2444:af8 pleskd]: Mpf request error: <
May 26 15:21:00 WINWEB01 : DBG [task:6280497:25527 457:2444:af8 pleskd]: Mpf request response: An attempt was made to load a program with an incorrect format. [<response><errorContext description="Could not load file or assembly 'System.Transactions.dll' or one of its dependencies. An attempt was made to load a program with an incorrect format." code="0x8007000b" executeSeqNo="1"><errorSource namespace="SynchronizationProvider" procedure="LockHostOperations"/></errorContext></response>]
  2. restart MPS server in order to re-initialize services and resubmit the task

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