User Profiles Sync - Event Viewer Errors

Question

While I'm not seeing any actual negative impact on the farm, I constantly get the following errors throughout the day (tied to syncs I believe) and would very much like to remedy them if possible:
Error type: Critical
Event ID: 5555
Task Category: User Profiles
Failure trying to synch web application <GUID>, ContentDB <GUID> Exception message was System.Data.SqlException: Lock request time out period exceeded.
Login failed for user '<Domain>\<User>'.
A severe error occurred on the current command.  The results, if any, should be discarded.
Error type: Critical
Event ID: 5555
Task Category: User Profiles
Failure trying to synch web application <GUID>, ContentDB <GUID> Exception message was System.InvalidOperationException: Operation is not valid due to the current state of the object.
Error type: Critical
Event ID: 6398
Task Category: Timer
The Execute method of job definition Microsoft.SharePoint.Administration.SPSqmTimerJobDefinition (ID <GUID>) threw an exception. More information is included below.
Data is Null.  This method or property cannot be called on Null values.
Error type: Critical
Event ID: 6398
Task Category: Timer
The Execute method of job definition Microsoft.Office.Server.Administration.UserProfileApplication+LanguageSynchronizationJob (ID <GUID>) threw an exception. More information is included below.
Lock request time out period exceeded.
Login failed for user '<Domain>\<User>'
A sever error occurred on the current command.  The results, if any, should be discarded.
Error type: Error
Event ID: 5586
Task Category: Database
Unknown SQL Exception 1222 occurred. Additional error information from SQL Server is included below.
Lock request time out period exceeded.
Login failed for user '<Domain>\<User>'
A sever error occurred on the current command.  The results, if any, should be discarded.
Additionally, the following error appear on the Database side.
Error type: Information
Event ID: 18456
Task Category: Logon
Login failed for user '<Domain>\<User>'. Reason: An exception was raised while revalidating the login on the connection. Check for previous errors. [CLIENT: <IP>]
Error type: Error
Event ID: 18056
Task Category: Server
The client was unable to reuse a session with SPID <X>, which had been reset for connection pooling.  The failure ID is 29. This error may have been caused by an earlier operation failing. Check the logs for failed operation immediately before this
error message.
I've tried to troubleshoot each of these errors independently hoping that it is one that is causing them all but so far nothing has worked.  The "Login failed" stood out to me the most but that account is the farm account and I've verified
the credentials and there are no other login failed type errors.  Again, the syncs themselves appear to be successful but these errors always occur.  Any help would be most appreciated.

Answer 1

And you did the last part also?
"Finally, and I’m not sure if this is necessary, but I read that you should change timer job “Timer Service Recycle” (Central Administration –> Job Definitions) to run at 06:30 PM.  This last step can be done through Central Administration. 
After doing this my errors went away.  I did however need to run a full user profile synchronization by going to Central Administration –> Manage Profile Service: SharedServicesSearch_UserProfile –> Start Profile Synchronization"
Sounds like a good reason, that the timer job runs at the same time as the application pool recycles, thus causing the connection to abort. Then retrying the connection, but a different ID, causing a lock to happen.
Besides that, it can be hard to say, as setting up the User Profile service application using the Wizard, can do some strange things :/