[teiid-issues] [JBoss JIRA] Commented: (TEIID-616) Start time of the system could be incorrect in rare cases where processes are brought down and back up

[Larry O'Leary (JIRA)]

    [ https://jira.jboss.org/jira/browse/TEIID-616?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12468932#action_12468932 ] 

Larry O'Leary commented on TEIID-616:
-------------------------------------

Do process have a reliable method of checking to see if any other processes are running?  If so, the way I would imagine it is like this:

Scenario 1:
mmprocess[1]: Started
mmprocess[1]: Are any other processes running?
mmprocess[1]: The answer appears to be no.  Set system start-up to: NOW()


Scenario 2:
mmprocess[1]: Started
mmprocess[1]: Are any other processes running?
mmprocess[1]: The answer appears to be no.  Set system start-up to: NOW()
mmprocess[2]: Started
mmprocess[2]: Are any other processes running?
mmprocess[2}: Appears mmprocess[1] is running.  Do not touch system start-up time.


Scenario 3:
mmprocess[1]: Started
mmprocess[1]: Are any other processes running?
mmprocess[1]: The answer appears to be no.  Set system start-up to: NOW()
mmprocess[2]: Started
mmprocess[2]: Are any other processes running?
mmprocess[2}: Appears mmprocess[1] is running.  Do not touch system start-up time.
mmprocess[1]: Shutting Down
mmprocess[1]: Started
mmprocess[1]: Are any other processes running?
mmprocess[1]: Appears mmprocess[2] is running.  Do not touch system start-up time.



Now, the only possible problem I can see is when starting up the system or bouncing the system.  In such a case, processes are being started concurrently and it is possible that by the time mmprocess[1] asks if any other processes are running, mmprocess[2] has already started and system start-up won't get set.

Scenario 4:
mmprocess[1]: Started
mmprocess[2]: Started
mmprocess[2]: Are any other processes running?
mmprocess[1]: Are any other processes running?
mmprocess[1]: Appears mmprocess[2] is running.  Do not touch system start-up time.
mmprocess[2}: Appears mmprocess[1] is running.  Do not touch system start-up time.


So, we would need a method to address scenario 4.  My guess is that a process won't register itself as running until after it has checked to see if any other processes are running.  In this case it creates a new issue which might not be so bad:

Scenario 5:
mmprocess[1]: Are any other processes running?
mmprocess[2]: Are any other processes running?
mmprocess[2]: The answer appears to be no.  Set system start-up to: NOW()
mmprocess[1]: The answer appears to be no.  Set system start-up to: NOW()
mmprocess[2]: Started
mmprocess[1]: Started


As you can see, the start-up time will be set by all processes that think they are the only running process.  This will result in the start-up time not being as precise but we are talking milliseconds in most cases and on a very slow system, maybe a few seconds.  Not too bad if you ask me.

> Start time of the system could be incorrect in rare cases where processes are brought down and back up
> ------------------------------------------------------------------------------------------------------
>
>                 Key: TEIID-616
>                 URL: https://jira.jboss.org/jira/browse/TEIID-616
>             Project: Teiid
>          Issue Type: Bug
>          Components: AdminApi, Server
>            Reporter: Van Halbert
>            Assignee: Steven Hawkins
>            Priority: Minor
>             Fix For: 6.1.1
>
>
> The system start time is determined by the Eldest Process start time.   This is not a 100% guaranteed to be true in all cases.   In a rare cases where proceses are brought down and backup, the oldest process start time might not represent how long the system had actually been running.

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