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Application server
It is a cluster resource used to control an application that must be kept highly available. It includes start and stop scripts. Output from these scripts will be logged in the hacmp.out file, if "set -x" is defined within the script. The exit code from the script will be monitored by PowerHA.
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Application Monitor


Once the application is started, there is a stabilization period, where appl. monitoring does not attempt to determine if the appl. is alive or not. This is called the stabilization period. Once the stabilization period has expired the appl. monitor is executed.
In long running mode, the monitor periodically checks that the application is running successfully. In startup mode only at startup.


If the appl. detected as failed, the retry counter is examined. If it is not zero, it is decremented and an appl. cleanup and restart is attempted. This process continnues until the retry counter is zero.
If retry counter reached 0 and the appl. failed again the failover action is examined.

As a protection mechanism, prior to invoking the application server start script, the cluster manager uses an application monitor to determine the status of the application

You can define Proces Appl. Monitoring (which will check if a process is running) or Custom Appl. Monitoring (which is a user defined script and its exit code will be checked by HACMP).

Process Application Monitoring Config:
Ext. Conf. -> Ext. Resources ->Conf. HACMP Appl. Servers -> Conf. HACMP Appl. Mon. ...

Process Monitor:(the values are in seconds)

* Monitor Name                                       [X11_APPL]
* Application Server(s) to Monitor                                                                                                                                            
* Monitor Mode                                       [Long-running monitoring]                                                                                                
* Processes to Monitor                               [xxx]
* Process Owner                                      [root]
  Instance Count                                     [1]                                                                                                                        
* Stabilization Interval                             [30]                   
* Restart Count                                      [3]                   
  Restart Interval                                   [66]   
* Action on Application Failure                      [fallover]                                                                                                                 
  Notify Method                                      []
  Cleanup Method                                     [/usr/local/scripts/cluster/X11_stop.ksh]
  Restart Method                                     [/usr/local/scripts/cluster/X11_start.ksh]


Processes to Monitor: give th name of the process from the output of ps -el (not ps -ef)
Stabilization Interval: The length of time the monitor will wait before resuming monitoring
Restart Count: The maximum times the application will be (re)started (the Failure Counter is connected with it), if it is not successful, then Action on Application Failure will be.
Restart Interval: the elapsed time the application must run before the Failure Counter is reset.
            If the Restart Interval time is reached the Failure Count is reset to 0.
            (is the time during which attempts will be made to restart the application)
Monitor Inetrval: (this is only at custom monitor) time between execution of the monitor event to see if the appl. is running.

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Suspend/Resume Application monitoring:
to suspend:
smitty hacmp -> System Management (C-SPOC) -> HACMP Resource Group and Application Management -> Suspend/Resume Application Monitoring - > Suspend Application Monitoring

to resume:
smitty hacmp -> System Management (C-SPOC) -> HACMP Resource Group and Application Management -> Suspend/Resume Application Monitoring - > Resume Application Monitoring

19 comments:

  1. thanks that was a good piece of learning i did today.

    regards
    rahul

    ReplyDelete
  2. Great info it is very useful ...

    ReplyDelete
  3. Nice definistion for Application Monitor..Thank you sir

    ReplyDelete
  4. Hi Balazs,

    Plz do mention command line to start/stop application monitoring...

    ReplyDelete
    Replies
    1. Hi,

      if I would know, I would definitely mention it :)

      Delete
  5. Nice piece of info
    ..
    I have a little question , do we need to have customize shall script to monitor HACMP ?

    Regards
    Manoj

    ReplyDelete
    Replies
    1. to monitor "application server" not HACMP, type error !

      in the Example provided by you i could see there is no option of defining application monitoring script !

      Please clarify..

      Delete
    2. Hi, yes, with custom monitoring you can use any scripts to check application availability.
      From HACMP Redbook:
      Custom monitors check the health of an application with a user-written custom monitor method... This gives the
      administrator the freedom to check for anything that can be defined as a determining factor in an application’s health.... A return code from the user-written monitor of zero (0) indicates that application is healthy, no further action is taken. A non-zero return code indicates that the application is not healthy and recovery actions are to take place."

      Delete
  6. If the last topic, u mentioned Resume/Suspend Monitoring, that means if you suspend the monitoring then it will simply failover the application to other node I guess?

    ReplyDelete
    Replies
    1. If you suspend the monitoring, you can do anything on the server (kill processes, stop network,,,), cluster will not failover.

      Delete
  7. can we have 2 application servers (SAP & MQ FTE) defined for Single Resource Group

    ReplyDelete