question: private InstanceState checkIn ( ) { final InstanceState state ; try { logger . debug ( "Getting instance state for {}" , instanceId ) ; state = getInstanceState ( instanceId ) ; } catch ( ResourceException e ) { logger . info ( "Error retrieving instance state for {}" , instanceId ) ; return null ; } try { if ( firstCheckin ) { state . updateStartup ( ) ; state . clearShutdown ( ) ; firstCheckin = false ; } switch ( state . getState ( ) ) { case InstanceState . STATE_RUNNING : state . updateTimestamp ( ) ; break ; case InstanceState . STATE_DOWN : state . setState ( InstanceState . STATE_RUNNING ) ; logger . debug ( "Instance {} state changing from {} to {}" , instanceId , InstanceState . STATE_DOWN , InstanceState . STATE_RUNNING ) ; state . updateTimestamp ( ) ; break ; case InstanceState . STATE_PROCESSING_DOWN : logger . debug ( "Instance {} is in state {}, waiting for recovery attempt to finish" , instanceId , state . getState ( ) ) ; return state ; } updateInstanceState ( instanceId , state ) ; logger . debug ( "Instance {} state updated successfully" , instanceId ) ; } catch ( ResourceException e ) { if ( e . getCode ( ) != ResourceException . CONFLICT ) { logger . warn ( "Error updating instance timestamp" , e ) ; } else { logger . info ( "Failed to set this instance state to {}" , state . getState ( ) ) ; return null ; } } return state ; }
target:  Updates the timestamp for this instance in the instance check-in map.