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As a rule, any Master Controller is in charge of running its own tasks. In addition, it takes over Failover tasks for which the owner is not visibly producing heartbeats indicating its health, and where no other healthy Master Controllers with better failover priority (lower value) are available. Each Master Controller has its own list of failover priorities, deciding which Master Controller becomes the next top MC in a Failover situation. For best behaviour, it is recommended to list all Master Controllers that are visible in the list of Failover Priorities. In order to prevent the local Master Controller becoming the top Master Controller for taking over its own "Suspend duty in Failover" Tasks in case of a manual failover,  it is common to specify all other Master Controllers first, and put the local Master Controllers' Failover Priority last.

Example:

MCFailover priorities order (ordered highest rank to lowest rank)Example
MC00
MC01,
MC01< MC02
,
< MC00

Three Master Controllers in a single synchronization pool with:

  1. MC00 and MC01
owning failover tasks,
  1. both own failover tasks.
  2. MC00 and MC01 take over from each other when the other is in Failover or down.
  3. MC02 has to take over from MC00 and MC01 when MC00
or
  1. and MC01 are
gone
  1. down or failed over.
  2. MC02 is not owning any Failover Tasks.

Each MC that is not in Failover mode can become top MC for Failover Tasks owned by other MCs as soon as no recent heartbeats (5 minutes threshold) are received from higher ordered remote MCs.



MC01MC00
,
< MC02
,
< MC01
MC02MC00
,
< MC01
,
< MC02


Status MC00Status MC01Status MC02Remarks
OKOKOKEach MC runs its own Tasks. No Failover Tasks are taken over.
Failed overOKOKMC01 runs additionally all Failover Task from MC00. MC00 will no longer run its own "Suspend duty in Failover" Tasks.
OKFailed overOKMC00 runs additionally all Failover Task from MC01. MC01 will no longer run its own "Suspend duty in Failover" Tasks.
OKOKFailed overNo visible effect since MC02 does not own Failover Tasks. MC02 is not no longer allowed to take over Failover tasks from other MCs.
Failed overFailed overOKMC02 runs additionally all Failover Task from MC00 and MC01. MC00 and MC01 will no longer run their own "Suspend duty in Failover" Tasks.
Failed overOKFailed overMC01 runs additionally all Failover Task from MC00. MC00 will no longer run its own "Suspend duty in Failover" Tasks. MC02 does not own Failover Tasks. MC02 is not is no longer allowed to take over Failover tasks from other MCs.
OKFailed overFailed overMC00 runs additionally all Failover Task from MC01. MC01 will no longer run its own "Suspend duty in Failover" Tasks. MC02 is not no longer allowed to take over Failover tasks from other MCs.
Failed overFailed overFailed overMC00 and MC01 will run their own "Suspend duty in Failover" Tasks since have each MC has become the top MC for their own Failover Tasks. The MCs are no longer allowed to take over Failover tasks from other MCs.