Managers

Managers ensure there are enough workers doing the right jobs, and may also provide services. They do not use system resources, and instead leave that to the workers.

By default managers can communicate with the leader and the workers, but only the leader can communicate with other managers. Arbitrary combinations are possible, however.

Managers have three start-up modes:

Cold start

When an application is being started for the first time. It needs to deploy backup managers and worker netlets, and generally get everything off the ground. This manager becomes the leader.

Joining

When the service is already running. This manager needs to join the existing management group as a backup.

Warm start

When the service was running until all the managers died. In this mode the manager has to revive the situation by getting the last service state, updating workers, and generally get everything back on track. Warm start is triggered not by an administrator, but by one of the hosting services--it notices application failure and then warm starts it.

Beatrix offers a basic Manager class which needs plugins added before it becomes usable.