NewFSM returns new FSM implementation based on initial state.

StateDestroyed State of worker, when no need to allocate new one.

StateErrored - error StateImpl (can't be used).

StateInactive - no associated process.

StateInvalid - indicates that WorkerProcess is being disabled and will be removed.

StateKilling - process is being forcibly stopped.

StateMaxJobsReached State of worker, when it reached executions limit.

StateReady - ready for job.

StateStopped - process has been terminated.

StateStopping - process is being softly stopped.

StateWorking - working on given payload.

Fsm is general https://en.wikipedia.org/wiki/Finite-state_machine to transition between worker states.