S_ST | Start/Stable state |
S_BT | Transition begun. Someone noticed an apparent membership change. |
S_TA | Transition acknowledged. Every node thought to be in the cluster has acknowledged the transition, (by sending a BT packet), or we've timed out waiting for them. |
S_US | Votes have been received, and we've been voted the transition leader. |
S_THEM | Votes have been received and another node was voted the transition leader. |
Below is the list of inputs to the finite state machine:
I_BT | Begin transition packet received, or transition event noted locally. |
I_RQBMP | Request for connectivity bitmap received. |
I_LBT | Last expected begin transition received, or timeout occurred. |
I_TIME | Timeout received |
I_VOTE | A vote was received from a node. More votes still expected. |
I_US | Final I_VOTE received (or timeout occurred), and we were elected |
I_THEM | Final I_VOTE received (or timeout occurred) and another node was elected transition leader. |
I_DONE | Transition complete signal from leader. |
The following are a list of actions the FSA takes:
A_BT | Send begin transition packet |
A_QBMR | Queue a request for a bitmap |
A_VOTE | Vote on what node should be transition leader |
A_RQBMP | Declare self winner by requesting a connectivity bitmap. |
A_DONE | Send out cluster membership bitmap. |