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41 lines
1.4 KiB
Go
41 lines
1.4 KiB
Go
package raft
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import (
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"io"
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)
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// FSM provides an interface that can be implemented by
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// clients to make use of the replicated log.
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type FSM interface {
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// Apply log is invoked once a log entry is committed.
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// It returns a value which will be made available in the
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// ApplyFuture returned by Raft.Apply method if that
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// method was called on the same Raft node as the FSM.
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Apply(*Log) interface{}
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// Snapshot is used to support log compaction. This call should
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// return an FSMSnapshot which can be used to save a point-in-time
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// snapshot of the FSM. Apply and Snapshot are not called in multiple
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// threads, but Apply will be called concurrently with Persist. This means
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// the FSM should be implemented in a fashion that allows for concurrent
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// updates while a snapshot is happening.
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Snapshot() (FSMSnapshot, error)
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// Restore is used to restore an FSM from a snapshot. It is not called
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// concurrently with any other command. The FSM must discard all previous
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// state.
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Restore(io.ReadCloser) error
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}
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// FSMSnapshot is returned by an FSM in response to a Snapshot
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// It must be safe to invoke FSMSnapshot methods with concurrent
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// calls to Apply.
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type FSMSnapshot interface {
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// Persist should dump all necessary state to the WriteCloser 'sink',
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// and call sink.Close() when finished or call sink.Cancel() on error.
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Persist(sink SnapshotSink) error
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// Release is invoked when we are finished with the snapshot.
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Release()
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}
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