88 lines
3 KiB
Go
88 lines
3 KiB
Go
package raft
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// LogType describes various types of log entries.
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type LogType uint8
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const (
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// LogCommand is applied to a user FSM.
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LogCommand LogType = iota
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// LogNoop is used to assert leadership.
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LogNoop
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// LogAddPeerDeprecated is used to add a new peer. This should only be used with
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// older protocol versions designed to be compatible with unversioned
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// Raft servers. See comments in config.go for details.
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LogAddPeerDeprecated
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// LogRemovePeerDeprecated is used to remove an existing peer. This should only be
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// used with older protocol versions designed to be compatible with
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// unversioned Raft servers. See comments in config.go for details.
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LogRemovePeerDeprecated
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// LogBarrier is used to ensure all preceding operations have been
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// applied to the FSM. It is similar to LogNoop, but instead of returning
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// once committed, it only returns once the FSM manager acks it. Otherwise
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// it is possible there are operations committed but not yet applied to
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// the FSM.
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LogBarrier
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// LogConfiguration establishes a membership change configuration. It is
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// created when a server is added, removed, promoted, etc. Only used
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// when protocol version 1 or greater is in use.
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LogConfiguration
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)
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// Log entries are replicated to all members of the Raft cluster
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// and form the heart of the replicated state machine.
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type Log struct {
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// Index holds the index of the log entry.
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Index uint64
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// Term holds the election term of the log entry.
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Term uint64
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// Type holds the type of the log entry.
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Type LogType
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// Data holds the log entry's type-specific data.
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Data []byte
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// Extensions holds an opaque byte slice of information for middleware. It
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// is up to the client of the library to properly modify this as it adds
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// layers and remove those layers when appropriate. This value is a part of
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// the log, so very large values could cause timing issues.
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//
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// N.B. It is _up to the client_ to handle upgrade paths. For instance if
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// using this with go-raftchunking, the client should ensure that all Raft
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// peers are using a version that can handle that extension before ever
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// actually triggering chunking behavior. It is sometimes sufficient to
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// ensure that non-leaders are upgraded first, then the current leader is
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// upgraded, but a leader changeover during this process could lead to
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// trouble, so gating extension behavior via some flag in the client
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// program is also a good idea.
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Extensions []byte
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}
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// LogStore is used to provide an interface for storing
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// and retrieving logs in a durable fashion.
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type LogStore interface {
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// FirstIndex returns the first index written. 0 for no entries.
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FirstIndex() (uint64, error)
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// LastIndex returns the last index written. 0 for no entries.
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LastIndex() (uint64, error)
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// GetLog gets a log entry at a given index.
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GetLog(index uint64, log *Log) error
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// StoreLog stores a log entry.
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StoreLog(log *Log) error
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// StoreLogs stores multiple log entries.
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StoreLogs(logs []*Log) error
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// DeleteRange deletes a range of log entries. The range is inclusive.
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DeleteRange(min, max uint64) error
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}
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