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