96 lines
2.1 KiB
Go
96 lines
2.1 KiB
Go
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package raft
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import (
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"hash/crc32"
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"fmt"
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"syscall"
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"bytes"
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"os"
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)
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//------------------------------------------------------------------------------
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//
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// Typedefs
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//
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//------------------------------------------------------------------------------
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// the in memory SnapShot struct
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type Snapshot struct {
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lastIndex uint64
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lastTerm uint64
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// cluster configuration.
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machineState int
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path string
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}
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// The request sent to a server to start from the snapshot.
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type SnapshotRequest struct {
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peer *Peer
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LeaderName string `json:"leaderName"`
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Snapshot *Snapshot `json:"snapShot"`
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}
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// The response returned from a server appending entries to the log.
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type SnapshotResponse struct {
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peer *Peer
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Term uint64 `json:"term"`
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Success bool `json:"success"`
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CommitIndex uint64 `json:"commitIndex"`
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}
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//------------------------------------------------------------------------------
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//
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// Constructors
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//
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//------------------------------------------------------------------------------
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// Creates a new Snapshot request.
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func NewSnapshotRequest(leaderName string, snapshot *Snapshot) *SnapshotRequest {
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return &SnapshotRequest{
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LeaderName: leaderName,
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Snapshot: snapshot,
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}
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}
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// Creates a new Snapshot response.
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func NewSnapshotResponse(term uint64, success bool, commitIndex uint64) *SnapshotResponse {
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return &SnapshotResponse{
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Term: term,
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Success: success,
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CommitIndex: commitIndex,
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}
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}
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func (ss *Snapshot) Save() error {
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// Write machine state to temporary buffer.
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var b bytes.Buffer
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if _, err := fmt.Fprintf(&b, "%v", ss.machineState); err != nil {
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return err
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}
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// Generate checksum.
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checksum := crc32.ChecksumIEEE(b.Bytes())
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// open file
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file, err := os.OpenFile(ss.path, os.O_CREATE|os.O_WRONLY, 0600)
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if err != nil {
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return err
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}
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// Write log entry with checksum.
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if _, err = fmt.Fprintf(file, "%08x\n%s\n%s\n%s", checksum, b.String(),
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ss.lastIndex, ss.lastTerm); err != nil {
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return err
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}
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// force the change writting to disk
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syscall.Fsync(int(file.Fd()))
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return err
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}
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func (ss *Snapshot) Remove() error {
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err := os.Remove(ss.path)
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return err
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}
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