open-consul/agent/consul/fsm/snapshot.go

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package fsm
import (
"fmt"
"time"
"github.com/armon/go-metrics"
"github.com/hashicorp/consul/agent/consul/state"
"github.com/hashicorp/consul/agent/structs"
"github.com/hashicorp/go-msgpack/codec"
"github.com/hashicorp/raft"
)
// snapshot is used to provide a snapshot of the current
// state in a way that can be accessed concurrently with operations
// that may modify the live state.
type snapshot struct {
state *state.Snapshot
}
// snapshotHeader is the first entry in our snapshot
type snapshotHeader struct {
// LastIndex is the last index that affects the data.
// This is used when we do the restore for watchers.
LastIndex uint64
}
// persister is a function used to help snapshot the FSM state.
type persister func(s *snapshot, sink raft.SnapshotSink, encoder *codec.Encoder) error
// persisters is a list of snapshot functions.
var persisters []persister
// registerPersister adds a new helper. This should be called at package
// init() time.
func registerPersister(fn persister) {
persisters = append(persisters, fn)
}
// restorer is a function used to load back a snapshot of the FSM state.
type restorer func(header *snapshotHeader, restore *state.Restore, decoder *codec.Decoder) error
// restorers is a map of restore functions by message type.
var restorers map[structs.MessageType]restorer
// registerRestorer adds a new helper. This should be called at package
// init() time.
func registerRestorer(msg structs.MessageType, fn restorer) {
if restorers == nil {
restorers = make(map[structs.MessageType]restorer)
}
if restorers[msg] != nil {
panic(fmt.Errorf("Message %d is already registered", msg))
}
restorers[msg] = fn
}
// Persist saves the FSM snapshot out to the given sink.
func (s *snapshot) Persist(sink raft.SnapshotSink) error {
defer metrics.MeasureSince([]string{"fsm", "persist"}, time.Now())
// Write the header
header := snapshotHeader{
LastIndex: s.state.LastIndex(),
}
encoder := codec.NewEncoder(sink, msgpackHandle)
if err := encoder.Encode(&header); err != nil {
sink.Cancel()
return err
}
// Run all the persisters to write the FSM state.
for _, fn := range persisters {
if err := fn(s, sink, encoder); err != nil {
sink.Cancel()
return err
}
}
return nil
}
func (s *snapshot) Release() {
s.state.Close()
}