terraform/internal/states/remote/state.go

245 lines
6.6 KiB
Go

package remote
import (
"bytes"
"fmt"
"sync"
uuid "github.com/hashicorp/go-uuid"
"github.com/hashicorp/terraform/internal/states"
"github.com/hashicorp/terraform/internal/states/statefile"
"github.com/hashicorp/terraform/internal/states/statemgr"
)
// State implements the State interfaces in the state package to handle
// reading and writing the remote state. This State on its own does no
// local caching so every persist will go to the remote storage and local
// writes will go to memory.
type State struct {
mu sync.Mutex
Client Client
// We track two pieces of meta data in addition to the state itself:
//
// lineage - the state's unique ID
// serial - the monotonic counter of "versions" of the state
//
// Both of these (along with state) have a sister field
// that represents the values read in from an existing source.
// All three of these values are used to determine if the new
// state has changed from an existing state we read in.
lineage, readLineage string
serial, readSerial uint64
state, readState *states.State
disableLocks bool
}
var _ statemgr.Full = (*State)(nil)
var _ statemgr.Migrator = (*State)(nil)
// statemgr.Reader impl.
func (s *State) State() *states.State {
s.mu.Lock()
defer s.mu.Unlock()
return s.state.DeepCopy()
}
// StateForMigration is part of our implementation of statemgr.Migrator.
func (s *State) StateForMigration() *statefile.File {
s.mu.Lock()
defer s.mu.Unlock()
return statefile.New(s.state.DeepCopy(), s.lineage, s.serial)
}
// statemgr.Writer impl.
func (s *State) WriteState(state *states.State) error {
s.mu.Lock()
defer s.mu.Unlock()
// We create a deep copy of the state here, because the caller also has
// a reference to the given object and can potentially go on to mutate
// it after we return, but we want the snapshot at this point in time.
s.state = state.DeepCopy()
return nil
}
// WriteStateForMigration is part of our implementation of statemgr.Migrator.
func (s *State) WriteStateForMigration(f *statefile.File, force bool) error {
s.mu.Lock()
defer s.mu.Unlock()
if !force {
checkFile := statefile.New(s.state, s.lineage, s.serial)
if err := statemgr.CheckValidImport(f, checkFile); err != nil {
return err
}
}
// The remote backend needs to pass the `force` flag through to its client.
// For backends that support such operations, inform the client
// that a force push has been requested
c, isForcePusher := s.Client.(ClientForcePusher)
if force && isForcePusher {
c.EnableForcePush()
}
// We create a deep copy of the state here, because the caller also has
// a reference to the given object and can potentially go on to mutate
// it after we return, but we want the snapshot at this point in time.
s.state = f.State.DeepCopy()
s.lineage = f.Lineage
s.serial = f.Serial
return nil
}
// statemgr.Refresher impl.
func (s *State) RefreshState() error {
s.mu.Lock()
defer s.mu.Unlock()
return s.refreshState()
}
// refreshState is the main implementation of RefreshState, but split out so
// that we can make internal calls to it from methods that are already holding
// the s.mu lock.
func (s *State) refreshState() error {
payload, err := s.Client.Get()
if err != nil {
return err
}
// no remote state is OK
if payload == nil {
s.readState = nil
s.lineage = ""
s.serial = 0
return nil
}
stateFile, err := statefile.Read(bytes.NewReader(payload.Data))
if err != nil {
return err
}
s.lineage = stateFile.Lineage
s.serial = stateFile.Serial
s.state = stateFile.State
// Properties from the remote must be separate so we can
// track changes as lineage, serial and/or state are mutated
s.readLineage = stateFile.Lineage
s.readSerial = stateFile.Serial
s.readState = s.state.DeepCopy()
return nil
}
// statemgr.Persister impl.
func (s *State) PersistState() error {
s.mu.Lock()
defer s.mu.Unlock()
if s.readState != nil {
lineageUnchanged := s.readLineage != "" && s.lineage == s.readLineage
serialUnchanged := s.readSerial != 0 && s.serial == s.readSerial
stateUnchanged := statefile.StatesMarshalEqual(s.state, s.readState)
if stateUnchanged && lineageUnchanged && serialUnchanged {
// If the state, lineage or serial haven't changed at all then we have nothing to do.
return nil
}
s.serial++
} else {
// We might be writing a new state altogether, but before we do that
// we'll check to make sure there isn't already a snapshot present
// that we ought to be updating.
err := s.refreshState()
if err != nil {
return fmt.Errorf("failed checking for existing remote state: %s", err)
}
if s.lineage == "" { // indicates that no state snapshot is present yet
lineage, err := uuid.GenerateUUID()
if err != nil {
return fmt.Errorf("failed to generate initial lineage: %v", err)
}
s.lineage = lineage
s.serial = 0
}
}
f := statefile.New(s.state, s.lineage, s.serial)
var buf bytes.Buffer
err := statefile.Write(f, &buf)
if err != nil {
return err
}
err = s.Client.Put(buf.Bytes())
if err != nil {
return err
}
// After we've successfully persisted, what we just wrote is our new
// reference state until someone calls RefreshState again.
// We've potentially overwritten (via force) the state, lineage
// and / or serial (and serial was incremented) so we copy over all
// three fields so everything matches the new state and a subsequent
// operation would correctly detect no changes to the lineage, serial or state.
s.readState = s.state.DeepCopy()
s.readLineage = s.lineage
s.readSerial = s.serial
return nil
}
// Lock calls the Client's Lock method if it's implemented.
func (s *State) Lock(info *statemgr.LockInfo) (string, error) {
s.mu.Lock()
defer s.mu.Unlock()
if s.disableLocks {
return "", nil
}
if c, ok := s.Client.(ClientLocker); ok {
return c.Lock(info)
}
return "", nil
}
// Unlock calls the Client's Unlock method if it's implemented.
func (s *State) Unlock(id string) error {
s.mu.Lock()
defer s.mu.Unlock()
if s.disableLocks {
return nil
}
if c, ok := s.Client.(ClientLocker); ok {
return c.Unlock(id)
}
return nil
}
// DisableLocks turns the Lock and Unlock methods into no-ops. This is intended
// to be called during initialization of a state manager and should not be
// called after any of the statemgr.Full interface methods have been called.
func (s *State) DisableLocks() {
s.disableLocks = true
}
// StateSnapshotMeta returns the metadata from the most recently persisted
// or refreshed persistent state snapshot.
//
// This is an implementation of statemgr.PersistentMeta.
func (s *State) StateSnapshotMeta() statemgr.SnapshotMeta {
return statemgr.SnapshotMeta{
Lineage: s.lineage,
Serial: s.serial,
}
}