terraform/state/local.go

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package state
import (
"bytes"
"encoding/json"
"fmt"
"io"
"io/ioutil"
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"os"
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"path/filepath"
"sync"
"time"
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multierror "github.com/hashicorp/go-multierror"
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"github.com/hashicorp/terraform/terraform"
)
// LocalState manages a state storage that is local to the filesystem.
type LocalState struct {
mu sync.Mutex
// Path is the path to read the state from. PathOut is the path to
// write the state to. If PathOut is not specified, Path will be used.
// If PathOut already exists, it will be overwritten.
Path string
PathOut string
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// the file handle corresponding to PathOut
stateFileOut *os.File
// While the stateFileOut will correspond to the lock directly,
// store and check the lock ID to maintain a strict state.Locker
// implementation.
lockID string
// created is set to true if stateFileOut didn't exist before we created it.
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// This is mostly so we can clean up empty files during tests, but doesn't
// hurt to remove file we never wrote to.
created bool
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state *terraform.State
readState *terraform.State
written bool
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}
// SetState will force a specific state in-memory for this local state.
func (s *LocalState) SetState(state *terraform.State) {
s.mu.Lock()
defer s.mu.Unlock()
state: more robust handling of state Serial Previously we relied on a constellation of coincidences for everything to work out correctly with state serials. In particular, callers needed to be very careful about mutating states (or not) because many different bits of code shared pointers to the same objects. Here we move to a model where all of the state managers always use distinct instances of state, copied when WriteState is called. This means that they are truly a snapshot of the state as it was at that call, even if the caller goes on mutating the state that was passed. We also adjust the handling of serials so that the state managers ignore any serials in incoming states and instead just treat each Persist as the next version after what was most recently Refreshed. (An exception exists for when nothing has been refreshed, e.g. because we are writing a state to a location for the first time. In that case we _do_ trust the caller, since the given state is either a new state or it's a copy of something we're migrating from elsewhere with its state and lineage intact.) The intent here is to allow the rest of Terraform to not worry about serials and state identity, and instead just treat the state as a mutable structure. We'll just snapshot it occasionally, when WriteState is called, and deal with serials _only_ at persist time. This is intended as a more robust version of #15423, which was a quick hotfix to an issue that resulted from our previous slopping handling of state serials but arguably makes the problem worse by depending on an additional coincidental behavior of the local backend's apply implementation.
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s.state = state.DeepCopy()
s.readState = state.DeepCopy()
}
// StateReader impl.
func (s *LocalState) State() *terraform.State {
return s.state.DeepCopy()
}
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// WriteState for LocalState always persists the state as well.
// TODO: this should use a more robust method of writing state, by first
// writing to a temp file on the same filesystem, and renaming the file over
// the original.
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//
// StateWriter impl.
func (s *LocalState) WriteState(state *terraform.State) error {
s.mu.Lock()
defer s.mu.Unlock()
if s.stateFileOut == nil {
if err := s.createStateFiles(); err != nil {
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return nil
}
}
defer s.stateFileOut.Sync()
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state: more robust handling of state Serial Previously we relied on a constellation of coincidences for everything to work out correctly with state serials. In particular, callers needed to be very careful about mutating states (or not) because many different bits of code shared pointers to the same objects. Here we move to a model where all of the state managers always use distinct instances of state, copied when WriteState is called. This means that they are truly a snapshot of the state as it was at that call, even if the caller goes on mutating the state that was passed. We also adjust the handling of serials so that the state managers ignore any serials in incoming states and instead just treat each Persist as the next version after what was most recently Refreshed. (An exception exists for when nothing has been refreshed, e.g. because we are writing a state to a location for the first time. In that case we _do_ trust the caller, since the given state is either a new state or it's a copy of something we're migrating from elsewhere with its state and lineage intact.) The intent here is to allow the rest of Terraform to not worry about serials and state identity, and instead just treat the state as a mutable structure. We'll just snapshot it occasionally, when WriteState is called, and deal with serials _only_ at persist time. This is intended as a more robust version of #15423, which was a quick hotfix to an issue that resulted from our previous slopping handling of state serials but arguably makes the problem worse by depending on an additional coincidental behavior of the local backend's apply implementation.
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s.state = state.DeepCopy() // don't want mutations before we actually get this written to disk
if s.readState != nil && s.state != nil {
// We don't trust callers to properly manage serials. Instead, we assume
// that a WriteState is always for the next version after what was
// most recently read.
s.state.Serial = s.readState.Serial
}
if _, err := s.stateFileOut.Seek(0, io.SeekStart); err != nil {
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return err
}
if err := s.stateFileOut.Truncate(0); err != nil {
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return err
}
if state == nil {
// if we have no state, don't write anything else.
return nil
}
state: more robust handling of state Serial Previously we relied on a constellation of coincidences for everything to work out correctly with state serials. In particular, callers needed to be very careful about mutating states (or not) because many different bits of code shared pointers to the same objects. Here we move to a model where all of the state managers always use distinct instances of state, copied when WriteState is called. This means that they are truly a snapshot of the state as it was at that call, even if the caller goes on mutating the state that was passed. We also adjust the handling of serials so that the state managers ignore any serials in incoming states and instead just treat each Persist as the next version after what was most recently Refreshed. (An exception exists for when nothing has been refreshed, e.g. because we are writing a state to a location for the first time. In that case we _do_ trust the caller, since the given state is either a new state or it's a copy of something we're migrating from elsewhere with its state and lineage intact.) The intent here is to allow the rest of Terraform to not worry about serials and state identity, and instead just treat the state as a mutable structure. We'll just snapshot it occasionally, when WriteState is called, and deal with serials _only_ at persist time. This is intended as a more robust version of #15423, which was a quick hotfix to an issue that resulted from our previous slopping handling of state serials but arguably makes the problem worse by depending on an additional coincidental behavior of the local backend's apply implementation.
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if !s.state.MarshalEqual(s.readState) {
s.state.Serial++
}
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if err := terraform.WriteState(s.state, s.stateFileOut); err != nil {
return err
}
s.written = true
return nil
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}
// PersistState for LocalState is a no-op since WriteState always persists.
//
// StatePersister impl.
func (s *LocalState) PersistState() error {
return nil
}
// StateRefresher impl.
func (s *LocalState) RefreshState() error {
s.mu.Lock()
defer s.mu.Unlock()
if s.PathOut == "" {
s.PathOut = s.Path
}
var reader io.Reader
// The s.Path file is only OK to read if we have not written any state out
// (in which case the same state needs to be read in), and no state output file
// has been opened (possibly via a lock) or the input path is different
// than the output path.
// This is important for Windows, as if the input file is the same as the
// output file, and the output file has been locked already, we can't open
// the file again.
if !s.written && (s.stateFileOut == nil || s.Path != s.PathOut) {
// we haven't written a state file yet, so load from Path
f, err := os.Open(s.Path)
if err != nil {
// It is okay if the file doesn't exist, we treat that as a nil state
if !os.IsNotExist(err) {
return err
}
// we need a non-nil reader for ReadState and an empty buffer works
// to return EOF immediately
reader = bytes.NewBuffer(nil)
} else {
defer f.Close()
reader = f
}
} else {
// no state to refresh
if s.stateFileOut == nil {
return nil
}
// we have a state file, make sure we're at the start
s.stateFileOut.Seek(0, io.SeekStart)
reader = s.stateFileOut
}
state, err := terraform.ReadState(reader)
// if there's no state we just assign the nil return value
if err != nil && err != terraform.ErrNoState {
return err
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}
s.state = state
state: more robust handling of state Serial Previously we relied on a constellation of coincidences for everything to work out correctly with state serials. In particular, callers needed to be very careful about mutating states (or not) because many different bits of code shared pointers to the same objects. Here we move to a model where all of the state managers always use distinct instances of state, copied when WriteState is called. This means that they are truly a snapshot of the state as it was at that call, even if the caller goes on mutating the state that was passed. We also adjust the handling of serials so that the state managers ignore any serials in incoming states and instead just treat each Persist as the next version after what was most recently Refreshed. (An exception exists for when nothing has been refreshed, e.g. because we are writing a state to a location for the first time. In that case we _do_ trust the caller, since the given state is either a new state or it's a copy of something we're migrating from elsewhere with its state and lineage intact.) The intent here is to allow the rest of Terraform to not worry about serials and state identity, and instead just treat the state as a mutable structure. We'll just snapshot it occasionally, when WriteState is called, and deal with serials _only_ at persist time. This is intended as a more robust version of #15423, which was a quick hotfix to an issue that resulted from our previous slopping handling of state serials but arguably makes the problem worse by depending on an additional coincidental behavior of the local backend's apply implementation.
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s.readState = s.state.DeepCopy()
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return nil
}
// Lock implements a local filesystem state.Locker.
func (s *LocalState) Lock(info *LockInfo) (string, error) {
s.mu.Lock()
defer s.mu.Unlock()
if s.stateFileOut == nil {
if err := s.createStateFiles(); err != nil {
return "", err
}
}
if s.lockID != "" {
return "", fmt.Errorf("state %q already locked", s.stateFileOut.Name())
}
if err := s.lock(); err != nil {
info, infoErr := s.lockInfo()
if infoErr != nil {
err = multierror.Append(err, infoErr)
}
lockErr := &LockError{
Info: info,
Err: err,
}
return "", lockErr
}
s.lockID = info.ID
return s.lockID, s.writeLockInfo(info)
}
func (s *LocalState) Unlock(id string) error {
s.mu.Lock()
defer s.mu.Unlock()
if s.lockID == "" {
return fmt.Errorf("LocalState not locked")
}
if id != s.lockID {
idErr := fmt.Errorf("invalid lock id: %q. current id: %q", id, s.lockID)
info, err := s.lockInfo()
if err != nil {
idErr = multierror.Append(idErr, err)
}
return &LockError{
Err: idErr,
Info: info,
}
}
os.Remove(s.lockInfoPath())
fileName := s.stateFileOut.Name()
unlockErr := s.unlock()
s.stateFileOut.Close()
s.stateFileOut = nil
s.lockID = ""
// clean up the state file if we created it an never wrote to it
stat, err := os.Stat(fileName)
if err == nil && stat.Size() == 0 && s.created {
os.Remove(fileName)
}
return unlockErr
}
// Open the state file, creating the directories and file as needed.
func (s *LocalState) createStateFiles() error {
if s.PathOut == "" {
s.PathOut = s.Path
}
// yes this could race, but we only use it to clean up empty files
if _, err := os.Stat(s.PathOut); os.IsNotExist(err) {
s.created = true
}
// Create all the directories
if err := os.MkdirAll(filepath.Dir(s.PathOut), 0755); err != nil {
return err
}
f, err := os.OpenFile(s.PathOut, os.O_RDWR|os.O_CREATE, 0666)
if err != nil {
return err
}
s.stateFileOut = f
return nil
}
// return the path for the lockInfo metadata.
func (s *LocalState) lockInfoPath() string {
stateDir, stateName := filepath.Split(s.Path)
if stateName == "" {
panic("empty state file path")
}
if stateName[0] == '.' {
stateName = stateName[1:]
}
return filepath.Join(stateDir, fmt.Sprintf(".%s.lock.info", stateName))
}
// lockInfo returns the data in a lock info file
func (s *LocalState) lockInfo() (*LockInfo, error) {
path := s.lockInfoPath()
infoData, err := ioutil.ReadFile(path)
if err != nil {
return nil, err
}
info := LockInfo{}
err = json.Unmarshal(infoData, &info)
if err != nil {
return nil, fmt.Errorf("state file %q locked, but could not unmarshal lock info: %s", s.Path, err)
}
return &info, nil
}
// write a new lock info file
func (s *LocalState) writeLockInfo(info *LockInfo) error {
path := s.lockInfoPath()
info.Path = s.Path
info.Created = time.Now().UTC()
err := ioutil.WriteFile(path, info.Marshal(), 0600)
if err != nil {
return fmt.Errorf("could not write lock info for %q: %s", s.Path, err)
}
return nil
}