terraform/state/state.go

224 lines
5.5 KiB
Go

package state
import (
"bytes"
"context"
"encoding/json"
"errors"
"fmt"
"math/rand"
"os"
"os/user"
"strings"
"text/template"
"time"
uuid "github.com/hashicorp/go-uuid"
"github.com/hashicorp/terraform/terraform"
)
var rngSource *rand.Rand
func init() {
rngSource = rand.New(rand.NewSource(time.Now().UnixNano()))
}
// State is the collection of all state interfaces.
type State interface {
StateReader
StateWriter
StateRefresher
StatePersister
Locker
}
// StateReader is the interface for things that can return a state. Retrieving
// the state here must not error. Loading the state fresh (an operation that
// can likely error) should be implemented by RefreshState. If a state hasn't
// been loaded yet, it is okay for State to return nil.
type StateReader interface {
State() *terraform.State
}
// StateWriter is the interface that must be implemented by something that
// can write a state. Writing the state can be cached or in-memory, as
// full persistence should be implemented by StatePersister.
type StateWriter interface {
WriteState(*terraform.State) error
}
// StateRefresher is the interface that is implemented by something that
// can load a state. This might be refreshing it from a remote location or
// it might simply be reloading it from disk.
type StateRefresher interface {
RefreshState() error
}
// StatePersister is implemented to truly persist a state. Whereas StateWriter
// is allowed to perhaps be caching in memory, PersistState must write the
// state to some durable storage.
type StatePersister interface {
PersistState() error
}
// Locker is implemented to lock state during command execution.
// The info parameter can be recorded with the lock, but the
// implementation should not depend in its value. The string returned by Lock
// is an ID corresponding to the lock acquired, and must be passed to Unlock to
// ensure that the correct lock is being released.
//
// Lock and Unlock may return an error value of type LockError which in turn
// can contain the LockInfo of a conflicting lock.
type Locker interface {
Lock(info *LockInfo) (string, error)
Unlock(id string) error
}
// test hook to verify that LockWithContext has attempted a lock
var postLockHook func()
// Lock the state, using the provided context for timeout and cancellation.
// This backs off slightly to an upper limit.
func LockWithContext(ctx context.Context, s State, info *LockInfo) (string, error) {
delay := time.Second
maxDelay := 16 * time.Second
for {
id, err := s.Lock(info)
if err == nil {
return id, nil
}
le, ok := err.(*LockError)
if !ok {
// not a lock error, so we can't retry
return "", err
}
if le == nil || le.Info == nil || le.Info.ID == "" {
// If we dont' have a complete LockError, there's something wrong with the lock
return "", err
}
if postLockHook != nil {
postLockHook()
}
// there's an existing lock, wait and try again
select {
case <-ctx.Done():
// return the last lock error with the info
return "", err
case <-time.After(delay):
if delay < maxDelay {
delay *= 2
}
}
}
}
// Generate a LockInfo structure, populating the required fields.
func NewLockInfo() *LockInfo {
// this doesn't need to be cryptographically secure, just unique.
// Using math/rand alleviates the need to check handle the read error.
// Use a uuid format to match other IDs used throughout Terraform.
buf := make([]byte, 16)
rngSource.Read(buf)
id, err := uuid.FormatUUID(buf)
if err != nil {
// this of course shouldn't happen
panic(err)
}
// don't error out on user and hostname, as we don't require them
userName := ""
if userInfo, err := user.Current(); err == nil {
userName = userInfo.Username
}
host, _ := os.Hostname()
info := &LockInfo{
ID: id,
Who: fmt.Sprintf("%s@%s", userName, host),
Version: terraform.Version,
Created: time.Now().UTC(),
}
return info
}
// LockInfo stores lock metadata.
//
// Only Operation and Info are required to be set by the caller of Lock.
type LockInfo struct {
// Unique ID for the lock. NewLockInfo provides a random ID, but this may
// be overridden by the lock implementation. The final value if ID will be
// returned by the call to Lock.
ID string
// Terraform operation, provided by the caller.
Operation string
// Extra information to store with the lock, provided by the caller.
Info string
// user@hostname when available
Who string
// Terraform version
Version string
// Time that the lock was taken.
Created time.Time
// Path to the state file when applicable. Set by the Lock implementation.
Path string
}
// Err returns the lock info formatted in an error
func (l *LockInfo) Err() error {
return errors.New(l.String())
}
// Marshal returns a string json representation of the LockInfo
func (l *LockInfo) Marshal() []byte {
js, err := json.Marshal(l)
if err != nil {
panic(err)
}
return js
}
// String return a multi-line string representation of LockInfo
func (l *LockInfo) String() string {
tmpl := `Lock Info:
ID: {{.ID}}
Path: {{.Path}}
Operation: {{.Operation}}
Who: {{.Who}}
Version: {{.Version}}
Created: {{.Created}}
Info: {{.Info}}
`
t := template.Must(template.New("LockInfo").Parse(tmpl))
var out bytes.Buffer
if err := t.Execute(&out, l); err != nil {
panic(err)
}
return out.String()
}
type LockError struct {
Info *LockInfo
Err error
}
func (e *LockError) Error() string {
var out []string
if e.Err != nil {
out = append(out, e.Err.Error())
}
if e.Info != nil {
out = append(out, e.Info.String())
}
return strings.Join(out, "\n")
}