terraform/internal/backend/remote-state/etcdv3/client.go

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package etcd
import (
"context"
"crypto/md5"
"encoding/json"
"fmt"
"sync"
"time"
etcdv3 "github.com/coreos/etcd/clientv3"
etcdv3sync "github.com/coreos/etcd/clientv3/concurrency"
"github.com/hashicorp/go-multierror"
"github.com/hashicorp/terraform/states/remote"
"github.com/hashicorp/terraform/states/statemgr"
)
const (
lockAcquireTimeout = 2 * time.Second
lockInfoSuffix = ".lockinfo"
)
// RemoteClient is a remote client that will store data in etcd.
type RemoteClient struct {
Client *etcdv3.Client
DoLock bool
Key string
etcdMutex *etcdv3sync.Mutex
etcdSession *etcdv3sync.Session
info *statemgr.LockInfo
mu sync.Mutex
modRevision int64
}
func (c *RemoteClient) Get() (*remote.Payload, error) {
c.mu.Lock()
defer c.mu.Unlock()
res, err := c.Client.KV.Get(context.TODO(), c.Key)
if err != nil {
return nil, err
}
if res.Count == 0 {
return nil, nil
}
if res.Count >= 2 {
return nil, fmt.Errorf("Expected a single result but got %d.", res.Count)
}
c.modRevision = res.Kvs[0].ModRevision
payload := res.Kvs[0].Value
md5 := md5.Sum(payload)
return &remote.Payload{
Data: payload,
MD5: md5[:],
}, nil
}
func (c *RemoteClient) Put(data []byte) error {
c.mu.Lock()
defer c.mu.Unlock()
res, err := etcdv3.NewKV(c.Client).Txn(context.TODO()).If(
etcdv3.Compare(etcdv3.ModRevision(c.Key), "=", c.modRevision),
).Then(
etcdv3.OpPut(c.Key, string(data)),
etcdv3.OpGet(c.Key),
).Commit()
if err != nil {
return err
}
if !res.Succeeded {
return fmt.Errorf("The transaction did not succeed.")
}
if len(res.Responses) != 2 {
return fmt.Errorf("Expected two responses but got %d.", len(res.Responses))
}
c.modRevision = res.Responses[1].GetResponseRange().Kvs[0].ModRevision
return nil
}
func (c *RemoteClient) Delete() error {
c.mu.Lock()
defer c.mu.Unlock()
_, err := c.Client.KV.Delete(context.TODO(), c.Key)
return err
}
func (c *RemoteClient) Lock(info *statemgr.LockInfo) (string, error) {
c.mu.Lock()
defer c.mu.Unlock()
if !c.DoLock {
return "", nil
}
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if c.etcdSession != nil {
return "", fmt.Errorf("state %q already locked", c.Key)
}
c.info = info
return c.lock()
}
func (c *RemoteClient) Unlock(id string) error {
c.mu.Lock()
defer c.mu.Unlock()
if !c.DoLock {
return nil
}
return c.unlock(id)
}
func (c *RemoteClient) deleteLockInfo(info *statemgr.LockInfo) error {
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res, err := c.Client.KV.Delete(context.TODO(), c.Key+lockInfoSuffix)
if err != nil {
return err
}
if res.Deleted == 0 {
return fmt.Errorf("No keys deleted for %s when deleting lock info.", c.Key+lockInfoSuffix)
}
return nil
}
func (c *RemoteClient) getLockInfo() (*statemgr.LockInfo, error) {
res, err := c.Client.KV.Get(context.TODO(), c.Key+lockInfoSuffix)
if err != nil {
return nil, err
}
if res.Count == 0 {
return nil, nil
}
li := &statemgr.LockInfo{}
err = json.Unmarshal(res.Kvs[0].Value, li)
if err != nil {
return nil, fmt.Errorf("Error unmarshaling lock info: %s.", err)
}
return li, nil
}
func (c *RemoteClient) putLockInfo(info *statemgr.LockInfo) error {
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c.info.Path = c.etcdMutex.Key()
c.info.Created = time.Now().UTC()
_, err := c.Client.KV.Put(context.TODO(), c.Key+lockInfoSuffix, string(c.info.Marshal()))
return err
}
func (c *RemoteClient) lock() (string, error) {
session, err := etcdv3sync.NewSession(c.Client)
if err != nil {
return "", nil
}
ctx, cancel := context.WithTimeout(context.TODO(), lockAcquireTimeout)
defer cancel()
mutex := etcdv3sync.NewMutex(session, c.Key)
if err1 := mutex.Lock(ctx); err1 != nil {
lockInfo, err2 := c.getLockInfo()
if err2 != nil {
return "", &statemgr.LockError{Err: err2}
}
return "", &statemgr.LockError{Info: lockInfo, Err: err1}
}
c.etcdMutex = mutex
c.etcdSession = session
err = c.putLockInfo(c.info)
if err != nil {
if unlockErr := c.unlock(c.info.ID); unlockErr != nil {
err = multierror.Append(err, unlockErr)
}
return "", err
}
return c.info.ID, nil
}
func (c *RemoteClient) unlock(id string) error {
if c.etcdMutex == nil {
return nil
}
var errs error
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if err := c.deleteLockInfo(c.info); err != nil {
errs = multierror.Append(errs, err)
}
if err := c.etcdMutex.Unlock(context.TODO()); err != nil {
errs = multierror.Append(errs, err)
}
if err := c.etcdSession.Close(); err != nil {
errs = multierror.Append(errs, err)
}
c.etcdMutex = nil
c.etcdSession = nil
return errs
}