mirror of
https://github.com/octoleo/restic.git
synced 2024-12-23 11:28:54 +00:00
311 lines
9.4 KiB
Go
311 lines
9.4 KiB
Go
// Copyright 2014 Google Inc. All Rights Reserved.
|
||
//
|
||
// Licensed under the Apache License, Version 2.0 (the "License");
|
||
// you may not use this file except in compliance with the License.
|
||
// You may obtain a copy of the License at
|
||
//
|
||
// http://www.apache.org/licenses/LICENSE-2.0
|
||
//
|
||
// Unless required by applicable law or agreed to in writing, software
|
||
// distributed under the License is distributed on an "AS IS" BASIS,
|
||
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
||
// See the License for the specific language governing permissions and
|
||
// limitations under the License.
|
||
|
||
package datastore
|
||
|
||
import (
|
||
"errors"
|
||
|
||
"golang.org/x/net/context"
|
||
"google.golang.org/grpc"
|
||
"google.golang.org/grpc/codes"
|
||
|
||
pb "google.golang.org/genproto/googleapis/datastore/v1"
|
||
)
|
||
|
||
// ErrConcurrentTransaction is returned when a transaction is rolled back due
|
||
// to a conflict with a concurrent transaction.
|
||
var ErrConcurrentTransaction = errors.New("datastore: concurrent transaction")
|
||
|
||
var errExpiredTransaction = errors.New("datastore: transaction expired")
|
||
|
||
type transactionSettings struct {
|
||
attempts int
|
||
}
|
||
|
||
// newTransactionSettings creates a transactionSettings with a given TransactionOption slice.
|
||
// Unconfigured options will be set to default values.
|
||
func newTransactionSettings(opts []TransactionOption) *transactionSettings {
|
||
s := &transactionSettings{attempts: 3}
|
||
for _, o := range opts {
|
||
o.apply(s)
|
||
}
|
||
return s
|
||
}
|
||
|
||
// TransactionOption configures the way a transaction is executed.
|
||
type TransactionOption interface {
|
||
apply(*transactionSettings)
|
||
}
|
||
|
||
// MaxAttempts returns a TransactionOption that overrides the default 3 attempt times.
|
||
func MaxAttempts(attempts int) TransactionOption {
|
||
return maxAttempts(attempts)
|
||
}
|
||
|
||
type maxAttempts int
|
||
|
||
func (w maxAttempts) apply(s *transactionSettings) {
|
||
if w > 0 {
|
||
s.attempts = int(w)
|
||
}
|
||
}
|
||
|
||
// Transaction represents a set of datastore operations to be committed atomically.
|
||
//
|
||
// Operations are enqueued by calling the Put and Delete methods on Transaction
|
||
// (or their Multi-equivalents). These operations are only committed when the
|
||
// Commit method is invoked. To ensure consistency, reads must be performed by
|
||
// using Transaction's Get method or by using the Transaction method when
|
||
// building a query.
|
||
//
|
||
// A Transaction must be committed or rolled back exactly once.
|
||
type Transaction struct {
|
||
id []byte
|
||
client *Client
|
||
ctx context.Context
|
||
mutations []*pb.Mutation // The mutations to apply.
|
||
pending map[int]*PendingKey // Map from mutation index to incomplete keys pending transaction completion.
|
||
}
|
||
|
||
// NewTransaction starts a new transaction.
|
||
func (c *Client) NewTransaction(ctx context.Context, opts ...TransactionOption) (*Transaction, error) {
|
||
for _, o := range opts {
|
||
if _, ok := o.(maxAttempts); ok {
|
||
return nil, errors.New("datastore: NewTransaction does not accept MaxAttempts option")
|
||
}
|
||
}
|
||
req := &pb.BeginTransactionRequest{
|
||
ProjectId: c.dataset,
|
||
}
|
||
resp, err := c.client.BeginTransaction(ctx, req)
|
||
if err != nil {
|
||
return nil, err
|
||
}
|
||
|
||
return &Transaction{
|
||
id: resp.Transaction,
|
||
ctx: ctx,
|
||
client: c,
|
||
mutations: nil,
|
||
pending: make(map[int]*PendingKey),
|
||
}, nil
|
||
}
|
||
|
||
// RunInTransaction runs f in a transaction. f is invoked with a Transaction
|
||
// that f should use for all the transaction's datastore operations.
|
||
//
|
||
// f must not call Commit or Rollback on the provided Transaction.
|
||
//
|
||
// If f returns nil, RunInTransaction commits the transaction,
|
||
// returning the Commit and a nil error if it succeeds. If the commit fails due
|
||
// to a conflicting transaction, RunInTransaction retries f with a new
|
||
// Transaction. It gives up and returns ErrConcurrentTransaction after three
|
||
// failed attempts (or as configured with MaxAttempts).
|
||
//
|
||
// If f returns non-nil, then the transaction will be rolled back and
|
||
// RunInTransaction will return the same error. The function f is not retried.
|
||
//
|
||
// Note that when f returns, the transaction is not committed. Calling code
|
||
// must not assume that any of f's changes have been committed until
|
||
// RunInTransaction returns nil.
|
||
//
|
||
// Since f may be called multiple times, f should usually be idempotent – that
|
||
// is, it should have the same result when called multiple times. Note that
|
||
// Transaction.Get will append when unmarshalling slice fields, so it is not
|
||
// necessarily idempotent.
|
||
func (c *Client) RunInTransaction(ctx context.Context, f func(tx *Transaction) error, opts ...TransactionOption) (*Commit, error) {
|
||
settings := newTransactionSettings(opts)
|
||
for n := 0; n < settings.attempts; n++ {
|
||
tx, err := c.NewTransaction(ctx)
|
||
if err != nil {
|
||
return nil, err
|
||
}
|
||
if err := f(tx); err != nil {
|
||
tx.Rollback()
|
||
return nil, err
|
||
}
|
||
if cmt, err := tx.Commit(); err != ErrConcurrentTransaction {
|
||
return cmt, err
|
||
}
|
||
}
|
||
return nil, ErrConcurrentTransaction
|
||
}
|
||
|
||
// Commit applies the enqueued operations atomically.
|
||
func (t *Transaction) Commit() (*Commit, error) {
|
||
if t.id == nil {
|
||
return nil, errExpiredTransaction
|
||
}
|
||
req := &pb.CommitRequest{
|
||
ProjectId: t.client.dataset,
|
||
TransactionSelector: &pb.CommitRequest_Transaction{Transaction: t.id},
|
||
Mutations: t.mutations,
|
||
Mode: pb.CommitRequest_TRANSACTIONAL,
|
||
}
|
||
t.id = nil
|
||
resp, err := t.client.client.Commit(t.ctx, req)
|
||
if err != nil {
|
||
if grpc.Code(err) == codes.Aborted {
|
||
return nil, ErrConcurrentTransaction
|
||
}
|
||
return nil, err
|
||
}
|
||
|
||
// Copy any newly minted keys into the returned keys.
|
||
commit := &Commit{}
|
||
for i, p := range t.pending {
|
||
if i >= len(resp.MutationResults) || resp.MutationResults[i].Key == nil {
|
||
return nil, errors.New("datastore: internal error: server returned the wrong mutation results")
|
||
}
|
||
key, err := protoToKey(resp.MutationResults[i].Key)
|
||
if err != nil {
|
||
return nil, errors.New("datastore: internal error: server returned an invalid key")
|
||
}
|
||
p.key = key
|
||
p.commit = commit
|
||
}
|
||
|
||
return commit, nil
|
||
}
|
||
|
||
// Rollback abandons a pending transaction.
|
||
func (t *Transaction) Rollback() error {
|
||
if t.id == nil {
|
||
return errExpiredTransaction
|
||
}
|
||
id := t.id
|
||
t.id = nil
|
||
_, err := t.client.client.Rollback(t.ctx, &pb.RollbackRequest{
|
||
ProjectId: t.client.dataset,
|
||
Transaction: id,
|
||
})
|
||
return err
|
||
}
|
||
|
||
// Get is the transaction-specific version of the package function Get.
|
||
// All reads performed during the transaction will come from a single consistent
|
||
// snapshot. Furthermore, if the transaction is set to a serializable isolation
|
||
// level, another transaction cannot concurrently modify the data that is read
|
||
// or modified by this transaction.
|
||
func (t *Transaction) Get(key *Key, dst interface{}) error {
|
||
opts := &pb.ReadOptions{
|
||
ConsistencyType: &pb.ReadOptions_Transaction{Transaction: t.id},
|
||
}
|
||
err := t.client.get(t.ctx, []*Key{key}, []interface{}{dst}, opts)
|
||
if me, ok := err.(MultiError); ok {
|
||
return me[0]
|
||
}
|
||
return err
|
||
}
|
||
|
||
// GetMulti is a batch version of Get.
|
||
func (t *Transaction) GetMulti(keys []*Key, dst interface{}) error {
|
||
if t.id == nil {
|
||
return errExpiredTransaction
|
||
}
|
||
opts := &pb.ReadOptions{
|
||
ConsistencyType: &pb.ReadOptions_Transaction{Transaction: t.id},
|
||
}
|
||
return t.client.get(t.ctx, keys, dst, opts)
|
||
}
|
||
|
||
// Put is the transaction-specific version of the package function Put.
|
||
//
|
||
// Put returns a PendingKey which can be resolved into a Key using the
|
||
// return value from a successful Commit. If key is an incomplete key, the
|
||
// returned pending key will resolve to a unique key generated by the
|
||
// datastore.
|
||
func (t *Transaction) Put(key *Key, src interface{}) (*PendingKey, error) {
|
||
h, err := t.PutMulti([]*Key{key}, []interface{}{src})
|
||
if err != nil {
|
||
if me, ok := err.(MultiError); ok {
|
||
return nil, me[0]
|
||
}
|
||
return nil, err
|
||
}
|
||
return h[0], nil
|
||
}
|
||
|
||
// PutMulti is a batch version of Put. One PendingKey is returned for each
|
||
// element of src in the same order.
|
||
func (t *Transaction) PutMulti(keys []*Key, src interface{}) ([]*PendingKey, error) {
|
||
if t.id == nil {
|
||
return nil, errExpiredTransaction
|
||
}
|
||
mutations, err := putMutations(keys, src)
|
||
if err != nil {
|
||
return nil, err
|
||
}
|
||
origin := len(t.mutations)
|
||
t.mutations = append(t.mutations, mutations...)
|
||
|
||
// Prepare the returned handles, pre-populating where possible.
|
||
ret := make([]*PendingKey, len(keys))
|
||
for i, key := range keys {
|
||
p := &PendingKey{}
|
||
if key.Incomplete() {
|
||
// This key will be in the final commit result.
|
||
t.pending[origin+i] = p
|
||
} else {
|
||
p.key = key
|
||
}
|
||
ret[i] = p
|
||
}
|
||
|
||
return ret, nil
|
||
}
|
||
|
||
// Delete is the transaction-specific version of the package function Delete.
|
||
// Delete enqueues the deletion of the entity for the given key, to be
|
||
// committed atomically upon calling Commit.
|
||
func (t *Transaction) Delete(key *Key) error {
|
||
err := t.DeleteMulti([]*Key{key})
|
||
if me, ok := err.(MultiError); ok {
|
||
return me[0]
|
||
}
|
||
return err
|
||
}
|
||
|
||
// DeleteMulti is a batch version of Delete.
|
||
func (t *Transaction) DeleteMulti(keys []*Key) error {
|
||
if t.id == nil {
|
||
return errExpiredTransaction
|
||
}
|
||
mutations, err := deleteMutations(keys)
|
||
if err != nil {
|
||
return err
|
||
}
|
||
t.mutations = append(t.mutations, mutations...)
|
||
return nil
|
||
}
|
||
|
||
// Commit represents the result of a committed transaction.
|
||
type Commit struct{}
|
||
|
||
// Key resolves a pending key handle into a final key.
|
||
func (c *Commit) Key(p *PendingKey) *Key {
|
||
if c != p.commit {
|
||
panic("PendingKey was not created by corresponding transaction")
|
||
}
|
||
return p.key
|
||
}
|
||
|
||
// PendingKey represents the key for newly-inserted entity. It can be
|
||
// resolved into a Key by calling the Key method of Commit.
|
||
type PendingKey struct {
|
||
key *Key
|
||
commit *Commit
|
||
}
|