mirror of
https://github.com/octoleo/restic.git
synced 2024-11-30 08:44:02 +00:00
280 lines
9.3 KiB
Go
280 lines
9.3 KiB
Go
// Copyright 2017 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 firestore
|
||
|
||
import (
|
||
"errors"
|
||
|
||
pb "google.golang.org/genproto/googleapis/firestore/v1beta1"
|
||
|
||
gax "github.com/googleapis/gax-go"
|
||
"golang.org/x/net/context"
|
||
"google.golang.org/grpc"
|
||
"google.golang.org/grpc/codes"
|
||
)
|
||
|
||
// Transaction represents a Firestore transaction.
|
||
type Transaction struct {
|
||
c *Client
|
||
ctx context.Context
|
||
id []byte
|
||
writes []*pb.Write
|
||
maxAttempts int
|
||
readOnly bool
|
||
readAfterWrite bool
|
||
}
|
||
|
||
// A TransactionOption is an option passed to Client.Transaction.
|
||
type TransactionOption interface {
|
||
config(t *Transaction)
|
||
}
|
||
|
||
// MaxAttempts is a TransactionOption that configures the maximum number of times to
|
||
// try a transaction. In defaults to DefaultTransactionMaxAttempts.
|
||
func MaxAttempts(n int) maxAttempts { return maxAttempts(n) }
|
||
|
||
type maxAttempts int
|
||
|
||
func (m maxAttempts) config(t *Transaction) { t.maxAttempts = int(m) }
|
||
|
||
// DefaultTransactionMaxAttempts is the default number of times to attempt a transaction.
|
||
const DefaultTransactionMaxAttempts = 5
|
||
|
||
// ReadOnly is a TransactionOption that makes the transaction read-only. Read-only
|
||
// transactions cannot issue write operations, but are more efficient.
|
||
var ReadOnly = ro{}
|
||
|
||
type ro struct{}
|
||
|
||
func (ro) config(t *Transaction) { t.readOnly = true }
|
||
|
||
var (
|
||
// ErrConcurrentTransaction is returned when a transaction is rolled back due
|
||
// to a conflict with a concurrent transaction.
|
||
ErrConcurrentTransaction = errors.New("firestore: concurrent transaction")
|
||
|
||
// Defined here for testing.
|
||
errReadAfterWrite = errors.New("firestore: read after write in transaction")
|
||
errWriteReadOnly = errors.New("firestore: write in read-only transaction")
|
||
errNonTransactionalOp = errors.New("firestore: non-transactional operation inside a transaction")
|
||
errNestedTransaction = errors.New("firestore: nested transaction")
|
||
)
|
||
|
||
type transactionInProgressKey struct{}
|
||
|
||
func checkTransaction(ctx context.Context) error {
|
||
if ctx.Value(transactionInProgressKey{}) != nil {
|
||
return errNonTransactionalOp
|
||
}
|
||
return nil
|
||
}
|
||
|
||
// RunTransaction runs f in a transaction. f should use the transaction it is given
|
||
// for all Firestore operations. For any operation requiring a context, f should use
|
||
// the context it is passed, not the first argument to RunTransaction.
|
||
//
|
||
// f must not call Commit or Rollback on the provided Transaction.
|
||
//
|
||
// If f returns nil, RunTransaction commits the transaction. If the commit fails due
|
||
// to a conflicting transaction, RunTransaction retries f. It gives up and returns
|
||
// ErrConcurrentTransaction after a number of attempts that can be configured with
|
||
// the MaxAttempts option. If the commit succeeds, RunTransaction returns a nil error.
|
||
//
|
||
// If f returns non-nil, then the transaction will be rolled back and
|
||
// this method 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
|
||
// RunTransaction returns nil.
|
||
//
|
||
// Since f may be called more than once, f should usually be idempotent – that is, it
|
||
// should have the same result when called multiple times.
|
||
func (c *Client) RunTransaction(ctx context.Context, f func(context.Context, *Transaction) error, opts ...TransactionOption) error {
|
||
if ctx.Value(transactionInProgressKey{}) != nil {
|
||
return errNestedTransaction
|
||
}
|
||
db := c.path()
|
||
t := &Transaction{
|
||
c: c,
|
||
ctx: withResourceHeader(ctx, db),
|
||
maxAttempts: DefaultTransactionMaxAttempts,
|
||
}
|
||
for _, opt := range opts {
|
||
opt.config(t)
|
||
}
|
||
var txOpts *pb.TransactionOptions
|
||
if t.readOnly {
|
||
txOpts = &pb.TransactionOptions{
|
||
Mode: &pb.TransactionOptions_ReadOnly_{&pb.TransactionOptions_ReadOnly{}},
|
||
}
|
||
}
|
||
var backoff gax.Backoff
|
||
// TODO(jba): use other than the standard backoff parameters?
|
||
// TODO(jba): get backoff time from gRPC trailer metadata? See extractRetryDelay in https://code.googlesource.com/gocloud/+/master/spanner/retry.go.
|
||
var err error
|
||
for i := 0; i < t.maxAttempts; i++ {
|
||
var res *pb.BeginTransactionResponse
|
||
res, err = t.c.c.BeginTransaction(t.ctx, &pb.BeginTransactionRequest{
|
||
Database: db,
|
||
Options: txOpts,
|
||
})
|
||
if err != nil {
|
||
return err
|
||
}
|
||
t.id = res.Transaction
|
||
err = f(context.WithValue(ctx, transactionInProgressKey{}, 1), t)
|
||
// Read after write can only be checked client-side, so we make sure to check
|
||
// even if the user does not.
|
||
if err == nil && t.readAfterWrite {
|
||
err = errReadAfterWrite
|
||
}
|
||
if err != nil {
|
||
t.rollback()
|
||
// Prefer f's returned error to rollback error.
|
||
return err
|
||
}
|
||
_, err = t.c.c.Commit(t.ctx, &pb.CommitRequest{
|
||
Database: t.c.path(),
|
||
Writes: t.writes,
|
||
Transaction: t.id,
|
||
})
|
||
// If a read-write transaction returns Aborted, retry.
|
||
// On success or other failures, return here.
|
||
if t.readOnly || grpc.Code(err) != codes.Aborted {
|
||
// According to the Firestore team, we should not roll back here
|
||
// if err != nil. But spanner does.
|
||
// See https://code.googlesource.com/gocloud/+/master/spanner/transaction.go#740.
|
||
return err
|
||
}
|
||
|
||
if txOpts == nil {
|
||
// txOpts can only be nil if is the first retry of a read-write transaction.
|
||
// (It is only set here and in the body of "if t.readOnly" above.)
|
||
// Mention the transaction ID in BeginTransaction so the service
|
||
// knows it is a retry.
|
||
txOpts = &pb.TransactionOptions{
|
||
Mode: &pb.TransactionOptions_ReadWrite_{
|
||
&pb.TransactionOptions_ReadWrite{RetryTransaction: t.id},
|
||
},
|
||
}
|
||
}
|
||
// Use exponential backoff to avoid contention with other running
|
||
// transactions.
|
||
if cerr := gax.Sleep(ctx, backoff.Pause()); cerr != nil {
|
||
err = cerr
|
||
break
|
||
}
|
||
}
|
||
// If we run out of retries, return the last error we saw (which should
|
||
// be the Aborted from Commit, or a context error).
|
||
if err != nil {
|
||
t.rollback()
|
||
}
|
||
return err
|
||
}
|
||
|
||
func (t *Transaction) rollback() {
|
||
_ = t.c.c.Rollback(t.ctx, &pb.RollbackRequest{
|
||
Database: t.c.path(),
|
||
Transaction: t.id,
|
||
})
|
||
// Ignore the rollback error.
|
||
// TODO(jba): Log it?
|
||
// Note: Rollback is idempotent so it will be retried by the gapic layer.
|
||
}
|
||
|
||
// Get gets the document in the context of the transaction.
|
||
func (t *Transaction) Get(dr *DocumentRef) (*DocumentSnapshot, error) {
|
||
if len(t.writes) > 0 {
|
||
t.readAfterWrite = true
|
||
return nil, errReadAfterWrite
|
||
}
|
||
docProto, err := t.c.c.GetDocument(t.ctx, &pb.GetDocumentRequest{
|
||
Name: dr.Path,
|
||
ConsistencySelector: &pb.GetDocumentRequest_Transaction{t.id},
|
||
})
|
||
if err != nil {
|
||
return nil, err
|
||
}
|
||
return newDocumentSnapshot(dr, docProto, t.c)
|
||
}
|
||
|
||
// A Queryer is a Query or a CollectionRef. CollectionRefs act as queries whose
|
||
// results are all the documents in the collection.
|
||
type Queryer interface {
|
||
query() *Query
|
||
}
|
||
|
||
// Documents returns a DocumentIterator based on given Query or CollectionRef. The
|
||
// results will be in the context of the transaction.
|
||
func (t *Transaction) Documents(q Queryer) *DocumentIterator {
|
||
if len(t.writes) > 0 {
|
||
t.readAfterWrite = true
|
||
return &DocumentIterator{err: errReadAfterWrite}
|
||
}
|
||
return &DocumentIterator{
|
||
ctx: t.ctx,
|
||
q: q.query(),
|
||
tid: t.id,
|
||
}
|
||
}
|
||
|
||
// Create adds a Create operation to the Transaction.
|
||
// See DocumentRef.Create for details.
|
||
func (t *Transaction) Create(dr *DocumentRef, data interface{}) error {
|
||
return t.addWrites(dr.newReplaceWrites(data, nil, Exists(false)))
|
||
}
|
||
|
||
// Set adds a Set operation to the Transaction.
|
||
// See DocumentRef.Set for details.
|
||
func (t *Transaction) Set(dr *DocumentRef, data interface{}, opts ...SetOption) error {
|
||
return t.addWrites(dr.newReplaceWrites(data, opts, nil))
|
||
}
|
||
|
||
// Delete adds a Delete operation to the Transaction.
|
||
// See DocumentRef.Delete for details.
|
||
func (t *Transaction) Delete(dr *DocumentRef, opts ...Precondition) error {
|
||
return t.addWrites(dr.newDeleteWrites(opts))
|
||
}
|
||
|
||
// UpdateMap adds a new Update operation to the Transaction.
|
||
// See DocumentRef.UpdateMap for details.
|
||
func (t *Transaction) UpdateMap(dr *DocumentRef, data map[string]interface{}, opts ...Precondition) error {
|
||
return t.addWrites(dr.newUpdateMapWrites(data, opts))
|
||
}
|
||
|
||
// UpdateStruct adds a new Update operation to the Transaction.
|
||
// See DocumentRef.UpdateStruct for details.
|
||
func (t *Transaction) UpdateStruct(dr *DocumentRef, fieldPaths []string, data interface{}, opts ...Precondition) error {
|
||
return t.addWrites(dr.newUpdateStructWrites(fieldPaths, data, opts))
|
||
}
|
||
|
||
// UpdatePaths adds a new Update operation to the Transaction.
|
||
// See DocumentRef.UpdatePaths for details.
|
||
func (t *Transaction) UpdatePaths(dr *DocumentRef, data []FieldPathUpdate, opts ...Precondition) error {
|
||
return t.addWrites(dr.newUpdatePathWrites(data, opts))
|
||
}
|
||
|
||
func (t *Transaction) addWrites(ws []*pb.Write, err error) error {
|
||
if t.readOnly {
|
||
return errWriteReadOnly
|
||
}
|
||
if err != nil {
|
||
return err
|
||
}
|
||
t.writes = append(t.writes, ws...)
|
||
return nil
|
||
}
|