435c0d9fc8
This PR switches the Nomad repository from using govendor to Go modules for managing dependencies. Aspects of the Nomad workflow remain pretty much the same. The usual Makefile targets should continue to work as they always did. The API submodule simply defers to the parent Nomad version on the repository, keeping the semantics of API versioning that currently exists.
116 lines
3.6 KiB
Go
116 lines
3.6 KiB
Go
// Copyright 2014 Google Inc. All rights reserved.
|
|
// Use of this source code is governed by the Apache 2.0
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package internal
|
|
|
|
// This file implements hooks for applying datastore transactions.
|
|
|
|
import (
|
|
"errors"
|
|
"reflect"
|
|
|
|
"github.com/golang/protobuf/proto"
|
|
netcontext "golang.org/x/net/context"
|
|
|
|
basepb "google.golang.org/appengine/internal/base"
|
|
pb "google.golang.org/appengine/internal/datastore"
|
|
)
|
|
|
|
var transactionSetters = make(map[reflect.Type]reflect.Value)
|
|
|
|
// RegisterTransactionSetter registers a function that sets transaction information
|
|
// in a protocol buffer message. f should be a function with two arguments,
|
|
// the first being a protocol buffer type, and the second being *datastore.Transaction.
|
|
func RegisterTransactionSetter(f interface{}) {
|
|
v := reflect.ValueOf(f)
|
|
transactionSetters[v.Type().In(0)] = v
|
|
}
|
|
|
|
// applyTransaction applies the transaction t to message pb
|
|
// by using the relevant setter passed to RegisterTransactionSetter.
|
|
func applyTransaction(pb proto.Message, t *pb.Transaction) {
|
|
v := reflect.ValueOf(pb)
|
|
if f, ok := transactionSetters[v.Type()]; ok {
|
|
f.Call([]reflect.Value{v, reflect.ValueOf(t)})
|
|
}
|
|
}
|
|
|
|
var transactionKey = "used for *Transaction"
|
|
|
|
func transactionFromContext(ctx netcontext.Context) *transaction {
|
|
t, _ := ctx.Value(&transactionKey).(*transaction)
|
|
return t
|
|
}
|
|
|
|
func withTransaction(ctx netcontext.Context, t *transaction) netcontext.Context {
|
|
return netcontext.WithValue(ctx, &transactionKey, t)
|
|
}
|
|
|
|
type transaction struct {
|
|
transaction pb.Transaction
|
|
finished bool
|
|
}
|
|
|
|
var ErrConcurrentTransaction = errors.New("internal: concurrent transaction")
|
|
|
|
func RunTransactionOnce(c netcontext.Context, f func(netcontext.Context) error, xg bool, readOnly bool, previousTransaction *pb.Transaction) (*pb.Transaction, error) {
|
|
if transactionFromContext(c) != nil {
|
|
return nil, errors.New("nested transactions are not supported")
|
|
}
|
|
|
|
// Begin the transaction.
|
|
t := &transaction{}
|
|
req := &pb.BeginTransactionRequest{
|
|
App: proto.String(FullyQualifiedAppID(c)),
|
|
}
|
|
if xg {
|
|
req.AllowMultipleEg = proto.Bool(true)
|
|
}
|
|
if previousTransaction != nil {
|
|
req.PreviousTransaction = previousTransaction
|
|
}
|
|
if readOnly {
|
|
req.Mode = pb.BeginTransactionRequest_READ_ONLY.Enum()
|
|
} else {
|
|
req.Mode = pb.BeginTransactionRequest_READ_WRITE.Enum()
|
|
}
|
|
if err := Call(c, "datastore_v3", "BeginTransaction", req, &t.transaction); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Call f, rolling back the transaction if f returns a non-nil error, or panics.
|
|
// The panic is not recovered.
|
|
defer func() {
|
|
if t.finished {
|
|
return
|
|
}
|
|
t.finished = true
|
|
// Ignore the error return value, since we are already returning a non-nil
|
|
// error (or we're panicking).
|
|
Call(c, "datastore_v3", "Rollback", &t.transaction, &basepb.VoidProto{})
|
|
}()
|
|
if err := f(withTransaction(c, t)); err != nil {
|
|
return &t.transaction, err
|
|
}
|
|
t.finished = true
|
|
|
|
// Commit the transaction.
|
|
res := &pb.CommitResponse{}
|
|
err := Call(c, "datastore_v3", "Commit", &t.transaction, res)
|
|
if ae, ok := err.(*APIError); ok {
|
|
/* TODO: restore this conditional
|
|
if appengine.IsDevAppServer() {
|
|
*/
|
|
// The Python Dev AppServer raises an ApplicationError with error code 2 (which is
|
|
// Error.CONCURRENT_TRANSACTION) and message "Concurrency exception.".
|
|
if ae.Code == int32(pb.Error_BAD_REQUEST) && ae.Detail == "ApplicationError: 2 Concurrency exception." {
|
|
return &t.transaction, ErrConcurrentTransaction
|
|
}
|
|
if ae.Code == int32(pb.Error_CONCURRENT_TRANSACTION) {
|
|
return &t.transaction, ErrConcurrentTransaction
|
|
}
|
|
}
|
|
return &t.transaction, err
|
|
}
|