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// Copyright 2022 The LUCI Authors.
// 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
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
package tryjob
import (
type executionState struct {
_kind string `gae:"$kind,TryjobExecutionState"`
_id int64 `gae:"$id,1"`
Run *datastore.Key `gae:"$parent"`
// EVersion is the version of this state. Start with 1.
EVersion int64 `gae:",noindex"`
// UpdateTime is exact time of when the state was last updated.
UpdateTime time.Time `gae:",noindex"`
State *ExecutionState
// LoadExecutionState loads the execution state of the given Run.
// Returns nil state and 0 version if execution state never exists for this
// Run before.
func LoadExecutionState(ctx context.Context, rid common.RunID) (state *ExecutionState, version int64, err error) {
es := &executionState{Run: datastore.MakeKey(ctx, common.RunKind, string(rid))}
switch err := datastore.Get(ctx, es); {
case err == datastore.ErrNoSuchEntity:
return nil, 0, nil
case err != nil:
return nil, 0, errors.Annotate(err, "failed to load tryjob execution state of run %q", rid).Tag(transient.Tag).Err()
return es.State, es.EVersion, nil
// SaveExecutionState saves new state for the run.
// Fails if the current version of the state is different from the provided
// `expectedVersion`. This typically means the state has changed since the
// last `LoadState`. `expectedVersion==0` means the state never exists for
// this Run before.
// Must be called in a transaction.
func SaveExecutionState(ctx context.Context, rid common.RunID, state *ExecutionState, expectedVersion int64) error {
if datastore.CurrentTransaction(ctx) == nil {
panic(fmt.Errorf("must be called in a transaction"))
switch _, latestStateVer, err := LoadExecutionState(ctx, rid); {
case err != nil:
return err
case latestStateVer != expectedVersion:
return errors.Reason("execution state has changed. before: %d, current: %d", expectedVersion, latestStateVer).Tag(transient.Tag).Err()
newState := &executionState{
Run: datastore.MakeKey(ctx, common.RunKind, string(rid)),
EVersion: latestStateVer + 1,
UpdateTime: clock.Now(ctx).UTC(),
State: state,
if err := datastore.Put(ctx, newState); err != nil {
return errors.Annotate(err, "failed to save execution state").Tag(transient.Tag).Err()
return nil