Initial distributor implementation

appengine/cmd/dm/mutate/ensure_attempt.go

 // Copyright 2015 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package mutate
 
 import (
         "github.com/luci/gae/service/datastore"
         "github.com/luci/luci-go/appengine/cmd/dm/model"
         "github.com/luci/luci-go/appengine/tumble"
         "github.com/luci/luci-go/common/api/dm/service/v1"
         "github.com/luci/luci-go/common/logging"
         "golang.org/x/net/context"
 )
 
 // EnsureAttempt ensures that the given Attempt exists. If it doesn't, it's
 // created in a NeedsExecution state.
 type EnsureAttempt struct {
         ID *dm.Attempt_ID
 }
 
 // Root implements tumble.Mutation.
 func (e *EnsureAttempt) Root(c context.Context) *datastore.Key {
-        return datastore.Get(c).KeyForObj(&model.Attempt{ID: *e.ID})
+        return model.AttemptKeyFromID(c, e.ID)
 }
 
 // RollForward implements tumble.Mutation.
 func (e *EnsureAttempt) RollForward(c context.Context) (muts []tumble.Mutation, err error) {
         ds := datastore.Get(c)
 
         a := model.MakeAttempt(c, e.ID)
-        err = ds.Get(a)
-        if err != datastore.ErrNoSuchEntity {
+        if err = ds.Get(a); err != datastore.ErrNoSuchEntity {
                 return
         }
 
         if err = ds.Put(a); err != nil {
                 logging.WithError(err).Errorf(logging.SetField(c, "id", e.ID), "in put")
         }
+        muts = append(muts, &ScheduleExecution{e.ID})
         return
 }
 
 func init() {
         tumble.Register((*EnsureAttempt)(nil))
 }