Add 'dsset' structure.

scheduler/appengine/engine/cron/demo/main.go

 // Copyright 2017 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
 //
 //      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 demo shows how cron.Machines can be hosted with Datastore and TQ.
 package demo
 
 import (
+        "fmt"
         "net/http"
+        "strconv"
+        "sync"
         "time"
 
         "golang.org/x/net/context"
 
         "github.com/golang/protobuf/proto"
         "github.com/luci/gae/service/datastore"
+        "github.com/luci/gae/service/info"
+        "github.com/luci/gae/service/memcache"
 
         "github.com/luci/luci-go/appengine/gaemiddleware"
+        "github.com/luci/luci-go/appengine/memlock"
         "github.com/luci/luci-go/common/clock"
         "github.com/luci/luci-go/common/data/rand/mathrand"
         "github.com/luci/luci-go/common/logging"
+        "github.com/luci/luci-go/common/retry/transient"
         "github.com/luci/luci-go/server/router"
 
         "github.com/luci/luci-go/scheduler/appengine/engine/cron"
+        "github.com/luci/luci-go/scheduler/appengine/engine/dsset"
         "github.com/luci/luci-go/scheduler/appengine/engine/internal"
         "github.com/luci/luci-go/scheduler/appengine/engine/tq"
         "github.com/luci/luci-go/scheduler/appengine/schedule"
 )
 
-var tasks = tq.Dispatcher{}
+var dispatcher = tq.Dispatcher{}
 
 type CronState struct {
         _extra datastore.PropertyMap `gae:"-,extra"`
 
         ID    string     `gae:"$id"`
         State cron.State `gae:",noindex"`
+
+        NextInvID  int64   `gae:",noindex"`
+        RunningSet []int64 `gae:",noindex"`
 }
 
 func (s *CronState) schedule() *schedule.Schedule {
         parsed, err := schedule.Parse(s.ID, 0)
         if err != nil {
                 panic(err)
         }
         return parsed
 }
 
-// evolve instantiates cron.Machine, calls the callback and submits emitted
-// actions.
+func pendingTriggersSet(c context.Context, jobID string) *dsset.Set {
+        return &dsset.Set{
+                ID:              "triggers:" + jobID,
+                ShardCount:      8,
+                TombstonesRoot:  datastore.KeyForObj(c, &CronState{ID: jobID}),
+                TombstonesDelay: 15 * time.Minute,
+        }
+}
+
+func recentlyFinishedSet(c context.Context, jobID string) *dsset.Set {
+        return &dsset.Set{
+                ID:              "finished:" + jobID,
+                ShardCount:      8,
+                TombstonesRoot:  datastore.KeyForObj(c, &CronState{ID: jobID}),
+                TombstonesDelay: 15 * time.Minute,
+        }
+}
+
+func pokeMachine(c context.Context, entity *CronState, cb func(context.Context, *cron.Machine) error) error {
+        machine := &cron.Machine{
+                Now:      clock.Now(c),
+                Schedule: entity.schedule(),
+                Nonce:    func() int64 { return mathrand.Get(c).Int63() + 1 },
+                State:    entity.State,
+        }
+
+        if err := cb(c, machine); err != nil {
+                return err
+        }
+
+        tasks := []*tq.Task{}
+        for _, action := range machine.Actions {
+                switch a := action.(type) {
+                case cron.TickLaterAction:
+                        logging.Infof(c, "Scheduling tick %d after %s", a.TickNonce, a.When.Sub(time.Now()))
+                        tasks = append(tasks, &tq.Task{
+                                Payload: &internal.TickLaterTask{JobId: entity.ID, TickNonce: a.TickNonce},
+                                ETA:     a.When,
+                        })
+                case cron.StartInvocationAction:
+                        tasks = append(tasks, &tq.Task{
+                                Payload: &internal.TriggerInvocationTask{JobId: entity.ID, TriggerId: mathrand.Get(c).Int63()},
+                        })
+                default:
+                        panic("unknown action type")
+                }
+        }
+        if err := dispatcher.AddTasks(c, tasks); err != nil {
+                return err
+        }
+
+        entity.State = machine.State
+        return nil
+}
+
 func evolve(c context.Context, id string, cb func(context.Context, *cron.Machine) error) error {
         err := datastore.RunInTransaction(c, func(c context.Context) error {
-                entity := CronState{ID: id}
-                if err := datastore.Get(c, &entity); err != nil && err != datastore.ErrNoSuchEntity {
+                entity := &CronState{ID: id}

[tandrii(chromium), 2017/07/31 18:58:46]

btw, why this change? I think entity object should be GC-ed with the stack.

+                if err := datastore.Get(c, entity); err != nil && err != datastore.ErrNoSuchEntity {
                         return err
                 }
-
-                machine := &cron.Machine{
-                        Now:      clock.Now(c),
-                        Schedule: entity.schedule(),
-                        Nonce:    func() int64 { return mathrand.Get(c).Int63() + 1 },
-                        State:    entity.State,
-                }
-
-                if err := cb(c, machine); err != nil {
+                if err := pokeMachine(c, entity, cb); err != nil {
                         return err
                 }
-
-                for _, action := range machine.Actions {
-                        var task tq.Task
-                        switch a := action.(type) {
-                        case cron.TickLaterAction:
-                                logging.Infof(c, "Scheduling tick %d after %s", a.TickNonce, a.When.Sub(time.Now()))
-                                task = tq.Task{
-                                        Payload: &internal.TickLaterTask{JobId: id, TickNonce: a.TickNonce},
-                                        ETA:     a.When,
-                                }
-                        case cron.StartInvocationAction:
-                                task = tq.Task{
-                                        Payload: &internal.StartInvocationTask{JobId: id},
-                                        Delay:   time.Second, // give the transaction time to land
-                                }
-                        default:
-                                panic("unknown action type")
-                        }
-                        if err := tasks.AddTask(c, &task); err != nil {
-                                return err
-                        }
-                }
-
-                entity.State = machine.State
-                return datastore.Put(c, &entity)
+                return datastore.Put(c, entity)
         }, nil)
-
-        if err != nil {
-                logging.Errorf(c, "FAIL - %s", err)
-        }
-        return err
+        return transient.Tag.Apply(err)
 }
 
 func startJob(c context.Context, id string) error {
         return evolve(c, id, func(c context.Context, m *cron.Machine) error {
                 // Forcefully restart the chain of tasks.
                 m.Disable()
                 m.Enable()
                 return nil
         })
 }
 
+func addTrigger(c context.Context, jobID, triggerID string) error {
+        logging.Infof(c, "Triggering %q - %q", jobID, triggerID)
+
+        // Add the trigger request to the pending set.
+        if err := pendingTriggersSet(c, jobID).Add(c, []dsset.Item{{ID: triggerID}}); err != nil {
+                return err
+        }
+
+        // Run a task that examines the pending set and makes decisions.
+        return kickTriageTask(c, jobID)
+}
+
+func kickTriageTask(c context.Context, jobID string) error {
+        // Throttle to once per 2 sec (and make sure it is always in the future).
+        eta := clock.Now(c).Unix()
+        eta = (eta/2 + 1) * 2
+        dedupKey := fmt.Sprintf("triage:%s:%d", jobID, eta)
+
+        // Use cheaper but crappier memcache as a first guard.
+        itm := memcache.NewItem(c, dedupKey).SetExpiration(time.Minute)
+        if memcache.Get(c, itm) == nil {
+                logging.Infof(c, "The triage task has already been scheduled")
+                return nil // already added!
+        }
+
+        err := dispatcher.AddTask(c, &tq.Task{
+                DeduplicationKey: dedupKey,
+                ETA:              time.Unix(eta, 0),
+                Payload:          &internal.TriageTriggersTask{JobId: jobID},
+        })
+        if err != nil {
+                return err
+        }
+        logging.Infof(c, "Scheduled the triage task")
+
+        // Best effort in setting memcache flag. No big deal if it fails.
+        memcache.Set(c, itm)
+        return nil
+}
+
 func handleTick(c context.Context, task proto.Message, execCount int) error {
         msg := task.(*internal.TickLaterTask)
         return evolve(c, msg.JobId, func(c context.Context, m *cron.Machine) error {
                 return m.OnTimerTick(msg.TickNonce)
         })
 }
 
-func handleInvocation(c context.Context, task proto.Message, execCount int) error {
-        msg := task.(*internal.StartInvocationTask)
-        logging.Infof(c, "INVOCATION of job %q has finished!", msg.JobId)
-        return evolve(c, msg.JobId, func(c context.Context, m *cron.Machine) error {
-                m.RewindIfNecessary()
-                return nil
+func handleTrigger(c context.Context, task proto.Message, execCount int) error {
+        msg := task.(*internal.TriggerInvocationTask)
+        return addTrigger(c, msg.JobId, fmt.Sprintf("cron:%d", msg.TriggerId))
+}
+
+func handleTriage(c context.Context, task proto.Message, execCount int) error {
+        msg := task.(*internal.TriageTriggersTask)
+        logging.Infof(c, "Triaging requests for %q", msg.JobId)
+
+        err := memlock.TryWithLock(c, "triageLock:"+msg.JobId, info.RequestID(c), func(context.Context) error {
+                logging.Infof(c, "Got the lock!")
+                return runTriage(c, msg.JobId)
         })
+        return transient.Tag.Apply(err)
+}
+
+func runTriage(c context.Context, jobID string) error {
+        wg := sync.WaitGroup{}
+        wg.Add(2)
+
+        var triggersList *dsset.Listing
+        var triggersErr error
+
+        var finishedList *dsset.Listing
+        var finishedErr error
+
+        // Grab all pending requests (and stuff to cleanup).
+        triggersSet := pendingTriggersSet(c, jobID)
+        go func() {
+                defer wg.Done()
+                triggersList, triggersErr = triggersSet.List(c)
+                if triggersErr == nil {
+                        logging.Infof(c, "Triggers: %d items, %d tombs to cleanup",
+                                len(triggersList.Items), len(triggersList.Tombstones))
+                }
+        }()
+
+        // Same for recently finished invocations.
+        finishedSet := recentlyFinishedSet(c, jobID)
+        go func() {
+                defer wg.Done()
+                finishedList, finishedErr = finishedSet.List(c)
+                if finishedErr == nil {
+                        logging.Infof(c, "Finished: %d items, %d tombs to cleanup",
+                                len(finishedList.Items), len(finishedList.Tombstones))
+                }
+        }()
+
+        wg.Wait()
+        switch {
+        case triggersErr != nil:
+                return triggersErr
+        case finishedErr != nil:
+                return finishedErr
+        }
+
+        // Do cleanups first.
+        if err := dsset.CleanupStorage(c, triggersList.Tombstones, finishedList.Tombstones); err != nil {
+                return err
+        }
+
+        var cleanup []*dsset.Tombstone
+        err := datastore.RunInTransaction(c, func(c context.Context) error {
+                state := &CronState{ID: jobID}
+                if err := datastore.Get(c, state); err != nil && err != datastore.ErrNoSuchEntity {
+                        return err
+                }
+
+                popOps := []*dsset.PopOp{}
+
+                // Tidy RunningSet by removing all recently finished invocations.
+                if !finishedList.Empty() {
+                        op, err := finishedSet.BeginPop(c, finishedList)
+                        if err != nil {
+                                return err
+                        }
+                        popOps = append(popOps, op)
+
+                        reallyFinished := map[int64]struct{}{}
+                        for _, itm := range finishedList.Items {
+                                if op.Pop(itm.ID) {
+                                        id, _ := strconv.ParseInt(itm.ID, 10, 64)
+                                        reallyFinished[id] = struct{}{}
+                                }
+                        }
+
+                        filtered := []int64{}
+                        for _, id := range state.RunningSet {
+                                if _, yep := reallyFinished[id]; yep {
+                                        logging.Infof(c, "Invocation finished-%d is acknowledged as finished", id)
+                                } else {
+                                        filtered = append(filtered, id)
+                                }
+                        }
+                        state.RunningSet = filtered
+                }
+
+                // Launch new invocations for each pending trigger.
+                if !triggersList.Empty() {
+                        op, err := triggersSet.BeginPop(c, triggersList)
+                        if err != nil {
+                                return err
+                        }
+                        popOps = append(popOps, op)
+
+                        batch := internal.LaunchInvocationsBatchTask{JobId: state.ID}
+                        for _, trigger := range triggersList.Items {
+                                if op.Pop(trigger.ID) {
+                                        logging.Infof(c, "Launching new launch-%d for trigger %s", state.NextInvID, trigger.ID)
+                                        state.RunningSet = append(state.RunningSet, state.NextInvID)
+                                        batch.InvId = append(batch.InvId, state.NextInvID)
+                                        state.NextInvID++
+                                }
+                        }
+                        // Transactionally trigger a batch with new invocations.
+                        if len(batch.InvId) != 0 {
+                                if err := dispatcher.AddTask(c, &tq.Task{Payload: &batch}); err != nil {
+                                        return err
+                                }
+                        }
+                }
+
+                // Submit set changes.
+                var err error
+                if cleanup, err = dsset.FinishPop(c, popOps...); err != nil {
+                        return err
+                }
+
+                logging.Infof(c, "Running invocations - %v", state.RunningSet)
+
+                // If nothing is running, poke the cron machine. Maybe it wants to start
+                // something.
+                if len(state.RunningSet) == 0 {
+                        err = pokeMachine(c, state, func(c context.Context, m *cron.Machine) error {
+                                m.RewindIfNecessary()
+                                return nil
+                        })
+                        if err != nil {
+                                return err
+                        }
+                }
+
+                // Done!
+                return datastore.Put(c, state)
+        }, nil)
+
+        if err == nil && len(cleanup) != 0 {
+                // Best effort cleanup of storage of consumed items.
+                logging.Infof(c, "Cleaning up storage of %d items", len(cleanup))
+                if err := dsset.CleanupStorage(c, cleanup); err != nil {
+                        logging.Warningf(c, "Best effort cleanup failed - %s", err)
+                }
+        }
+
+        return transient.Tag.Apply(err)
+}
+
+func handleBatchLaunch(c context.Context, task proto.Message, execCount int) error {
+        msg := task.(*internal.LaunchInvocationsBatchTask)
+        logging.Infof(c, "Batch launch for %q", msg.JobId)
+
+        tasks := []*tq.Task{}
+        for _, invId := range msg.InvId {
+                logging.Infof(c, "Launching inv-%d", invId)
+                tasks = append(tasks, &tq.Task{
+                        DeduplicationKey: fmt.Sprintf("inv:%s:%d", msg.JobId, invId),
+                        Payload: &internal.LaunchInvocationTask{
+                                JobId: msg.JobId,
+                                InvId: invId,
+                        },
+                })
+        }
+
+        return dispatcher.AddTasks(c, tasks)
+}
+
+func handleLaunchTask(c context.Context, task proto.Message, execCount int) error {
+        msg := task.(*internal.LaunchInvocationTask)
+        logging.Infof(c, "Executing invocation %q: exec-%d", msg.JobId, msg.InvId)
+
+        // There can be more stuff here. But we just finish the invocation right away.
+
+        finishedSet := recentlyFinishedSet(c, msg.JobId)
+        err := finishedSet.Add(c, []dsset.Item{
+                {ID: fmt.Sprintf("%d", msg.InvId)},
+        })
+        if err != nil {
+                return err
+        }
+
+        // Kick the triage now that the set of running invocations has been modified.
+        return kickTriageTask(c, msg.JobId)
 }
 
 func init() {
         r := router.New()
         gaemiddleware.InstallHandlers(r)
 
-        tasks.RegisterTask(&internal.TickLaterTask{}, handleTick, "default", nil)
-        tasks.RegisterTask(&internal.StartInvocationTask{}, handleInvocation, "default", nil)
-        tasks.InstallRoutes(r, gaemiddleware.BaseProd())
+        dispatcher.RegisterTask(&internal.TickLaterTask{}, handleTick, "timers", nil)
+        dispatcher.RegisterTask(&internal.TriggerInvocationTask{}, handleTrigger, "triggers", nil)
+        dispatcher.RegisterTask(&internal.TriageTriggersTask{}, handleTriage, "triages", nil)
+        dispatcher.RegisterTask(&internal.LaunchInvocationsBatchTask{}, handleBatchLaunch, "launches", nil)
+        dispatcher.RegisterTask(&internal.LaunchInvocationTask{}, handleLaunchTask, "invocations", nil)
+        dispatcher.InstallRoutes(r, gaemiddleware.BaseProd())
 
         // Kick-start a bunch of jobs by visiting:
         //
         // http://localhost:8080/start/with 10s interval
         // http://localhost:8080/start/with 5s interval
         // http://localhost:8080/start/0 * * * * * * *
         //
         // And the look at the logs.
 
         r.GET("/start/:JobID", gaemiddleware.BaseProd(), func(c *router.Context) {
                 jobID := c.Params.ByName("JobID")
                 if err := startJob(c.Context, jobID); err != nil {
                         panic(err)
                 }
         })
 
+        r.GET("/trigger/:JobID", gaemiddleware.BaseProd(), func(c *router.Context) {
+                jobID := c.Params.ByName("JobID")
+                triggerID := fmt.Sprintf("manual:%d", clock.Now(c.Context).UnixNano())
+                if err := addTrigger(c.Context, jobID, triggerID); err != nil {
+                        panic(err)
+                }
+        })
+
         http.DefaultServeMux.Handle("/", r)
 }