fn: paused and evicted container stats (#1209)

* fn: paused and evicted container stats

With this change, now stats reports paused state
as well as incidents of container exit due to evictions.

* fn: update/document state transitions in state tracker

There's no case of a transition moving from done to waiting. This
must be deprecated behavior.

api/agent/agent.go

@@ -898,13 +898,18 @@ func (a *agent) runHotReq(ctx context.Context, call *call, state ContainerState,
 			return false
 		}
 		isFrozen = true
+		state.UpdateState(ctx, ContainerStatePaused, call.slots)
 	}
 
 	evictor := a.evictor.GetEvictor(call.ID, call.slotHashId, call.Memory+uint64(call.TmpFsSize), uint64(call.CPUs))
 
-	state.UpdateState(ctx, ContainerStateIdle, call.slots)
+	if !isFrozen {
+		state.UpdateState(ctx, ContainerStateIdle, call.slots)
+	}
 	s := call.slots.queueSlot(slot)
 
+	isEvictEvent := false
+
 	for {
 		select {
 		case <-s.trigger: // slot already consumed
@@ -918,10 +923,12 @@ func (a *agent) runHotReq(ctx context.Context, call *call, state ContainerState,
 					return false
 				}
 				isFrozen = true
+				state.UpdateState(ctx, ContainerStatePaused, call.slots)
 			}
 			continue
 		case <-evictor.C:
 			logger.Debug("attempting hot function eject")
+			isEvictEvent = true
 		case <-ejectTimer.C:
 			// we've been idle too long, now we are ejectable
 			a.evictor.RegisterEvictor(evictor)
@@ -940,6 +947,9 @@ func (a *agent) runHotReq(ctx context.Context, call *call, state ContainerState,
 	// otherwise continue processing the request
 	if call.slots.acquireSlot(s) {
 		slot.Close(ctx)
+		if isEvictEvent {
+			statsContainerEvicted(ctx)
+		}
 		return false
 	}
 

api/agent/slots.go

@@ -163,6 +163,7 @@ func (a *slotQueue) isIdle() bool {
 		a.stats.containerStates[ContainerStateWait] == 0 &&
 		a.stats.containerStates[ContainerStateStart] == 0 &&
 		a.stats.containerStates[ContainerStateIdle] == 0 &&
+		a.stats.containerStates[ContainerStatePaused] == 0 &&
 		a.stats.containerStates[ContainerStateBusy] == 0
 
 	a.statsLock.Unlock()
@@ -180,7 +181,7 @@ func (a *slotQueue) getStats() slotQueueStats {
 
 func isNewContainerNeeded(cur *slotQueueStats) bool {
 
-	idleWorkers := cur.containerStates[ContainerStateIdle]
+	idleWorkers := cur.containerStates[ContainerStateIdle] + cur.containerStates[ContainerStatePaused]
 	starters := cur.containerStates[ContainerStateStart]
 	startWaiters := cur.containerStates[ContainerStateWait]
 

api/agent/state_trackers.go

@@ -47,12 +47,13 @@ const (
 )
 
 const (
-	ContainerStateNone  ContainerStateType = iota // uninitialized
-	ContainerStateWait                            // resource (cpu + mem) waiting
-	ContainerStateStart                           // launching
-	ContainerStateIdle                            // running idle
-	ContainerStateBusy                            // running busy
-	ContainerStateDone                            // exited/failed/done
+	ContainerStateNone   ContainerStateType = iota // uninitialized
+	ContainerStateWait                             // resource (cpu + mem) waiting
+	ContainerStateStart                            // launching
+	ContainerStateIdle                             // running: idle but not paused
+	ContainerStatePaused                           // running: idle but paused
+	ContainerStateBusy                             // running: busy
+	ContainerStateDone                             // exited/failed/done
 	ContainerStateMax
 )
 
@@ -61,14 +62,16 @@ var containerGaugeKeys = [ContainerStateMax]string{
 	"container_wait_total",
 	"container_start_total",
 	"container_idle_total",
+	"container_paused_total",
 	"container_busy_total",
-	"container_done_total",
 }
+
 var containerTimeKeys = [ContainerStateMax]string{
 	"",
 	"container_wait_duration_seconds",
 	"container_start_duration_seconds",
 	"container_idle_duration_seconds",
+	"container_paused_duration_seconds",
 	"container_busy_duration_seconds",
 }
 
@@ -101,6 +104,10 @@ func (c *requestState) UpdateState(ctx context.Context, newState RequestStateTyp
 	}
 }
 
+func isIdleState(state ContainerStateType) bool {
+	return state == ContainerStateIdle || state == ContainerStatePaused
+}
+
 func (c *containerState) UpdateState(ctx context.Context, newState ContainerStateType, slots *slotQueue) {
 
 	var now time.Time
@@ -109,11 +116,13 @@ func (c *containerState) UpdateState(ctx context.Context, newState ContainerStat
 
 	c.lock.Lock()
 
-	// except for 1) switching back to idle from busy (hot containers) or 2)
-	// to waiting from done, otherwise we can only move forward in states
+	// Only the following state transitions are allowed:
+	// 1) any move forward in states as per ContainerStateType order
+	// 2) move back: from paused to idle
+	// 3) move back: from busy to idle/paused
 	if c.state < newState ||
-		(c.state == ContainerStateBusy && newState == ContainerStateIdle) ||
-		(c.state == ContainerStateDone && newState == ContainerStateIdle) {
+		(c.state == ContainerStatePaused && newState == ContainerStateIdle) ||
+		(c.state == ContainerStateBusy && isIdleState(newState)) {
 
 		now = time.Now()
 		oldState = c.state

api/agent/stats.go

@@ -66,6 +66,10 @@ func statsLBAgentRunnerExecLatency(ctx context.Context, dur time.Duration) {
 	stats.Record(ctx, runnerExecLatencyMeasure.M(int64(dur/time.Millisecond)))
 }
 
+func statsContainerEvicted(ctx context.Context) {
+	stats.Record(ctx, containerEvictedMeasure.M(0))
+}
+
 const (
 	// TODO we should probably prefix these with calls_ ?
 	queuedMetricName     = "queued"
@@ -77,6 +81,8 @@ const (
 	errorsMetricName     = "errors"
 	serverBusyMetricName = "server_busy"
 
+	containerEvictedMetricName = "container_evictions"
+
 	// Reported By LB
 	runnerSchedLatencyMetricName = "lb_runner_sched_latency"
 	runnerExecLatencyMetricName  = "lb_runner_exec_latency"
@@ -96,6 +102,8 @@ var (
 	containerGaugeMeasures = initContainerGaugeMeasures()
 	containerTimeMeasures  = initContainerTimeMeasures()
 
+	containerEvictedMeasure = common.MakeMeasure(containerEvictedMetricName, "containers evicted", "")
+
 	// Reported By LB: How long does a runner scheduler wait for a committed call? eg. wait/launch/pull containers
 	runnerSchedLatencyMeasure = common.MakeMeasure(runnerSchedLatencyMetricName, "Runner Scheduler Latency Reported By LBAgent", "msecs")
 	// Reported By LB: Function execution time inside a container.
@@ -179,6 +187,13 @@ func RegisterContainerViews(tagKeys []string, latencyDist []float64) {
 			logrus.WithError(err).Fatal("cannot register view")
 		}
 	}
+
+	err := view.Register(
+		common.CreateView(containerEvictedMeasure, view.Count(), tagKeys),
+	)
+	if err != nil {
+		logrus.WithError(err).Fatal("cannot register view")
+	}
 }
 
 // initDockerMeasures initializes Docker related measures