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Multi-cursor: pending task count monitoring & mitigation (#3275)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,230 @@ | ||
| // The MIT License | ||
| // | ||
| // Copyright (c) 2020 Temporal Technologies Inc. All rights reserved. | ||
| // | ||
| // Copyright (c) 2020 Uber Technologies, Inc. | ||
| // | ||
| // Permission is hereby granted, free of charge, to any person obtaining a copy | ||
| // of this software and associated documentation files (the "Software"), to deal | ||
| // in the Software without restriction, including without limitation the rights | ||
| // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | ||
| // copies of the Software, and to permit persons to whom the Software is | ||
| // furnished to do so, subject to the following conditions: | ||
| // | ||
| // The above copyright notice and this permission notice shall be included in | ||
| // all copies or substantial portions of the Software. | ||
| // | ||
| // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
| // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | ||
| // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | ||
| // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | ||
| // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | ||
| // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | ||
| // THE SOFTWARE. | ||
|
|
||
| package queues | ||
|
|
||
| import ( | ||
| "time" | ||
|
|
||
| "golang.org/x/exp/slices" | ||
|
|
||
| "go.temporal.io/server/common/collection" | ||
| "go.temporal.io/server/common/namespace" | ||
| "go.temporal.io/server/service/history/tasks" | ||
| ) | ||
|
|
||
| const ( | ||
| targetLoadFactor = 0.8 | ||
| clearSliceThrottleDuration = 10 * time.Second | ||
| ) | ||
|
|
||
| type ( | ||
| actionQueuePendingTask struct { | ||
| attributes *AlertAttributesQueuePendingTaskCount | ||
| monitor Monitor | ||
| maxReaderCount int | ||
| completionFn actionCompletionFn | ||
|
|
||
| // state of the action, used when running the action | ||
| tasksPerNamespace map[namespace.ID]int | ||
| pendingTaskPerNamespacePerSlice map[Slice]map[namespace.ID]int | ||
| slicesPerNamespace map[namespace.ID][]Slice | ||
| namespaceToClearPerSlice map[Slice][]namespace.ID | ||
| } | ||
| ) | ||
|
|
||
| func newQueuePendingTaskAction( | ||
| attributes *AlertAttributesQueuePendingTaskCount, | ||
| monitor Monitor, | ||
| maxReaderCount int, | ||
| completionFn actionCompletionFn, | ||
| ) Action { | ||
| return &actionQueuePendingTask{ | ||
| attributes: attributes, | ||
| monitor: monitor, | ||
| maxReaderCount: maxReaderCount, | ||
| completionFn: completionFn, | ||
| } | ||
| } | ||
|
|
||
| func (a *actionQueuePendingTask) Run(readerGroup *ReaderGroup) { | ||
| defer a.completionFn() | ||
|
|
||
| // first check if the alert is still valid | ||
| if a.monitor.GetTotalPendingTaskCount() <= a.attributes.CiriticalPendingTaskCount { | ||
| return | ||
| } | ||
|
|
||
| // then try to shrink existing slices, which may reduce pending task count | ||
| readers := readerGroup.Readers() | ||
| if a.tryShrinkSlice(readers) { | ||
| return | ||
| } | ||
|
|
||
| // have to unload pending tasks to reduce pending task count | ||
| a.init() | ||
| a.gatherStatistics(readers) | ||
| a.findSliceToClear( | ||
| a.monitor.GetTotalPendingTaskCount(), | ||
| int(float64(a.attributes.CiriticalPendingTaskCount)*targetLoadFactor), | ||
| ) | ||
| a.splitAndClearSlice(readers, readerGroup) | ||
| } | ||
|
|
||
| func (a *actionQueuePendingTask) tryShrinkSlice( | ||
| readers map[int32]Reader, | ||
| ) bool { | ||
| for _, reader := range readers { | ||
| reader.ShrinkSlices() | ||
| } | ||
| return a.monitor.GetTotalPendingTaskCount() <= a.attributes.CiriticalPendingTaskCount | ||
| } | ||
|
|
||
| func (a *actionQueuePendingTask) init() { | ||
| a.tasksPerNamespace = make(map[namespace.ID]int) | ||
| a.pendingTaskPerNamespacePerSlice = make(map[Slice]map[namespace.ID]int) | ||
| a.slicesPerNamespace = make(map[namespace.ID][]Slice) | ||
| a.namespaceToClearPerSlice = make(map[Slice][]namespace.ID) | ||
| } | ||
|
|
||
| func (a *actionQueuePendingTask) gatherStatistics( | ||
| readers map[int32]Reader, | ||
| ) { | ||
| // gather statistic for | ||
| // 1. total # of pending tasks per namespace | ||
| // 2. for each slice, # of pending taks per namespace | ||
| // 3. for each namespace, a list of slices that contains pending tasks from that namespace, | ||
| // reversely ordered by slice range. Upon unloading, first unload newer slices. | ||
| for _, reader := range readers { | ||
| reader.WalkSlices(func(s Slice) { | ||
| a.pendingTaskPerNamespacePerSlice[s] = s.TaskStats().PendingPerNamespace | ||
| for namespaceID, pendingTaskCount := range a.pendingTaskPerNamespacePerSlice[s] { | ||
| a.tasksPerNamespace[namespaceID] += pendingTaskCount | ||
| a.slicesPerNamespace[namespaceID] = append(a.slicesPerNamespace[namespaceID], s) | ||
| } | ||
| }) | ||
| } | ||
| for _, sliceList := range a.slicesPerNamespace { | ||
| slices.SortFunc(sliceList, func(this, that Slice) bool { | ||
| thisMin := this.Scope().Range.InclusiveMin | ||
| thatMin := that.Scope().Range.InclusiveMin | ||
| return thisMin.CompareTo(thatMin) > 0 | ||
| }) | ||
| } | ||
| } | ||
|
|
||
| func (a *actionQueuePendingTask) findSliceToClear( | ||
| currentPendingTasks int, | ||
| targetPendingTasks int, | ||
| ) { | ||
| // order namespace by # of pending tasks | ||
| namespaceIDs := make([]namespace.ID, 0, len(a.tasksPerNamespace)) | ||
| for namespaceID := range a.tasksPerNamespace { | ||
| namespaceIDs = append(namespaceIDs, namespaceID) | ||
| } | ||
| pq := collection.NewPriorityQueueWithItems( | ||
| func(this, that namespace.ID) bool { | ||
| return a.tasksPerNamespace[this] > a.tasksPerNamespace[that] | ||
| }, | ||
| namespaceIDs, | ||
| ) | ||
|
|
||
| for currentPendingTasks > targetPendingTasks && !pq.IsEmpty() { | ||
| namespaceID := pq.Remove() | ||
|
|
||
| sliceList := a.slicesPerNamespace[namespaceID] | ||
| if len(sliceList) == 0 { | ||
| panic("Found namespace with non-zero pending task count but has no correspoding Slice") | ||
| } | ||
|
|
||
| // pop the first slice in the list | ||
| sliceToClear := sliceList[0] | ||
| sliceList = sliceList[1:] | ||
| a.slicesPerNamespace[namespaceID] = sliceList | ||
|
|
||
| a.tasksPerNamespace[namespaceID] -= a.pendingTaskPerNamespacePerSlice[sliceToClear][namespaceID] | ||
| if a.tasksPerNamespace[namespaceID] > 0 { | ||
| pq.Add(namespaceID) | ||
| } | ||
|
|
||
| a.namespaceToClearPerSlice[sliceToClear] = append(a.namespaceToClearPerSlice[sliceToClear], namespaceID) | ||
| } | ||
| } | ||
|
|
||
| func (a *actionQueuePendingTask) splitAndClearSlice( | ||
| readers map[int32]Reader, | ||
| readerGroup *ReaderGroup, | ||
| ) { | ||
| for readerID, reader := range readers { | ||
| if readerID == int32(a.maxReaderCount)-1 { | ||
| // we can't do further split, have to clear entire slice | ||
| cleared := false | ||
| reader.ClearSlices(func(s Slice) bool { | ||
| _, ok := a.namespaceToClearPerSlice[s] | ||
| cleared = cleared || ok | ||
| return ok | ||
| }) | ||
| if cleared { | ||
| reader.Pause(clearSliceThrottleDuration) | ||
| } | ||
| continue | ||
| } | ||
|
|
||
| var splitSlices []Slice | ||
| reader.SplitSlices(func(s Slice) ([]Slice, bool) { | ||
| namespaceIDs, ok := a.namespaceToClearPerSlice[s] | ||
| if !ok { | ||
| return nil, false | ||
| } | ||
|
|
||
| namespaceIDStrings := make([]string, 0, len(namespaceIDs)) | ||
| for _, namespaceID := range namespaceIDs { | ||
| namespaceIDStrings = append(namespaceIDStrings, namespaceID.String()) | ||
| } | ||
|
|
||
| split, remain := s.SplitByPredicate(tasks.NewNamespacePredicate(namespaceIDStrings)) | ||
| split.Clear() | ||
| splitSlices = append(splitSlices, split) | ||
| return []Slice{remain}, true | ||
| }) | ||
|
|
||
| if len(splitSlices) == 0 { | ||
| continue | ||
| } | ||
|
|
||
| nextReader, ok := readerGroup.ReaderByID(readerID + 1) | ||
| if ok { | ||
| nextReader.MergeSlices(splitSlices...) | ||
| } else { | ||
| nextReader = readerGroup.NewReader(readerID+1, splitSlices...) | ||
| } | ||
| nextReader.Pause(clearSliceThrottleDuration) | ||
| } | ||
|
|
||
| // it's likely that after a split, slice range can be shrinked | ||
| // as tasks blocking the min key from moving have been moved to another slice/reader | ||
| for _, reader := range readers { | ||
| reader.ShrinkSlices() | ||
| } | ||
| } |
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