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[apache#30083][prism] Factor out hold tracking to dedicated structures (
apache#31105) * [prism] Factor out hold tracking to dedicated structures * review comment-reorder move code out of ladder. --------- Co-authored-by: lostluck <13907733+lostluck@users.noreply.github.com>
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105 changes: 105 additions & 0 deletions
105
sdks/go/pkg/beam/runners/prism/internal/engine/holds.go
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,105 @@ | ||
| // Licensed to the Apache Software Foundation (ASF) under one or more | ||
| // contributor license agreements. See the NOTICE file distributed with | ||
| // this work for additional information regarding copyright ownership. | ||
| // The ASF licenses this file to You 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 engine | ||
|
|
||
| import ( | ||
| "container/heap" | ||
| "fmt" | ||
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| "github.com/apache/beam/sdks/v2/go/pkg/beam/core/graph/mtime" | ||
| ) | ||
|
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| // holdHeap orders holds based on their timestamps | ||
| // so we can always find the minimum timestamp of pending holds. | ||
| type holdHeap []mtime.Time | ||
|
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| func (h holdHeap) Len() int { return len(h) } | ||
| func (h holdHeap) Less(i, j int) bool { return h[i] < h[j] } | ||
| func (h holdHeap) Swap(i, j int) { h[i], h[j] = h[j], h[i] } | ||
|
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| func (h *holdHeap) Push(x any) { | ||
| // Push and Pop use pointer receivers because they modify the slice's length, | ||
| // not just its contents. | ||
| *h = append(*h, x.(mtime.Time)) | ||
| } | ||
|
|
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| func (h *holdHeap) Pop() any { | ||
| old := *h | ||
| n := len(old) | ||
| x := old[n-1] | ||
| *h = old[0 : n-1] | ||
| return x | ||
| } | ||
|
|
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| // holdTracker track the watermark holds for a stage. | ||
| // | ||
| // Timers hold back the watermark until they fire, but multiple | ||
| // timers may set the same watermark hold. | ||
| // To track when the watermark may advance further this structure maintains | ||
| // counts for each set watermark hold. | ||
| // As timers are processed, their associated holds are removed, reducing the counts. | ||
| // | ||
| // A heap of the hold times is kept so we have quick access to the minimum hold, for calculating | ||
| // how to advance the watermark. | ||
| type holdTracker struct { | ||
| heap holdHeap | ||
| counts map[mtime.Time]int | ||
| } | ||
|
|
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| func newHoldTracker() *holdTracker { | ||
| return &holdTracker{ | ||
| counts: map[mtime.Time]int{}, | ||
| } | ||
| } | ||
|
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| // Drop the given hold count. When the count of a hold time reaches zero, it's | ||
| // removed from the heap. Drop panics if holds become negative. | ||
| func (ht *holdTracker) Drop(hold mtime.Time, v int) { | ||
| n := ht.counts[hold] - v | ||
| if n > 0 { | ||
| ht.counts[hold] = n | ||
| return | ||
| } else if n < 0 { | ||
| panic(fmt.Sprintf("prism error: negative watermark hold count %v for time %v", n, hold)) | ||
| } | ||
| delete(ht.counts, hold) | ||
| for i, h := range ht.heap { | ||
| if hold == h { | ||
| heap.Remove(&ht.heap, i) | ||
| break | ||
| } | ||
| } | ||
| } | ||
|
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| // Add a hold a number of times to heap. If the hold time isn't already present in the heap, it is added. | ||
| func (ht *holdTracker) Add(hold mtime.Time, v int) { | ||
| // Mark the hold in the heap. | ||
| ht.counts[hold] = ht.counts[hold] + v | ||
|
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| if len(ht.counts) != len(ht.heap) { | ||
| // Since there's a difference, the hold should not be in the heap, so we add it. | ||
| heap.Push(&ht.heap, hold) | ||
| } | ||
| } | ||
|
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| // Min returns the earliest hold in the heap. Returns [mtime.MaxTimestamp] if the heap is empty. | ||
| func (ht *holdTracker) Min() mtime.Time { | ||
| minWatermarkHold := mtime.MaxTimestamp | ||
| if len(ht.heap) > 0 { | ||
| minWatermarkHold = ht.heap[0] | ||
| } | ||
| return minWatermarkHold | ||
| } |
115 changes: 115 additions & 0 deletions
115
sdks/go/pkg/beam/runners/prism/internal/engine/holds_test.go
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,115 @@ | ||
| // Licensed to the Apache Software Foundation (ASF) under one or more | ||
| // contributor license agreements. See the NOTICE file distributed with | ||
| // this work for additional information regarding copyright ownership. | ||
| // The ASF licenses this file to You 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 engine | ||
|
|
||
| import ( | ||
| "testing" | ||
|
|
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| "github.com/apache/beam/sdks/v2/go/pkg/beam/core/graph/mtime" | ||
| ) | ||
|
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| func TestHoldTracker(t *testing.T) { | ||
|
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| type op func(*holdTracker) | ||
| add := func(hold mtime.Time, count int) op { | ||
| return func(ht *holdTracker) { | ||
| ht.Add(hold, count) | ||
| } | ||
| } | ||
|
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| drop := func(hold mtime.Time, count int) op { | ||
| return func(ht *holdTracker) { | ||
| ht.Drop(hold, count) | ||
| } | ||
| } | ||
|
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| tests := []struct { | ||
| name string | ||
| ops []op | ||
| wantMin mtime.Time | ||
| wantLen int | ||
| }{ | ||
| { | ||
| name: "zero-max", | ||
| wantMin: mtime.MaxTimestamp, | ||
| wantLen: 0, | ||
| }, { | ||
|
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| name: "one-min", | ||
| ops: []op{ | ||
| add(mtime.MinTimestamp, 1), | ||
| }, | ||
| wantMin: mtime.MinTimestamp, | ||
| wantLen: 1, | ||
| }, { | ||
|
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| name: "cleared-max", | ||
| ops: []op{ | ||
| add(mtime.MinTimestamp, 1), | ||
| drop(mtime.MinTimestamp, 1), | ||
| }, | ||
| wantMin: mtime.MaxTimestamp, | ||
| wantLen: 0, | ||
| }, { | ||
| name: "cleared-non-eogw", | ||
| ops: []op{ | ||
| add(mtime.MinTimestamp, 1), | ||
| add(mtime.EndOfGlobalWindowTime, 1), | ||
| drop(mtime.MinTimestamp, 1), | ||
| }, | ||
| wantMin: mtime.EndOfGlobalWindowTime, | ||
| wantLen: 1, | ||
| }, { | ||
| name: "uncleared-non-min", | ||
| ops: []op{ | ||
| add(mtime.MinTimestamp, 2), | ||
| add(mtime.EndOfGlobalWindowTime, 1), | ||
| drop(mtime.MinTimestamp, 1), | ||
| }, | ||
| wantMin: mtime.MinTimestamp, | ||
| wantLen: 2, | ||
| }, { | ||
| name: "uncleared-non-min", | ||
| ops: []op{ | ||
| add(1, 1), | ||
| add(2, 1), | ||
| add(3, 1), | ||
| drop(2, 1), | ||
| add(4, 1), | ||
| add(3, 1), | ||
| drop(1, 1), | ||
| add(2, 1), | ||
| drop(4, 1), | ||
| }, | ||
| wantMin: 2, | ||
| wantLen: 2, | ||
| }, | ||
| } | ||
| for _, test := range tests { | ||
| t.Run(test.name, func(t *testing.T) { | ||
| tracker := newHoldTracker() | ||
| for _, op := range test.ops { | ||
| op(tracker) | ||
| } | ||
| if got, want := tracker.Min(), test.wantMin; got != want { | ||
| t.Errorf("tracker.heap.Min() = %v, want %v", got, want) | ||
| } | ||
| if got, want := tracker.heap.Len(), test.wantLen; got != want { | ||
| t.Errorf("tracker.heap.Len() = %v, want %v", got, want) | ||
| } | ||
| }) | ||
| } | ||
| } |
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