mirror of https://github.com/prometheus/prometheus
Marco Pracucci
4 years ago
parent
f690b811c5
commit
b92c03023d
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// Copyright 2021 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package storage
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import (
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"math"
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"github.com/prometheus/prometheus/tsdb/chunkenc"
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)
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// MemoizedSeriesIterator wraps an iterator with a buffer to look-back the previous element.
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type MemoizedSeriesIterator struct {
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it chunkenc.Iterator
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delta int64
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lastTime int64
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ok bool
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// Keep track of the previously returned value.
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prevTime int64
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prevValue float64
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}
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// NewMemoizedEmptyIterator is like NewMemoizedIterator but it's initialised with an empty iterator.
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func NewMemoizedEmptyIterator(delta int64) *MemoizedSeriesIterator {
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return NewMemoizedIterator(chunkenc.NewNopIterator(), delta)
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}
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// NewMemoizedIterator returns a new iterator that buffers the values within the
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// time range of the current element and the duration of delta before.
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func NewMemoizedIterator(it chunkenc.Iterator, delta int64) *MemoizedSeriesIterator {
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bit := &MemoizedSeriesIterator{
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delta: delta,
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prevTime: math.MinInt64,
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}
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bit.Reset(it)
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return bit
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}
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// Reset the internal state to reuse the wrapper with the provided iterator.
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func (b *MemoizedSeriesIterator) Reset(it chunkenc.Iterator) {
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b.it = it
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b.lastTime = math.MinInt64
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b.ok = true
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b.prevTime = math.MinInt64
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it.Next()
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}
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// PeekPrev returns the previous element of the iterator. If there is none buffered,
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// ok is false.
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func (b *MemoizedSeriesIterator) PeekPrev() (t int64, v float64, ok bool) {
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if b.prevTime == math.MinInt64 {
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return 0, 0, false
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}
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return b.prevTime, b.prevValue, true
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}
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// Seek advances the iterator to the element at time t or greater.
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func (b *MemoizedSeriesIterator) Seek(t int64) bool {
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t0 := t - b.delta
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if t0 > b.lastTime {
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// Reset the previously stored element because the seek advanced
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// more than the delta.
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b.prevTime = math.MinInt64
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b.ok = b.it.Seek(t0)
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if !b.ok {
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return false
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}
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b.lastTime, _ = b.it.At()
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}
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if b.lastTime >= t {
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return true
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}
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for b.Next() {
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if b.lastTime >= t {
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return true
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}
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}
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return false
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}
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// Next advances the iterator to the next element.
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func (b *MemoizedSeriesIterator) Next() bool {
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if !b.ok {
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return false
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}
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// Keep track of the previous element.
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b.prevTime, b.prevValue = b.it.At()
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b.ok = b.it.Next()
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if b.ok {
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b.lastTime, _ = b.it.At()
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}
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return b.ok
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}
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// Values returns the current element of the iterator.
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func (b *MemoizedSeriesIterator) Values() (int64, float64) {
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return b.it.At()
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}
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// Err returns the last encountered error.
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func (b *MemoizedSeriesIterator) Err() error {
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return b.it.Err()
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}
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@ -0,0 +1,85 @@
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// Copyright 2021 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package storage
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import (
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"testing"
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"github.com/stretchr/testify/require"
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)
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func TestMemoizedSeriesIterator(t *testing.T) {
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var it *MemoizedSeriesIterator
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sampleEq := func(ets int64, ev float64) {
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ts, v := it.Values()
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require.Equal(t, ets, ts, "timestamp mismatch")
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require.Equal(t, ev, v, "value mismatch")
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}
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prevSampleEq := func(ets int64, ev float64, eok bool) {
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ts, v, ok := it.PeekPrev()
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require.Equal(t, eok, ok, "exist mismatch")
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require.Equal(t, ets, ts, "timestamp mismatch")
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require.Equal(t, ev, v, "value mismatch")
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}
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it = NewMemoizedIterator(NewListSeriesIterator(samples{
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sample{t: 1, v: 2},
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sample{t: 2, v: 3},
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sample{t: 3, v: 4},
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sample{t: 4, v: 5},
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sample{t: 5, v: 6},
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sample{t: 99, v: 8},
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sample{t: 100, v: 9},
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sample{t: 101, v: 10},
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}), 2)
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require.True(t, it.Seek(-123), "seek failed")
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sampleEq(1, 2)
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prevSampleEq(0, 0, false)
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require.True(t, it.Next(), "next failed")
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sampleEq(2, 3)
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prevSampleEq(1, 2, true)
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require.True(t, it.Next(), "next failed")
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require.True(t, it.Next(), "next failed")
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require.True(t, it.Next(), "next failed")
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sampleEq(5, 6)
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prevSampleEq(4, 5, true)
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require.True(t, it.Seek(5), "seek failed")
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sampleEq(5, 6)
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prevSampleEq(4, 5, true)
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require.True(t, it.Seek(101), "seek failed")
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sampleEq(101, 10)
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prevSampleEq(100, 9, true)
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require.False(t, it.Next(), "next succeeded unexpectedly")
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}
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func BenchmarkMemoizedSeriesIterator(b *testing.B) {
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// Simulate a 5 minute rate.
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it := NewMemoizedIterator(newFakeSeriesIterator(int64(b.N), 30), 5*60)
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b.SetBytes(int64(b.N * 16))
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b.ReportAllocs()
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b.ResetTimer()
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for it.Next() {
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// scan everything
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}
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require.NoError(b, it.Err())
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}
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