tidb tsheap 源码
tidb tsheap 代码
文件路径：/br/pkg/streamhelper/tsheap.go
// Copyright 2022 PingCAP, Inc. Licensed under Apache-2.0.
package streamhelper
import (
"encoding/hex"
"fmt"
"strings"
"sync"
"time"
"github.com/google/btree"
"github.com/pingcap/errors"
berrors "github.com/pingcap/tidb/br/pkg/errors"
"github.com/pingcap/tidb/br/pkg/logutil"
"github.com/pingcap/tidb/br/pkg/redact"
"github.com/pingcap/tidb/br/pkg/utils"
"github.com/pingcap/tidb/kv"
"github.com/tikv/client-go/v2/oracle"
"go.uber.org/zap/zapcore"
)
// CheckpointsCache is the heap-like cache for checkpoints.
//
// "Checkpoint" is the "Resolved TS" of some range.
// A resolved ts is a "watermark" for the system, which:
// - implies there won't be any transactions (in some range) commit with `commit_ts` smaller than this TS.
// - is monotonic increasing.
// A "checkpoint" is a "safe" Resolved TS, which:
// - is a TS *less than* the real resolved ts of now.
// - is based on range (it only promises there won't be new committed txns in the range).
// - the checkpoint of union of ranges is the minimal checkpoint of all ranges.
// As an example:
/*
+----------------------------------+
^-----------^ (Checkpoint = 42)
^---------------^ (Checkpoint = 76)
^-----------------------^ (Checkpoint = min(42, 76) = 42)
*/
// For calculating the global checkpoint, we can make a heap-like structure:
// Checkpoint Ranges
// 42 -> {[0, 8], [16, 100]}
// 1002 -> {[8, 16]}
// 1082 -> {[100, inf]}
// For now, the checkpoint of range [8, 16] and [100, inf] won't affect the global checkpoint
// directly, so we can try to advance only the ranges of {[0, 8], [16, 100]} (which's checkpoint is steal).
// Once them get advance, the global checkpoint would be advanced then,
// and we don't need to update all ranges (because some new ranges don't need to be advanced so quickly.)
type CheckpointsCache interface {
fmt.Stringer
// InsertRange inserts a range with specified TS to the cache.
InsertRange(ts uint64, rng kv.KeyRange)
// InsertRanges inserts a set of ranges that sharing checkpoint to the cache.
InsertRanges(rst RangesSharesTS)
// CheckpointTS returns the now global (union of all ranges) checkpoint of the cache.
CheckpointTS() uint64
// PopRangesWithGapGT pops the ranges which's checkpoint is
PopRangesWithGapGT(d time.Duration) []*RangesSharesTS
// Check whether the ranges in the cache is integrate.
ConsistencyCheck(ranges []kv.KeyRange) error
// Clear the cache.
Clear()
}
// NoOPCheckpointCache is used when cache disabled.
type NoOPCheckpointCache struct{}
func (NoOPCheckpointCache) InsertRange(ts uint64, rng kv.KeyRange) {}
func (NoOPCheckpointCache) InsertRanges(rst RangesSharesTS) {}
func (NoOPCheckpointCache) Clear() {}
func (NoOPCheckpointCache) String() string {
return "NoOPCheckpointCache"
}
func (NoOPCheckpointCache) CheckpointTS() uint64 {
panic("invalid state: NoOPCheckpointCache should never be used in advancing!")
}
func (NoOPCheckpointCache) PopRangesWithGapGT(d time.Duration) []*RangesSharesTS {
panic("invalid state: NoOPCheckpointCache should never be used in advancing!")
}
func (NoOPCheckpointCache) ConsistencyCheck([]kv.KeyRange) error {
return errors.Annotatef(berrors.ErrUnsupportedOperation, "invalid state: NoOPCheckpointCache should never be used in advancing!")
}
// RangesSharesTS is a set of ranges shares the same timestamp.
type RangesSharesTS struct {
TS uint64
Ranges []kv.KeyRange
}
func (rst *RangesSharesTS) Zap() zapcore.ObjectMarshaler {
return zapcore.ObjectMarshalerFunc(func(oe zapcore.ObjectEncoder) error {
rngs := rst.Ranges
if len(rst.Ranges) > 3 {
rngs = rst.Ranges[:3]
}
oe.AddUint64("checkpoint", rst.TS)
return oe.AddArray("items", zapcore.ArrayMarshalerFunc(func(ae zapcore.ArrayEncoder) error {
return ae.AppendObject(zapcore.ObjectMarshalerFunc(func(oe1 zapcore.ObjectEncoder) error {
for _, rng := range rngs {
oe1.AddString("start-key", redact.String(hex.EncodeToString(rng.StartKey)))
oe1.AddString("end-key", redact.String(hex.EncodeToString(rng.EndKey)))
}
return nil
}))
}))
})
}
func (rst *RangesSharesTS) String() string {
// Make a more friendly string.
return fmt.Sprintf("@%sR%d", oracle.GetTimeFromTS(rst.TS).Format("0405"), len(rst.Ranges))
}
func (rst *RangesSharesTS) Less(other btree.Item) bool {
return rst.TS < other.(*RangesSharesTS).TS
}
// Checkpoints is a heap that collects all checkpoints of
// regions, it supports query the latest checkpoint fast.
// This structure is thread safe.
type Checkpoints struct {
tree *btree.BTree
mu sync.Mutex
}
func NewCheckpoints() *Checkpoints {
return &Checkpoints{
tree: btree.New(32),
}
}
// String formats the slowest 5 ranges sharing TS to string.
func (h *Checkpoints) String() string {
h.mu.Lock()
defer h.mu.Unlock()
b := new(strings.Builder)
count := 0
total := h.tree.Len()
h.tree.Ascend(func(i btree.Item) bool {
rst := i.(*RangesSharesTS)
b.WriteString(rst.String())
b.WriteString(";")
count++
return count < 5
})
if total-count > 0 {
fmt.Fprintf(b, "O%d", total-count)
}
return b.String()
}
// InsertRanges insert a RangesSharesTS directly to the tree.
func (h *Checkpoints) InsertRanges(r RangesSharesTS) {
h.mu.Lock()
defer h.mu.Unlock()
if items := h.tree.Get(&r); items != nil {
i := items.(*RangesSharesTS)
i.Ranges = append(i.Ranges, r.Ranges...)
} else {
h.tree.ReplaceOrInsert(&r)
}
}
// InsertRange inserts the region and its TS into the region tree.
func (h *Checkpoints) InsertRange(ts uint64, rng kv.KeyRange) {
h.mu.Lock()
defer h.mu.Unlock()
r := h.tree.Get(&RangesSharesTS{TS: ts})
if r == nil {
r = &RangesSharesTS{TS: ts}
h.tree.ReplaceOrInsert(r)
}
rr := r.(*RangesSharesTS)
rr.Ranges = append(rr.Ranges, rng)
}
// Clear removes all records in the checkpoint cache.
func (h *Checkpoints) Clear() {
h.mu.Lock()
defer h.mu.Unlock()
h.tree.Clear(false)
}
// PopRangesWithGapGT pops ranges with gap greater than the specified duration.
// NOTE: maybe make something like `DrainIterator` for better composing?
func (h *Checkpoints) PopRangesWithGapGT(d time.Duration) []*RangesSharesTS {
h.mu.Lock()
defer h.mu.Unlock()
result := []*RangesSharesTS{}
for {
item, ok := h.tree.Min().(*RangesSharesTS)
if !ok {
return result
}
if time.Since(oracle.GetTimeFromTS(item.TS)) >= d {
result = append(result, item)
h.tree.DeleteMin()
} else {
return result
}
}
}
// CheckpointTS returns the cached checkpoint TS by the current state of the cache.
func (h *Checkpoints) CheckpointTS() uint64 {
h.mu.Lock()
defer h.mu.Unlock()
item, ok := h.tree.Min().(*RangesSharesTS)
if !ok {
return 0
}
return item.TS
}
// ConsistencyCheck checks whether the tree contains the full range of key space.
func (h *Checkpoints) ConsistencyCheck(rangesIn []kv.KeyRange) error {
h.mu.Lock()
rangesReal := make([]kv.KeyRange, 0, 1024)
h.tree.Ascend(func(i btree.Item) bool {
rangesReal = append(rangesReal, i.(*RangesSharesTS).Ranges...)
return true
})
h.mu.Unlock()
r := CollapseRanges(len(rangesReal), func(i int) kv.KeyRange { return rangesReal[i] })
ri := CollapseRanges(len(rangesIn), func(i int) kv.KeyRange { return rangesIn[i] })
return errors.Annotatef(checkIntervalIsSubset(r, ri), "ranges: (current) %s (not in) %s", logutil.StringifyKeys(r),
logutil.StringifyKeys(ri))
}
// A simple algorithm to detect non-overlapped ranges.
// It maintains the "current" probe, and let the ranges to check "consume" it.
// For example:
// toCheck: |_____________________| |_____________|
// . ^checking
// subsetOf: |_________| |_______| |__________|
// . ^probing
// probing is the subrange of checking, consume it and move forward the probe.
// toCheck: |_____________________| |_____________|
// . ^checking
// subsetOf: |_________| |_______| |__________|
// . ^probing
// consume it, too.
// toCheck: |_____________________| |_____________|
// . ^checking
// subsetOf: |_________| |_______| |__________|
// . ^probing
// checking is at the left of probing and no overlaps, moving it forward.
// toCheck: |_____________________| |_____________|
// . ^checking
// subsetOf: |_________| |_______| |__________|
// . ^probing
// consume it. all subset ranges are consumed, check passed.
func checkIntervalIsSubset(toCheck []kv.KeyRange, subsetOf []kv.KeyRange) error {
i := 0
si := 0
for {
// We have checked all ranges.
if si >= len(subsetOf) {
return nil
}
// There are some ranges doesn't reach the end.
if i >= len(toCheck) {
return errors.Annotatef(berrors.ErrPiTRMalformedMetadata,
"there remains a range doesn't be fully consumed: %s",
logutil.StringifyRange(subsetOf[si]))
}
checking := toCheck[i]
probing := subsetOf[si]
// checking: |___________|
// probing: |_________|
// A rare case: the "first" range is out of bound or not fully covers the probing range.
if utils.CompareBytesExt(checking.StartKey, false, probing.StartKey, false) > 0 {
holeEnd := checking.StartKey
if utils.CompareBytesExt(holeEnd, false, probing.EndKey, true) > 0 {
holeEnd = probing.EndKey
}
return errors.Annotatef(berrors.ErrPiTRMalformedMetadata, "probably a hole in key ranges: %s", logutil.StringifyRange{
StartKey: probing.StartKey,
EndKey: holeEnd,
})
}
// checking: |_____|
// probing: |_______|
// Just move forward checking.
if utils.CompareBytesExt(checking.EndKey, true, probing.StartKey, false) < 0 {
i += 1
continue
}
// checking: |_________|
// probing: |__________________|
// Given all of the ranges are "collapsed", the next checking range must
// not be adjacent with the current checking range.
// And hence there must be a "hole" in the probing key space.
if utils.CompareBytesExt(checking.EndKey, true, probing.EndKey, true) < 0 {
next := probing.EndKey
if i+1 < len(toCheck) {
next = toCheck[i+1].EndKey
}
return errors.Annotatef(berrors.ErrPiTRMalformedMetadata, "probably a hole in key ranges: %s", logutil.StringifyRange{
StartKey: checking.EndKey,
EndKey: next,
})
}
// checking: |________________|
// probing: |_____________|
// The current checking range fills the current probing range,
// or the current checking range is out of the current range.
// let's move the probing forward.
si += 1
}
}
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