adjust parameter for pipelined memdb by failpoint (#1205)

* adjust parameter for pipelined memdb by failpoint

Signed-off-by: you06 <you1474600@gmail.com>

* update comment

Signed-off-by: you06 <you1474600@gmail.com>

---------

Signed-off-by: you06 <you1474600@gmail.com>
Co-authored-by: cfzjywxk <lsswxrxr@163.com>

internal/unionstore/pipelined_memdb.go

@@ -44,6 +44,7 @@ type PipelinedMemDB struct {
 	len, size               int    // len and size records the total flushed and onflushing memdb.
 	generation              uint64
 	entryLimit, bufferLimit uint64
+	flushOption             flushOption
 }
 
 const (
@@ -57,6 +58,30 @@ const (
 	ForceFlushSizeThreshold = 128 * 1024 * 1024 // 128MB
 )
 
+type flushOption struct {
+	MinFlushKeys            int
+	MinFlushSize            int
+	ForceFlushSizeThreshold int
+}
+
+func newFlushOption() flushOption {
+	opt := flushOption{
+		MinFlushKeys:            MinFlushKeys,
+		MinFlushSize:            MinFlushSize,
+		ForceFlushSizeThreshold: ForceFlushSizeThreshold,
+	}
+	if val, err := util.EvalFailpoint("pipelinedMemDBMinFlushKeys"); err == nil && val != nil {
+		opt.MinFlushKeys = val.(int)
+	}
+	if val, err := util.EvalFailpoint("pipelinedMemDBMinFlushSize"); err == nil && val != nil {
+		opt.MinFlushSize = val.(int)
+	}
+	if val, err := util.EvalFailpoint("pipelinedMemDBForceFlushSizeThreshold"); err == nil && val != nil {
+		opt.ForceFlushSizeThreshold = val.(int)
+	}
+	return opt
+}
+
 type pipelinedMemDBSkipRemoteBuffer struct{}
 
 // TODO: skip remote buffer by context is too obscure, add a new method to read local buffer.
@@ -73,6 +98,7 @@ type BufferBatchGetter func(ctx context.Context, keys [][]byte) (map[string][]by
 func NewPipelinedMemDB(bufferBatchGetter BufferBatchGetter, flushFunc FlushFunc) *PipelinedMemDB {
 	memdb := newMemDB()
 	memdb.setSkipMutex(true)
+	flushOptoin := newFlushOption()
 	return &PipelinedMemDB{
 		memDB:             memdb,
 		errCh:             make(chan error, 1),
@@ -82,6 +108,7 @@ func NewPipelinedMemDB(bufferBatchGetter BufferBatchGetter, flushFunc FlushFunc)
 		// keep entryLimit and bufferLimit same with the memdb's default values.
 		entryLimit:  memdb.entrySizeLimit,
 		bufferLimit: memdb.bufferSizeLimit,
+		flushOption: flushOptoin,
 	}
 }
 
@@ -221,10 +248,10 @@ func (p *PipelinedMemDB) needFlush() bool {
 	// MinFlushSize <= size < ForceFlushSizeThreshold && keys < MinFlushKeys, do not flush.
 	// MinFlushSize <= size < ForceFlushSizeThreshold && keys >= MinFlushKeys, flush.
 	// size >= ForceFlushSizeThreshold, flush.
-	if size < MinFlushSize || (p.memDB.Len() < MinFlushKeys && size < ForceFlushSizeThreshold) {
+	if size < p.flushOption.MinFlushSize || (p.memDB.Len() < p.flushOption.MinFlushKeys && size < p.flushOption.ForceFlushSizeThreshold) {
 		return false
 	}
-	if p.onFlushing.Load() && size < ForceFlushSizeThreshold {
+	if p.onFlushing.Load() && size < p.flushOption.ForceFlushSizeThreshold {
 		return false
 	}
 	return true

internal/unionstore/pipelined_memdb_test.go

@@ -20,8 +20,10 @@ import (
 	"testing"
 	"time"
 
+	"github.com/pingcap/failpoint"
 	"github.com/stretchr/testify/require"
 	tikverr "github.com/tikv/client-go/v2/error"
+	"github.com/tikv/client-go/v2/util"
 )
 
 func emptyBufferBatchGetter(ctx context.Context, keys [][]byte) (map[string][]byte, error) {
@@ -297,3 +299,44 @@ func TestErrorIterator(t *testing.T) {
 	iteratorToErr(memdb.SnapshotIter(nil, nil))
 	iteratorToErr(memdb.SnapshotIterReverse(nil, nil))
 }
+
+func TestPipelinedAdjustFlushCondition(t *testing.T) {
+	util.EnableFailpoints()
+	memdb := NewPipelinedMemDB(emptyBufferBatchGetter, func(_ uint64, db *MemDB) error { return nil })
+	memdb.Set([]byte("key"), []byte("value"))
+	flushed, err := memdb.Flush(false)
+	require.Nil(t, err)
+	require.False(t, flushed)
+
+	// can flush even only 1 key
+	require.Nil(t, failpoint.Enable("tikvclient/pipelinedMemDBMinFlushKeys", `return(1)`))
+	require.Nil(t, failpoint.Enable("tikvclient/pipelinedMemDBMinFlushSize", `return(1)`))
+	memdb = NewPipelinedMemDB(emptyBufferBatchGetter, func(_ uint64, db *MemDB) error { return nil })
+	memdb.Set([]byte("key"), []byte("value"))
+	flushed, err = memdb.Flush(false)
+	require.Nil(t, err)
+	require.True(t, flushed)
+
+	// need 2 keys to flush
+	require.Nil(t, failpoint.Enable("tikvclient/pipelinedMemDBMinFlushKeys", `return(2)`))
+	require.Nil(t, failpoint.Enable("tikvclient/pipelinedMemDBMinFlushSize", `return(1)`))
+	memdb = NewPipelinedMemDB(emptyBufferBatchGetter, func(_ uint64, db *MemDB) error { return nil })
+	memdb.Set([]byte("key"), []byte("value"))
+	flushed, err = memdb.Flush(false)
+	require.Nil(t, err)
+	require.False(t, flushed)
+
+	// need 2 keys to flush, but force threshold reached
+	require.Nil(t, failpoint.Enable("tikvclient/pipelinedMemDBMinFlushKeys", `return(2)`))
+	require.Nil(t, failpoint.Enable("tikvclient/pipelinedMemDBMinFlushSize", `return(1)`))
+	require.Nil(t, failpoint.Enable("tikvclient/pipelinedMemDBForceFlushSizeThreshold", `return(2)`))
+	memdb = NewPipelinedMemDB(emptyBufferBatchGetter, func(_ uint64, db *MemDB) error { return nil })
+	memdb.Set([]byte("key"), []byte("value"))
+	flushed, err = memdb.Flush(false)
+	require.Nil(t, err)
+	require.True(t, flushed)
+
+	require.Nil(t, failpoint.Disable("tikvclient/pipelinedMemDBMinFlushKeys"))
+	require.Nil(t, failpoint.Disable("tikvclient/pipelinedMemDBMinFlushSize"))
+	require.Nil(t, failpoint.Disable("tikvclient/pipelinedMemDBForceFlushSizeThreshold"))
+}

txnkv/txnsnapshot/snapshot.go

@@ -204,8 +204,13 @@ func (s *KVSnapshot) BatchGet(ctx context.Context, keys [][]byte) (map[string][]
 	return s.BatchGetWithTier(ctx, keys, BatchGetSnapshotTier)
 }
 
+// BatchGet tiers indicate the read tier of the batch get request.
+// BatchGet read keys in regions. The keys location and region error retry mechanism are shared.
 const (
+	// BatchGetSnapshotTier indicates the batch get reads from a snapshot.
 	BatchGetSnapshotTier = 1 << iota
+	// BatchGetBufferTier indicates the batch get reads from the pipelined flushed buffer, only read locks in the current txn.
+	// this only works when the txn is created with a pipelined memdb, unless an error will be returned.
 	BatchGetBufferTier
 )