app/vminsert/netstorage: improve ingestion performance when a single vmstorage node is slower than other vmstorage nodes

Previously the ingestion performance has been limited by the slowest vmstorage node.
Now vminsert should re-route data from the slowest vmstorage node to the remaining nodes.

README.md

@@ -250,6 +250,8 @@ Each instance type - `vminsert`, `vmselect` and `vmstorage` - can run on the mos
 * The recommended total number of vCPU cores for all the `vminsert` instances can be calculated from the ingestion rate: `vCPUs = ingestion_rate / 150K`.
 * The recommended number of vCPU cores per each `vminsert` instance should equal to the number of `vmstorage` instances in the cluster.
 * The amount of RAM per each `vminsert` instance should be 1GB or more. RAM is used as a buffer for spikes in ingestion rate.
+  The maximum amount of used RAM per `vminsert` node can be tuned with `-memory.allowedPercent` command-line flag. For instance, `-memory.allowedPercent=20`
+  limits the maximum amount of used RAM to 20% of the available RAM on the host system.
 * Sometimes `-rpc.disableCompression` command-line flag on `vminsert` instances could increase ingestion capacity at the cost
   of higher network bandwidth usage between `vminsert` and `vmstorage`.
 

app/vminsert/netstorage/insert_ctx.go

@@ -6,10 +6,8 @@ import (
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/auth"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/bytesutil"
-	"github.com/VictoriaMetrics/VictoriaMetrics/lib/consts"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/encoding"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/httpserver"
-	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/prompb"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/storage"
 	xxhash "github.com/cespare/xxhash/v2"
@@ -25,8 +23,6 @@ type InsertCtx struct {
 
 	bufRowss  []bufRows
 	labelsBuf []byte
-
-	resultCh chan error
 }
 
 type bufRows struct {
@@ -34,11 +30,15 @@ type bufRows struct {
 	rows int
 }
 
+func (br *bufRows) reset() {
+	br.buf = br.buf[:0]
+	br.rows = 0
+}
+
 func (br *bufRows) pushTo(sn *storageNode) error {
 	bufLen := len(br.buf)
 	err := sn.push(br.buf, br.rows)
-	br.buf = br.buf[:0]
-	br.rows = 0
+	br.reset()
 	if err != nil {
 		return &httpserver.ErrorWithStatusCode{
 			Err:        fmt.Errorf("cannot send %d bytes to storageNode %q: %s", bufLen, sn.dialer.Addr(), err),
@@ -61,16 +61,9 @@ func (ctx *InsertCtx) Reset() {
 		ctx.bufRowss = make([]bufRows, len(storageNodes))
 	}
 	for i := range ctx.bufRowss {
-		br := &ctx.bufRowss[i]
-		br.buf = br.buf[:0]
-		br.rows = 0
+		ctx.bufRowss[i].reset()
 	}
 	ctx.labelsBuf = ctx.labelsBuf[:0]
-	if ctx.resultCh == nil {
-		ctx.resultCh = make(chan error, len(storageNodes))
-	} else if len(ctx.resultCh) > 0 {
-		logger.Panicf("BUG: ctx.resultCh must be empty on Reset; got %d items", len(ctx.resultCh))
-	}
 }
 
 // AddLabelBytes adds (name, value) label to ctx.Labels.
@@ -125,7 +118,7 @@ func (ctx *InsertCtx) WriteDataPointExt(at *auth.Token, storageNodeIdx int, metr
 	br := &ctx.bufRowss[storageNodeIdx]
 	sn := storageNodes[storageNodeIdx]
 	bufNew := storage.MarshalMetricRow(br.buf, metricNameRaw, timestamp, value)
-	if len(bufNew) >= consts.MaxInsertPacketSize {
+	if len(bufNew) >= maxBufSizePerStorageNode {
 		// Send buf to storageNode, since it is too big.
 		if err := br.pushTo(sn); err != nil {
 			return err
@@ -140,23 +133,13 @@ func (ctx *InsertCtx) WriteDataPointExt(at *auth.Token, storageNodeIdx int, metr
 
 // FlushBufs flushes ctx bufs to remote storage nodes.
 func (ctx *InsertCtx) FlushBufs() error {
-	// Send per-storageNode bufs in parallel.
-	resultCh := ctx.resultCh
-	resultChLen := 0
+	var firstErr error
 	for i := range ctx.bufRowss {
 		br := &ctx.bufRowss[i]
 		if len(br.buf) == 0 {
 			continue
 		}
-		resultChLen++
-		go func(br *bufRows, sn *storageNode) {
-			resultCh <- br.pushTo(sn)
-		}(br, storageNodes[i])
-	}
-	var firstErr error
-	for i := 0; i < resultChLen; i++ {
-		err := <-resultCh
-		if err != nil && firstErr == nil {
+		if err := br.pushTo(storageNodes[i]); err != nil && firstErr == nil {
 			firstErr = err
 		}
 	}

app/vminsert/netstorage/netstorage.go

@@ -5,8 +5,10 @@ import (
 	"fmt"
 	"io"
 	"sync"
+	"sync/atomic"
 	"time"
 
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/bytesutil"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/consts"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/encoding"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/handshake"
@@ -16,14 +18,23 @@ import (
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/storage"
 	"github.com/VictoriaMetrics/metrics"
 	xxhash "github.com/cespare/xxhash/v2"
+	jump "github.com/lithammer/go-jump-consistent-hash"
 )
 
 var disableRPCCompression = flag.Bool(`rpc.disableCompression`, false, "Disable compression of RPC traffic. This reduces CPU usage at the cost of higher network bandwidth usage")
 
-// push pushes buf to sn.
+func (sn *storageNode) isBroken() bool {
+	return atomic.LoadUint32(&sn.broken) != 0
+}
+
+// push pushes buf to sn internal bufs.
 //
-// It falls back to sending data to another vmstorage node if sn is currently
-// unavailable.
+// This function doesn't block on fast path.
+// It may block only if all the storageNodes cannot handle the incoming ingestion rate.
+// This blocking provides backpressure to the caller.
+//
+// The function falls back to sending data to other vmstorage nodes
+// if sn is currently unavailable or overloaded.
 //
 // rows is the number of rows in the buf.
 func (sn *storageNode) push(buf []byte, rows int) error {
@@ -32,103 +43,116 @@ func (sn *storageNode) push(buf []byte, rows int) error {
 	}
 	sn.rowsPushed.Add(rows)
 
-	sn.mu.Lock()
-	defer sn.mu.Unlock()
-
-	if sn.broken {
-		// The vmstorage node is broken. Re-route buf to healthy vmstorage nodes.
-		if !addToReroutedBuf(buf, rows) {
-			rowsLostTotal.Add(rows)
-			return fmt.Errorf("%d rows dropped because of reroutedBuf overflows %d bytes", rows, reroutedBufMaxSize)
+	if sn.isBroken() {
+		// The vmstorage node is temporarily broken. Re-route buf to healthy vmstorage nodes.
+		if err := addToReroutedBuf(buf, rows); err != nil {
+			return fmt.Errorf("%d rows dropped because the current vsmtorage is unavailable and %s", rows, err)
 		}
 		sn.rowsReroutedFromHere.Add(rows)
 		return nil
 	}
 
-	if len(sn.buf)+len(buf) <= maxBufSizePerStorageNode {
+	sn.brLock.Lock()
+	if len(sn.br.buf)+len(buf) <= maxBufSizePerStorageNode {
 		// Fast path: the buf contents fits sn.buf.
-		sn.buf = append(sn.buf, buf...)
-		sn.rows += rows
+		sn.br.buf = append(sn.br.buf, buf...)
+		sn.br.rows += rows
+		sn.brLock.Unlock()
 		return nil
 	}
+	sn.brLock.Unlock()
 
 	// Slow path: the buf contents doesn't fit sn.buf.
-	// Flush sn.buf to vmstorage and then add buf to sn.buf.
-	if err := sn.flushBufLocked(); err != nil {
-		// Failed to flush or re-route sn.buf to vmstorage nodes.
-		// The sn.buf is already dropped by flushBufLocked.
-		// Drop buf too, since there is little sense in trying to rescue it.
-		rowsLostTotal.Add(rows)
-		return err
+	// This means that the current vmstorage is slow or will become broken soon.
+	// Re-route buf to healthy vmstorage nodes.
+	if err := addToReroutedBuf(buf, rows); err != nil {
+		return fmt.Errorf("%d rows dropped because the current vmstorage buf is full and %s", rows, err)
 	}
-
-	// Successful flush.
-	sn.buf = append(sn.buf, buf...)
-	sn.rows += rows
+	sn.rowsReroutedFromHere.Add(rows)
 	return nil
 }
 
-func (sn *storageNode) sendReroutedRow(buf []byte) error {
-	sn.mu.Lock()
-	defer sn.mu.Unlock()
+var closedCh = func() <-chan struct{} {
+	ch := make(chan struct{})
+	close(ch)
+	return ch
+}()
 
-	if sn.broken {
-		return errBrokenStorageNode
-	}
-	if len(sn.buf)+len(buf) > maxBufSizePerStorageNode {
-		return fmt.Errorf("cannot put %d bytes into vmstorage buffer, since its size cannot exceed %d bytes", len(sn.buf)+len(buf), maxBufSizePerStorageNode)
-	}
-	sn.buf = append(sn.buf, buf...)
-	sn.rows++
-	return nil
-}
-
-var errBrokenStorageNode = fmt.Errorf("the vmstorage node is temporarily broken")
-
-func (sn *storageNode) flushBufLocked() error {
-	err := sn.sendBufLocked(sn.buf)
-	if err == nil {
-		// Successful flush. Remove broken flag.
-		sn.broken = false
-		sn.rowsSent.Add(sn.rows)
-		sn.buf = sn.buf[:0]
-		sn.rows = 0
-		return nil
-	}
-
-	// Couldn't flush sn.buf to vmstorage. Mark sn as broken
-	// and try re-routing sn.buf to healthy vmstorage nodes.
-	sn.broken = true
-	if addToReroutedBuf(sn.buf, sn.rows) {
-		// Successfully re-routed data to healthy nodes.
-		sn.buf = sn.buf[:0]
-		sn.rows = 0
-		return nil
-	}
-	// Preserve sn.buf when it cannot be sent to healthy nodes
-	// in the hope the error will disappear on the next call to flushBufLocked.
-	//
-	// This should fix https://github.com/VictoriaMetrics/VictoriaMetrics/issues/294 .
-	return err
-}
-
-func (sn *storageNode) sendBufLocked(buf []byte) error {
-	if len(buf) == 0 {
-		return nil
-	}
-	if sn.bc == nil {
-		if err := sn.dial(); err != nil {
-			return fmt.Errorf("cannot dial %q: %s", sn.dialer.Addr(), err)
+func (sn *storageNode) run(stopCh <-chan struct{}) {
+	ticker := time.NewTicker(time.Second)
+	defer ticker.Stop()
+	var br bufRows
+	var bc *handshake.BufferedConn
+	var err error
+	var waitCh <-chan struct{}
+	mustStop := false
+	for !mustStop {
+		sn.brLock.Lock()
+		bufLen := len(sn.br.buf)
+		sn.brLock.Unlock()
+		waitCh = nil
+		if len(br.buf) == 0 && bufLen > maxBufSizePerStorageNode/4 {
+			// Do not sleep, since sn.br.buf contains enough data to process.
+			waitCh = closedCh
+		}
+		select {
+		case <-stopCh:
+			mustStop = true
+			// Make sure the sn.buf is flushed last time before returning
+			// in order to send the remaining bits of data.
+		case <-ticker.C:
+		case <-waitCh:
+		}
+		if len(br.buf) == 0 {
+			sn.brLock.Lock()
+			sn.br, br = br, sn.br
+			sn.brLock.Unlock()
+		}
+		if bc == nil {
+			bc, err = sn.dial()
+			if err != nil {
+				// Mark sn as broken in order to prevent sending additional data to it until it is recovered.
+				atomic.StoreUint32(&sn.broken, 1)
+				if len(br.buf) == 0 {
+					continue
+				}
+				logger.Errorf("re-routing %d bytes with %d rows to other storage nodes because cannot dial storageNode %q: %s",
+					len(br.buf), br.rows, sn.dialer.Addr(), err)
+				if addToReroutedBufNonblock(br.buf, br.rows) {
+					sn.rowsReroutedFromHere.Add(br.rows)
+					br.reset()
+				}
+				continue
+			}
+		}
+		if err = sendToConn(bc, br.buf); err == nil {
+			// Successfully sent buf to bc. Remove broken flag from sn.
+			atomic.StoreUint32(&sn.broken, 0)
+			sn.rowsSent.Add(br.rows)
+			br.reset()
+			continue
+		}
+		// Couldn't flush buf to sn. Mark sn as broken
+		// and try re-routing buf to healthy vmstorage nodes.
+		if err = bc.Close(); err != nil {
+			logger.Errorf("cannot close connection to storageNode %q: %s", sn.dialer.Addr(), err)
+			// continue executing the code below.
+		}
+		bc = nil
+		sn.connectionErrors.Inc()
+		atomic.StoreUint32(&sn.broken, 1)
+		if addToReroutedBufNonblock(br.buf, br.rows) {
+			sn.rowsReroutedFromHere.Add(br.rows)
+			br.reset()
 		}
 	}
-	if err := sn.sendToConn(sn.bc, buf); err != nil {
-		sn.closeBrokenConn()
-		return err
-	}
-	return nil
 }
 
-func (sn *storageNode) sendToConn(bc *handshake.BufferedConn, buf []byte) error {
+func sendToConn(bc *handshake.BufferedConn, buf []byte) error {
+	if len(buf) == 0 {
+		// Nothing to send
+		return nil
+	}
 	timeoutSeconds := len(buf) / 3e5
 	if timeoutSeconds < 60 {
 		timeoutSeconds = 60
@@ -141,8 +165,10 @@ func (sn *storageNode) sendToConn(bc *handshake.BufferedConn, buf []byte) error
 	// sizeBuf guarantees that the rows batch will be either fully
 	// read or fully discarded on the vmstorage side.
 	// sizeBuf is used for read optimization in vmstorage.
-	sn.sizeBuf = encoding.MarshalUint64(sn.sizeBuf[:0], uint64(len(buf)))
-	if _, err := bc.Write(sn.sizeBuf); err != nil {
+	sizeBuf := sizeBufPool.Get()
+	defer sizeBufPool.Put(sizeBuf)
+	sizeBuf.B = encoding.MarshalUint64(sizeBuf.B[:0], uint64(len(buf)))
+	if _, err := bc.Write(sizeBuf.B); err != nil {
 		return fmt.Errorf("cannot write data size %d: %s", len(buf), err)
 	}
 	if _, err := bc.Write(buf); err != nil {
@@ -158,20 +184,22 @@ func (sn *storageNode) sendToConn(bc *handshake.BufferedConn, buf []byte) error
 	if err := bc.SetReadDeadline(deadline); err != nil {
 		return fmt.Errorf("cannot set read deadline for reading `ack` to vmstorage: %s", err)
 	}
-	if _, err := io.ReadFull(bc, sn.sizeBuf[:1]); err != nil {
+	if _, err := io.ReadFull(bc, sizeBuf.B[:1]); err != nil {
 		return fmt.Errorf("cannot read `ack` from vmstorage: %s", err)
 	}
-	if sn.sizeBuf[0] != 1 {
-		return fmt.Errorf("unexpected `ack` received from vmstorage; got %d; want %d", sn.sizeBuf[0], 1)
+	if sizeBuf.B[0] != 1 {
+		return fmt.Errorf("unexpected `ack` received from vmstorage; got %d; want %d", sizeBuf.B[0], 1)
 	}
 	return nil
 }
 
-func (sn *storageNode) dial() error {
+var sizeBufPool bytesutil.ByteBufferPool
+
+func (sn *storageNode) dial() (*handshake.BufferedConn, error) {
 	c, err := sn.dialer.Dial()
 	if err != nil {
 		sn.dialErrors.Inc()
-		return err
+		return nil, err
 	}
 	compressionLevel := 1
 	if *disableRPCCompression {
@@ -181,87 +209,73 @@ func (sn *storageNode) dial() error {
 	if err != nil {
 		_ = c.Close()
 		sn.handshakeErrors.Inc()
-		return fmt.Errorf("handshake error: %s", err)
-	}
-	sn.bc = bc
-	return nil
-}
-
-func (sn *storageNode) closeBrokenConn() {
-	if sn.bc == nil {
-		return
-	}
-	_ = sn.bc.Close()
-	sn.bc = nil
-	sn.connectionErrors.Inc()
-}
-
-func (sn *storageNode) run(stopCh <-chan struct{}) {
-	ticker := time.NewTicker(time.Second)
-	defer ticker.Stop()
-	mustStop := false
-	for !mustStop {
-		select {
-		case <-stopCh:
-			mustStop = true
-			// Make sure flushBufLocked is called last time before returning
-			// in order to send the remaining bits of data.
-		case <-ticker.C:
-		}
-
-		sn.mu.Lock()
-		if err := sn.flushBufLocked(); err != nil {
-			sn.closeBrokenConn()
-			logger.Errorf("cannot flush data to storageNode %q: %s", sn.dialer.Addr(), err)
-		}
-		sn.mu.Unlock()
+		return nil, fmt.Errorf("handshake error: %s", err)
 	}
+	return bc, nil
 }
 
 func rerouteWorker(stopCh <-chan struct{}) {
 	ticker := time.NewTicker(time.Second)
 	defer ticker.Stop()
-	var buf []byte
+	var br bufRows
+	var waitCh <-chan struct{}
 	mustStop := false
 	for !mustStop {
+		reroutedBRLock.Lock()
+		bufLen := len(reroutedBR.buf)
+		reroutedBRLock.Unlock()
+		waitCh = nil
+		if len(br.buf) == 0 && bufLen > reroutedBufMaxSize/4 {
+			// Do not sleep if reroutedBR contains enough data to process.
+			waitCh = closedCh
+		}
 		select {
 		case <-stopCh:
 			mustStop = true
-			// Make sure spreadReroutedBufToStorageNodes is called last time before returning
+			// Make sure reroutedBR is re-routed last time before returning
 			// in order to reroute the remaining data to healthy vmstorage nodes.
 		case <-ticker.C:
+		case <-waitCh:
 		}
-
-		var err error
-		buf, err = spreadReroutedBufToStorageNodes(buf[:0])
-		if err != nil {
+		if len(br.buf) == 0 {
+			reroutedBRLock.Lock()
+			reroutedBR, br = br, reroutedBR
+			reroutedBRLock.Unlock()
+		}
+		reroutedBRCond.Broadcast()
+		if len(br.buf) == 0 {
+			// Nothing to re-route.
+			continue
+		}
+		sns := getHealthyStorageNodes()
+		if len(sns) == 0 {
+			// No more vmstorage nodes to write data to.
 			rerouteErrors.Inc()
-			logger.Errorf("cannot reroute data among healthy vmstorage nodes: %s", err)
+			logger.Errorf("cannot send rerouted rows because all the storage nodes are unhealthy")
+			// Do not reset br in the hope it could be sent next time.
+			continue
 		}
+		spreadReroutedBufToStorageNodes(sns, &br)
+		// There is no need in br.reset() here, since it is already done in spreadReroutedBufToStorageNodes.
 	}
+	// Notify all the blocked addToReroutedBuf callers, so they may finish the work.
+	reroutedBRCond.Broadcast()
 }
 
 // storageNode is a client sending data to vmstorage node.
 type storageNode struct {
-	mu sync.Mutex
-
-	// Buffer with data that needs to be written to vmstorage node.
-	buf []byte
-
-	// The number of rows buf contains at the moment.
-	rows int
-
-	// Temporary buffer for encoding marshaled buf size.
-	sizeBuf []byte
-
-	// broken is set to true if the given vmstorage node is temporarily unhealthy.
+	// broken is set to non-zero if the given vmstorage node is temporarily unhealthy.
 	// In this case the data is re-routed to the remaining healthy vmstorage nodes.
-	broken bool
+	broken uint32
+
+	// brLock protects br.
+	brLock sync.Mutex
+
+	// Buffer with data that needs to be written to the storage node.
+	br bufRows
 
 	dialer *netutil.TCPDialer
 
-	bc *handshake.BufferedConn
-
 	// The number of dial errors to vmstorage node.
 	dialErrors *metrics.Counter
 
@@ -321,15 +335,15 @@ func InitStorageNodes(addrs []string) {
 			rowsReroutedToHere:   metrics.NewCounter(fmt.Sprintf(`vm_rpc_rows_rerouted_to_here_total{name="vminsert", addr=%q}`, addr)),
 		}
 		_ = metrics.NewGauge(fmt.Sprintf(`vm_rpc_rows_pending{name="vminsert", addr=%q}`, addr), func() float64 {
-			sn.mu.Lock()
-			n := sn.rows
-			sn.mu.Unlock()
+			sn.brLock.Lock()
+			n := sn.br.rows
+			sn.brLock.Unlock()
 			return float64(n)
 		})
 		_ = metrics.NewGauge(fmt.Sprintf(`vm_rpc_buf_pending_bytes{name="vminsert", addr=%q}`, addr), func() float64 {
-			sn.mu.Lock()
-			n := len(sn.buf)
-			sn.mu.Unlock()
+			sn.brLock.Lock()
+			n := len(sn.br.buf)
+			sn.brLock.Unlock()
 			return float64(n)
 		})
 		storageNodes = append(storageNodes, sn)
@@ -340,11 +354,17 @@ func InitStorageNodes(addrs []string) {
 		}(addr)
 	}
 
-	maxBufSizePerStorageNode = memory.Allowed() / 4 / len(storageNodes)
+	maxBufSizePerStorageNode = memory.Allowed() / 8 / len(storageNodes)
 	if maxBufSizePerStorageNode > consts.MaxInsertPacketSize {
 		maxBufSizePerStorageNode = consts.MaxInsertPacketSize
 	}
 	reroutedBufMaxSize = memory.Allowed() / 16
+	if reroutedBufMaxSize < maxBufSizePerStorageNode {
+		reroutedBufMaxSize = maxBufSizePerStorageNode
+	}
+	if reroutedBufMaxSize > maxBufSizePerStorageNode*len(storageNodes) {
+		reroutedBufMaxSize = maxBufSizePerStorageNode * len(storageNodes)
+	}
 	rerouteWorkerWG.Add(1)
 	go func() {
 		rerouteWorker(rerouteWorkerStopCh)
@@ -361,136 +381,175 @@ func Stop() {
 	storageNodesWG.Wait()
 }
 
-func addToReroutedBuf(buf []byte, rows int) bool {
-	reroutedLock.Lock()
-	defer reroutedLock.Unlock()
-	if len(reroutedBuf)+len(buf) > reroutedBufMaxSize {
-		reroutedBufOverflows.Inc()
-		return false
+// addToReroutedBuf adds buf to reroutedBR.
+//
+// It waits until the reroutedBR has enough space for buf or if Stop is called.
+// This guarantees backpressure if the ingestion rate exceeds vmstorage nodes'
+// ingestion rate capacity.
+//
+// It returns non-nil error only in the following cases:
+//
+//   - if all the storage nodes are unhealthy.
+//   - if Stop is called.
+func addToReroutedBuf(buf []byte, rows int) error {
+	if len(buf) > reroutedBufMaxSize {
+		logger.Panicf("BUG: len(buf)=%d cannot exceed reroutedBufMaxSize=%d", len(buf), reroutedBufMaxSize)
 	}
-	reroutedBuf = append(reroutedBuf, buf...)
-	reroutedRows += rows
+
+	reroutedBRLock.Lock()
+	defer reroutedBRLock.Unlock()
+
+	for len(reroutedBR.buf)+len(buf) > reroutedBufMaxSize {
+		if getHealthyStorageNodesCount() == 0 {
+			rowsLostTotal.Add(rows)
+			return fmt.Errorf("all the vmstorage nodes are unavailable and reroutedBR has no enough space for storing %d bytes; only %d bytes left in reroutedBR",
+				len(buf), reroutedBufMaxSize-len(reroutedBR.buf))
+		}
+		select {
+		case <-rerouteWorkerStopCh:
+			rowsLostTotal.Add(rows)
+			return fmt.Errorf("rerouteWorker cannot send the data since it is stopped")
+		default:
+		}
+
+		// The reroutedBR.buf has no enough space for len(buf). Wait while the reroutedBR.buf is be sent by rerouteWorker.
+		reroutedBufWaits.Inc()
+		reroutedBRCond.Wait()
+	}
+	reroutedBR.buf = append(reroutedBR.buf, buf...)
+	reroutedBR.rows += rows
 	reroutesTotal.Inc()
-	return true
+	return nil
 }
 
-func spreadReroutedBufToStorageNodes(swapBuf []byte) ([]byte, error) {
-	healthyStorageNodes := getHealthyStorageNodes()
-	if len(healthyStorageNodes) == 0 {
-		// No more vmstorage nodes to write data to.
-		return swapBuf, fmt.Errorf("all the storage nodes are unhealthy")
+// addToReroutedBufNonblock adds buf to reroutedBR.
+//
+// It returns true if buf has been successfully added to reroutedBR.
+func addToReroutedBufNonblock(buf []byte, rows int) bool {
+	if len(buf) > reroutedBufMaxSize {
+		logger.Panicf("BUG: len(buf)=%d cannot exceed reroutedBufMaxSize=%d", len(buf), reroutedBufMaxSize)
 	}
-
-	reroutedLock.Lock()
-	reroutedBuf, swapBuf = swapBuf[:0], reroutedBuf
-	rows := reroutedRows
-	reroutedRows = 0
-	reroutedLock.Unlock()
-
-	if len(swapBuf) == 0 {
-		// Nothing to re-route.
-		return swapBuf, nil
+	reroutedBRLock.Lock()
+	ok := len(reroutedBR.buf)+len(buf) <= reroutedBufMaxSize
+	if ok {
+		reroutedBR.buf = append(reroutedBR.buf, buf...)
+		reroutedBR.rows += rows
+		reroutesTotal.Inc()
 	}
+	reroutedBRLock.Unlock()
+	return ok
+}
 
+func getHealthyStorageNodesCount() int {
+	n := 0
+	for _, sn := range storageNodes {
+		if !sn.isBroken() {
+			n++
+		}
+	}
+	return n
+}
+
+func getHealthyStorageNodes() []*storageNode {
+	sns := make([]*storageNode, 0, len(storageNodes)-1)
+	for _, sn := range storageNodes {
+		if !sn.isBroken() {
+			sns = append(sns, sn)
+		}
+	}
+	return sns
+}
+
+func spreadReroutedBufToStorageNodes(sns []*storageNode, br *bufRows) {
 	var mr storage.MetricRow
-	src := swapBuf
 	rowsProcessed := 0
+	src := br.buf
 	for len(src) > 0 {
 		tail, err := mr.Unmarshal(src)
 		if err != nil {
-			logger.Panicf("BUG: cannot unmarshal recently marshaled MetricRow: %s", err)
+			logger.Panicf("BUG: cannot unmarshal MetricRow from reroutedBR.buf: %s", err)
 		}
 		rowBuf := src[:len(src)-len(tail)]
 		src = tail
 
-		// Use non-consistent hashing instead of jump hash in order to re-route rows
-		// equally among healthy vmstorage nodes.
-		// This should spread the increased load among healthy vmstorage nodes.
-		h := xxhash.Sum64(mr.MetricNameRaw)
-		idx := h % uint64(len(healthyStorageNodes))
+		idx := uint64(0)
+		if len(sns) > 1 {
+			h := xxhash.Sum64(mr.MetricNameRaw)
+			idx = uint64(jump.Hash(h, int32(len(sns))))
+		}
 		attempts := 0
 		for {
-			sn := healthyStorageNodes[idx]
-			err := sn.sendReroutedRow(rowBuf)
-			if err == nil {
-				sn.rowsReroutedToHere.Inc()
+			sn := sns[idx]
+			if sn.sendReroutedRow(rowBuf) {
+				// The row has been successfully re-routed to sn.
 				break
 			}
 
-			// Cannot send data to sn. Try sending to the next vmstorage node.
+			// Cannot re-route data to sn. Try sending to the next vmstorage node.
 			idx++
-			if idx >= uint64(len(healthyStorageNodes)) {
+			if idx >= uint64(len(sns)) {
 				idx = 0
 			}
 			attempts++
-			if attempts < len(healthyStorageNodes) {
+			if attempts < len(sns) {
 				continue
 			}
-			// There are no healthy nodes.
-			// Try returning the remaining data to reroutedBuf if it has enough free space.
-			rowsRemaining := rows - rowsProcessed
-			recovered := false
-			reroutedLock.Lock()
-			if len(rowBuf)+len(tail)+len(reroutedBuf) <= reroutedBufMaxSize {
-				swapBuf = append(swapBuf[:0], rowBuf...)
-				swapBuf = append(swapBuf, tail...)
-				swapBuf = append(swapBuf, reroutedBuf...)
-				reroutedBuf, swapBuf = swapBuf, reroutedBuf[:0]
-				reroutedRows += rowsRemaining
-				recovered = true
-			}
-			reroutedLock.Unlock()
-			if recovered {
-				return swapBuf, nil
-			}
-			rowsLostTotal.Add(rowsRemaining)
-			return swapBuf, fmt.Errorf("all the %d vmstorage nodes are unavailable; lost %d rows; last error: %s", len(storageNodes), rowsRemaining, err)
+
+			// There is no enough buffer space in all the vmstorage nodes.
+			// Return the remaining data to br.buf, so it may be processed later.
+			br.buf = append(br.buf[:0], rowBuf...)
+			br.buf = append(br.buf, src...)
+			br.rows -= rowsProcessed
+			return
 		}
 		rowsProcessed++
 	}
-	if rowsProcessed != rows {
-		logger.Panicf("BUG: unexpected number of rows processed; got %d; want %d", rowsProcessed, rows)
+	if rowsProcessed != br.rows {
+		logger.Panicf("BUG: unexpected number of rows processed; got %d; want %d", rowsProcessed, br.rows)
 	}
 	reroutedRowsProcessed.Add(rowsProcessed)
-	return swapBuf, nil
+	br.reset()
+}
+
+func (sn *storageNode) sendReroutedRow(buf []byte) bool {
+	if sn.isBroken() {
+		return false
+	}
+	sn.brLock.Lock()
+	ok := len(sn.br.buf)+len(buf) <= maxBufSizePerStorageNode
+	if ok {
+		sn.br.buf = append(sn.br.buf, buf...)
+		sn.br.rows++
+		sn.rowsReroutedToHere.Inc()
+	}
+	sn.brLock.Unlock()
+	return ok
 }
 
 var (
 	maxBufSizePerStorageNode int
 
-	reroutedLock       sync.Mutex
-	reroutedBuf        []byte
-	reroutedRows       int
+	reroutedBR         bufRows
+	reroutedBRLock     sync.Mutex
+	reroutedBRCond     = sync.NewCond(&reroutedBRLock)
 	reroutedBufMaxSize int
 
 	reroutedRowsProcessed = metrics.NewCounter(`vm_rpc_rerouted_rows_processed_total{name="vminsert"}`)
-	reroutedBufOverflows  = metrics.NewCounter(`vm_rpc_rerouted_buf_overflows_total{name="vminsert"}`)
+	reroutedBufWaits      = metrics.NewCounter(`vm_rpc_rerouted_buf_waits_total{name="vminsert"}`)
 	reroutesTotal         = metrics.NewCounter(`vm_rpc_reroutes_total{name="vminsert"}`)
 	_                     = metrics.NewGauge(`vm_rpc_rerouted_rows_pending{name="vminsert"}`, func() float64 {
-		reroutedLock.Lock()
-		n := reroutedRows
-		reroutedLock.Unlock()
+		reroutedBRLock.Lock()
+		n := reroutedBR.rows
+		reroutedBRLock.Unlock()
 		return float64(n)
 	})
 	_ = metrics.NewGauge(`vm_rpc_rerouted_buf_pending_bytes{name="vminsert"}`, func() float64 {
-		reroutedLock.Lock()
-		n := len(reroutedBuf)
-		reroutedLock.Unlock()
+		reroutedBRLock.Lock()
+		n := len(reroutedBR.buf)
+		reroutedBRLock.Unlock()
 		return float64(n)
 	})
 
 	rerouteErrors = metrics.NewCounter(`vm_rpc_reroute_errors_total{name="vminsert"}`)
 	rowsLostTotal = metrics.NewCounter(`vm_rpc_rows_lost_total{name="vminsert"}`)
 )
-
-func getHealthyStorageNodes() []*storageNode {
-	sns := make([]*storageNode, 0, len(storageNodes)-1)
-	for _, sn := range storageNodes {
-		sn.mu.Lock()
-		if !sn.broken {
-			sns = append(sns, sn)
-		}
-		sn.mu.Unlock()
-	}
-	return sns
-}

docs/Cluster-VictoriaMetrics.md

@@ -250,6 +250,8 @@ Each instance type - `vminsert`, `vmselect` and `vmstorage` - can run on the mos
 * The recommended total number of vCPU cores for all the `vminsert` instances can be calculated from the ingestion rate: `vCPUs = ingestion_rate / 150K`.
 * The recommended number of vCPU cores per each `vminsert` instance should equal to the number of `vmstorage` instances in the cluster.
 * The amount of RAM per each `vminsert` instance should be 1GB or more. RAM is used as a buffer for spikes in ingestion rate.
+  The maximum amount of used RAM per `vminsert` node can be tuned with `-memory.allowedPercent` command-line flag. For instance, `-memory.allowedPercent=20`
+  limits the maximum amount of used RAM to 20% of the available RAM on the host system.
 * Sometimes `-rpc.disableCompression` command-line flag on `vminsert` instances could increase ingestion capacity at the cost
   of higher network bandwidth usage between `vminsert` and `vmstorage`.