Add vmstorageUserTimeout flags to configure TCP user timeout (Linux)

`TCP_USER_TIMEOUT` (since Linux 2.6.37) specifies the maximum amount of
time that transmitted data may remain unacknowledged before TCP will
forcibly close the connection and return `ETIMEDOUT` to the application.

Setting a low TCP user timeout allows RPC connections quickly reroute
around unavailable storage nodes during network interruptions.

app/vminsert/netstorage/netstorage.go

@@ -32,6 +32,10 @@ var (
 	disableRerouting      = flag.Bool("disableRerouting", true, "Whether to disable re-routing when some of vmstorage nodes accept incoming data at slower speed compared to other storage nodes. Disabled re-routing limits the ingestion rate by the slowest vmstorage node. On the other side, disabled re-routing minimizes the number of active time series in the cluster during rolling restarts and during spikes in series churn rate. See also -dropSamplesOnOverload")
 	dropSamplesOnOverload = flag.Bool("dropSamplesOnOverload", false, "Whether to drop incoming samples if the destination vmstorage node is overloaded and/or unavailable. This prioritizes cluster availability over consistency, e.g. the cluster continues accepting all the ingested samples, but some of them may be dropped if vmstorage nodes are temporarily unavailable and/or overloaded. The drop of samples happens before the replication, so it's not recommended to use this flag with -replicationFactor enabled.")
 	vmstorageDialTimeout  = flag.Duration("vmstorageDialTimeout", 5*time.Second, "Timeout for establishing RPC connections from vminsert to vmstorage")
+	vmstorageUserTimeout  = flag.Duration("vmstorageUserTimeout", 0, "TCP user timeout for RPC connections from vminsert to vmstorage (Linux only). "+
+		"When greater than 0, it specifies the maximum amount of time transmitted data may remain unacknowledged before the TCP connection is closed."+
+		"Setting a low TCP user timeout allows inserts to reroute around unresponsive storage nodes faster than the full insert timeout (at least 60 seconds)."+
+		"By default, this timeout is disabled.")
 )
 
 var errStorageReadOnly = errors.New("storage node is read only")
@@ -516,7 +520,7 @@ func initStorageNodes(addrs []string, hashSeed uint64) *storageNodesBucket {
 			addr += ":8400"
 		}
 		sn := &storageNode{
-			dialer: netutil.NewTCPDialer(ms, "vminsert", addr, *vmstorageDialTimeout),
+			dialer: netutil.NewTCPDialer(ms, "vminsert", addr, *vmstorageDialTimeout, *vmstorageUserTimeout),
 
 			stopCh: stopCh,
 

app/vmselect/netstorage/netstorage.go

@@ -42,6 +42,11 @@ var (
 	maxSamplesPerSeries  = flag.Int("search.maxSamplesPerSeries", 30e6, "The maximum number of raw samples a single query can scan per each time series. See also -search.maxSamplesPerQuery")
 	maxSamplesPerQuery   = flag.Int("search.maxSamplesPerQuery", 1e9, "The maximum number of raw samples a single query can process across all time series. This protects from heavy queries, which select unexpectedly high number of raw samples. See also -search.maxSamplesPerSeries")
 	vmstorageDialTimeout = flag.Duration("vmstorageDialTimeout", 5*time.Second, "Timeout for establishing RPC connections from vmselect to vmstorage")
+	vmstorageUserTimeout = flag.Duration("vmstorageUserTimeout", 0, "TCP user timeout for RPC connections from vmselect to vmstorage (Linux only). "+
+		"When greater than 0, it specifies the maximum amount of time transmitted data may remain unacknowledged before the TCP connection is closed. "+
+		"Setting a low TCP user timeout allows queries to ignore unresponsive storage nodes faster than the max query duration. "+
+		"By default, this timeout is disabled. "+
+		"See also -search.maxQueryDuration")
 )
 
 // Result is a single timeseries result.
@@ -2753,7 +2758,7 @@ func newStorageNode(ms *metrics.Set, addr string) *storageNode {
 		addr += ":8401"
 	}
 	// There is no need in requests compression, since vmselect requests are usually very small.
-	connPool := netutil.NewConnPool(ms, "vmselect", addr, handshake.VMSelectClient, 0, *vmstorageDialTimeout)
+	connPool := netutil.NewConnPool(ms, "vmselect", addr, handshake.VMSelectClient, 0, *vmstorageDialTimeout, *vmstorageUserTimeout)
 
 	sn := &storageNode{
 		connPool: connPool,

lib/netutil/conn_pool.go

@@ -49,9 +49,9 @@ type connWithTimestamp struct {
 // The compression is disabled if compressionLevel <= 0.
 //
 // Call ConnPool.MustStop when the returned ConnPool is no longer needed.
-func NewConnPool(ms *metrics.Set, name, addr string, handshakeFunc handshake.Func, compressionLevel int, dialTimeout time.Duration) *ConnPool {
+func NewConnPool(ms *metrics.Set, name, addr string, handshakeFunc handshake.Func, compressionLevel int, dialTimeout time.Duration, userTimeout time.Duration) *ConnPool {
 	cp := &ConnPool{
-		d:                 NewTCPDialer(ms, name, addr, dialTimeout),
+		d:                 NewTCPDialer(ms, name, addr, dialTimeout, userTimeout),
 		concurrentDialsCh: make(chan struct{}, 8),
 
 		name:             name,

lib/netutil/conn_pool_test.go

@@ -44,7 +44,7 @@ func testConnPoolStartStop(t *testing.T, name string, ms *metrics.Set) {
 	var cps []*ConnPool
 	for i := 0; i < 5; i++ {
 		addr := fmt.Sprintf("host-%d", i)
-		cp := NewConnPool(ms, name, addr, handshake.VMSelectClient, compressLevel, dialTimeout)
+		cp := NewConnPool(ms, name, addr, handshake.VMSelectClient, compressLevel, dialTimeout, 0)
 		cps = append(cps, cp)
 	}
 	for _, cp := range cps {

lib/netutil/tcpdialer.go

@@ -3,6 +3,7 @@ package netutil
 import (
 	"fmt"
 	"net"
+	"syscall"
 	"time"
 
 	"github.com/VictoriaMetrics/metrics"
@@ -12,7 +13,7 @@ import (
 //
 // The name is used in metric tags for the returned dialer.
 // The name must be unique among dialers.
-func NewTCPDialer(ms *metrics.Set, name, addr string, dialTimeout time.Duration) *TCPDialer {
+func NewTCPDialer(ms *metrics.Set, name, addr string, dialTimeout time.Duration, userTimeout time.Duration) *TCPDialer {
 	d := &TCPDialer{
 		d: &net.Dialer{
 			Timeout: dialTimeout,
@@ -27,6 +28,17 @@ func NewTCPDialer(ms *metrics.Set, name, addr string, dialTimeout time.Duration)
 		dialErrors: ms.NewCounter(fmt.Sprintf(`vm_tcpdialer_errors_total{name=%q, addr=%q, type="dial"}`, name, addr)),
 	}
 	d.connMetrics.init(ms, "vm_tcpdialer", name, addr)
+	if userTimeout > 0 {
+		d.d.Control = func(network, address string, c syscall.RawConn) (err error) {
+			controlErr := c.Control(func(fd uintptr) {
+				err = setTCPUserTimeout(fd, userTimeout)
+			})
+			if controlErr != nil {
+				return controlErr
+			}
+			return err
+		}
+	}
 	return d
 }
 

lib/netutil/tcpdialer_default.go

@@ -0,0 +1,12 @@
+//go:build !linux
+// +build !linux
+
+package netutil
+
+import (
+	"time"
+)
+
+func setTCPUserTimeout(fd uintptr, timeout time.Duration) error {
+	return nil
+}

lib/netutil/tcpdialer_linux.go

@@ -0,0 +1,12 @@
+package netutil
+
+import (
+	"golang.org/x/sys/unix"
+	"syscall"
+	"time"
+)
+
+func setTCPUserTimeout(fd uintptr, timeout time.Duration) error {
+	return syscall.SetsockoptInt(
+		int(fd), syscall.IPPROTO_TCP, unix.TCP_USER_TIMEOUT, int(timeout.Milliseconds()))
+}