Ensure all topo read calls consider --topo_read_concurrency

changelog/22.0/22.0.0/summary.md

@@ -10,7 +10,7 @@
   - **[VTOrc Config File Changes](#vtorc-config-file-changes)**
 - **[Minor Changes](#minor-changes)**
   - **[VTTablet Flags](#flags-vttablet)**
-
+  - **[Topology read concurrency behaviour changes](#topo-read-concurrency-changes)**
 
 ## <a id="major-changes"/>Major Changes</a>
 
@@ -67,3 +67,9 @@ To upgrade to the newer version of the configuration file, first switch to using
 - `twopc_abandon_age` flag now supports values in the time.Duration format (e.g., 1s, 2m, 1h). 
 While the flag will continue to accept float values (interpreted as seconds) for backward compatibility, 
 **float inputs are deprecated** and will be removed in a future release.
+
+### <a id="topo-read-concurrency-changes"/>`--topo_read_concurrency` behaviour changes
+
+The `--topo_read_concurrency` flag was added to all components that access the topology and the provided limit is now applied separately for each global or local cell _(default `32`)_.
+
+All topology read calls _(`Get`, `GetVersion`, `List` and `ListDir`)_ now respect this per-cell limit. Previous to this version a single limit was applied to all cell calls and it was not respected by many topology calls.

go/flags/endtoend/vtbackup.txt

@@ -231,6 +231,7 @@ Flags:
       --topo_global_root string                                     the path of the global topology data in the global topology server
       --topo_global_server_address string                           the address of the global topology server
       --topo_implementation string                                  the topology implementation to use
+      --topo_read_concurrency int                                   Maximum concurrency of topo reads per global or local cell. (default 32)
       --topo_zk_auth_file string                                    auth to use when connecting to the zk topo server, file contents should be <scheme>:<auth>, e.g., digest:user:pass
       --topo_zk_base_timeout duration                               zk base timeout (see zk.Connect) (default 30s)
       --topo_zk_max_concurrency int                                 maximum number of pending requests to send to a Zookeeper server. (default 64)

go/flags/endtoend/vtcombo.txt

@@ -374,7 +374,7 @@ Flags:
       --topo_global_root string                                          the path of the global topology data in the global topology server
       --topo_global_server_address string                                the address of the global topology server
       --topo_implementation string                                       the topology implementation to use
-      --topo_read_concurrency int                                        Concurrency of topo reads. (default 32)
+      --topo_read_concurrency int                                        Maximum concurrency of topo reads per global or local cell. (default 32)
       --topo_zk_auth_file string                                         auth to use when connecting to the zk topo server, file contents should be <scheme>:<auth>, e.g., digest:user:pass
       --topo_zk_base_timeout duration                                    zk base timeout (see zk.Connect) (default 30s)
       --topo_zk_max_concurrency int                                      maximum number of pending requests to send to a Zookeeper server. (default 64)

go/flags/endtoend/vtctld.txt

@@ -164,7 +164,7 @@ Flags:
       --topo_global_root string                                          the path of the global topology data in the global topology server
       --topo_global_server_address string                                the address of the global topology server
       --topo_implementation string                                       the topology implementation to use
-      --topo_read_concurrency int                                        Concurrency of topo reads. (default 32)
+      --topo_read_concurrency int                                        Maximum concurrency of topo reads per global or local cell. (default 32)
       --topo_zk_auth_file string                                         auth to use when connecting to the zk topo server, file contents should be <scheme>:<auth>, e.g., digest:user:pass
       --topo_zk_base_timeout duration                                    zk base timeout (see zk.Connect) (default 30s)
       --topo_zk_max_concurrency int                                      maximum number of pending requests to send to a Zookeeper server. (default 64)

go/flags/endtoend/vtgate.txt

@@ -223,7 +223,7 @@ Flags:
       --topo_global_root string                                          the path of the global topology data in the global topology server
       --topo_global_server_address string                                the address of the global topology server
       --topo_implementation string                                       the topology implementation to use
-      --topo_read_concurrency int                                        Concurrency of topo reads. (default 32)
+      --topo_read_concurrency int                                        Maximum concurrency of topo reads per global or local cell. (default 32)
       --topo_zk_auth_file string                                         auth to use when connecting to the zk topo server, file contents should be <scheme>:<auth>, e.g., digest:user:pass
       --topo_zk_base_timeout duration                                    zk base timeout (see zk.Connect) (default 30s)
       --topo_zk_max_concurrency int                                      maximum number of pending requests to send to a Zookeeper server. (default 64)

go/flags/endtoend/vtorc.txt

@@ -98,7 +98,7 @@ Flags:
       --topo_global_root string                                     the path of the global topology data in the global topology server
       --topo_global_server_address string                           the address of the global topology server
       --topo_implementation string                                  the topology implementation to use
-      --topo_read_concurrency int                                   Concurrency of topo reads. (default 32)
+      --topo_read_concurrency int                                   Maximum concurrency of topo reads per global or local cell. (default 32)
       --topo_zk_auth_file string                                    auth to use when connecting to the zk topo server, file contents should be <scheme>:<auth>, e.g., digest:user:pass
       --topo_zk_base_timeout duration                               zk base timeout (see zk.Connect) (default 30s)
       --topo_zk_max_concurrency int                                 maximum number of pending requests to send to a Zookeeper server. (default 64)

go/flags/endtoend/vttablet.txt

@@ -376,6 +376,7 @@ Flags:
       --topo_global_root string                                          the path of the global topology data in the global topology server
       --topo_global_server_address string                                the address of the global topology server
       --topo_implementation string                                       the topology implementation to use
+      --topo_read_concurrency int                                        Maximum concurrency of topo reads per global or local cell. (default 32)
       --topo_zk_auth_file string                                         auth to use when connecting to the zk topo server, file contents should be <scheme>:<auth>, e.g., digest:user:pass
       --topo_zk_base_timeout duration                                    zk base timeout (see zk.Connect) (default 30s)
       --topo_zk_max_concurrency int                                      maximum number of pending requests to send to a Zookeeper server. (default 64)

go/vt/discovery/healthcheck.go

@@ -373,7 +373,7 @@ func NewHealthCheck(ctx context.Context, retryDelay, healthCheckTimeout time.Dur
 		if c == "" {
 			continue
 		}
-		topoWatchers = append(topoWatchers, NewTopologyWatcher(ctx, topoServer, hc, filters, c, refreshInterval, refreshKnownTablets, topo.DefaultConcurrency))
+		topoWatchers = append(topoWatchers, NewTopologyWatcher(ctx, topoServer, hc, filters, c, refreshInterval, refreshKnownTablets, topo.DefaultReadConcurrency))
 	}
 
 	hc.topoWatchers = topoWatchers

go/vt/discovery/topology_watcher.go

@@ -26,16 +26,13 @@ import (
 	"sync"
 	"time"
 
-	"vitess.io/vitess/go/vt/topo/topoproto"
-
-	"vitess.io/vitess/go/vt/key"
-
 	"vitess.io/vitess/go/stats"
 	"vitess.io/vitess/go/trace"
-
+	"vitess.io/vitess/go/vt/key"
 	"vitess.io/vitess/go/vt/log"
-	"vitess.io/vitess/go/vt/proto/topodata"
+	topodatapb "vitess.io/vitess/go/vt/proto/topodata"
 	"vitess.io/vitess/go/vt/topo"
+	"vitess.io/vitess/go/vt/topo/topoproto"
 )
 
 const (
@@ -56,7 +53,7 @@ var (
 // tabletInfo is used internally by the TopologyWatcher struct.
 type tabletInfo struct {
 	alias  string
-	tablet *topodata.Tablet
+	tablet *topodatapb.Tablet
 }
 
 // TopologyWatcher polls the topology periodically for changes to
@@ -70,7 +67,7 @@ type TopologyWatcher struct {
 	cell                string
 	refreshInterval     time.Duration
 	refreshKnownTablets bool
-	concurrency         int
+	concurrency         int64
 	ctx                 context.Context
 	cancelFunc          context.CancelFunc
 	// wg keeps track of all launched Go routines.
@@ -92,7 +89,7 @@ type TopologyWatcher struct {
 
 // NewTopologyWatcher returns a TopologyWatcher that monitors all
 // the tablets in a cell, and reloads them as needed.
-func NewTopologyWatcher(ctx context.Context, topoServer *topo.Server, hc HealthCheck, f TabletFilter, cell string, refreshInterval time.Duration, refreshKnownTablets bool, topoReadConcurrency int) *TopologyWatcher {
+func NewTopologyWatcher(ctx context.Context, topoServer *topo.Server, hc HealthCheck, f TabletFilter, cell string, refreshInterval time.Duration, refreshKnownTablets bool, topoReadConcurrency int64) *TopologyWatcher {
 	tw := &TopologyWatcher{
 		topoServer:          topoServer,
 		healthcheck:         hc,
@@ -112,7 +109,7 @@ func NewTopologyWatcher(ctx context.Context, topoServer *topo.Server, hc HealthC
 }
 
 func (tw *TopologyWatcher) getTablets() ([]*topo.TabletInfo, error) {
-	return tw.topoServer.GetTabletsByCell(tw.ctx, tw.cell, &topo.GetTabletsByCellOptions{Concurrency: tw.concurrency})
+	return tw.topoServer.GetTabletsByCell(tw.ctx, tw.cell, nil)
 }
 
 // Start starts the topology watcher.
@@ -271,14 +268,14 @@ func (tw *TopologyWatcher) TopoChecksum() uint32 {
 // to be applied as an additional filter on the list of tablets returned by its getTablets function.
 type TabletFilter interface {
 	// IsIncluded returns whether tablet is included in this filter
-	IsIncluded(tablet *topodata.Tablet) bool
+	IsIncluded(tablet *topodatapb.Tablet) bool
 }
 
 // TabletFilters contains filters for tablets.
 type TabletFilters []TabletFilter
 
 // IsIncluded returns true if a tablet passes all filters.
-func (tf TabletFilters) IsIncluded(tablet *topodata.Tablet) bool {
+func (tf TabletFilters) IsIncluded(tablet *topodatapb.Tablet) bool {
 	for _, filter := range tf {
 		if !filter.IsIncluded(tablet) {
 			return false
@@ -299,7 +296,7 @@ type FilterByShard struct {
 type filterShard struct {
 	keyspace string
 	shard    string
-	keyRange *topodata.KeyRange // only set if shard is also a KeyRange
+	keyRange *topodatapb.KeyRange // only set if shard is also a KeyRange
 }
 
 // NewFilterByShard creates a new FilterByShard for use by a
@@ -344,7 +341,7 @@ func NewFilterByShard(filters []string) (*FilterByShard, error) {
 }
 
 // IsIncluded returns true iff the tablet's keyspace and shard match what we have.
-func (fbs *FilterByShard) IsIncluded(tablet *topodata.Tablet) bool {
+func (fbs *FilterByShard) IsIncluded(tablet *topodatapb.Tablet) bool {
 	canonical, kr, err := topo.ValidateShardName(tablet.Shard)
 	if err != nil {
 		log.Errorf("Error parsing shard name %v, will ignore tablet: %v", tablet.Shard, err)
@@ -384,7 +381,7 @@ func NewFilterByKeyspace(selectedKeyspaces []string) *FilterByKeyspace {
 }
 
 // IsIncluded returns true if the tablet's keyspace matches what we have.
-func (fbk *FilterByKeyspace) IsIncluded(tablet *topodata.Tablet) bool {
+func (fbk *FilterByKeyspace) IsIncluded(tablet *topodatapb.Tablet) bool {
 	_, exist := fbk.keyspaces[tablet.Keyspace]
 	return exist
 }
@@ -403,7 +400,7 @@ func NewFilterByTabletTags(tabletTags map[string]string) *FilterByTabletTags {
 }
 
 // IsIncluded returns true if the tablet's tags match what we expect.
-func (fbtg *FilterByTabletTags) IsIncluded(tablet *topodata.Tablet) bool {
+func (fbtg *FilterByTabletTags) IsIncluded(tablet *topodatapb.Tablet) bool {
 	if fbtg.tags == nil {
 		return true
 	}

go/vt/topo/keyspace.go

@@ -22,44 +22,26 @@ import (
 	"sort"
 	"sync"
 
-	"github.com/spf13/pflag"
 	"golang.org/x/sync/errgroup"
 
 	"vitess.io/vitess/go/constants/sidecar"
+	"vitess.io/vitess/go/event"
 	"vitess.io/vitess/go/sqlescape"
 	"vitess.io/vitess/go/vt/key"
-	"vitess.io/vitess/go/vt/servenv"
-	"vitess.io/vitess/go/vt/vterrors"
-
-	"vitess.io/vitess/go/event"
 	"vitess.io/vitess/go/vt/log"
-	"vitess.io/vitess/go/vt/topo/events"
-
 	topodatapb "vitess.io/vitess/go/vt/proto/topodata"
 	vtrpcpb "vitess.io/vitess/go/vt/proto/vtrpc"
+	"vitess.io/vitess/go/vt/topo/events"
+	"vitess.io/vitess/go/vt/vterrors"
 )
 
 // This file contains keyspace utility functions.
 
-// Default concurrency to use in order to avoid overhwelming the topo server.
-var DefaultConcurrency = 32
-
 // shardKeySuffix is the suffix of a shard key.
 // The full key looks like this:
 // /vitess/global/keyspaces/customer/shards/80-/Shard
 const shardKeySuffix = "Shard"
 
-func registerFlags(fs *pflag.FlagSet) {
-	fs.IntVar(&DefaultConcurrency, "topo_read_concurrency", DefaultConcurrency, "Concurrency of topo reads.")
-}
-
-func init() {
-	servenv.OnParseFor("vtcombo", registerFlags)
-	servenv.OnParseFor("vtctld", registerFlags)
-	servenv.OnParseFor("vtgate", registerFlags)
-	servenv.OnParseFor("vtorc", registerFlags)
-}
-
 // KeyspaceInfo is a meta struct that contains metadata to give the
 // data more context and convenience. This is the main way we interact
 // with a keyspace.
@@ -210,7 +192,7 @@ func (ts *Server) UpdateKeyspace(ctx context.Context, ki *KeyspaceInfo) error {
 type FindAllShardsInKeyspaceOptions struct {
 	// Concurrency controls the maximum number of concurrent calls to GetShard.
 	// If <= 0, Concurrency is set to 1.
-	Concurrency int
+	Concurrency int64
 }
 
 // FindAllShardsInKeyspace reads and returns all the existing shards in a
@@ -228,7 +210,7 @@ func (ts *Server) FindAllShardsInKeyspace(ctx context.Context, keyspace string,
 		opt = &FindAllShardsInKeyspaceOptions{}
 	}
 	if opt.Concurrency <= 0 {
-		opt.Concurrency = DefaultConcurrency
+		opt.Concurrency = DefaultReadConcurrency
 	}
 
 	// Unescape the keyspace name as this can e.g. come from the VSchema where

go/vt/topo/server.go

@@ -49,6 +49,7 @@ import (
 	"sync"
 
 	"github.com/spf13/pflag"
+	"golang.org/x/sync/semaphore"
 
 	"vitess.io/vitess/go/vt/log"
 	"vitess.io/vitess/go/vt/proto/topodata"
@@ -181,6 +182,9 @@ var (
 
 	FlagBinaries = []string{"vttablet", "vtctl", "vtctld", "vtcombo", "vtgate",
 		"vtorc", "vtbackup"}
+
+	// Default read concurrency to use in order to avoid overhwelming the topo server.
+	DefaultReadConcurrency int64 = 32
 )
 
 func init() {
@@ -193,6 +197,7 @@ func registerTopoFlags(fs *pflag.FlagSet) {
 	fs.StringVar(&topoImplementation, "topo_implementation", topoImplementation, "the topology implementation to use")
 	fs.StringVar(&topoGlobalServerAddress, "topo_global_server_address", topoGlobalServerAddress, "the address of the global topology server")
 	fs.StringVar(&topoGlobalRoot, "topo_global_root", topoGlobalRoot, "the path of the global topology data in the global topology server")
+	fs.Int64Var(&DefaultReadConcurrency, "topo_read_concurrency", DefaultReadConcurrency, "Maximum concurrency of topo reads per global or local cell.")
 }
 
 // RegisterFactory registers a Factory for an implementation for a Server.
@@ -208,19 +213,20 @@ func RegisterFactory(name string, factory Factory) {
 // NewWithFactory creates a new Server based on the given Factory.
 // It also opens the global cell connection.
 func NewWithFactory(factory Factory, serverAddress, root string) (*Server, error) {
+	globalReadSem := semaphore.NewWeighted(DefaultReadConcurrency)
 	conn, err := factory.Create(GlobalCell, serverAddress, root)
 	if err != nil {
 		return nil, err
 	}
-	conn = NewStatsConn(GlobalCell, conn)
+	conn = NewStatsConn(GlobalCell, conn, globalReadSem)
 
 	var connReadOnly Conn
 	if factory.HasGlobalReadOnlyCell(serverAddress, root) {
 		connReadOnly, err = factory.Create(GlobalReadOnlyCell, serverAddress, root)
 		if err != nil {
 			return nil, err
 		}
-		connReadOnly = NewStatsConn(GlobalReadOnlyCell, connReadOnly)
+		connReadOnly = NewStatsConn(GlobalReadOnlyCell, connReadOnly, globalReadSem)
 	} else {
 		connReadOnly = conn
 	}
@@ -302,7 +308,8 @@ func (ts *Server) ConnForCell(ctx context.Context, cell string) (Conn, error) {
 	conn, err := ts.factory.Create(cell, ci.ServerAddress, ci.Root)
 	switch {
 	case err == nil:
-		conn = NewStatsConn(cell, conn)
+		cellReadSem := semaphore.NewWeighted(DefaultReadConcurrency)
+		conn = NewStatsConn(cell, conn, cellReadSem)
 		ts.cellConns[cell] = cellConn{ci, conn}
 		return conn, nil
 	case IsErrType(err, NoNode):

go/vt/topo/shard.go

@@ -658,16 +658,8 @@ func (ts *Server) GetTabletsByShardCell(ctx context.Context, keyspace, shard str
 		}
 	}
 
-	// Divide the concurrency limit by the number of cells. If there are more
-	// cells than the limit, default to concurrency of 1.
-	cellConcurrency := 1
-	if len(cells) < DefaultConcurrency {
-		cellConcurrency = DefaultConcurrency / len(cells)
-	}
-
 	mu := sync.Mutex{}
 	eg, ctx := errgroup.WithContext(ctx)
-	eg.SetLimit(DefaultConcurrency)
 
 	tablets := make([]*TabletInfo, 0, len(cells))
 	var kss *KeyspaceShard
@@ -678,7 +670,6 @@ func (ts *Server) GetTabletsByShardCell(ctx context.Context, keyspace, shard str
 		}
 	}
 	options := &GetTabletsByCellOptions{
-		Concurrency:   cellConcurrency,
 		KeyspaceShard: kss,
 	}
 	for _, cell := range cells {