config: add global_reads field to ZoneConfig

Closes #57689.

This commit adds a new global_reads field to the ZoneConfig struct.
global_reads specifies whether transactions operating over the range(s)
should be configured to provide non-blocking behavior, meaning that
reads can be served consistently from all replicas and do not block on
writes. In exchange, writes get pushed into the future and must wait on
commit to ensure linearizability. For more, see:
https://github.com/cockroachdb/cockroach/blob/master/docs/RFCS/20200811_non_blocking_txns.md

Release note (sql change): A new, unused field called "global_reads" was
added to zone configurations. The field does not yet have any effect.

pkg/config/zonepb/zone.go

@@ -418,6 +418,12 @@ func (z *ZoneConfig) CopyFromZone(other ZoneConfig, fieldList []tree.Name) {
 				z.RangeMaxBytes = proto.Int64(*other.RangeMaxBytes)
 			}
 		}
+		if fieldName == "global_reads" {
+			z.GlobalReads = nil
+			if other.GlobalReads != nil {
+				z.GlobalReads = proto.Bool(*other.GlobalReads)
+			}
+		}
 		if fieldName == "gc.ttlseconds" {
 			z.GC = nil
 			if other.GC != nil {

pkg/config/zonepb/zone.proto

@@ -97,7 +97,15 @@ message ZoneConfig {
   // in the zone config hierarchy, up to the default policy if necessary.
   optional GCPolicy gc = 4 [(gogoproto.customname) = "GC"];
 
-  // NumReplicas specifies the desired number of replicas
+  // GlobalReads specifies whether transactions operating over the range(s)
+  // should be configured to provide non-blocking behavior, meaning that reads
+  // can be served consistently from all replicas and do not block on writes. In
+  // exchange, writes get pushed into the future and must wait on commit to
+  // ensure linearizability. For more, see:
+  //   https://github.com/cockroachdb/cockroach/blob/master/docs/RFCS/20200811_non_blocking_txns.md
+  optional bool global_reads = 12 [(gogoproto.moretags) = "yaml:\"global_reads\""];
+
+  // NumReplicas specifies the desired number of replicas.
   optional int32 num_replicas = 5 [(gogoproto.moretags) = "yaml:\"num_replicas\""];
 
   // Constraints constrains which stores the replicas can be stored on. The

pkg/config/zonepb/zone_test.go

@@ -394,6 +394,7 @@ func TestZoneConfigMarshalYAML(t *testing.T) {
 		GC: &GCPolicy{
 			TTLSeconds: 1,
 		},
+		GlobalReads: proto.Bool(true),
 		NumReplicas: proto.Int32(1),
 	}
 
@@ -407,6 +408,7 @@ func TestZoneConfigMarshalYAML(t *testing.T) {
 range_max_bytes: 1
 gc:
   ttlseconds: 1
+global_reads: true
 num_replicas: 1
 constraints: []
 lease_preferences: []
@@ -428,6 +430,7 @@ lease_preferences: []
 range_max_bytes: 1
 gc:
   ttlseconds: 1
+global_reads: true
 num_replicas: 1
 constraints: [+duck=foo]
 lease_preferences: []
@@ -458,6 +461,7 @@ lease_preferences: []
 range_max_bytes: 1
 gc:
   ttlseconds: 1
+global_reads: true
 num_replicas: 1
 constraints: [foo, +duck=foo, -duck=foo]
 lease_preferences: []
@@ -480,6 +484,7 @@ lease_preferences: []
 range_max_bytes: 1
 gc:
   ttlseconds: 1
+global_reads: true
 num_replicas: 1
 constraints: {+duck=foo: 3}
 lease_preferences: []
@@ -511,6 +516,7 @@ lease_preferences: []
 range_max_bytes: 1
 gc:
   ttlseconds: 1
+global_reads: true
 num_replicas: 1
 constraints: {'foo,+duck=foo,-duck=foo': 3}
 lease_preferences: []
@@ -548,6 +554,7 @@ lease_preferences: []
 range_max_bytes: 1
 gc:
   ttlseconds: 1
+global_reads: true
 num_replicas: 1
 constraints: {'+duck=bar1,+duck=bar2': 1, +duck=foo: 2}
 lease_preferences: []
@@ -559,6 +566,7 @@ lease_preferences: []
 range_max_bytes: 1
 gc:
   ttlseconds: 1
+global_reads: true
 num_replicas: 1
 constraints: []
 lease_preferences: []
@@ -580,6 +588,7 @@ lease_preferences: []
 range_max_bytes: 1
 gc:
   ttlseconds: 1
+global_reads: true
 num_replicas: 1
 constraints: []
 lease_preferences: [[+duck=foo]]
@@ -626,6 +635,7 @@ lease_preferences: [[+duck=foo]]
 range_max_bytes: 1
 gc:
   ttlseconds: 1
+global_reads: true
 num_replicas: 1
 constraints: [+duck=foo]
 lease_preferences: [[+duck=bar1, +duck=bar2], [-duck=foo]]

pkg/config/zonepb/zone_yaml.go

@@ -202,6 +202,7 @@ type marshalableZoneConfig struct {
 	RangeMinBytes                *int64            `json:"range_min_bytes" yaml:"range_min_bytes"`
 	RangeMaxBytes                *int64            `json:"range_max_bytes" yaml:"range_max_bytes"`
 	GC                           *GCPolicy         `json:"gc"`
+	GlobalReads                  *bool             `json:"global_reads" yaml:"global_reads"`
 	NumReplicas                  *int32            `json:"num_replicas" yaml:"num_replicas"`
 	Constraints                  ConstraintsList   `json:"constraints" yaml:"constraints,flow"`
 	LeasePreferences             []LeasePreference `json:"lease_preferences" yaml:"lease_preferences,flow"`
@@ -222,6 +223,9 @@ func zoneConfigToMarshalable(c ZoneConfig) marshalableZoneConfig {
 		tempGC := *c.GC
 		m.GC = &tempGC
 	}
+	if c.GlobalReads != nil {
+		m.GlobalReads = proto.Bool(*c.GlobalReads)
+	}
 	if c.NumReplicas != nil && *c.NumReplicas != 0 {
 		m.NumReplicas = proto.Int32(*c.NumReplicas)
 	}
@@ -250,6 +254,9 @@ func zoneConfigFromMarshalable(m marshalableZoneConfig, c ZoneConfig) ZoneConfig
 		tempGC := *m.GC
 		c.GC = &tempGC
 	}
+	if m.GlobalReads != nil {
+		c.GlobalReads = proto.Bool(*m.GlobalReads)
+	}
 	if m.NumReplicas != nil {
 		c.NumReplicas = proto.Int32(*m.NumReplicas)
 	}

pkg/kv/kvserver/replica.go

@@ -678,6 +678,10 @@ func (r *Replica) SetZoneConfig(zone *zonepb.ZoneConfig) {
 
 			r.mu.largestPreviousMaxRangeSizeBytes = 0
 		}
+
+		// TODO(nvanbenschoten): use the new zone.GlobalReads field to configure
+		// closed timestamp lead/lag, once we have per-range closed timestamp
+		// trackers.
 	}
 	r.mu.zone = zone
 }

pkg/sql/logictest/testdata/logic_test/crdb_internal

@@ -282,7 +282,7 @@ SELECT zone_id, target FROM crdb_internal.zones ORDER BY 1
 query T
 SELECT quote_literal(raw_config_yaml) FROM crdb_internal.zones WHERE zone_id = 0
 ----
-e'range_min_bytes: 134217728\nrange_max_bytes: 536870912\ngc:\n  ttlseconds: 90000\nnum_replicas: 3\nconstraints: []\nlease_preferences: []\n'
+e'range_min_bytes: 134217728\nrange_max_bytes: 536870912\ngc:\n  ttlseconds: 90000\nglobal_reads: null\nnum_replicas: 3\nconstraints: []\nlease_preferences: []\n'
 
 query T
 SELECT raw_config_sql FROM crdb_internal.zones WHERE zone_id = 0

pkg/sql/logictest/testdata/logic_test/zone_config

@@ -75,6 +75,7 @@ ALTER TABLE a CONFIGURE ZONE USING
   range_min_bytes = 200000 + 1,
   range_max_bytes = 300000 + 1,
   gc.ttlseconds = 3000 + 600,
+  global_reads = true,
   num_replicas = floor(1.2)::int,
   constraints = '[+region=test]',
   lease_preferences = '[[+region=test]]'
@@ -86,12 +87,14 @@ WHERE feature_name IN (
   'sql.schema.zone_config.table.range_min_bytes',
   'sql.schema.zone_config.table.range_max_bytes',
   'sql.schema.zone_config.table.gc.ttlseconds',
+  'sql.schema.zone_config.table.global_reads',
   'sql.schema.zone_config.table.num_replicas',
   'sql.schema.zone_config.table.constraints'
 ) AND usage_count > 0 ORDER BY feature_name
 ----
 sql.schema.zone_config.table.constraints
 sql.schema.zone_config.table.gc.ttlseconds
+sql.schema.zone_config.table.global_reads
 sql.schema.zone_config.table.num_replicas
 sql.schema.zone_config.table.range_max_bytes
 sql.schema.zone_config.table.range_min_bytes
@@ -103,6 +106,7 @@ SELECT zone_id, raw_config_sql FROM [SHOW ZONE CONFIGURATION FOR TABLE a]
     range_min_bytes = 200001,
     range_max_bytes = 300001,
     gc.ttlseconds = 3600,
+    global_reads = true,
     num_replicas = 1,
     constraints = '[+region=test]',
     lease_preferences = '[[+region=test]]'
@@ -118,6 +122,7 @@ SELECT zone_id, raw_config_sql FROM [SHOW ZONE CONFIGURATION FOR TABLE a]
     range_min_bytes = 200001,
     range_max_bytes = 400000,
     gc.ttlseconds = 3600,
+    global_reads = true,
     num_replicas = 1,
     constraints = '[+region=test]',
     lease_preferences = '[[+region=test]]'
@@ -154,6 +159,7 @@ SELECT zone_id, raw_config_sql FROM [SHOW ZONE CONFIGURATION FOR TABLE a]
     range_min_bytes = 200001,
     range_max_bytes = 400000,
     gc.ttlseconds = 3600,
+    global_reads = true,
     num_replicas = 1,
     constraints = '[+region=test]',
     lease_preferences = '[[+region=test]]'

pkg/sql/set_zone_config.go

@@ -67,6 +67,7 @@ var supportedZoneConfigOptions = map[tree.Name]struct {
 	"range_min_bytes": {types.Int, func(c *zonepb.ZoneConfig, d tree.Datum) { c.RangeMinBytes = proto.Int64(int64(tree.MustBeDInt(d))) }},
 	"range_max_bytes": {types.Int, func(c *zonepb.ZoneConfig, d tree.Datum) { c.RangeMaxBytes = proto.Int64(int64(tree.MustBeDInt(d))) }},
 	"num_replicas":    {types.Int, func(c *zonepb.ZoneConfig, d tree.Datum) { c.NumReplicas = proto.Int32(int32(tree.MustBeDInt(d))) }},
+	"global_reads":    {types.Bool, func(c *zonepb.ZoneConfig, d tree.Datum) { c.GlobalReads = proto.Bool(bool(tree.MustBeDBool(d))) }},
 	"gc.ttlseconds": {types.Int, func(c *zonepb.ZoneConfig, d tree.Datum) {
 		c.GC = &zonepb.GCPolicy{TTLSeconds: int32(tree.MustBeDInt(d))}
 	}},

pkg/sql/show_zone_config.go

@@ -184,36 +184,43 @@ func zoneConfigToSQL(zs *tree.ZoneSpecifier, zone *zonepb.ZoneConfig) (string, e
 	prefs = strings.TrimSpace(prefs)
 
 	useComma := false
+	maybeWriteComma := func(f *tree.FmtCtx) {
+		if useComma {
+			f.Printf(",\n")
+		}
+		useComma = true
+	}
+
 	f := tree.NewFmtCtx(tree.FmtParsable)
 	f.WriteString("ALTER ")
 	f.FormatNode(zs)
 	f.WriteString(" CONFIGURE ZONE USING\n")
 	if zone.RangeMinBytes != nil {
+		maybeWriteComma(f)
 		f.Printf("\trange_min_bytes = %d", *zone.RangeMinBytes)
-		useComma = true
 	}
 	if zone.RangeMaxBytes != nil {
-		writeComma(f, useComma)
+		maybeWriteComma(f)
 		f.Printf("\trange_max_bytes = %d", *zone.RangeMaxBytes)
-		useComma = true
 	}
 	if zone.GC != nil {
-		writeComma(f, useComma)
+		maybeWriteComma(f)
 		f.Printf("\tgc.ttlseconds = %d", zone.GC.TTLSeconds)
-		useComma = true
+	}
+	if zone.GlobalReads != nil {
+		maybeWriteComma(f)
+		f.Printf("\tglobal_reads = %t", *zone.GlobalReads)
 	}
 	if zone.NumReplicas != nil {
-		writeComma(f, useComma)
+		maybeWriteComma(f)
 		f.Printf("\tnum_replicas = %d", *zone.NumReplicas)
-		useComma = true
 	}
 	if !zone.InheritedConstraints {
-		writeComma(f, useComma)
+		maybeWriteComma(f)
 		f.Printf("\tconstraints = %s", lex.EscapeSQLString(constraints))
-		useComma = true
 	}
 	if !zone.InheritedLeasePreferences {
-		writeComma(f, useComma)
+		maybeWriteComma(f)
 		f.Printf("\tlease_preferences = %s", lex.EscapeSQLString(prefs))
 	}
 	return f.String(), nil
@@ -317,13 +324,6 @@ func generateZoneConfigIntrospectionValues(
 	return nil
 }
 
-// Writes a comma followed by a newline if useComma is true.
-func writeComma(f *tree.FmtCtx, useComma bool) {
-	if useComma {
-		f.Printf(",\n")
-	}
-}
-
 func yamlMarshalFlow(v interface{}) (string, error) {
 	var buf bytes.Buffer
 	e := yaml.NewEncoder(&buf)