migration: plumb in a dialer, executor, kv.DB, and liveness

The migration manager will need all of the above in order to execute
migrations. It'll need:
- A `Dialer`, to send out migration RPCs to individual nodes in the
  cluster.
- A handle on `Liveness`, to figure out which nodes are part of the
  cluster
- An `Executor`, for migrations to inspect/set internal SQL state, and
  to log progress into a dedicated system table
- A `kv.DB`, for migrations to inspect/set internal KV state, and to
  send out Migrate requests to ranges for execute below-Raft migrations

For more details, see the RFC (cockroachdb#48843). The fully "fleshed" out version
of this manager was originally prototyped in cockroachdb#56107. This PR is simply
pulling out the boring bits from there to move things along.

Release note: None

pkg/migration/BUILD.bazel

@@ -9,7 +9,11 @@ go_library(
     importpath = "github.com/cockroachdb/cockroach/pkg/migration",
     visibility = ["//visibility:public"],
     deps = [
+        "//pkg/kv",
+        "//pkg/kv/kvserver/liveness/livenesspb",
         "//pkg/roachpb",
+        "//pkg/rpc/nodedialer",
+        "//pkg/sql",
         "//vendor/github.com/cockroachdb/logtags",
     ],
 )

pkg/migration/manager.go

@@ -24,7 +24,11 @@ package migration
 import (
 	"context"
 
+	"github.com/cockroachdb/cockroach/pkg/kv"
+	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/liveness/livenesspb"
 	"github.com/cockroachdb/cockroach/pkg/roachpb"
+	"github.com/cockroachdb/cockroach/pkg/rpc/nodedialer"
+	"github.com/cockroachdb/cockroach/pkg/sql"
 	"github.com/cockroachdb/logtags"
 )
 
@@ -52,21 +56,37 @@ type Migration func(context.Context, *Helper) error
 
 // Manager is the instance responsible for executing migrations across the
 // cluster.
-type Manager struct{}
+type Manager struct {
+	dialer   *nodedialer.Dialer
+	nl       nodeLiveness
+	executor *sql.InternalExecutor
+	db       *kv.DB
+}
 
 // Helper captures all the primitives required to fully specify a migration.
 type Helper struct {
-	// TODO(irfansharif): We'll want to hold on to the Manager here, to
-	// have access to all of its constituent components.
+	*Manager
+}
+
+// nodeLiveness is the subset of the interface satisfied by CRDB's node liveness
+// component that the migration manager relies upon.
+type nodeLiveness interface {
+	GetLivenessesFromKV(context.Context) ([]livenesspb.Liveness, error)
+	IsLive(roachpb.NodeID) (bool, error)
 }
 
 // NewManager constructs a new Manager.
 //
-// TODO(irfansharif): We'll need to eventually plumb in a few things here. We'll
-// need a handle on node liveness, a node dialer, a lease manager, an internal
-// executor, and a kv.DB.
-func NewManager() *Manager {
-	return &Manager{}
+// TODO(irfansharif): We'll need to eventually plumb in on a lease manager here.
+func NewManager(
+	dialer *nodedialer.Dialer, nl nodeLiveness, executor *sql.InternalExecutor, db *kv.DB,
+) *Manager {
+	return &Manager{
+		dialer:   dialer,
+		executor: executor,
+		db:       db,
+		nl:       nl,
+	}
 }
 
 // MigrateTo runs the set of migrations required to upgrade the cluster version
@@ -97,7 +117,7 @@ func (m *Manager) MigrateTo(ctx context.Context, targetV roachpb.Version) error
 	var vs []roachpb.Version
 
 	for _, version := range vs {
-		_ = &Helper{}
+		_ = &Helper{Manager: m}
 		// TODO(irfansharif): We'll want to out the version gate to every node
 		// in the cluster. Each node will want to persist the version, bump the
 		// local version gates, and then return. The migration associated with

pkg/server/server_sql.go

@@ -112,7 +112,8 @@ type sqlServer struct {
 type sqlServerOptionalKVArgs struct {
 	// nodesStatusServer gives access to the NodesStatus service.
 	nodesStatusServer serverpb.OptionalNodesStatusServer
-	// Narrowed down version of *NodeLiveness. Used by jobs and DistSQLPlanner
+	// Narrowed down version of *NodeLiveness. Used by jobs, DistSQLPlanner, and
+	// migration manager.
 	nodeLiveness optionalnodeliveness.Container
 	// Gossip is relied upon by distSQLCfg (execinfra.ServerConfig), the executor
 	// config, the DistSQL planner, the table statistics cache, the statements
@@ -430,8 +431,9 @@ func newSQLServer(ctx context.Context, cfg sqlServerArgs) (*sqlServer, error) {
 	}
 
 	var isLive func(roachpb.NodeID) (bool, error)
-	if nl, ok := cfg.nodeLiveness.Optional(47900); ok {
-		isLive = nl.IsLive
+	nodeLiveness, ok := cfg.nodeLiveness.Optional(47900)
+	if ok {
+		isLive = nodeLiveness.IsLive
 	} else {
 		// We're on a SQL tenant, so this is the only node DistSQL will ever
 		// schedule on - always returning true is fine.
@@ -440,7 +442,6 @@ func newSQLServer(ctx context.Context, cfg sqlServerArgs) (*sqlServer, error) {
 		}
 	}
 
-	migrationMgr := migration.NewManager()
 	*execCfg = sql.ExecutorConfig{
 		Settings:                cfg.Settings,
 		NodeInfo:                nodeInfo,
@@ -467,9 +468,6 @@ func newSQLServer(ctx context.Context, cfg sqlServerArgs) (*sqlServer, error) {
 		RangeDescriptorCache:    cfg.distSender.RangeDescriptorCache(),
 		RoleMemberCache:         &sql.MembershipCache{},
 		TestingKnobs:            sqlExecutorTestingKnobs,
-		VersionUpgradeHook: func(ctx context.Context, targetV roachpb.Version) error {
-			return migrationMgr.MigrateTo(ctx, targetV)
-		},
 
 		DistSQLPlanner: sql.NewDistSQLPlanner(
 			ctx,
@@ -638,6 +636,21 @@ func newSQLServer(ctx context.Context, cfg sqlServerArgs) (*sqlServer, error) {
 	)
 	execCfg.StmtDiagnosticsRecorder = stmtDiagnosticsRegistry
 
+	if cfg.TenantID == roachpb.SystemTenantID {
+		// We only need to attach a version upgrade hook if we're the system
+		// tenant. Regular tenants are disallowed from changing cluster
+		// versions.
+		migrationMgr := migration.NewManager(
+			cfg.nodeDialer,
+			nodeLiveness,
+			cfg.circularInternalExecutor,
+			cfg.db,
+		)
+		execCfg.VersionUpgradeHook = func(ctx context.Context, targetV roachpb.Version) error {
+			return migrationMgr.MigrateTo(ctx, targetV)
+		}
+	}
+
 	temporaryObjectCleaner := sql.NewTemporaryObjectCleaner(
 		cfg.Settings,
 		cfg.db,