tenantcapabilities: introduce a decoder for tenant capabilities

This patch introduces a decoder, which takes raw KVs from the
system.tenants table and decodes them into
(TenantID, TenantCapability) pairs.

This is currently unusued. In a future commit, we'll establish a
rangefeed over the `system.tenants` table to maintain a cached view
of the global capabilities state. This decoder will be used to parse the
rangefeed output. Looking towards such a watcher component, the decoder
is placed in the `tenantcapabilitieswatcher` package.

References cockroachdb#94643

Epic: CRDB-18503

Release note: None

pkg/BUILD.bazel

@@ -229,6 +229,7 @@ ALL_TESTS = [
     "//pkg/kv/kvserver/uncertainty:uncertainty_test",
     "//pkg/kv/kvserver:kvserver_test",
     "//pkg/kv:kv_test",
+    "//pkg/multitenant/tenantcapabilities/tenantcapabilitieswatcher:tenantcapabilitieswatcher_test",
     "//pkg/obsservice/obslib/ingest:ingest_test",
     "//pkg/roachpb:roachpb_disallowed_imports_test",
     "//pkg/roachpb:roachpb_test",
@@ -1262,6 +1263,9 @@ GO_TARGETS = [
     "//pkg/multitenant/multitenantcpu:multitenantcpu",
     "//pkg/multitenant/multitenantio:multitenantio",
     "//pkg/multitenant/tenantcapabilities/tenantcapabilitiespb:tenantcapabilitiespb",
+    "//pkg/multitenant/tenantcapabilities/tenantcapabilitieswatcher:tenantcapabilitieswatcher",
+    "//pkg/multitenant/tenantcapabilities/tenantcapabilitieswatcher:tenantcapabilitieswatcher_test",
+    "//pkg/multitenant/tenantcapabilities:tenantcapabilities",
     "//pkg/multitenant/tenantcostmodel:tenantcostmodel",
     "//pkg/multitenant:multitenant",
     "//pkg/obs:obs",
@@ -2593,7 +2597,9 @@ GET_X_DATA_TARGETS = [
     "//pkg/multitenant:get_x_data",
     "//pkg/multitenant/multitenantcpu:get_x_data",
     "//pkg/multitenant/multitenantio:get_x_data",
+    "//pkg/multitenant/tenantcapabilities:get_x_data",
     "//pkg/multitenant/tenantcapabilities/tenantcapabilitiespb:get_x_data",
+    "//pkg/multitenant/tenantcapabilities/tenantcapabilitieswatcher:get_x_data",
     "//pkg/multitenant/tenantcostmodel:get_x_data",
     "//pkg/obs:get_x_data",
     "//pkg/obsservice/cmd/obsservice:get_x_data",

pkg/multitenant/tenantcapabilities/BUILD.bazel

@@ -1 +1,15 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
 load("//build/bazelutil/unused_checker:unused.bzl", "get_x_data")
+
+go_library(
+    name = "tenantcapabilities",
+    srcs = ["capabilities.go"],
+    importpath = "github.com/cockroachdb/cockroach/pkg/multitenant/tenantcapabilities",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//pkg/multitenant/tenantcapabilities/tenantcapabilitiespb",
+        "//pkg/roachpb",
+    ],
+)
+
+get_x_data(name = "get_x_data")

pkg/multitenant/tenantcapabilities/capabilities.go

@@ -0,0 +1,22 @@
+// Copyright 2023 The Cockroach Authors.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+package tenantcapabilities
+
+import (
+	"github.com/cockroachdb/cockroach/pkg/multitenant/tenantcapabilities/tenantcapabilitiespb"
+	"github.com/cockroachdb/cockroach/pkg/roachpb"
+)
+
+// CapabilitiesEntry ties together a tenantID with its capabilities.
+type CapabilitiesEntry struct {
+	TenantID           roachpb.TenantID
+	TenantCapabilities tenantcapabilitiespb.TenantCapabilities
+}

pkg/multitenant/tenantcapabilities/tenantcapabilitieswatcher/BUILD.bazel

@@ -0,0 +1,51 @@
+load("//build/bazelutil/unused_checker:unused.bzl", "get_x_data")
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "tenantcapabilitieswatcher",
+    srcs = ["decoder.go"],
+    importpath = "github.com/cockroachdb/cockroach/pkg/multitenant/tenantcapabilities/tenantcapabilitieswatcher",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//pkg/keys",
+        "//pkg/multitenant/tenantcapabilities",
+        "//pkg/roachpb",
+        "//pkg/sql/catalog",
+        "//pkg/sql/catalog/descpb",
+        "//pkg/sql/catalog/systemschema",
+        "//pkg/sql/rowenc",
+        "//pkg/sql/rowenc/valueside",
+        "//pkg/sql/sem/tree",
+        "//pkg/sql/types",
+        "//pkg/util/protoutil",
+        "@com_github_cockroachdb_errors//:errors",
+    ],
+)
+
+go_test(
+    name = "tenantcapabilitieswatcher_test",
+    srcs = [
+        "decoder_test.go",
+        "main_test.go",
+    ],
+    args = ["-test.timeout=295s"],
+    embed = [":tenantcapabilitieswatcher"],
+    deps = [
+        "//pkg/base",
+        "//pkg/keys",
+        "//pkg/multitenant/tenantcapabilities/tenantcapabilitiespb",
+        "//pkg/roachpb",
+        "//pkg/security/securityassets",
+        "//pkg/security/securitytest",
+        "//pkg/server",
+        "//pkg/sql/catalog/descpb",
+        "//pkg/testutils/serverutils",
+        "//pkg/testutils/sqlutils",
+        "//pkg/testutils/testcluster",
+        "//pkg/util/leaktest",
+        "//pkg/util/protoutil",
+        "@com_github_stretchr_testify//require",
+    ],
+)
+
+get_x_data(name = "get_x_data")

pkg/multitenant/tenantcapabilities/tenantcapabilitieswatcher/decoder.go

@@ -0,0 +1,91 @@
+// Copyright 2023 The Cockroach Authors.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+package tenantcapabilitieswatcher
+
+import (
+	"github.com/cockroachdb/cockroach/pkg/keys"
+	"github.com/cockroachdb/cockroach/pkg/multitenant/tenantcapabilities"
+	"github.com/cockroachdb/cockroach/pkg/roachpb"
+	"github.com/cockroachdb/cockroach/pkg/sql/catalog"
+	"github.com/cockroachdb/cockroach/pkg/sql/catalog/descpb"
+	"github.com/cockroachdb/cockroach/pkg/sql/catalog/systemschema"
+	"github.com/cockroachdb/cockroach/pkg/sql/rowenc"
+	"github.com/cockroachdb/cockroach/pkg/sql/rowenc/valueside"
+	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
+	"github.com/cockroachdb/cockroach/pkg/sql/types"
+	"github.com/cockroachdb/cockroach/pkg/util/protoutil"
+	"github.com/cockroachdb/errors"
+)
+
+// decoder decodes rows from system.tenants. It's not
+// safe for concurrent use.
+type decoder struct {
+	alloc   tree.DatumAlloc
+	columns []catalog.Column
+	decoder valueside.Decoder
+}
+
+// newDecoder constructs and returns a decoder.
+func newDecoder() *decoder {
+	columns := systemschema.TenantsTable.PublicColumns()
+	return &decoder{
+		columns: columns,
+		decoder: valueside.MakeDecoder(columns),
+	}
+}
+
+func (d *decoder) decode(kv roachpb.KeyValue) (tenantcapabilities.CapabilitiesEntry, error) {
+	// First we decode the tenantID from the key.
+	var tenID roachpb.TenantID
+	types := []*types.T{d.columns[0].GetType()}
+	tenantIDRow := make([]rowenc.EncDatum, 1)
+	_, _, err := rowenc.DecodeIndexKey(keys.SystemSQLCodec, types, tenantIDRow, nil /* colDirs */, kv.Key)
+	if err != nil {
+		return tenantcapabilities.CapabilitiesEntry{}, err
+	}
+	if err := tenantIDRow[0].EnsureDecoded(types[0], &d.alloc); err != nil {
+		return tenantcapabilities.CapabilitiesEntry{},
+			errors.NewAssertionErrorWithWrappedErrf(err, "failed to decode key in system.tenants %v", kv.Key)
+	}
+	tenID, err = roachpb.MakeTenantID(uint64(tree.MustBeDInt(tenantIDRow[0].Datum)))
+	if err != nil {
+		return tenantcapabilities.CapabilitiesEntry{}, err
+	}
+
+	// The remaining columns are stored in the value; we're just interested in the
+	// info column.
+	if !kv.Value.IsPresent() {
+		return tenantcapabilities.CapabilitiesEntry{},
+			errors.AssertionFailedf("missing value for tenant: %v", tenID)
+	}
+
+	bytes, err := kv.Value.GetTuple()
+	if err != nil {
+		return tenantcapabilities.CapabilitiesEntry{}, err
+	}
+	datums, err := d.decoder.Decode(&d.alloc, bytes)
+	if err != nil {
+		return tenantcapabilities.CapabilitiesEntry{}, err
+	}
+
+	var tenantInfo descpb.TenantInfo
+	if i := datums[2]; i != tree.DNull {
+		infoBytes := tree.MustBeDBytes(i)
+		if err := protoutil.Unmarshal([]byte(infoBytes), &tenantInfo); err != nil {
+			return tenantcapabilities.CapabilitiesEntry{}, errors.Wrapf(err, "failed to unmarshall tenant info")
+		}
+	}
+
+	return tenantcapabilities.CapabilitiesEntry{
+		TenantID:           tenID,
+		TenantCapabilities: tenantInfo.Capabilities,
+	}, nil
+}

pkg/multitenant/tenantcapabilities/tenantcapabilitieswatcher/decoder_test.go

@@ -0,0 +1,84 @@
+// Copyright 2023 The Cockroach Authors.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+package tenantcapabilitieswatcher
+
+import (
+	"context"
+	"fmt"
+	"testing"
+
+	"github.com/cockroachdb/cockroach/pkg/base"
+	"github.com/cockroachdb/cockroach/pkg/keys"
+	"github.com/cockroachdb/cockroach/pkg/multitenant/tenantcapabilities/tenantcapabilitiespb"
+	"github.com/cockroachdb/cockroach/pkg/roachpb"
+	"github.com/cockroachdb/cockroach/pkg/sql/catalog/descpb"
+	"github.com/cockroachdb/cockroach/pkg/testutils/sqlutils"
+	"github.com/cockroachdb/cockroach/pkg/testutils/testcluster"
+	"github.com/cockroachdb/cockroach/pkg/util/leaktest"
+	"github.com/cockroachdb/cockroach/pkg/util/protoutil"
+	"github.com/stretchr/testify/require"
+)
+
+// TestDecodeCapabilities verifies that we can correctly decode
+// TenantCapabilities stored in the system.tenants table.
+func TestDecodeCapabilities(t *testing.T) {
+	defer leaktest.AfterTest(t)()
+
+	ctx := context.Background()
+	tc := testcluster.StartTestCluster(t, 1, base.TestClusterArgs{
+		ServerArgs: base.TestServerArgs{
+			DisableDefaultTestTenant: true, // system.tenants only exists for the system tenant
+		},
+	})
+	defer tc.Stopper().Stop(ctx)
+
+	const dummyTableName = "dummy_system_tenants"
+	tdb := sqlutils.MakeSQLRunner(tc.ServerConn(0))
+	tdb.Exec(t, fmt.Sprintf("CREATE TABLE %s (LIKE system.tenants INCLUDING ALL)", dummyTableName))
+
+	var dummyTableID uint32
+	tdb.QueryRow(t, fmt.Sprintf(
+		`SELECT table_id FROM crdb_internal.tables WHERE name = '%s'`, dummyTableName),
+	).Scan(&dummyTableID)
+
+	tenantID, err := roachpb.MakeTenantID(10)
+	require.NoError(t, err)
+	info := descpb.TenantInfo{
+		Capabilities: tenantcapabilitiespb.TenantCapabilities{
+			CanAdminSplit: true,
+		},
+	}
+	buf, err := protoutil.Marshal(&info)
+	require.NoError(t, err)
+	tdb.Exec(
+		t,
+		fmt.Sprintf("INSERT INTO %s (id, active, info) VALUES ($1, $2, $3)", dummyTableName),
+		tenantID.ToUint64(), true /* active */, buf,
+	)
+
+	// Read the row	.
+	k := keys.SystemSQLCodec.IndexPrefix(dummyTableID, keys.TenantsTablePrimaryKeyIndexID)
+	rows, err := tc.Server(0).DB().Scan(ctx, k, k.PrefixEnd(), 0 /* maxRows */)
+	require.NoError(t, err)
+	require.Len(t, rows, 1)
+
+	// Decode and verify.
+	row := rows[0]
+	decoder := newDecoder()
+	got, err := decoder.decode(roachpb.KeyValue{
+		Key:   row.Key,
+		Value: *row.Value,
+	})
+	require.NoError(t, err)
+
+	require.Equal(t, tenantID, got.TenantID)
+	require.Equal(t, info.Capabilities, got.TenantCapabilities)
+}

pkg/multitenant/tenantcapabilities/tenantcapabilitieswatcher/main_test.go

@@ -0,0 +1,31 @@
+// Copyright 2023 The Cockroach Authors.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+package tenantcapabilitieswatcher
+
+import (
+	"os"
+	"testing"
+
+	"github.com/cockroachdb/cockroach/pkg/security/securityassets"
+	"github.com/cockroachdb/cockroach/pkg/security/securitytest"
+	"github.com/cockroachdb/cockroach/pkg/server"
+	"github.com/cockroachdb/cockroach/pkg/testutils/serverutils"
+	"github.com/cockroachdb/cockroach/pkg/testutils/testcluster"
+)
+
+func TestMain(m *testing.M) {
+	securityassets.SetLoader(securitytest.EmbeddedAssets)
+	serverutils.InitTestServerFactory(server.TestServerFactory)
+	serverutils.InitTestClusterFactory(testcluster.TestClusterFactory)
+	os.Exit(m.Run())
+}
+
+//go:generate ../../../util/leaktest/add-leaktest.sh *_test.go