Merge keyserver & userapi (#2972)

As discussed yesterday, a first draft of merging the keyserver and the
userapi.

userapi/storage/postgres/key_changes_table.go

@@ -0,0 +1,127 @@
+// Copyright 2020 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package postgres
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"fmt"
+
+	"github.com/matrix-org/dendrite/internal"
+	"github.com/matrix-org/dendrite/internal/sqlutil"
+	"github.com/matrix-org/dendrite/userapi/storage/postgres/deltas"
+	"github.com/matrix-org/dendrite/userapi/storage/tables"
+)
+
+var keyChangesSchema = `
+-- Stores key change information about users. Used to determine when to send updated device lists to clients.
+CREATE SEQUENCE IF NOT EXISTS keyserver_key_changes_seq;
+CREATE TABLE IF NOT EXISTS keyserver_key_changes (
+	change_id BIGINT PRIMARY KEY DEFAULT nextval('keyserver_key_changes_seq'),
+    user_id TEXT NOT NULL,
+    CONSTRAINT keyserver_key_changes_unique_per_user UNIQUE (user_id)
+);
+`
+
+// Replace based on user ID. We don't care how many times the user's keys have changed, only that they
+// have changed, hence we can just keep bumping the change ID for this user.
+const upsertKeyChangeSQL = "" +
+	"INSERT INTO keyserver_key_changes (user_id)" +
+	" VALUES ($1)" +
+	" ON CONFLICT ON CONSTRAINT keyserver_key_changes_unique_per_user" +
+	" DO UPDATE SET change_id = nextval('keyserver_key_changes_seq')" +
+	" RETURNING change_id"
+
+const selectKeyChangesSQL = "" +
+	"SELECT user_id, change_id FROM keyserver_key_changes WHERE change_id > $1 AND change_id <= $2"
+
+type keyChangesStatements struct {
+	db                   *sql.DB
+	upsertKeyChangeStmt  *sql.Stmt
+	selectKeyChangesStmt *sql.Stmt
+}
+
+func NewPostgresKeyChangesTable(db *sql.DB) (tables.KeyChanges, error) {
+	s := &keyChangesStatements{
+		db: db,
+	}
+	_, err := db.Exec(keyChangesSchema)
+	if err != nil {
+		return s, err
+	}
+
+	if err = executeMigration(context.Background(), db); err != nil {
+		return nil, err
+	}
+	return s, sqlutil.StatementList{
+		{&s.upsertKeyChangeStmt, upsertKeyChangeSQL},
+		{&s.selectKeyChangesStmt, selectKeyChangesSQL},
+	}.Prepare(db)
+}
+
+func executeMigration(ctx context.Context, db *sql.DB) error {
+	// TODO: Remove when we are sure we are not having goose artefacts in the db
+	// This forces an error, which indicates the migration is already applied, since the
+	// column partition was removed from the table
+	migrationName := "keyserver: refactor key changes"
+
+	var cName string
+	err := db.QueryRowContext(ctx, "select column_name from information_schema.columns where table_name = 'keyserver_key_changes' AND column_name = 'partition'").Scan(&cName)
+	if err != nil {
+		if errors.Is(err, sql.ErrNoRows) { // migration was already executed, as the column was removed
+			if err = sqlutil.InsertMigration(ctx, db, migrationName); err != nil {
+				return fmt.Errorf("unable to manually insert migration '%s': %w", migrationName, err)
+			}
+			return nil
+		}
+		return err
+	}
+	m := sqlutil.NewMigrator(db)
+	m.AddMigrations(sqlutil.Migration{
+		Version: migrationName,
+		Up:      deltas.UpRefactorKeyChanges,
+	})
+
+	return m.Up(ctx)
+}
+
+func (s *keyChangesStatements) InsertKeyChange(ctx context.Context, userID string) (changeID int64, err error) {
+	err = s.upsertKeyChangeStmt.QueryRowContext(ctx, userID).Scan(&changeID)
+	return
+}
+
+func (s *keyChangesStatements) SelectKeyChanges(
+	ctx context.Context, fromOffset, toOffset int64,
+) (userIDs []string, latestOffset int64, err error) {
+	latestOffset = fromOffset
+	rows, err := s.selectKeyChangesStmt.QueryContext(ctx, fromOffset, toOffset)
+	if err != nil {
+		return nil, 0, err
+	}
+	defer internal.CloseAndLogIfError(ctx, rows, "selectKeyChangesStmt: rows.close() failed")
+	for rows.Next() {
+		var userID string
+		var offset int64
+		if err := rows.Scan(&userID, &offset); err != nil {
+			return nil, 0, err
+		}
+		if offset > latestOffset {
+			latestOffset = offset
+		}
+		userIDs = append(userIDs, userID)
+	}
+	return
+}