Initial Store & Forward Implementation (#2917)

This adds store & forward relays into dendrite for p2p.
A few things have changed:
- new relay api serves new http endpoints for s&f federation
- updated outbound federation queueing which will attempt to forward
using s&f if appropriate
- database entries to track s&f relays for other nodes

relayapi/storage/postgres/relay_queue_json_table.go

@@ -0,0 +1,113 @@
+// Copyright 2022 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"
+
+	"github.com/lib/pq"
+	"github.com/matrix-org/dendrite/internal"
+	"github.com/matrix-org/dendrite/internal/sqlutil"
+)
+
+const relayQueueJSONSchema = `
+-- The relayapi_queue_json table contains event contents that
+-- we are storing for future forwarding. 
+CREATE TABLE IF NOT EXISTS relayapi_queue_json (
+	-- The JSON NID. This allows cross-referencing to find the JSON blob.
+	json_nid BIGSERIAL,
+	-- The JSON body. Text so that we preserve UTF-8.
+	json_body TEXT NOT NULL
+);
+
+CREATE UNIQUE INDEX IF NOT EXISTS relayapi_queue_json_json_nid_idx
+	ON relayapi_queue_json (json_nid);
+`
+
+const insertQueueJSONSQL = "" +
+	"INSERT INTO relayapi_queue_json (json_body)" +
+	" VALUES ($1)" +
+	" RETURNING json_nid"
+
+const deleteQueueJSONSQL = "" +
+	"DELETE FROM relayapi_queue_json WHERE json_nid = ANY($1)"
+
+const selectQueueJSONSQL = "" +
+	"SELECT json_nid, json_body FROM relayapi_queue_json" +
+	" WHERE json_nid = ANY($1)"
+
+type relayQueueJSONStatements struct {
+	db             *sql.DB
+	insertJSONStmt *sql.Stmt
+	deleteJSONStmt *sql.Stmt
+	selectJSONStmt *sql.Stmt
+}
+
+func NewPostgresRelayQueueJSONTable(db *sql.DB) (s *relayQueueJSONStatements, err error) {
+	s = &relayQueueJSONStatements{
+		db: db,
+	}
+	_, err = s.db.Exec(relayQueueJSONSchema)
+	if err != nil {
+		return
+	}
+
+	return s, sqlutil.StatementList{
+		{&s.insertJSONStmt, insertQueueJSONSQL},
+		{&s.deleteJSONStmt, deleteQueueJSONSQL},
+		{&s.selectJSONStmt, selectQueueJSONSQL},
+	}.Prepare(db)
+}
+
+func (s *relayQueueJSONStatements) InsertQueueJSON(
+	ctx context.Context, txn *sql.Tx, json string,
+) (int64, error) {
+	stmt := sqlutil.TxStmt(txn, s.insertJSONStmt)
+	var lastid int64
+	if err := stmt.QueryRowContext(ctx, json).Scan(&lastid); err != nil {
+		return 0, err
+	}
+	return lastid, nil
+}
+
+func (s *relayQueueJSONStatements) DeleteQueueJSON(
+	ctx context.Context, txn *sql.Tx, nids []int64,
+) error {
+	stmt := sqlutil.TxStmt(txn, s.deleteJSONStmt)
+	_, err := stmt.ExecContext(ctx, pq.Int64Array(nids))
+	return err
+}
+
+func (s *relayQueueJSONStatements) SelectQueueJSON(
+	ctx context.Context, txn *sql.Tx, jsonNIDs []int64,
+) (map[int64][]byte, error) {
+	blobs := map[int64][]byte{}
+	stmt := sqlutil.TxStmt(txn, s.selectJSONStmt)
+	rows, err := stmt.QueryContext(ctx, pq.Int64Array(jsonNIDs))
+	if err != nil {
+		return nil, err
+	}
+	defer internal.CloseAndLogIfError(ctx, rows, "selectJSON: rows.close() failed")
+	for rows.Next() {
+		var nid int64
+		var blob []byte
+		if err = rows.Scan(&nid, &blob); err != nil {
+			return nil, err
+		}
+		blobs[nid] = blob
+	}
+	return blobs, err
+}