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/tables/interface.go

@@ -0,0 +1,66 @@
+// 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 tables
+
+import (
+	"context"
+	"database/sql"
+
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+// RelayQueue table contains a mapping of server name to transaction id and the corresponding nid.
+// These are the transactions being stored for the given destination server.
+// The nids correspond to entries in the RelayQueueJSON table.
+type RelayQueue interface {
+	// Adds a new transaction_id: server_name mapping with associated json table nid to the table.
+	// Will ensure only one transaction id is present for each server_name: nid mapping.
+	// Adding duplicates will silently do nothing.
+	InsertQueueEntry(ctx context.Context, txn *sql.Tx, transactionID gomatrixserverlib.TransactionID, serverName gomatrixserverlib.ServerName, nid int64) error
+
+	// Removes multiple entries from the table corresponding the the list of nids provided.
+	// If any of the provided nids don't match a row in the table, that deletion is considered
+	// successful.
+	DeleteQueueEntries(ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, jsonNIDs []int64) error
+
+	// Get a list of nids associated with the provided server name.
+	// Returns up to `limit` nids. The entries are returned oldest first.
+	// Will return an empty list if no matches were found.
+	SelectQueueEntries(ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, limit int) ([]int64, error)
+
+	// Get the number of entries in the table associated with the provided server name.
+	// If there are no matching rows, a count of 0 is returned with err set to nil.
+	SelectQueueEntryCount(ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName) (int64, error)
+}
+
+// RelayQueueJSON table contains a map of nid to the raw transaction json.
+type RelayQueueJSON interface {
+	// Adds a new transaction to the table.
+	// Adding a duplicate transaction will result in a new row being added and a new unique nid.
+	// return: unique nid representing this entry.
+	InsertQueueJSON(ctx context.Context, txn *sql.Tx, json string) (int64, error)
+
+	// Removes multiple nids from the table.
+	// If any of the provided nids don't match a row in the table, that deletion is considered
+	// successful.
+	DeleteQueueJSON(ctx context.Context, txn *sql.Tx, nids []int64) error
+
+	// Get the transaction json corresponding to the provided nids.
+	// Will return a partial result containing any matching nid from the table.
+	// Will return an empty map if no matches were found.
+	// It is the caller's responsibility to deal with the results appropriately.
+	// return: map indexed by nid of each matching transaction json.
+	SelectQueueJSON(ctx context.Context, txn *sql.Tx, jsonNIDs []int64) (map[int64][]byte, error)
+}