Add input API for adding invites to the roomserver. (#187)

* Add input API for adding invites to the roomserver.

This API handles invites received over federation that occur outside of a room.

* Add some docstring for withTransaction

* Use a nicer pattern for wrapping transactions

* Fix MembershipUpdater method to not commit the transaction before returning it

* Use the Transaction interface from common

src/github.com/matrix-org/dendrite/common/sql.go

@@ -18,6 +18,24 @@ import (
 	"database/sql"
 )
 
+// A Transaction is something that can be committed or rolledback.
+type Transaction interface {
+	// Commit the transaction
+	Commit() error
+	// Rollback the transaction.
+	Rollback() error
+}
+
+// EndTransaction ends a transaction.
+// If the transaction succeeded then it is committed, otherwise it is rolledback.
+func EndTransaction(txn Transaction, succeeded *bool) {
+	if *succeeded {
+		txn.Commit()
+	} else {
+		txn.Rollback()
+	}
+}
+
 // WithTransaction runs a block of code passing in an SQL transaction
 // If the code returns an error or panics then the transactions is rolledback
 // Otherwise the transaction is committed.
@@ -26,16 +44,14 @@ func WithTransaction(db *sql.DB, fn func(txn *sql.Tx) error) (err error) {
 	if err != nil {
 		return
 	}
-	defer func() {
-		if r := recover(); r != nil {
-			txn.Rollback()
-			panic(r)
-		} else if err != nil {
-			txn.Rollback()
-		} else {
-			err = txn.Commit()
-		}
-	}()
+	succeeded := false
+	defer EndTransaction(txn, &succeeded)
+
 	err = fn(txn)
+	if err != nil {
+		return
+	}
+
+	succeeded = true
 	return
 }

src/github.com/matrix-org/dendrite/roomserver/api/input.go

@@ -68,9 +68,17 @@ type InputRoomEvent struct {
 	SendAsServer string `json:"send_as_server"`
 }
 
+// InputInviteEvent is a matrix invite event received over federation without
+// the usual context a matrix room event would have. We usually do not have
+// access to the events needed to check the event auth rules for the invite.
+type InputInviteEvent struct {
+	Event gomatrixserverlib.Event `json:"event"`
+}
+
 // InputRoomEventsRequest is a request to InputRoomEvents
 type InputRoomEventsRequest struct {
 	InputRoomEvents   []InputRoomEvent   `json:"input_room_events"`
+	InputInviteEvents []InputInviteEvent `json:"input_invite_events"`
 }
 
 // InputRoomEventsResponse is a response to InputRoomEvents

src/github.com/matrix-org/dendrite/roomserver/input/events.go

@@ -15,6 +15,9 @@
 package input
 
 import (
+	"fmt"
+
+	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/roomserver/state"
 	"github.com/matrix-org/dendrite/roomserver/types"
@@ -39,6 +42,8 @@ type RoomEventDatabase interface {
 	GetLatestEventsForUpdate(roomNID types.RoomNID) (updater types.RoomRecentEventsUpdater, err error)
 	// Lookup the string event IDs for a list of numeric event IDs
 	EventIDs(eventNIDs []types.EventNID) (map[types.EventNID]string, error)
+	// Build a membership updater for the target user in a room.
+	MembershipUpdater(roomID, targerUserID string) (types.MembershipUpdater, error)
 }
 
 // OutputRoomEventWriter has the APIs needed to write an event to the output logs.
@@ -103,13 +108,64 @@ func processRoomEvent(db RoomEventDatabase, ow OutputRoomEventWriter, input api.
 		return err
 	}
 
-	// TODO:
-	//  * Caculate the new current state for the room if the forward extremities have changed.
-	//  * Work out the delta between the new current state and the previous current state.
-	//  * Work out the visibility of the event.
-	//  * Write a message to the output logs containing:
-	//      - The event itself
-	//      - The visiblity of the event, i.e. who is allowed to see the event.
-	//      - The changes to the current state of the room.
+	return nil
+}
+
+func processInviteEvent(db RoomEventDatabase, ow OutputRoomEventWriter, input api.InputInviteEvent) (err error) {
+	if input.Event.StateKey() == nil {
+		return fmt.Errorf("invite must be a state event")
+	}
+
+	roomID := input.Event.RoomID()
+	targetUserID := *input.Event.StateKey()
+
+	updater, err := db.MembershipUpdater(roomID, targetUserID)
+	if err != nil {
+		return err
+	}
+	succeeded := false
+	defer common.EndTransaction(updater, &succeeded)
+
+	if updater.IsJoin() {
+		// If the user is joined to the room then that takes precedence over this
+		// invite event. It makes little sense to move a user that is already
+		// joined to the room into the invite state.
+		// This could plausibly happen if an invite request raced with a join
+		// request for a user. For example if a user was invited to a public
+		// room and they joined the room at the same time as the invite was sent.
+		// The other way this could plausibly happen is if an invite raced with
+		// a kick. For example if a user was kicked from a room in error and in
+		// response someone else in the room re-invited them then it is possible
+		// for the invite request to race with the leave event so that the
+		// target receives invite before it learns that it has been kicked.
+		// There are a few ways this could be plausibly handled in the roomserver.
+		// 1) Store the invite, but mark it as retired. That will result in the
+		//    permanent rejection of that invite event. So even if the target
+		//    user leaves the room and the invite is retransmitted it will be
+		//    ignored. However a new invite with a new event ID would still be
+		//    accepted.
+		// 2) Silently discard the invite event. This means that if the event
+		//    was retransmitted at a later date after the target user had left
+		//    the room we would accept the invite. However since we hadn't told
+		//    the sending server that the invite had been discarded it would
+		//    have no reason to attempt to retry.
+		// 3) Signal the sending server that the user is already joined to the
+		//    room.
+		// For now we will implement option 2. Since in the abesence of a retry
+		// mechanism it will be equivalent to option 1, and we don't have a
+		// signalling mechanism to implement option 3.
+		return nil
+	}
+
+	outputUpdates, err := updateToInviteMembership(updater, &input.Event, nil)
+	if err != nil {
+		return err
+	}
+
+	if err = ow.WriteOutputEvents(roomID, outputUpdates); err != nil {
+		return err
+	}
+
+	succeeded = true
 	return nil
 }

src/github.com/matrix-org/dendrite/roomserver/input/input.go

@@ -61,6 +61,11 @@ func (r *RoomserverInputAPI) InputRoomEvents(
 			return err
 		}
 	}
+	for i := range request.InputInviteEvents {
+		if err := processInviteEvent(r.DB, r, request.InputInviteEvents[i]); err != nil {
+			return err
+		}
+	}
 	return nil
 }
 

src/github.com/matrix-org/dendrite/roomserver/input/latest_events.go

@@ -17,6 +17,7 @@ package input
 import (
 	"bytes"
 
+	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/roomserver/state"
 	"github.com/matrix-org/dendrite/roomserver/types"
@@ -52,25 +53,19 @@ func updateLatestEvents(
 	if err != nil {
 		return
 	}
-	defer func() {
-		if err == nil {
-			// Commit if there wasn't an error.
-			// Set the returned err value if we encounter an error committing.
-			// This only works because err is a named return.
-			err = updater.Commit()
-		} else {
-			// Ignore any error we get rolling back since we don't want to
-			// clobber the current error
-			// TODO: log the error here.
-			updater.Rollback()
-		}
-	}()
+	succeeded := false
+	defer common.EndTransaction(updater, &succeeded)
 
 	u := latestEventsUpdater{
 		db: db, updater: updater, ow: ow, roomNID: roomNID,
 		stateAtEvent: stateAtEvent, event: event, sendAsServer: sendAsServer,
 	}
-	return u.doUpdateLatestEvents()
+	if err = u.doUpdateLatestEvents(); err != nil {
+		return err
+	}
+
+	succeeded = true
+	return
 }
 
 // latestEventsUpdater tracks the state used to update the latest events in the

src/github.com/matrix-org/dendrite/roomserver/storage/rooms_table.go

@@ -80,15 +80,23 @@ func (s *roomStatements) prepare(db *sql.DB) (err error) {
 	}.prepare(db)
 }
 
-func (s *roomStatements) insertRoomNID(roomID string) (types.RoomNID, error) {
+func (s *roomStatements) insertRoomNID(txn *sql.Tx, roomID string) (types.RoomNID, error) {
 	var roomNID int64
-	err := s.insertRoomNIDStmt.QueryRow(roomID).Scan(&roomNID)
+	stmt := s.insertRoomNIDStmt
+	if txn != nil {
+		stmt = txn.Stmt(stmt)
+	}
+	err := stmt.QueryRow(roomID).Scan(&roomNID)
 	return types.RoomNID(roomNID), err
 }
 
-func (s *roomStatements) selectRoomNID(roomID string) (types.RoomNID, error) {
+func (s *roomStatements) selectRoomNID(txn *sql.Tx, roomID string) (types.RoomNID, error) {
 	var roomNID int64
-	err := s.selectRoomNIDStmt.QueryRow(roomID).Scan(&roomNID)
+	stmt := s.selectRoomNIDStmt
+	if txn != nil {
+		stmt = txn.Stmt(stmt)
+	}
+	err := stmt.QueryRow(roomID).Scan(&roomNID)
 	return types.RoomNID(roomNID), err
 }
 

src/github.com/matrix-org/dendrite/roomserver/storage/storage.go

@@ -53,7 +53,7 @@ func (d *Database) StoreEvent(event gomatrixserverlib.Event, authEventNIDs []typ
 		err              error
 	)
 
-	if roomNID, err = d.assignRoomNID(event.RoomID()); err != nil {
+	if roomNID, err = d.assignRoomNID(nil, event.RoomID()); err != nil {
 		return 0, types.StateAtEvent{}, err
 	}
 
@@ -104,15 +104,15 @@ func (d *Database) StoreEvent(event gomatrixserverlib.Event, authEventNIDs []typ
 	}, nil
 }
 
-func (d *Database) assignRoomNID(roomID string) (types.RoomNID, error) {
+func (d *Database) assignRoomNID(txn *sql.Tx, roomID string) (types.RoomNID, error) {
 	// Check if we already have a numeric ID in the database.
-	roomNID, err := d.statements.selectRoomNID(roomID)
+	roomNID, err := d.statements.selectRoomNID(txn, roomID)
 	if err == sql.ErrNoRows {
 		// We don't have a numeric ID so insert one into the database.
-		roomNID, err = d.statements.insertRoomNID(roomID)
+		roomNID, err = d.statements.insertRoomNID(txn, roomID)
 		if err == sql.ErrNoRows {
 			// We raced with another insert so run the select again.
-			roomNID, err = d.statements.selectRoomNID(roomID)
+			roomNID, err = d.statements.selectRoomNID(txn, roomID)
 		}
 	}
 	return roomNID, err
@@ -329,7 +329,7 @@ func (u *roomRecentEventsUpdater) MembershipUpdater(targetUserNID types.EventSta
 
 // RoomNID implements query.RoomserverQueryAPIDB
 func (d *Database) RoomNID(roomID string) (types.RoomNID, error) {
-	roomNID, err := d.statements.selectRoomNID(roomID)
+	roomNID, err := d.statements.selectRoomNID(nil, roomID)
 	if err == sql.ErrNoRows {
 		return 0, nil
 	}
@@ -380,6 +380,38 @@ func (d *Database) StateEntriesForTuples(
 	return d.statements.bulkSelectFilteredStateBlockEntries(stateBlockNIDs, stateKeyTuples)
 }
 
+// MembershipUpdater implements input.RoomEventDatabase
+func (d *Database) MembershipUpdater(roomID, targetUserID string) (types.MembershipUpdater, error) {
+	txn, err := d.db.Begin()
+	if err != nil {
+		return nil, err
+	}
+	succeeded := false
+	defer func() {
+		if !succeeded {
+			txn.Rollback()
+		}
+	}()
+
+	roomNID, err := d.assignRoomNID(txn, roomID)
+	if err != nil {
+		return nil, err
+	}
+
+	targetUserNID, err := d.assignStateKeyNID(txn, targetUserID)
+	if err != nil {
+		return nil, err
+	}
+
+	updater, err := d.membershipUpdaterTxn(txn, roomNID, targetUserNID)
+	if err != nil {
+		return nil, err
+	}
+
+	succeeded = true
+	return updater, nil
+}
+
 type membershipUpdater struct {
 	transaction
 	d             *Database

src/github.com/matrix-org/dendrite/roomserver/types/types.go

@@ -16,6 +16,7 @@
 package types
 
 import (
+	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/gomatrixserverlib"
 )
 
@@ -135,14 +136,6 @@ type StateEntryList struct {
 	StateEntries  []StateEntry
 }
 
-// A Transaction is something that can be committed or rolledback.
-type Transaction interface {
-	// Commit the transaction
-	Commit() error
-	// Rollback the transaction.
-	Rollback() error
-}
-
 // A RoomRecentEventsUpdater is used to update the recent events in a room.
 // (On postgresql this wraps a database transaction that holds a "FOR UPDATE"
 //  lock on the row in the rooms table holding the latest events for the room.)
@@ -175,7 +168,7 @@ type RoomRecentEventsUpdater interface {
 	// It will share the same transaction as this updater.
 	MembershipUpdater(targetUserNID EventStateKeyNID) (MembershipUpdater, error)
 	// Implements Transaction so it can be committed or rolledback
-	Transaction
+	common.Transaction
 }
 
 // A MembershipUpdater is used to update the membership of a user in a room.
@@ -200,7 +193,7 @@ type MembershipUpdater interface {
 	// Returns a list of invite event IDs that this state change retired.
 	SetToLeave(senderUserID string, eventID string) (inviteEventIDs []string, err error)
 	// Implements Transaction so it can be committed or rolledback.
-	Transaction
+	common.Transaction
 }
 
 // A MissingEventError is an error that happened because the roomserver was