Add FederationClient interface to federationsender (#1284)

* Add FederationClient interface to federationsender

- Use a shim struct in HTTP mode to keep the same API as `FederationClient`.
- Use `federationsender` instead of `FederationClient` in `keyserver`.

* Pointers not values

* Review comments

* Fix unit tests

* Rejig backoff

* Unbreak test

* Remove debug logs

* Review comments and linting

federationsender/internal/api.go

@@ -1,11 +1,16 @@
 package internal
 
 import (
+	"context"
+	"time"
+
+	"github.com/matrix-org/dendrite/federationsender/api"
 	"github.com/matrix-org/dendrite/federationsender/queue"
 	"github.com/matrix-org/dendrite/federationsender/statistics"
 	"github.com/matrix-org/dendrite/federationsender/storage"
 	"github.com/matrix-org/dendrite/internal/config"
-	"github.com/matrix-org/dendrite/roomserver/api"
+	roomserverAPI "github.com/matrix-org/dendrite/roomserver/api"
+	"github.com/matrix-org/gomatrix"
 	"github.com/matrix-org/gomatrixserverlib"
 )
 
@@ -14,7 +19,7 @@ type FederationSenderInternalAPI struct {
 	db         storage.Database
 	cfg        *config.FederationSender
 	statistics *statistics.Statistics
-	rsAPI      api.RoomserverInternalAPI
+	rsAPI      roomserverAPI.RoomserverInternalAPI
 	federation *gomatrixserverlib.FederationClient
 	keyRing    *gomatrixserverlib.KeyRing
 	queues     *queue.OutgoingQueues
@@ -22,7 +27,7 @@ type FederationSenderInternalAPI struct {
 
 func NewFederationSenderInternalAPI(
 	db storage.Database, cfg *config.FederationSender,
-	rsAPI api.RoomserverInternalAPI,
+	rsAPI roomserverAPI.RoomserverInternalAPI,
 	federation *gomatrixserverlib.FederationClient,
 	keyRing *gomatrixserverlib.KeyRing,
 	statistics *statistics.Statistics,
@@ -38,3 +43,96 @@ func NewFederationSenderInternalAPI(
 		queues:     queues,
 	}
 }
+
+func (a *FederationSenderInternalAPI) isBlacklistedOrBackingOff(s gomatrixserverlib.ServerName) (*statistics.ServerStatistics, error) {
+	stats := a.statistics.ForServer(s)
+	until, blacklisted := stats.BackoffInfo()
+	if blacklisted {
+		return stats, &api.FederationClientError{
+			Blacklisted: true,
+		}
+	}
+	now := time.Now()
+	if until != nil && now.Before(*until) {
+		return stats, &api.FederationClientError{
+			RetryAfter: time.Until(*until),
+		}
+	}
+
+	return stats, nil
+}
+
+func failBlacklistableError(err error, stats *statistics.ServerStatistics) (until time.Time, blacklisted bool) {
+	if err == nil {
+		return
+	}
+	mxerr, ok := err.(gomatrix.HTTPError)
+	if !ok {
+		return stats.Failure()
+	}
+	if mxerr.Code >= 500 && mxerr.Code < 600 {
+		return stats.Failure()
+	}
+	return
+}
+
+func (a *FederationSenderInternalAPI) doRequest(
+	s gomatrixserverlib.ServerName, request func() (interface{}, error),
+) (interface{}, error) {
+	stats, err := a.isBlacklistedOrBackingOff(s)
+	if err != nil {
+		return nil, err
+	}
+	res, err := request()
+	if err != nil {
+		until, blacklisted := failBlacklistableError(err, stats)
+		now := time.Now()
+		var retryAfter time.Duration
+		if until.After(now) {
+			retryAfter = time.Until(until)
+		}
+		return res, &api.FederationClientError{
+			Err:         err.Error(),
+			Blacklisted: blacklisted,
+			RetryAfter:  retryAfter,
+		}
+	}
+	stats.Success()
+	return res, nil
+}
+
+func (a *FederationSenderInternalAPI) GetUserDevices(
+	ctx context.Context, s gomatrixserverlib.ServerName, userID string,
+) (gomatrixserverlib.RespUserDevices, error) {
+	ires, err := a.doRequest(s, func() (interface{}, error) {
+		return a.federation.GetUserDevices(ctx, s, userID)
+	})
+	if err != nil {
+		return gomatrixserverlib.RespUserDevices{}, err
+	}
+	return ires.(gomatrixserverlib.RespUserDevices), nil
+}
+
+func (a *FederationSenderInternalAPI) ClaimKeys(
+	ctx context.Context, s gomatrixserverlib.ServerName, oneTimeKeys map[string]map[string]string,
+) (gomatrixserverlib.RespClaimKeys, error) {
+	ires, err := a.doRequest(s, func() (interface{}, error) {
+		return a.federation.ClaimKeys(ctx, s, oneTimeKeys)
+	})
+	if err != nil {
+		return gomatrixserverlib.RespClaimKeys{}, err
+	}
+	return ires.(gomatrixserverlib.RespClaimKeys), nil
+}
+
+func (a *FederationSenderInternalAPI) QueryKeys(
+	ctx context.Context, s gomatrixserverlib.ServerName, keys map[string][]string,
+) (gomatrixserverlib.RespQueryKeys, error) {
+	ires, err := a.doRequest(s, func() (interface{}, error) {
+		return a.federation.QueryKeys(ctx, s, keys)
+	})
+	if err != nil {
+		return gomatrixserverlib.RespQueryKeys{}, err
+	}
+	return ires.(gomatrixserverlib.RespQueryKeys), nil
+}