Replace networkHistory.offlineClients with clients

Keep the ring buffer alive even if all clients are connected. Keep the
ID of the latest delivered message even for online clients.

As-is, this is a net downgrade: memory usage increases because ring
buffers aren't free'd anymore. However upcoming commits will replace the
ring buffer with log files. This change makes reading from log files
easier.

downstream.go

@@ -864,17 +864,11 @@ func (dc *downstreamConn) sendNetworkHistory(net *network) {
 			continue
 		}
 
-		seq, ok := history.offlineClients[dc.clientName]
+		seq, ok := history.clients[dc.clientName]
 		if !ok {
 			continue
 		}
-		delete(history.offlineClients, dc.clientName)
-
-		// If all clients have received history, no need to keep the
-		// ring buffer around
-		if len(history.offlineClients) == 0 {
-			delete(net.history, target)
-		}
+		history.clients[dc.clientName] = history.ring.Cur()
 
 		consumer := history.ring.NewConsumer(seq)
 

upstream.go

@@ -1635,33 +1635,34 @@ func (uc *upstreamConn) appendHistory(entity string, msg *irc.Message) {
 		detached = ch.Detached
 	}
 
-	// If no client is offline, no need to append the message to the buffer
-	if len(uc.network.offlineClients) == 0 && !detached {
-		return
-	}
-
 	history, ok := uc.network.history[entity]
 	if !ok {
 		history = &networkHistory{
-			offlineClients: make(map[string]uint64),
+			clients: make(map[string]uint64),
 			ring:    NewRing(uc.srv.RingCap),
 		}
 		uc.network.history[entity] = history
 
 		for clientName, _ := range uc.network.offlineClients {
-			history.offlineClients[clientName] = 0
+			history.clients[clientName] = 0
 		}
 
 		if detached {
 			// If the channel is detached, online clients act as offline
 			// clients too
 			uc.forEachDownstream(func(dc *downstreamConn) {
-				history.offlineClients[dc.clientName] = 0
+				history.clients[dc.clientName] = 0
 			})
 		}
 	}
 
 	history.ring.Produce(msg)
+
+	if !detached {
+		uc.forEachDownstream(func(dc *downstreamConn) {
+			history.clients[dc.clientName] = history.ring.Cur()
+		})
+	}
 }
 
 // produce appends a message to the logs, adds it to the history and forwards

user.go

@@ -51,7 +51,7 @@ type eventDownstreamDisconnected struct {
 type eventStop struct{}
 
 type networkHistory struct {
-	offlineClients map[string]uint64 // indexed by client name
+	clients map[string]uint64 // indexed by client name
 	ring    *Ring             // can be nil if there are no offline clients
 }
 
@@ -193,9 +193,6 @@ func (net *network) createUpdateChannel(ch *Channel) error {
 			net.user.srv.Logger.Printf("network %q: detaching channel %q", net.GetName(), ch.Name)
 			net.forEachDownstream(func(dc *downstreamConn) {
 				net.offlineClients[dc.clientName] = struct{}{}
-				if history != nil {
-					history.offlineClients[dc.clientName] = history.ring.Cur()
-				}
 
 				dc.SendMessage(&irc.Message{
 					Prefix:  dc.prefix(),
@@ -423,12 +420,6 @@ func (u *user) run() {
 				}
 
 				net.offlineClients[dc.clientName] = struct{}{}
-				for target, history := range net.history {
-					if ch, ok := net.channels[target]; ok && ch.Detached {
-						continue
-					}
-					history.offlineClients[dc.clientName] = history.ring.Cur()
-				}
 			})
 
 			u.forEachUpstream(func(uc *upstreamConn) {