Sink pool cleanup and organization; better future support when we add more sinks

router/router_server.go

@@ -188,8 +188,7 @@ func deleteServer(c *gin.Context) {
 	// as well.
 	s.CtxCancel()
 	s.Events().Destroy()
-	s.LogSink().Destroy()
-	s.InstallSink().Destroy()
+	s.DestroyAllSinks()
 	s.Websockets().CancelAll()
 
 	// Remove any pending remote file downloads for the server.

router/websocket/listeners.go

@@ -91,8 +91,8 @@ func (h *Handler) listenForServerEvents(ctx context.Context) error {
 	logOutput := make(chan []byte)
 	installOutput := make(chan []byte)
 	h.server.Events().On(eventChan, e...)
-	h.server.LogSink().On(logOutput)
-	h.server.InstallSink().On(installOutput)
+	h.server.Sink(server.LogSink).On(logOutput)
+	h.server.Sink(server.InstallSink).On(installOutput)
 
 	onError := func(evt string, err2 error) {
 		h.Logger().WithField("event", evt).WithField("error", err2).Error("failed to send event over server websocket")
@@ -148,8 +148,8 @@ func (h *Handler) listenForServerEvents(ctx context.Context) error {
 
 	// These functions will automatically close the channel if it hasn't been already.
 	h.server.Events().Off(eventChan, e...)
-	h.server.LogSink().Off(logOutput)
-	h.server.InstallSink().Off(installOutput)
+	h.server.Sink(server.LogSink).Off(logOutput)
+	h.server.Sink(server.InstallSink).Off(installOutput)
 
 	// If the internal context is stopped it is either because the parent context
 	// got canceled or because we ran into an error. If the "err" variable is nil

server/install.go

@@ -507,9 +507,9 @@ func (ip *InstallationProcess) Execute() (string, error) {
 	return r.ID, nil
 }
 
-// Streams the output of the installation process to a log file in the server configuration
-// directory, as well as to a websocket listener so that the process can be viewed in
-// the panel by administrators.
+// StreamOutput streams the output of the installation process to a log file in
+// the server configuration directory, as well as to a websocket listener so
+// that the process can be viewed in the panel by administrators.
 func (ip *InstallationProcess) StreamOutput(ctx context.Context, id string) error {
 	reader, err := ip.client.ContainerLogs(ctx, id, types.ContainerLogsOptions{
 		ShowStdout: true,
@@ -521,7 +521,7 @@ func (ip *InstallationProcess) StreamOutput(ctx context.Context, id string) erro
 	}
 	defer reader.Close()
 
-	err = system.ScanReader(reader, ip.Server.InstallSink().Push)
+	err = system.ScanReader(reader, ip.Server.Sink(InstallSink).Push)
 	if err != nil {
 		ip.Server.Log().WithFields(log.Fields{"container_id": id, "error": err}).Warn("error processing install output lines")
 	}

server/listeners.go

@@ -83,7 +83,7 @@ func (s *Server) processConsoleOutputEvent(v []byte) {
 
 	// If we are not throttled, go ahead and output the data.
 	if !t.Throttled() {
-		s.LogSink().Push(v)
+		s.Sink(LogSink).Push(v)
 	}
 
 	// Also pass the data along to the console output channel.

server/server.go

@@ -71,6 +71,8 @@ type Server struct {
 	wsBag       *WebsocketBag
 	wsBagLocker sync.Mutex
 
+	sinks map[SinkName]*sinkPool
+
 	logSink     *sinkPool
 	installSink *sinkPool
 }
@@ -86,9 +88,10 @@ func New(client remote.Client) (*Server, error) {
 		installing:   system.NewAtomicBool(false),
 		transferring: system.NewAtomicBool(false),
 		restoring:    system.NewAtomicBool(false),
-
-		logSink:     newSinkPool(),
-		installSink: newSinkPool(),
+		sinks: map[SinkName]*sinkPool{
+			LogSink:     newSinkPool(),
+			InstallSink: newSinkPool(),
+		},
 	}
 	if err := defaults.Set(&s); err != nil {
 		return nil, errors.Wrap(err, "server: could not set default values for struct")
@@ -355,11 +358,3 @@ func (s *Server) ToAPIResponse() APIResponse {
 		Configuration: *s.Config(),
 	}
 }
-
-func (s *Server) LogSink() *sinkPool {
-	return s.logSink
-}
-
-func (s *Server) InstallSink() *sinkPool {
-	return s.installSink
-}

server/sink.go

@@ -2,52 +2,70 @@ package server
 
 import (
 	"sync"
-	"time"
+)
+
+// SinkName represents one of the registered sinks for a server.
+type SinkName string
+
+const (
+	// LogSink handles console output for game servers, including messages being
+	// sent via Wings to the console instance.
+	LogSink SinkName = "log"
+	// InstallSink handles installation output for a server.
+	InstallSink SinkName = "install"
 )
 
 // sinkPool represents a pool with sinks.
 type sinkPool struct {
-	mx    sync.RWMutex
+	mu    sync.RWMutex
 	sinks []chan []byte
 }
 
-// newSinkPool returns a new empty sinkPool.
+// newSinkPool returns a new empty sinkPool. A sink pool generally lives with a
+// server instance for it's full lifetime.
 func newSinkPool() *sinkPool {
 	return &sinkPool{}
 }
 
-// Off removes a sink from the pool.
+// On adds a channel to the sink pool instance.
+func (p *sinkPool) On(c chan []byte) {
+	p.mu.Lock()
+	p.sinks = append(p.sinks, c)
+	p.mu.Unlock()
+}
+
+// Off removes a given channel from the sink pool. If no matching sink is found
+// this function is a no-op. If a matching channel is found, it will be removed.
 func (p *sinkPool) Off(c chan []byte) {
-	p.mx.Lock()
-	defer p.mx.Unlock()
+	p.mu.Lock()
+	defer p.mu.Unlock()
 
 	sinks := p.sinks
-
 	for i, sink := range sinks {
 		if c != sink {
 			continue
 		}
+
+		// We need to maintain the order of the sinks in the slice we're tracking,
+		// so shift everything to the left, rather than changing the order of the
+		// elements.
 		copy(sinks[i:], sinks[i+1:])
 		sinks[len(sinks)-1] = nil
 		sinks = sinks[:len(sinks)-1]
+
+		// Update our tracked sinks, and close the matched channel.
 		p.sinks = sinks
 		close(c)
+
 		return
 	}
 }
 
-// On adds a sink on the pool.
-func (p *sinkPool) On(c chan []byte) {
-	p.mx.Lock()
-	defer p.mx.Unlock()
-
-	p.sinks = append(p.sinks, c)
-}
-
-// Destroy destroys the pool by removing and closing all sinks.
+// Destroy destroys the pool by removing and closing all sinks and destroying
+// all of the channels that are present.
 func (p *sinkPool) Destroy() {
-	p.mx.Lock()
-	defer p.mx.Unlock()
+	p.mu.Lock()
+	defer p.mu.Unlock()
 
 	for _, c := range p.sinks {
 		close(c)
@@ -56,17 +74,35 @@ func (p *sinkPool) Destroy() {
 	p.sinks = nil
 }
 
-// Push pushes a message to all registered sinks.
-func (p *sinkPool) Push(v []byte) {
-	p.mx.RLock()
+// Push sends a given message to each of the channels registered in the pool.
+func (p *sinkPool) Push(data []byte) {
+	p.mu.RLock()
 	for _, c := range p.sinks {
-		// TODO: should this be done in parallel?
 		select {
-		// Send the log output to the channel
-		case c <- v:
-		// Timeout after 100 milliseconds, this will cause the write to the channel to be cancelled.
-		case <-time.After(100 * time.Millisecond):
+		// Send the event data over to the channels.
+		case c <- data:
 		}
 	}
-	p.mx.RUnlock()
+	p.mu.RUnlock()
+}
+
+// Sink returns the instantiated and named sink for a server. If the sink has
+// not been configured yet this function will cause a panic condition.
+func (s *Server) Sink(name SinkName) *sinkPool {
+	sink, ok := s.sinks[name]
+	if !ok {
+		s.Log().Fatalf("attempt to access nil sink: %s", name)
+	}
+	return sink
+}
+
+// DestroyAllSinks iterates over all of the sinks configured for the server and
+// destroys their instances. Note that this will cause a panic if you attempt
+// to call Server.Sink() again after. This function is only used when a server
+// is being deleted from the system.
+func (s *Server) DestroyAllSinks() {
+	s.Log().Info("destroying all registered sinks for server instance")
+	for _, sink := range s.sinks {
+		sink.Destroy()
+	}
 }