Disable HTTP server for readonly instances

cmd/replds/server.go

@@ -4,6 +4,9 @@ import (
 	"context"
 	"flag"
 	"log"
+	"os"
+	"os/signal"
+	"syscall"
 
 	"git.autistici.org/ai3/go-common/serverutil"
 	"github.com/google/subcommands"
@@ -56,12 +59,20 @@ func (c *serverCmd) Execute(_ context.Context, f *flag.FlagSet, _ ...interface{}
 	}
 	defer srv.Close()
 
-	httpSrv := replds.NewHTTPServer(srv)
+	// If this is a readonly server, just wait for a termination
+	// signal, otherwise start the HTTP server for our API.
+	if config.Server.Readonly {
+		sigCh := make(chan os.Signal)
+		signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)
+		<-sigCh
+	} else {
+		httpSrv := replds.NewHTTPServer(srv)
 
-	log.Printf("starting replds on %s", config.Server.Addr)
-	if err := serverutil.Serve(httpSrv.Handler(), config.HTTPServer, config.Server.Addr); err != nil {
-		log.Printf("error: %v", err)
-		return subcommands.ExitFailure
+		log.Printf("starting replds on %s", config.Server.Addr)
+		if err := serverutil.Serve(httpSrv.Handler(), config.HTTPServer, config.Server.Addr); err != nil {
+			log.Printf("error: %v", err)
+			return subcommands.ExitFailure
+		}
 	}
 
 	return subcommands.ExitSuccess

server.go

@@ -214,7 +214,9 @@ func (s *Server) doSetNodes(ctx context.Context, nodes []*Node, updatePeers bool
 
 	var res SetNodesResponse
 	if updatePeers {
-		// Ping remote nodes with updated state.
+		// Ping remote nodes with the updated state. This
+		// reduces the latency of update propagation (we don't
+		// have to wait until the peers poll us).
 		res.HostsOk = 1
 		for _, peer := range s.peers {
 			err := s.network.Client(peer).internalUpdateNodes(ctx, &internalUpdateNodesRequest{
@@ -419,6 +421,9 @@ func (s *Server) pollPeerRequest(peer string) (bool, error) {
 	peerName := stripHTTP(peer)
 	peerRequests.With(prometheus.Labels{"peer": peerName}).Inc()
 
+	// Create a shallow copy of the list of the Nodes we know
+	// about, containing just path/timestamp, to send to the peer
+	// in our GetNodes request.
 	s.mx.Lock()
 	var req internalGetNodesRequest
 	for _, node := range s.nodes {
@@ -443,6 +448,7 @@ func (s *Server) pollPeerRequest(peer string) (bool, error) {
 		return false, nil
 	}
 
+	// Update the internal state with the new data.
 	return resp.Partial, s.internalUpdateNodes(ctx, &internalUpdateNodesRequest{Nodes: resp.Nodes})
 }