From 9d840638403fff9b37ac5557a9d66961fd888938 Mon Sep 17 00:00:00 2001
From: Tsachi Herman <tsachi@algorand.com>
Date: Thu, 2 Jan 2020 16:41:32 -0500
Subject: [PATCH 1/2] Make gracefull exit of a node that is waiting for
 WaitForBlock call.

---
 daemon/algod/api/server/lib/common.go         |  5 ++-
 daemon/algod/api/server/router.go             |  4 +-
 daemon/algod/api/server/v1/handlers/errors.go |  1 +
 .../algod/api/server/v1/handlers/handlers.go  |  3 ++
 daemon/algod/server.go                        | 40 ++++++++-----------
 5 files changed, 25 insertions(+), 28 deletions(-)

diff --git a/daemon/algod/api/server/lib/common.go b/daemon/algod/api/server/lib/common.go
index 736d6f557b..1d2576cdca 100644
--- a/daemon/algod/api/server/lib/common.go
+++ b/daemon/algod/api/server/lib/common.go
@@ -43,8 +43,9 @@ type Routes []Route
 // ReqContext is passed to each of the handlers below via wrapCtx, allowing
 // handlers to interact with the node
 type ReqContext struct {
-	Node *node.AlgorandFullNode
-	Log  logging.Logger
+	Node     *node.AlgorandFullNode
+	Log      logging.Logger
+	Shutdown <-chan struct{}
 }
 
 // ErrorResponse sets the specified status code (should != 200), and fills in the
diff --git a/daemon/algod/api/server/router.go b/daemon/algod/api/server/router.go
index 8697dd73d7..b1fa3288eb 100644
--- a/daemon/algod/api/server/router.go
+++ b/daemon/algod/api/server/router.go
@@ -106,7 +106,7 @@ func registerHandlers(router *mux.Router, prefix string, routes lib.Routes, ctx
 }
 
 // NewRouter builds and returns a new router from routes
-func NewRouter(logger logging.Logger, node *node.AlgorandFullNode, apiToken string) *mux.Router {
+func NewRouter(logger logging.Logger, node *node.AlgorandFullNode, shutdown <-chan struct{}, apiToken string) *mux.Router {
 	router := mux.NewRouter().StrictSlash(true)
 
 	// Middleware
@@ -115,7 +115,7 @@ func NewRouter(logger logging.Logger, node *node.AlgorandFullNode, apiToken stri
 	router.Use(middlewares.CORS)
 
 	// Request Context
-	ctx := lib.ReqContext{Node: node, Log: logger}
+	ctx := lib.ReqContext{Node: node, Log: logger, Shutdown: shutdown}
 
 	// Registers /debug/pprof handler under root path and under /urlAuth path
 	// to support header or url-provided token.
diff --git a/daemon/algod/api/server/v1/handlers/errors.go b/daemon/algod/api/server/v1/handlers/errors.go
index 58992e25ce..c5e6540cd7 100644
--- a/daemon/algod/api/server/v1/handlers/errors.go
+++ b/daemon/algod/api/server/v1/handlers/errors.go
@@ -40,5 +40,6 @@ var (
 	errNoRoundsSpecified                   = "Indexer is not enabled, firstRound and lastRound must be specified"
 	errNoTxnSpecified                      = "no transaction ID was specified"
 	errTransactionNotFound                 = "couldn't find the required transaction in the required range"
+	errServiceShuttingDown                 = "operation aborted as server is shutting down"
 	errUnknownTransactionType              = "found a transaction with an unknown type"
 )
diff --git a/daemon/algod/api/server/v1/handlers/handlers.go b/daemon/algod/api/server/v1/handlers/handlers.go
index 98ae8529a5..665923425d 100644
--- a/daemon/algod/api/server/v1/handlers/handlers.go
+++ b/daemon/algod/api/server/v1/handlers/handlers.go
@@ -419,6 +419,9 @@ func WaitForBlock(ctx lib.ReqContext, w http.ResponseWriter, r *http.Request) {
 	}
 
 	select {
+	case <-ctx.Shutdown:
+		lib.ErrorResponse(w, http.StatusInternalServerError, err, errServiceShuttingDown, ctx.Log)
+		return
 	case <-time.After(1 * time.Minute):
 	case <-ctx.Node.Ledger().Wait(basics.Round(queryRound + 1)):
 	}
diff --git a/daemon/algod/server.go b/daemon/algod/server.go
index c2f2732d3e..f83603ea5a 100644
--- a/daemon/algod/server.go
+++ b/daemon/algod/server.go
@@ -55,9 +55,7 @@ type Server struct {
 	node                 *node.AlgorandFullNode
 	metricCollector      *metrics.MetricService
 	metricServiceStarted bool
-
-	stopping deadlock.Mutex
-	stopped  bool
+	stopping             chan struct{}
 }
 
 // Initialize creates a Node instance with applicable network services
@@ -178,9 +176,11 @@ func (s *Server) Start() {
 		os.Exit(1)
 	}
 
+	s.stopping = make(chan struct{})
+
 	// use the data dir as the static file dir (for our API server), there's
 	// no need to separate the two yet. This lets us serve the swagger.json file.
-	apiHandler := apiServer.NewRouter(s.log, s.node, apiToken)
+	apiHandler := apiServer.NewRouter(s.log, s.node, s.stopping, apiToken)
 
 	addr := cfg.EndpointAddress
 	if addr == "" {
@@ -202,8 +202,6 @@ func (s *Server) Start() {
 		WriteTimeout: time.Duration(cfg.RestWriteTimeoutSeconds) * time.Second,
 	}
 
-	defer s.Stop()
-
 	tcpListener := listener.(*net.TCPListener)
 	errChan := make(chan error, 1)
 	go func() {
@@ -227,30 +225,26 @@ func (s *Server) Start() {
 	c := make(chan os.Signal)
 	signal.Notify(c, os.Interrupt, syscall.SIGTERM, syscall.SIGINT)
 	signal.Ignore(syscall.SIGHUP)
-	go func() {
-		sig := <-c
+
+	fmt.Printf("Node running and accepting RPC requests over HTTP on port %v. Press Ctrl-C to exit\n", addr)
+	select {
+	case err := <-errChan:
+		if err != nil {
+			s.log.Warn(err)
+		} else {
+			s.log.Info("Node exited successfully")
+		}
+		s.Stop()
+	case sig := <-c:
 		fmt.Printf("Exiting on %v\n", sig)
 		s.Stop()
 		os.Exit(0)
-	}()
-
-	fmt.Printf("Node running and accepting RPC requests over HTTP on port %v. Press Ctrl-C to exit\n", addr)
-	err = <-errChan
-	if err != nil {
-		s.log.Warn(err)
-	} else {
-		s.log.Info("Node exited successfully")
 	}
 }
 
 // Stop initiates a graceful shutdown of the node by shutting down the network server.
 func (s *Server) Stop() {
-	s.stopping.Lock()
-	defer s.stopping.Unlock()
-
-	if s.stopped {
-		return
-	}
+	close(s.stopping)
 
 	// Attempt to log a shutdown event before we exit...
 	s.log.Event(telemetryspec.ApplicationState, telemetryspec.ShutdownEvent)
@@ -275,8 +269,6 @@ func (s *Server) Stop() {
 	os.Remove(s.pidFile)
 	os.Remove(s.netFile)
 	os.Remove(s.netListenFile)
-
-	s.stopped = true
 }
 
 // OverridePhonebook is used to replace the phonebook associated with

From b17f3c7146752833b7aa5cf38466d30a86e233b0 Mon Sep 17 00:00:00 2001
From: Tsachi Herman <tsachi@algorand.com>
Date: Thu, 2 Jan 2020 18:45:50 -0500
Subject: [PATCH 2/2] Add comment.

---
 daemon/algod/server.go | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/daemon/algod/server.go b/daemon/algod/server.go
index f83603ea5a..015d4b76b3 100644
--- a/daemon/algod/server.go
+++ b/daemon/algod/server.go
@@ -244,6 +244,8 @@ func (s *Server) Start() {
 
 // Stop initiates a graceful shutdown of the node by shutting down the network server.
 func (s *Server) Stop() {
+	// close the s.stopping, which would signal the rest api router that any pending commands
+	// should be aborted.
 	close(s.stopping)
 
 	// Attempt to log a shutdown event before we exit...