From 80dc0b97a94c7ad945fe323f8fc4418562b2e2c2 Mon Sep 17 00:00:00 2001
From: Milos Gajdos <milosgajdos83@gmail.com>
Date: Fri, 23 Aug 2019 15:00:29 +0100
Subject: [PATCH 1/2] Make server starts and stops idempotent

---
 server/grpc/grpc.go  | 35 +++++++++++++++++++++++++++++++++--
 server/rpc_server.go | 30 +++++++++++++++++++++++++++++-
 2 files changed, 62 insertions(+), 3 deletions(-)

diff --git a/server/grpc/grpc.go b/server/grpc/grpc.go
index bb968d94..86025a9d 100644
--- a/server/grpc/grpc.go
+++ b/server/grpc/grpc.go
@@ -53,6 +53,8 @@ type grpcServer struct {
 	opts        server.Options
 	handlers    map[string]server.Handler
 	subscribers map[*subscriber][]broker.Subscriber
+	// marks the serve as started
+	started bool
 	// used for first registration
 	registered bool
 }
@@ -454,7 +456,10 @@ func (g *grpcServer) newCodec(contentType string) (codec.NewCodec, error) {
 }
 
 func (g *grpcServer) Options() server.Options {
+	g.RLock()
 	opts := g.opts
+	g.RUnlock()
+
 	return opts
 }
 
@@ -700,7 +705,14 @@ func (g *grpcServer) Deregister() error {
 }
 
 func (g *grpcServer) Start() error {
-	config := g.opts
+	g.RLock()
+	if g.started {
+		g.RUnlock()
+		return nil
+	}
+	g.RUnlock()
+
+	config := g.Options()
 
 	// micro: config.Transport.Listen(config.Address)
 	ts, err := net.Listen("tcp", config.Address)
@@ -781,13 +793,32 @@ func (g *grpcServer) Start() error {
 		config.Broker.Disconnect()
 	}()
 
+	// mark the server as started
+	g.Lock()
+	g.started = true
+	g.Unlock()
+
 	return nil
 }
 
 func (g *grpcServer) Stop() error {
+	g.RLock()
+	if !g.started {
+		g.RUnlock()
+		return nil
+	}
+	g.RUnlock()
+
 	ch := make(chan error)
 	g.exit <- ch
-	return <-ch
+
+	var err error
+	select {
+	case err = <-ch:
+		g.started = false
+	}
+
+	return err
 }
 
 func (g *grpcServer) String() string {
diff --git a/server/rpc_server.go b/server/rpc_server.go
index f7ce74ec..4b825a8b 100644
--- a/server/rpc_server.go
+++ b/server/rpc_server.go
@@ -30,6 +30,8 @@ type rpcServer struct {
 	opts        Options
 	handlers    map[string]Handler
 	subscribers map[*subscriber][]broker.Subscriber
+	// marks the serve as started
+	started bool
 	// used for first registration
 	registered bool
 	// graceful exit
@@ -584,6 +586,13 @@ func (s *rpcServer) Deregister() error {
 }
 
 func (s *rpcServer) Start() error {
+	s.RLock()
+	if s.started {
+		s.RUnlock()
+		return nil
+	}
+	s.RUnlock()
+
 	config := s.Options()
 
 	// start listening on the transport
@@ -708,13 +717,32 @@ func (s *rpcServer) Start() error {
 		s.Unlock()
 	}()
 
+	// mark the server as started
+	s.Lock()
+	s.started = true
+	s.Unlock()
+
 	return nil
 }
 
 func (s *rpcServer) Stop() error {
+	s.RLock()
+	if !s.started {
+		s.RUnlock()
+		return nil
+	}
+	s.RUnlock()
+
 	ch := make(chan error)
 	s.exit <- ch
-	return <-ch
+
+	var err error
+	select {
+	case err = <-ch:
+		s.started = false
+	}
+
+	return err
 }
 
 func (s *rpcServer) String() string {

From ba99f037fbffd18af0077862beae9cb271122dfa Mon Sep 17 00:00:00 2001
From: Milos Gajdos <milosgajdos83@gmail.com>
Date: Fri, 23 Aug 2019 15:07:08 +0100
Subject: [PATCH 2/2] Lock started flag when changing it.

---
 server/grpc/grpc.go  | 2 ++
 server/rpc_server.go | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/server/grpc/grpc.go b/server/grpc/grpc.go
index 86025a9d..4dcd6d73 100644
--- a/server/grpc/grpc.go
+++ b/server/grpc/grpc.go
@@ -815,7 +815,9 @@ func (g *grpcServer) Stop() error {
 	var err error
 	select {
 	case err = <-ch:
+		g.Lock()
 		g.started = false
+		g.Unlock()
 	}
 
 	return err
diff --git a/server/rpc_server.go b/server/rpc_server.go
index 4b825a8b..c02b893a 100644
--- a/server/rpc_server.go
+++ b/server/rpc_server.go
@@ -739,7 +739,9 @@ func (s *rpcServer) Stop() error {
 	var err error
 	select {
 	case err = <-ch:
+		s.Lock()
 		s.started = false
+		s.Unlock()
 	}
 
 	return err