refactor(influxdb): Refactor trace code for clarity and reliability

refactor(influxdb): Refactor trace code for clarity and reliability

* Make startProfile a method of Server.  startProfile() is only used one
  place.  We bother to copy the Server.CPUProfile and Server.MemProfile
  values out of our Server struct into it's parameters.  It makes more
  sense to make startProfile() a method of Server and have it access
  those members directory via its receiver value.

* Have startProfile() return an error instead of log.Fatal()ing.  We can
  simply propagate the error up the stack and let the caller handle the
  error -- we shouldn't be exiting deep in the bowels of a non-main
  package.

* Capture and return errors from pprof.StartCPUProfile(). Currently
  there is only one possible error it can return but if it returns an
  error, we should handle it.

* add CPUProfileWriteCloser and MemProfileWriteCloser to Server struct.

* make stopProfile() a method of Server

* remove prof variable

* fix captialization of log messages.

cmd/influxd/run/server.go

@@ -89,8 +89,10 @@ type Server struct {
 	reportingDisabled bool
 
 	// Profiling
-	CPUProfile string
-	MemProfile string
+	CPUProfile            string
+	CPUProfileWriteCloser io.WriteCloser
+	MemProfile            string
+	MemProfileWriteCloser io.WriteCloser
 
 	// httpAPIAddr is the host:port combination for the main HTTP API for querying and writing data
 	httpAPIAddr string
@@ -372,8 +374,10 @@ func (s *Server) Err() <-chan error { return s.err }
 
 // Open opens the meta and data store and all services.
 func (s *Server) Open() error {
-	// Start profiling, if set.
-	startProfile(s.CPUProfile, s.MemProfile)
+	// Start profiling if requested.
+	if err := s.startProfile(); err != nil {
+		return err
+	}
 
 	// Open shared TCP connection.
 	ln, err := net.Listen("tcp", s.BindAddress)
@@ -465,7 +469,7 @@ func (s *Server) Open() error {
 
 // Close shuts down the meta and data stores and all services.
 func (s *Server) Close() error {
-	stopProfile()
+	s.stopProfile()
 
 	// Close the listener first to stop any new connections
 	if s.Listener != nil {
@@ -581,47 +585,56 @@ type Service interface {
 }
 
 // prof stores the file locations of active profiles.
-var prof struct {
-	cpu *os.File
-	mem *os.File
-}
-
 // StartProfile initializes the cpu and memory profile, if specified.
-func startProfile(cpuprofile, memprofile string) {
-	if cpuprofile != "" {
-		f, err := os.Create(cpuprofile)
+func (s *Server) startProfile() error {
+	if s.CPUProfile != "" {
+		f, err := os.Create(s.CPUProfile)
 		if err != nil {
-			log.Fatalf("cpuprofile: %v", err)
+			return fmt.Errorf("cpuprofile: %v", err)
 		}
-		log.Printf("writing CPU profile to: %s\n", cpuprofile)
-		prof.cpu = f
-		pprof.StartCPUProfile(prof.cpu)
+
+		s.CPUProfileWriteCloser = f
+		if err := pprof.StartCPUProfile(s.CPUProfileWriteCloser); err != nil {
+			return err
+		}
+
+		log.Printf("Writing CPU profile to: %s\n", s.CPUProfile)
 	}
 
-	if memprofile != "" {
-		f, err := os.Create(memprofile)
+	if s.MemProfile != "" {
+		f, err := os.Create(s.MemProfile)
 		if err != nil {
-			log.Fatalf("memprofile: %v", err)
+			return fmt.Errorf("memprofile: %v", err)
 		}
-		log.Printf("writing mem profile to: %s\n", memprofile)
-		prof.mem = f
+
+		s.MemProfileWriteCloser = f
 		runtime.MemProfileRate = 4096
+
+		log.Printf("Writing mem profile to: %s\n", s.MemProfile)
 	}
 
+	return nil
 }
 
 // StopProfile closes the cpu and memory profiles if they are running.
-func stopProfile() {
-	if prof.cpu != nil {
+func (s *Server) stopProfile() error {
+	if s.CPUProfileWriteCloser != nil {
 		pprof.StopCPUProfile()
-		prof.cpu.Close()
+		if err := s.CPUProfileWriteCloser.Close(); err != nil {
+			return err
+		}
 		log.Println("CPU profile stopped")
 	}
-	if prof.mem != nil {
-		pprof.Lookup("heap").WriteTo(prof.mem, 0)
-		prof.mem.Close()
+
+	if s.MemProfileWriteCloser != nil {
+		pprof.Lookup("heap").WriteTo(s.MemProfileWriteCloser, 0)
+		if err := s.MemProfileWriteCloser.Close(); err != nil {
+			return err
+		}
 		log.Println("mem profile stopped")
 	}
+
+	return nil
 }
 
 // monitorPointsWriter is a wrapper around `coordinator.PointsWriter` that helps