From 1e793a1c524179e1d4503ccda1a29dc95360e10e Mon Sep 17 00:00:00 2001
From: Michael Baird <mbaird@umbel.com>
Date: Mon, 12 Jun 2017 13:16:19 -0500
Subject: [PATCH] Count open file handles as a StatsD metric.

---
 server.go             | 31 +++++++++++++++++++++++++++++++
 server/server_test.go | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+)

diff --git a/server.go b/server.go
index f9719c563..7f2027f10 100644
--- a/server.go
+++ b/server.go
@@ -24,8 +24,10 @@ import (
 	"net/http"
 	"net/url"
 	"os"
+	"os/exec"
 	"runtime"
 	"strconv"
+	"strings"
 	"sync"
 	"time"
 
@@ -486,6 +488,9 @@ func (s *Server) monitorRuntime() {
 		// Record the number of go routines
 		s.Holder.Stats.Gauge("goroutines", float64(runtime.NumGoroutine()), 1.0)
 
+		// Open File handles
+		s.Holder.Stats.Gauge("OpenFiles", float64(CountOpenFiles()), 1.0)
+
 		// Runtime memory metrics
 		runtime.ReadMemStats(&m)
 		s.Holder.Stats.Gauge("HeapAlloc", float64(m.HeapAlloc), 1.0)
@@ -496,6 +501,32 @@ func (s *Server) monitorRuntime() {
 	}
 }
 
+// CountOpenFiles on opperating systems that support lsof
+func CountOpenFiles() int {
+	count := 0
+
+	switch runtime.GOOS {
+	case "darwin":
+		fallthrough
+	case "linux":
+		fallthrough
+	case "unix":
+		fallthrough
+	case "freebsd":
+		out, err := exec.Command("/bin/sh", "-c", fmt.Sprintf("lsof -p %v", os.Getpid())).Output()
+		if err != nil {
+			log.Fatal(err)
+		}
+		lines := strings.Split(string(out), "\n")
+		count = len(lines) - 1
+	case "windows":
+		// TODO: count open file handles on windows
+	default:
+
+	}
+	return count
+}
+
 // StatusHandler specifies two methods which an object must implement to share
 // state in the cluster. These are used by the GossipNodeSet to implement the
 // LocalState and MergeRemoteState methods of memberlist.Delegate
diff --git a/server/server_test.go b/server/server_test.go
index cd82ba007..f1ee11b23 100644
--- a/server/server_test.go
+++ b/server/server_test.go
@@ -25,7 +25,9 @@ import (
 	"net"
 	"net/http"
 	"os"
+	"path/filepath"
 	"reflect"
+	"runtime"
 	"sort"
 	"strconv"
 	"strings"
@@ -372,6 +374,42 @@ path = "/path/to/plugins"
 	}
 }
 
+// tempMkdir makes a temporary directory
+func tempMkdir(t *testing.T) string {
+	dir, err := ioutil.TempDir("", "pilosatemp")
+	if err != nil {
+		t.Fatalf("failed to create test directory: %s", err)
+	}
+	return dir
+}
+
+// Ensure the file handle count is working
+func TestCountOpenFiles(t *testing.T) {
+	// Windows is not supported yet
+	supported := []string{"darwin", "linux", "unix", "freebsd"}
+	sort.Strings(supported)
+	i := sort.Search(len(supported),
+		func(i int) bool { return supported[i] >= runtime.GOOS })
+	if i == len(supported) {
+		return
+	}
+
+	// Create directory store temp file
+	testDir := tempMkdir(t)
+	defer os.RemoveAll(testDir)
+
+	count := pilosa.CountOpenFiles()
+	testFile := filepath.Join(testDir, "test.txt")
+	_, err := os.Create(testFile)
+	if err != nil {
+		t.Fatalf("create test file failed: %s", err)
+	}
+
+	if pilosa.CountOpenFiles() < count+1 {
+		t.Error("Invalid open file handle count")
+	}
+}
+
 // Ensure program can send/receive broadcast messages.
 func TestMain_SendReceiveMessage(t *testing.T) {
 	m0 := MustRunMain()