Added ability to use unix socket instead http connection (#1)

* Add ability to use unix socket instead http requests to server
- Feature: Added parameter `web.socket-path` which sets path
           to an unix socket file. The program uses http server
           if the parameter is empty.
- Feature: Added parameter `web.socket-permissions` which set
           file permissions to an unix socket file. Default value
           is 0640.

Signed-off-by: Stepan Oksanichenko <soksanichenko@cloudlinux.com>

Author: Stepan Oksanichenko

Makefile

@@ -105,6 +105,8 @@ update_fixtures:
 test-e2e: build collector/fixtures/sys/.unpacked
 	@echo ">> running end-to-end tests"
 	./end-to-end-test.sh
+	@echo ">> running end-to-end tests with unix socket"
+	./end-to-end-test.sh -s
 
 .PHONY: skip-test-e2e
 skip-test-e2e:

end-to-end-test.sh

@@ -57,6 +57,7 @@ cd "$(dirname $0)"
 
 port="$((10000 + (RANDOM % 10000)))"
 tmpdir=$(mktemp -d /tmp/node_exporter_e2e_test.XXXXXX)
+unix_socket="${tmpdir}/node_exporter.socket"
 
 skip_re="^(go_|node_exporter_build_info|node_scrape_collector_duration_seconds|process_|node_textfile_mtime_seconds)"
 
@@ -67,8 +68,8 @@ case "${arch}" in
   *) fixture='collector/fixtures/e2e-output.txt' ;;
 esac
 
-keep=0; update=0; verbose=0
-while getopts 'hkuv' opt
+keep=0; update=0; verbose=0; socket=0;
+while getopts 'hkuvs' opt
 do
   case "$opt" in
     k)
@@ -77,6 +78,9 @@ do
     u)
       update=1
       ;;
+    s)
+      socket=1
+      ;;
     v)
       verbose=1
       set -x
@@ -86,6 +90,7 @@ do
       echo "  -k: keep temporary files and leave node_exporter running"
       echo "  -u: update fixture"
       echo "  -v: verbose output"
+      echo "  -s: use unix socket"
       exit 1
       ;;
   esac
@@ -97,6 +102,14 @@ then
     exit 1
 fi
 
+if [ ${socket} -ne 0 ]; then
+  touch "${unix_socket}"
+  connection_params="--web.socket-path=${unix_socket}"
+else
+  connection_params="--web.listen-address=127.0.0.1:${port}"
+fi
+
+
 ./node_exporter \
   --path.procfs="collector/fixtures/proc" \
   --path.sysfs="collector/fixtures/sys" \
@@ -107,7 +120,7 @@ fi
   --collector.qdisc.fixtures="collector/fixtures/qdisc/" \
   --collector.netclass.ignored-devices="(bond0|dmz|int)" \
   --collector.cpu.info \
-  --web.listen-address "127.0.0.1:${port}" \
+  ${connection_params} \
   --log.level="debug" > "${tmpdir}/node_exporter.log" 2>&1 &
 
 echo $! > "${tmpdir}/node_exporter.pid"
@@ -129,11 +142,21 @@ EOF
 
   if [ ${keep} -eq 0 ]
   then
-    kill -9 "$(cat ${tmpdir}/node_exporter.pid)"
+    kill "$(cat ${tmpdir}/node_exporter.pid)"
     # This silences the "Killed" message
     set +e
     wait "$(cat ${tmpdir}/node_exporter.pid)" > /dev/null 2>&1
+    rc=0
+    if [ ${socket} -ne 0 ]; then
+      if ls -l "${unix_socket}" &> /dev/null; then
+        echo "Node exporter didn't remove the socket file after it exiting"
+        rc=1
+      fi
+    fi
     rm -rf "${tmpdir}"
+    # We should exit with non-zero code,
+    # if node exporter didn't remove the socket file.
+    exit $rc
   fi
 }
 
@@ -153,8 +176,13 @@ get() {
 }
 
 sleep 1
-
-get "127.0.0.1:${port}/metrics" | grep -E -v "${skip_re}" > "${tmpdir}/e2e-output.txt"
+(
+  if [ ${socket} -ne 0 ]; then
+    curl -s -X GET --unix-socket "${unix_socket}" ./metrics
+  else
+    get "127.0.0.1:${port}/metrics"
+  fi
+) | grep -E -v "${skip_re}" > "${tmpdir}/e2e-output.txt"
 
 diff -u \
   "${fixture}" \

node_exporter.go

@@ -15,10 +15,14 @@ package main
 
 import (
 	"fmt"
+	"github.com/prometheus/node_exporter/https"
+	"net"
 	"net/http"
 	_ "net/http/pprof"
 	"os"
+	"os/signal"
 	"sort"
+	"syscall"
 
 	"github.com/prometheus/common/promlog"
 	"github.com/prometheus/common/promlog/flag"
@@ -29,7 +33,6 @@ import (
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/prometheus/common/version"
 	"github.com/prometheus/node_exporter/collector"
-	"github.com/prometheus/node_exporter/https"
 	kingpin "gopkg.in/alecthomas/kingpin.v2"
 )
 
@@ -137,7 +140,19 @@ func (h *handler) innerHandler(filters ...string) (http.Handler, error) {
 }
 
 func main() {
+
+	done := make(chan os.Signal, 1)
+	signal.Notify(done, syscall.SIGINT, syscall.SIGTERM)
+
 	var (
+		socketPath = kingpin.Flag(
+			"web.socket-path",
+			"Path to a unix socket file on which to expose metrics and web interface.",
+		).String()
+		socketPermissions = kingpin.Flag(
+			"web.socket-permissions",
+			"Permissions of unix socket file.",
+		).Default("0640").Int32()
 		listenAddress = kingpin.Flag(
 			"web.listen-address",
 			"Address on which to expose metrics and web interface.",
@@ -188,10 +203,42 @@ func main() {
 			</html>`))
 	})
 
-	level.Info(logger).Log("msg", "Listening on", "address", *listenAddress)
-	server := &http.Server{Addr: *listenAddress}
-	if err := https.Listen(server, *configFile, logger); err != nil {
-		level.Error(logger).Log("err", err)
-		os.Exit(1)
+	humanAddress := "address " + *listenAddress
+	if *socketPath != "" {
+		humanAddress = "path " + *socketPath
 	}
+	var server *http.Server
+	var serve func() error
+	level.Info(logger).Log("msg", "Listening on", "address", humanAddress)
+	server = &http.Server{}
+	if *socketPath == "" {
+		server = &http.Server{Addr: *listenAddress}
+		serve = func() error {
+			return https.Listen(server, *configFile, logger)
+		}
+	} else {
+		os.Remove(*socketPath)
+		unixListener, err := net.Listen("unix", *socketPath)
+		if err != nil {
+			level.Error(logger).Log("err", err)
+			os.Exit(1)
+		}
+		if err := os.Chmod(*socketPath, os.FileMode(*socketPermissions)); err != nil {
+			level.Error(logger).Log("err", err)
+			os.Exit(1)
+		}
+		serve = func() error {
+			return server.Serve(unixListener)
+		}
+	}
+	go func() {
+		if err := serve(); err != nil {
+			level.Error(logger).Log("err", err)
+			os.Exit(1)
+		}
+	}()
+	<-done
+	level.Info(logger).Log("msg", "Connection closed on", humanAddress)
+	server.Close()
+	os.Exit(0)
 }