Re-implement ability to use unix socket instead http connection

Author: rkoliada-cl

Makefile

@@ -123,6 +123,8 @@ tools:
 test-e2e: build collector/fixtures/sys/.unpacked collector/fixtures/udev/.unpacked tools
 @echo ">> running end-to-end tests"
 ./end-to-end-test.sh -e "$(E2E_EXTRA_FLAGS)"
+@echo ">> running end-to-end tests with unix socket"
+./end-to-end-test.sh -e "$(E2E_EXTRA_FLAGS)" -s
 
 .PHONY: skip-test-e2e
 skip-test-e2e:

end-to-end-test.sh

@@ -105,6 +105,7 @@ 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|node_time_(zone|seconds)|node_network_(receive|transmit)_(bytes|packets)_total)"
 
@@ -127,8 +128,8 @@ case "${arch}" in
  ;;
 esac
 
-extra_flags=""; keep=0; update=0; verbose=0
-while getopts 'e:hkuv' opt
+extra_flags=""; keep=0; update=0; verbose=0; socket=0
+while getopts 'e:hkuvs' opt
 do
  case "$opt" in
  e)
@@ -140,15 +141,19 @@ do
  u)
  update=1
  ;;
+ s)
+ socket=1
+ ;;
  v)
  verbose=1
  set -x
  ;;
  *)
- echo "Usage: $0 [-k] [-u] [-v]"
+ echo "Usage: $0 [-k] [-u] [-v] [-s]"
  echo " -k: keep temporary files and leave node_exporter running"
  echo " -u: update fixture_metrics"
  echo " -v: verbose output"
+ echo " -s: use unix socket"
  exit 1
  ;;
  esac
@@ -260,6 +265,13 @@ echo "IGNORED FLAGS============"
 echo "${ignored_flags:1}"| tr ' ' '\n' | sort | uniq
 echo "========================="
 
+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.rootfs="collector/fixtures" \
  --path.procfs="collector/fixtures/proc" \
@@ -268,7 +280,7 @@ echo "========================="
  $(for c in ${supported_enabled_collectors}; do echo --collector.${c} ; done) \
  $(for c in ${supported_disabled_collectors}; do echo --no-collector.${c} ; done) \
  ${filtered_collector_flags} \
- --web.listen-address "127.0.0.1:${port}" \
+ ${connection_params} \
  --log.level="debug" > "${tmpdir}/node_exporter.log" 2>&1 &
 
 echo $! > "${tmpdir}/node_exporter.pid"
@@ -302,7 +314,17 @@ EOF
  # 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}"
+ if [ $rc -ne 0 ]; then
+ exit $rc
+ fi
  fi
 }
 
@@ -323,7 +345,13 @@ get() {
 
 sleep 1
 
-get "127.0.0.1:${port}/metrics" | grep --text -E -v "${skip_re}" > "${generated_metrics}"
+(
+ if [ ${socket} -ne 0 ]; then
+ curl -s -X GET --unix-socket "${unix_socket}" http://localhost/metrics
+ else
+ get "127.0.0.1:${port}/metrics"
+ fi
+) | grep --text -E -v "${skip_re}" > "${generated_metrics}"
 
 # The following ignore-list is only applicable to the VMs used to run E2E tests on platforms for which containerized environments are not available.
 # However, owing to this, there are some non-deterministic metrics that end up generating samples, unlike their containerized counterparts, for e.g., node_network_receive_bytes_total. 

node_exporter.go

@@ -16,13 +16,16 @@ package main
 import (
 "fmt"
 "log/slog"
+"net"
 "net/http"
 _ "net/http/pprof"
 "os"
+"os/signal"
 "os/user"
 "runtime"
 "slices"
 "sort"
+"syscall"
 
 "github.com/prometheus/common/promslog"
 "github.com/prometheus/common/promslog/flag"
@@ -181,6 +184,14 @@ func (h *handler) innerHandler(filters ...string) (http.Handler, error) {
 
 func main() {
 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()
 metricsPath = kingpin.Flag(
 "web.telemetry-path",
 "Path under which to expose metrics.",
@@ -244,8 +255,38 @@ func main() {
 }
 
 server := &http.Server{}
-if err := web.ListenAndServe(server, toolkitFlags, logger); err != nil {
-logger.Error(err.Error())
-os.Exit(1)
+if *socketPath != "" {
+os.Remove(*socketPath)
+unixListener, err := net.Listen("unix", *socketPath)
+if err != nil {
+logger.Error("Error listening on socket", "err", err)
+os.Exit(1)
+}
+if err := os.Chmod(*socketPath, os.FileMode(*socketPermissions)); err != nil {
+logger.Error("Error changing socket permissions", "err", err)
+os.Exit(1)
+}
+defer os.Remove(*socketPath)
+
+go func() {
+if err := server.Serve(unixListener); err != nil && err != http.ErrServerClosed {
+logger.Error("Error serving", "err", err)
+os.Exit(1)
+}
+}()
+
+done := make(chan os.Signal, 1)
+signal.Notify(done, syscall.SIGINT, syscall.SIGTERM)
+logger.Info("Listening on", "path", *socketPath)
+<-done
+logger.Info("Connection closed on", "path", *socketPath)
+server.Close()
+os.Remove(*socketPath)
+os.Exit(0)
+} else {
+if err := web.ListenAndServe(server, toolkitFlags, logger); err != nil {
+logger.Error(err.Error())
+os.Exit(1)
+}
 }
 }