Add unix socket support for supervisord collector (#1592)

* Add unix socket support for supervisord collector

For example:
  --collector.supervisord.url=unix:///var/run/supervisor.sock

Fixes prometheus/node_exporter#262

Signed-off-by: Paul Cameron <cameronpm@gmail.com>

2 files changed, 23 insertions, 1 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2f85f51..a640db2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -29,6 +29,7 @@
 * [ENHANCEMENT] Add check for systemd version before attempting to query certain metrics. #1413
 * [ENHANCEMENT] Add new counters for flush requests in Linux 5.5 #1548
 * [ENHANCEMENT] The sockstat collector now exposes IPv6 statistics in addition to the existing IPv4 support. #1552
+* [ENHANCEMENT] Add unix socket support for supervisord collector #262
 * [BUGFIX] Renamed label `state` to `name` on `node_systemd_service_restart_total`. #1393
 * [BUGFIX] Fix netdev nil reference on Darwin #1414
 * [BUGFIX] Strip path.rootfs from mountpoint labels #1421
diff --git a/collector/supervisord.go b/collector/supervisord.go
index a182062..33f3b8a 100644
--- a/collector/supervisord.go
+++ b/collector/supervisord.go
@@ -16,7 +16,12 @@
 package collector
 
 import (
+        "context"
         "fmt"
+        "net"
+        "net/http"
+        "net/url"
+        "time"
 
         "github.com/go-kit/kit/log"
         "github.com/go-kit/kit/log/level"
@@ -27,6 +32,7 @@ import (
 
 var (
         supervisordURL = kingpin.Flag("collector.supervisord.url", "XML RPC endpoint.").Default("http://localhost:9001/RPC2").String()
+        xrpc           *xmlrpc.Client
 )
 
 type supervisordCollector struct {
@@ -47,6 +53,21 @@ func NewSupervisordCollector(logger log.Logger) (Collector, error) {
                 subsystem  = "supervisord"
                 labelNames = []string{"name", "group"}
         )
+
+        if u, err := url.Parse(*supervisordURL); err == nil && u.Scheme == "unix" {
+                // Fake the URI scheme as http, since net/http.*Transport.roundTrip will complain
+                // about a non-http(s) transport.
+                xrpc = xmlrpc.NewClient("http://unix/RPC2")
+                xrpc.HttpClient.Transport = &http.Transport{
+                        DialContext: func(ctx context.Context, _, _ string) (net.Conn, error) {
+                                d := net.Dialer{Timeout: 10 * time.Second}
+                                return d.DialContext(ctx, "unix", u.Path)
+                        },
+                }
+        } else {
+                xrpc = xmlrpc.NewClient(*supervisordURL)
+        }
+
         return &supervisordCollector{
                 upDesc: prometheus.NewDesc(
                         prometheus.BuildFQName(namespace, subsystem, "up"),
@@ -111,7 +132,7 @@ func (c *supervisordCollector) Update(ch chan<- prometheus.Metric) error {
                 PID           int    `xmlrpc:"pid"`
         }
 
-        res, err := xmlrpc.Call(*supervisordURL, "supervisor.getAllProcessInfo")
+        res, err := xrpc.Call("supervisor.getAllProcessInfo")
         if err != nil {
                 return fmt.Errorf("unable to call supervisord: %s", err)
         }