add systemd socket listener activation

Signed-off-by: Perry Naseck <[email protected]>

go.mod

@@ -3,6 +3,7 @@ module github.com/prometheus/exporter-toolkit
 go 1.17
 
 require (
+	github.com/coreos/go-systemd/v22 v22.3.2
 	github.com/go-kit/log v0.2.1
 	github.com/pkg/errors v0.9.1
 	github.com/prometheus/common v0.34.0

go.sum

@@ -53,6 +53,8 @@ github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e/go.mod h1:nSuG5e5P
 github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1/go.mod h1:Q3SI9o4m/ZMnBNeIyt5eFwwo7qiLfzFZmjNmxjkiQlU=
 github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
 github.com/cncf/udpa/go v0.0.0-20191209042840-269d4d468f6f/go.mod h1:M8M6+tZqaGXZJjfX53e64911xZQV5JYwmTeXPW+k8Sc=
+github.com/coreos/go-systemd/v22 v22.3.2 h1:D9/bQk5vlXQFZ6Kwuu6zaiXJ9oTPe68++AzAJc1DzSI=
+github.com/coreos/go-systemd/v22 v22.3.2/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -75,6 +77,7 @@ github.com/go-logfmt/logfmt v0.5.0/go.mod h1:wCYkCAKZfumFQihp8CzCvQ3paCTfi41vtzG
 github.com/go-logfmt/logfmt v0.5.1 h1:otpy5pqBCBZ1ng9RQ0dPu4PN7ba75Y/aA+UpowDyNVA=
 github.com/go-logfmt/logfmt v0.5.1/go.mod h1:WYhtIu8zTZfxdn5+rREduYbwxfcBr/Vr6KEVveWlfTs=
 github.com/go-stack/stack v1.8.0/go.mod h1:v0f6uXyyMGvRgIKkXu+yp6POWl0qKG85gN/melR3HDY=
+github.com/godbus/dbus/v5 v5.0.4/go.mod h1:xhWf0FNVPg57R7Z0UbKHbJfkEywrmjJnf7w5xrFpKfA=
 github.com/gogo/protobuf v1.1.1/go.mod h1:r8qH/GZQm5c6nD/R0oafs1akxWv10x8SbQlK7atdtwQ=
 github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
 github.com/golang/groupcache v0.0.0-20190702054246-869f871628b6/go.mod h1:cIg4eruTrX1D+g88fzRXU5OdNfaM+9IcxsU14FzY7Hc=

web/tls_config.go

@@ -22,6 +22,7 @@ import (
 	"net/http"
 	"path/filepath"
 
+	"github.com/coreos/go-systemd/v22/activation"
 	"github.com/go-kit/log"
 	"github.com/go-kit/log/level"
 	"github.com/pkg/errors"
@@ -188,6 +189,23 @@ func ListenAndServe(server *http.Server, tlsConfigPath string, logger log.Logger
 	return Serve(listener, server, tlsConfigPath, logger)
 }
 
+// UseActivatedSocketAndServe starts the server on the systemd socket activated
+// listener. Based on the file tlsConfigPath, TLS or basic auth could be
+// enabled.
+func UseActivatedSocketAndServe(server *http.Server, tlsConfigPath string, logger log.Logger) error {
+	listeners, err := activation.Listeners()
+	if err != nil {
+		return err
+	}
+	if len(listeners) < 1 {
+		return errors.New("No socket activation file descriptors found")
+	}
+	if len(listeners) > 1 {
+		return errors.New("More than one socket activation file descriptor found")
+	}
+	return Serve(listeners[0], server, tlsConfigPath, logger)
+}
+
 // Server starts the server on the given listener. Based on the file
 // tlsConfigPath, TLS or basic auth could be enabled.
 func Serve(l net.Listener, server *http.Server, tlsConfigPath string, logger log.Logger) error {