Document socket activation.

.gitignore

@@ -0,0 +1 @@
+.*.vim

cmd/circologd/activation.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"net"
+
+	"github.com/coreos/go-systemd/activation"
+)
+
+func Listeners() ([]net.Listener, error) {
+	files := activation.Files(false)
+	listeners := make([]net.Listener, len(files))
+
+	for i, f := range files {
+		if pc, err := net.FileListener(f); err == nil {
+			listeners[i] = pc
+			f.Close()
+		}
+	}
+	return listeners, nil
+}
+
+// PacketConns returns a slice containing a net.PacketConn for each matching socket type
+// passed to this process.
+//
+// The order of the file descriptors is preserved in the returned slice.
+// Nil values are used to fill any gaps. For example if systemd were to return file descriptors
+// corresponding with "udp, tcp, udp", then the slice would contain {net.PacketConn, nil, net.PacketConn}
+func PacketConns() ([]net.PacketConn, error) {
+	files := activation.Files(false)
+	conns := make([]net.PacketConn, len(files))
+
+	for i, f := range files {
+		if pc, err := net.FilePacketConn(f); err == nil {
+			conns[i] = pc
+			f.Close()
+		}
+	}
+	return conns, nil
+}

cmd/circologd/main.go

@@ -17,17 +17,24 @@ import (
 	syslog "gopkg.in/mcuadros/go-syslog.v2"
 )
 
+var socketsToRemove []string
+
 func cleanSocket(socket string) {
 	if err := os.Remove(socket); err != nil {
 		fmt.Fprintln(os.Stderr, "Error cleaning", socket, ":", err)
 	}
 }
 
+func removeAtExit(socket string) {
+	socketsToRemove = append(socketsToRemove, socket)
+}
+
 func main() {
 	var err error
+	var syslogSocket SyslogSocket
 	var logFmt formatter.SyslogRFC
 	logFmt.Format = syslog.Automatic
-	syslogSocketPath := flag.String("syslogd-socket", "", "The socket to listen to syslog addresses")
+	flag.Var(&syslogSocket, "syslogd-socket", "The socket to listen to syslog addresses")
 	// dumpSocketPath := flag.String("dump-socket", "/run/buffer.sock", "The socket that user will connect to in order to receive logs")
 	bufsize := flag.Int("buffer-size", 1000, "Number of messages to keep")
 	syslogAddr := flag.String("syslog-addr", "127.0.0.1:9514", "Address:port where to listen for syslog messages")
@@ -50,18 +57,30 @@ func main() {
 	server.SetFormat(logFmt.Format)
 	fmt.Printf("Syslog format set to: %s\n", logFmt.String())
 	server.SetHandler(handler)
-	if *syslogSocketPath != "" {
-		if err = server.ListenUnixgram(*syslogSocketPath); err != nil {
-			fmt.Fprintln(os.Stderr, "argh", err)
-			os.Exit(1)
+	if syslogSocket.isSocketActivated {
+		fmt.Printf("Binding to socket `%s` [syslog]\n", syslogSocket.String())
+		if syslogSocket.Listener != nil {
+			fmt.Println("(stream)")
+			server.Listen(syslogSocket.Listener)
+		} else {
+			fmt.Println("(datagram)", syslogSocket.Conn)
+			server.ListenDgram(syslogSocket.Conn)
 		}
-		defer cleanSocket(*syslogSocketPath)
-		fmt.Printf("Binding socket `%s` [syslog]\n", *syslogSocketPath)
 	} else {
-		fmt.Printf("Binding address `%s` [syslog]\n", *syslogAddr)
-		if err = server.ListenUDP(*syslogAddr); err != nil {
-			fmt.Fprintln(os.Stderr, "argh", err)
-			os.Exit(1)
+		syslogSocketPath := syslogSocket.Path
+		if syslogSocketPath != "" {
+			if err = server.ListenUnixgram(syslogSocketPath); err != nil {
+				fmt.Fprintln(os.Stderr, "argh", err)
+				os.Exit(1)
+			}
+			fmt.Printf("Binding socket `%s` [syslog]\n", syslogSocketPath)
+			removeAtExit(syslogSocketPath)
+		} else {
+			fmt.Printf("Binding address `%s` [syslog]\n", *syslogAddr)
+			if err = server.ListenUDP(*syslogAddr); err != nil {
+				fmt.Fprintln(os.Stderr, "argh", err)
+				os.Exit(1)
+			}
 		}
 	}
 	if err = server.Boot(); err != nil {
@@ -77,7 +96,7 @@ func main() {
 			fmt.Fprintln(os.Stderr, "Error binding HTTP unix domain socket", err)
 			return
 		}
-		defer cleanSocket(*querySocket)
+		removeAtExit(*querySocket)
 		go func() {
 			if err := httpQueryServer.Serve(unixListener); err != nil && err != http.ErrServerClosed {
 				fmt.Fprintln(os.Stderr, "error binding", *querySocket, ":", err)
@@ -102,7 +121,7 @@ func main() {
 			fmt.Fprintln(os.Stderr, "Error binding HTTP unix domain socket", err)
 			return
 		}
-		defer cleanSocket(*ctlSocket)
+		removeAtExit(*ctlSocket)
 		go func() {
 			if err := httpCtlServer.Serve(unixListener); err != nil && err != http.ErrServerClosed {
 				fmt.Fprintln(os.Stderr, "error binding:", err)
@@ -152,6 +171,9 @@ func main() {
 				if err := httpCtlServer.Shutdown(nil); err != nil {
 					fmt.Fprintln(os.Stderr, "Error closing control server:", err)
 				}
+				for _, socket := range socketsToRemove {
+					cleanSocket(socket)
+				}
 				return
 			}
 		}

cmd/circologd/sockets.go

@@ -0,0 +1,50 @@
+package main
+
+import (
+	"net"
+)
+
+// SyslogSocket is a struct eventually containing a net.Listener
+// ready with messages, and a Path in case the Listener is not present.
+type SyslogSocket struct {
+	Listener          net.Listener
+	Conn              net.PacketConn
+	Path              string
+	isSocketActivated bool
+}
+
+// Set from command-line
+func (s *SyslogSocket) Set(v string) error {
+	err := s.getActivationSocket()
+	if err == nil && (s.Conn != nil || s.Listener != nil) {
+		s.isSocketActivated = true
+	}
+	if !s.isSocketActivated {
+		s.Path = v
+	}
+	return nil
+}
+
+func (s *SyslogSocket) String() string {
+	if s.isSocketActivated {
+		return "systemd-provided"
+	}
+	return s.Path
+}
+
+func (s *SyslogSocket) getActivationSocket() error {
+	conns, err := PacketConns()
+	if err == nil && len(conns) > 0 && conns[0] != nil {
+		s.Conn = conns[0]
+		return nil
+	}
+	listeners, err := Listeners()
+	if err != nil {
+		return err
+	}
+	if len(listeners) == 0 {
+		return nil
+	}
+	s.Listener = listeners[0]
+	return nil
+}

docs/docs/systemd.md

@@ -69,4 +69,26 @@ Here is a working unit for this:
 ### journald with socket activation
 
 To run circologd as non-root, while listening on a root-owned socket (`/run/systemd/journal/syslog`) use
-socket activation
+socket activation. Create a unit in `/etc/systemd/system/circolog.service`:
+
+    [Unit]
+    Description=In-memory logging
+
+    [Service]
+    User=nobody
+    Group=nogroup
+    ExecStart=/usr/local/sbin/circologd -syslogd-socket "" -buffer-size 2000 -query-socket /run/circolog/query.sock
+
+    [Install]
+    WantedBy=multi-user.target
+
+Then symlink the `syslog.service` unit to the newly created one:
+
+    ln -sf /etc/systemd/system/circolog.service /etc/systemd/system/syslog.service
+
+and restart the service:
+
+    systemctl daemon-reload
+    systemctl restart syslog.service
+
+Now circolog is activated and receives messages from `journald`.

docs/mkdocs.yml

@@ -4,5 +4,6 @@ nav:
     - Install: install.md
     - Queries: query.md
     - Hacking: hacking.md
+    - Systemd: systemd.md
 repo_url: https://git.lattuga.net/boyska/circolog
 repo_name: 'Repository'

vendor/gopkg.in/mcuadros/go-syslog.v2

@@ -1 +1 @@
-Subproject commit cf9010332939e9bd80638ef5db53c5547ca30588
+Subproject commit 166aad3f993ce4a67bf486e62d637c834c8a8fe6