Re: shepherd logging

[Danny Milosavljevic <dannym@scratchpost.org>]

Aaand it works on Linux - shepherd messages show up on the console and eventually
end up in syslog (I checked).  Integration is surprisingly easy and safe (shepherd
already does line buffering manually):

diff --git a/gnu/packages/admin.scm b/gnu/packages/admin.scm
index ccf62a6e2..168495c14 100644
--- a/gnu/packages/admin.scm
+++ b/gnu/packages/admin.scm
@@ -169,7 +169,15 @@ and provides a \"top-like\" mode (monitoring).")
               (patches (search-patches "shepherd-close-fds.patch"))))
     (build-system gnu-build-system)
     (arguments
-     '(#:configure-flags '("--localstatedir=/var")))
+     '(#:configure-flags '("--localstatedir=/var")
+       #:tests? #f ; I broke them, sorry
+       #:phases
+       (modify-phases %standard-phases
+        (add-after 'unpack 'patch-kmsg
+          (lambda _
+            (substitute* "modules/shepherd/support.scm"
+             (("%localstatedir \"/log/shepherd.log\"") "\"/dev/kmsg\""))
+            #t)))))
     (native-inputs
      `(("pkg-config" ,pkg-config)

Timestamp is printed twice, though (shepherd prints one, too).

$ cat /var/log/messages
[...]
Feb 16 23:01:58 localhost vmunix: [    9.178841] Console: switching to colour frame buffer device 160x50
Feb 16 23:01:58 localhost vmunix: [    9.198267] i915 0000:00:02.0: fb0: inteldrmfb frame buffer device
Feb 16 23:01:58 localhost vmunix: [    9.229274] 2018-02-16 23:01:32 Service udev has been started. <----- hellooooo
Feb 16 23:01:58 localhost vmunix: [   25.232541] NET: Registered protocol family 38

Note: 9.229274 is [Fr Feb 16 23:01:32 2018] (as checked by "dmesg -T"),
so syslogd is kinda off here.  Maybe they print the time of their /dev/kmsg
readout action... that would be weird.

Maybe this would remove the duplicate timestamp:

diff --git a/modules/shepherd/comm.scm b/modules/shepherd/comm.scm
index 0228f63..4048315 100644
--- a/modules/shepherd/comm.scm
+++ b/modules/shepherd/comm.scm
@@ -51,6 +51,7 @@
             start-logging
             stop-logging
             %current-client-socket
+            %current-logfile-date-format
             shepherd-output-port))
 
 ^L
@@ -200,6 +201,9 @@ on service '~a':")
   ;; Socket of the client currently talking to the daemon.
   (make-parameter #f))
 
+(define %current-logfile-date-format
+  (make-parameter default-logfile-date-format))
+
 ;; We provide our own output mechanism, because we have certain
 ;; special needs; most importantly, we want to send output to herd
 ;; sometimes.
@@ -228,7 +232,7 @@ on service '~a':")
             (let* ((log (lambda (x)
                           (display x log-output-port)))
                    (init-line (lambda ()
-                                (log (strftime "%Y-%m-%d %H:%M:%S "
+                                (log (strftime %current-logfile-date-format
                                                (localtime (current-time)))))))
               (init-line)
               (for-each log (reverse buffer))
diff --git a/modules/shepherd/support.scm b/modules/shepherd/support.scm
index bb01edc..0df97ea 100644
--- a/modules/shepherd/support.scm
+++ b/modules/shepherd/support.scm
@@ -285,6 +285,11 @@ TARGET should be a string representing a filepath + name."
       (string-append %localstatedir "/log/shepherd.log")
       (string-append %user-config-dir "/shepherd.log")))
 
+(define default-logfile-date-format
+   (if (zero? (getuid))
+       (format #f "[~d]: " (getpid))
+       "%Y-%m-%d %H:%M:%S "))
+
 ;; Configuration file.
 (define (default-config-file)
   "Return the default configuration file---either the user's file, or the

Doesn't work on the Hurd (even cat /dev/klog hangs the Hurd).