Subject: bug#32665: Shepherd is stuck waiting for /var/run/nginx/pid

From: [email-masked] (Ludovic Courtès)
Date: Sat, 08 Sep 2018 18:53:13 +0200

Hello Clément,

Commit 9fc2922794ffaae48e0a7c536e530ea2e0d46cf3 adds a loop to the nginx
service that checks for /var/run/nginx/pid.  Unfortunately, on berlin
that loop never ends because the file is not created (on berlin we use a
“hand-written” nginx config file that lacks a “pid” directive; see
guix-maintenance.git.)

I think there are two things to address:

  1. Don’t look for a PID file when passed a hand-written config file;

  2. Make sure the loop always terminates, similar to what
    ‘make-forkexec-constructor’ does.

The patch below fixes that.  The second patch fixes the ‘stop’
procedure.

Thoughts?

Ludo’.

>From c9daf228a69c24cff6ba5508a3b67ebe3c702a2b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludovic=20Court=C3=A8s?= <[email-masked]>
Date: Sat, 8 Sep 2018 18:48:48 +0200
Subject: [PATCH 1/2] services: nginx: Don't read PID file when passed a custom
 config file.

Fixes <https://bugs.gnu.org/XXX>.

* gnu/services/web.scm (nginx-shepherd-service): Check whether FILE is
true and don't read the PID file if it is; use 'read-pid-file' instead
of a potentially endless loop.
---
 gnu/services/web.scm | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/gnu/services/web.scm b/gnu/services/web.scm
index 3778efd04..1c993b29f 100644
--- a/gnu/services/web.scm
+++ b/gnu/services/web.scm
@@ -610,14 +610,12 @@ of index files."
                  (match '#$args
                    (("-s" . _) #t)
                    (_
-                    (let loop ((duration 0))
-                      ;; https://bugs.launchpad.net/ubuntu/+source/nginx/+bug/1581864/comments/7
-                      (sleep duration)
-                      (if (file-exists? #$pid-file)
-                          (let ((pid (call-with-input-file #$pid-file read)))
-                            ;; it could be #<eof>
-                            (if (integer? pid) pid (loop 1)))
-                          (loop 1)))))))))
+                    ;; When FILE is true, we cannot be sure that PID-FILE will
+                    ;; be created, so assume it won't show up.  When FILE is
+                    ;; false, read PID-FILE.
+                    #$(if file
+                          #~#t
+                          #~(read-pid-file #$pid-file))))))))
 
      ;; TODO: Add 'reload' action.
      (list (shepherd-service
-- 
2.18.0

>From 211a820dbd37926f07f9245ab42cbaf6fb0264bb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludovic=20Court=C3=A8s?= <[email-masked]>
Date: Sat, 8 Sep 2018 18:50:55 +0200
Subject: [PATCH 2/2] services: nginx: 'stop' returns #f.

Previously we'd return #t, which the Shepherd would consider a failure
to stop the service.

* gnu/services/web.scm (nginx-shepherd-service): In 'nginx-action',
return #f when stopping the service.
---
 gnu/services/web.scm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gnu/services/web.scm b/gnu/services/web.scm
index 1c993b29f..df82a6de6 100644
--- a/gnu/services/web.scm
+++ b/gnu/services/web.scm
@@ -608,7 +608,7 @@ of index files."
                                (default-nginx-config config))
                          #$@args)
                  (match '#$args
-                   (("-s" . _) #t)
+                   (("-s" . _) #f)
                    (_
                     ;; When FILE is true, we cannot be sure that PID-FILE will
                     ;; be created, so assume it won't show up.  When FILE is
-- 
2.18.0