[bug#55080] [PATCH shepherd] service: Gracefully handle non-existing log directories.

[bug#55080] [PATCH shepherd] service: Gracefully handle non-existing log directories.

[Liliana Marie Prikler]

* gnu/packages/services.scm (%service-file-logger): New variable,
implementing...
(service-file-logger): ... the old behaviour of this variable.  Catch system
errors from %service-file-logger and handle them.
---
 modules/shepherd/service.scm | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/modules/shepherd/service.scm b/modules/shepherd/service.scm
index 013347b..567a08b 100644
--- a/modules/shepherd/service.scm
+++ b/modules/shepherd/service.scm
@@ -873,9 +873,9 @@ daemon writing FILE is running in a separate PID namespace."
               (try-again)
               (apply throw args)))))))
 
-(define (service-file-logger file input)
-  "Return a thunk meant to run as a fiber that reads from INPUT and logs it to
-FILE."
+(define (%service-file-logger file input)
+  "Like 'service-file-logger', but doesn't handle the case in which FILE does
+not exist."
   (let* ((fd     (open-fdes file (logior O_CREAT O_WRONLY O_APPEND) #o640))
          (output (fdopen fd "al")))
     (set-port-encoding! output "UTF-8")
@@ -894,6 +894,19 @@ FILE."
                  (format output "~a~a~%" prefix line)
                  (loop))))))))))
 
+(define (service-file-logger file input)
+  "Return a thunk meant to run as a fiber that reads from INPUT and logs it to
+FILE."
+  (catch 'system-error
+    (lambda ()
+      (%service-file-logger file input))
+    (lambda args
+      (if (= ENOENT (system-error-errno args))
+          (begin
+            (mkdir-p (dirname file))
+            (%service-file-logger file input))
+          (apply throw args)))))
+
 (define (service-builtin-logger command input)
   "Return a thunk meant to run as a fiber that reads from INPUT and logs to
 'log-output-port'."
-- 
2.35.1

[bug#55080] [PATCH shepherd] service: Gracefully handle non-existing log directories.

[Ludovic Courtès]

Hi,

Liliana Marie Prikler <liliana.prikler@gmail.com> skribis:

> * gnu/packages/services.scm (%service-file-logger): New variable,
> implementing...
> (service-file-logger): ... the old behaviour of this variable.  Catch system
> errors from %service-file-logger and handle them.

[...]

> +(define (service-file-logger file input)
> +  "Return a thunk meant to run as a fiber that reads from INPUT and logs it to
> +FILE."
> +  (catch 'system-error
> +    (lambda ()
> +      (%service-file-logger file input))
> +    (lambda args
> +      (if (= ENOENT (system-error-errno args))
> +          (begin
> +            (mkdir-p (dirname file))
> +            (%service-file-logger file input))
> +          (apply throw args)))))

I wonder to what extent automatically creating log directories is a good
idea.  A potential drawback is if shepherd creates them with unexpected
ownership or permissions.

Did you encounter this issue while working on services?

Am I right that the Shepherd 0.8 had the same problem?

Thanks,
Ludo’.

[bug#55080] [PATCH shepherd] service: Gracefully handle non-existing log directories.

[Liliana Marie Prikler]

Am Samstag, dem 30.04.2022 um 16:15 +0200 schrieb Ludovic Courtès:
> 
> > +(define (service-file-logger file input)
> > +  "Return a thunk meant to run as a fiber that reads from INPUT
> > and logs it to
> > +FILE."
> > +  (catch 'system-error
> > +    (lambda ()
> > +      (%service-file-logger file input))
> > +    (lambda args
> > +      (if (= ENOENT (system-error-errno args))
> > +          (begin
> > +            (mkdir-p (dirname file))
> > +            (%service-file-logger file input))
> > +          (apply throw args)))))
> 
> I wonder to what extent automatically creating log directories is a
> good idea.  A potential drawback is if shepherd creates them with
> unexpected ownership or permissions.
As far as I know, those logs should be managed by shepherd, no?  It
just redirects stdout/stderr there, or is there something special going
on?

> Did you encounter this issue while working on services?
> 
> Am I right that the Shepherd 0.8 had the same problem?
It might be, I don't know.  I've encountered this for non-existing log
directory, so a reproducer would be setting #:log-file to $test-tmp-
directory/does-not-exist/log and check for each service.

Cheers 

[bug#55080] [PATCH shepherd] service: Gracefully handle non-existing log directories.

[Ludovic Courtès]

Liliana Marie Prikler <liliana.prikler@gmail.com> skribis:

> Am Samstag, dem 30.04.2022 um 16:15 +0200 schrieb Ludovic Courtès:

[...]

>> Did you encounter this issue while working on services?
>> 
>> Am I right that the Shepherd 0.8 had the same problem?
> It might be, I don't know.  I've encountered this for non-existing log
> directory, so a reproducer would be setting #:log-file to $test-tmp-
> directory/does-not-exist/log and check for each service.

Usually /var/log and similar directories are created not by shepherd but
by Guix System, the distro being used, or whatever.  That’s why I wonder
if it’s shepherd’s job to do that.

I was asking how you encountered it to better understand in which
circumstances the problem can occur in practice and what the failure
more is like.

Thanks,
Ludo’.

[bug#55080] [PATCH shepherd] service: Gracefully handle non-existing log directories.

[Liliana Marie Prikler]

Am Sonntag, dem 01.05.2022 um 15:32 +0200 schrieb Ludovic Courtès:
> > 
> > > Did you encounter this issue while working on services?
> > > 
> > > Am I right that the Shepherd 0.8 had the same problem?
> > It might be, I don't know.  I've encountered this for non-existing
> > log directory, so a reproducer would be setting #:log-file to
> > $test-tmp-directory/does-not-exist/log and check for each service.
> 
> Usually /var/log and similar directories are created not by shepherd
> but by Guix System, the distro being used, or whatever.  That’s why I
> wonder if it’s shepherd’s job to do that.
Hmm, it might not be.  Still, I wouldn't like shepherd to fail in such
a weird manner if the log file can't be created.  Should we write a
warning to shepherd's log and redirect to /dev/null instead?  Should we
just kill the service?

bug#55080: [PATCH shepherd] service: Gracefully handle non-existing log directories.

[Ludovic Courtès]

Hi Liliana,

Liliana Marie Prikler <liliana.prikler@gmail.com> skribis:

> Am Sonntag, dem 01.05.2022 um 15:32 +0200 schrieb Ludovic Courtès:
>> > 
>> > > Did you encounter this issue while working on services?
>> > > 
>> > > Am I right that the Shepherd 0.8 had the same problem?
>> > It might be, I don't know.  I've encountered this for non-existing
>> > log directory, so a reproducer would be setting #:log-file to
>> > $test-tmp-directory/does-not-exist/log and check for each service.
>> 
>> Usually /var/log and similar directories are created not by shepherd
>> but by Guix System, the distro being used, or whatever.  That’s why I
>> wonder if it’s shepherd’s job to do that.
> Hmm, it might not be.  Still, I wouldn't like shepherd to fail in such
> a weird manner if the log file can't be created.

I reread this thread and I concur.  Patch finally pushed as
b0d3f625543bcb32e94167c27cba153f9fc03acd.

Thanks,
Ludo’.