[bug#44922] [PATCH 6/6] monitoring: Support extra options for the Prometheus node exporter.

[Christopher Baines]

There are plenty of options supported that the Guix configuration record
doesn't help you with, so add this field to allow users to do their own thing.

* gnu/services/monitoring.scm (<prometheus-node-exporter-configuration>): Add
extra-options field.
(prometheus-node-exporter-shepherd-service): Handle the extra options.
* doc/guix.texi (Prometheus Node Exporter Service): Document this.
---
 doc/guix.texi               | 3 +++
 gnu/services/monitoring.scm | 9 ++++++---
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 6cd65b8739..dc624d89ec 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -21918,6 +21918,9 @@ This directory can be used to export metrics specific 
to this machine.
 Files containing metrics in the text format, with the filename ending in
 @code{.prom} should be placed in this directory.
 
+@item @code{extra-options} (default: @code{'()})
+Extra options to pass to the Prometheus node exporter.
+
 @end table
 @end deftp
 
diff --git a/gnu/services/monitoring.scm b/gnu/services/monitoring.scm
index c4bae229b8..4b6f8ed623 100644
--- a/gnu/services/monitoring.scm
+++ b/gnu/services/monitoring.scm
@@ -128,7 +128,9 @@ HTTP.")
   (web-listen-address prometheus-node-exporter-web-listen-address
                       (default ":9100"))
   (textfile-directory prometheus-node-exporter-textfile-directory
-                      (default "/var/lib/prometheus/node-exporter")))
+                      (default "/var/lib/prometheus/node-exporter"))
+  (extra-options      prometheus-node-exporter-extra-options
+                      (default '())))
 
 (define %prometheus-node-exporter-accounts
   (list (user-account
@@ -145,7 +147,7 @@ HTTP.")
 (define prometheus-node-exporter-shepherd-service
   (match-lambda
     (( $ <prometheus-node-exporter-configuration>
-         package web-listen-address textfile-directory)
+         package web-listen-address textfile-directory extra-options)
      (list
       (shepherd-service
        (documentation "Prometheus node exporter.")
@@ -157,7 +159,8 @@ HTTP.")
                        #$@(if textfile-directory
                               (list "--collector.textfile.directory"
                                     textfile-directory)
-                              '()))
+                              '())
+                       #$@extra-options)
                  #:user "prometheus-node-exporter"
                  #:group "prometheus-node-exporter"
                  #:log-file "/var/log/prometheus-node-exporter.log"))
-- 
2.29.2