From afb6b8185d4142eaaa1fc46e0971155d71b324f9 Mon Sep 17 00:00:00 2001
From: Christopher Baines <mail@cbaines.net>
Date: Thu, 7 Sep 2023 15:13:56 +0100
Subject: Include metrics for ports and file descriptors

---
 nar-herder/server.scm | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/nar-herder/server.scm b/nar-herder/server.scm
index 01de6d8..525d70b 100644
--- a/nar-herder/server.scm
+++ b/nar-herder/server.scm
@@ -21,6 +21,7 @@
   #:use-module (srfi srfi-11)
   #:use-module (srfi srfi-34)
   #:use-module (srfi srfi-71)
+  #:use-module (ice-9 ftw)
   #:use-module (ice-9 iconv)
   #:use-module (ice-9 match)
   #:use-module (ice-9 threads)
@@ -99,6 +100,29 @@
             (metric-set metric value))))
        metrics))))
 
+(define (get-port-metrics-updater registry)
+  (let ((ports-metric
+         (make-gauge-metric registry "guile_ports_total"))
+        (fds-metric
+         (make-gauge-metric registry "file_descriptors_total")))
+    (lambda ()
+      (let ((count 0))
+        (port-for-each
+         (lambda _
+           (set! count (+ 1 count))))
+
+        (metric-set ports-metric count))
+
+      (metric-set
+       fds-metric
+       (length
+        ;; In theory 'scandir' cannot return #f, but in practice,
+        ;; we've seen it before.
+        (or (scandir "/proc/self/fd"
+                     (lambda (file)
+                       (not (member file '("." "..")))))
+            '()))))))
+
 (define (serve-fixed-output-file input compression proc)
   ;; TODO It's hard with fold-archive from (guix serialization) to
   ;; read just the singular file from the archive, so the following
@@ -200,6 +224,9 @@
   (define gc-metrics-updater
     (get-gc-metrics-updater metrics-registry))
 
+  (define port-metrics-updater
+    (get-port-metrics-updater metrics-registry))
+
   (define guile-time-metrics-updater
     (let ((internal-real-time
            (make-gauge-metric metrics-registry "guile_internal_real_time"))
@@ -493,6 +520,7 @@
                #f))
       (((or 'HEAD 'GET) "metrics")
        (gc-metrics-updater)
+       (port-metrics-updater)
        (guile-time-metrics-updater)
        (increment-request-metric "metrics" "200")
 
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