From 4aaf902eb45b3a4c1003f854bda56c516fdf4f5b Mon Sep 17 00:00:00 2001
From: Christopher Baines <mail@cbaines.net>
Date: Sun, 12 Nov 2023 13:39:14 +0000
Subject: Add get-gc-metrics-updater

---
 prometheus.scm | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/prometheus.scm b/prometheus.scm
index 04f24d8..447ba08 100644
--- a/prometheus.scm
+++ b/prometheus.scm
@@ -44,7 +44,9 @@
             metric-set
             metric-observe
 
-            call-with-duration-metric))
+            call-with-duration-metric
+
+            get-gc-metrics-updater))
 
 (define-record-type <metrics-registry>
   (make-metrics-registry-record metrics-hash namespace)
@@ -558,3 +560,28 @@ This procedure takes care of atomically replacing the file."
       (lambda (key . args)
         (false-if-exception (delete-file template))))))
 
+(define (get-gc-metrics-updater registry)
+  (define metrics
+    `((gc-time-taken
+       . ,(make-gauge-metric registry "guile_gc_time_taken"))
+      (heap-size
+       . ,(make-gauge-metric registry "guile_heap_size"))
+      (heap-free-size
+       . ,(make-gauge-metric registry "guile_heap_free_size"))
+      (heap-total-allocated
+       . ,(make-gauge-metric registry "guile_heap_total_allocated"))
+      (heap-allocated-since-gc
+       . ,(make-gauge-metric registry "guile_allocated_since_gc"))
+      (protected-objects
+       . ,(make-gauge-metric registry "guile_gc_protected_objects"))
+      (gc-times
+       . ,(make-gauge-metric registry "guile_gc_times"))))
+
+  (lambda ()
+    (let ((stats (gc-stats)))
+      (for-each
+       (match-lambda
+         ((name . metric)
+          (let ((value (assq-ref stats name)))
+            (metric-set metric value))))
+       metrics))))
-- 
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