1 files changed, 38 insertions, 26 deletions
diff --git a/prometheus.scm b/prometheus.scm
index 024f578..d6889e1 100644
--- a/prometheus.scm
+++ b/prometheus.scm
@@ -367,30 +367,42 @@ so that it can receive and store the metric values."
 
   (hash-for-each
    (lambda (name metric)
-     (hash-for-each
-      (lambda (label-values value)
-        (simple-format
-         port
-         "~A~A~A ~A\n"
-         (or (and=> (metrics-registry-namespace registry)
-                    (lambda (namespace)
-                      (string-append namespace "_")))
-             "")
-         name
-         (if (null? label-values)
-             ""
-             (string-append
-              "{"
-              (string-join (map
-                            (match-lambda
-                              ((label . value)
-                               (simple-format
-                                #f
-                                "~A=\"~A\""
-                                label value)))
-                            label-values)
-                           ",")
-              "}"))
-         value))
-      (metric-values metric)))
+     (let ((full-name
+            (string-append
+             (or (and=> (metrics-registry-namespace registry)
+                        (lambda (namespace)
+                          (string-append namespace "_")))
+                 "")
+             name)))
+
+       (and=> (metric-docstring metric)
+              (lambda (docstring)
+                (simple-format
+                 port
+                 "# HELP ~A ~A\n"
+                 full-name
+                 docstring)))
+
+       (hash-for-each
+        (lambda (label-values value)
+          (simple-format
+           port
+           "~A~A ~A\n"
+           full-name
+           (if (null? label-values)
+               ""
+               (string-append
+                "{"
+                (string-join (map
+                              (match-lambda
+                                ((label . value)
+                                 (simple-format
+                                  #f
+                                  "~A=\"~A\""
+                                  label value)))
+                              label-values)
+                             ",")
+                "}"))
+           value))
+        (metric-values metric))))
    (metrics-registry-metrics-hash registry)))