From 45e8fa53195f6328f6a7880753c3f7185b512bfa Mon Sep 17 00:00:00 2001
From: Your Name <graham@grahamc.com>
Date: Wed, 18 Aug 2021 15:42:03 -0400
Subject: [PATCH] hydra-notify: support sending diagnostic dumps to STDERR on
 request

---
 doc/manual/src/monitoring/README.md | 10 ++++++++++
 src/script/hydra-notify             |  6 ++++++
 2 files changed, 16 insertions(+)

diff --git a/doc/manual/src/monitoring/README.md b/doc/manual/src/monitoring/README.md
index 67fb3961..1f17a64d 100644
--- a/doc/manual/src/monitoring/README.md
+++ b/doc/manual/src/monitoring/README.md
@@ -21,3 +21,13 @@ for details on enabling and configuring the exporter.
 
 The notification exporter exposes metrics on a per-plugin, per-event-type basis: execution
 durations, frequency, successes, and failures.
+
+### Diagnostic Dump
+
+The notification daemon can also dump its metrics to stderr whether or not the exporter
+is configured. This is particularly useful for cases where metrics data is needed but the
+exporter was not enabled.
+
+To trigger this diagnostic dump, send a Postgres notification with the
+`hydra_notify_dump_metrics` channel and no payload. See
+[Re-sending a notification](../notifications.md#re-sending-a-notification).
diff --git a/src/script/hydra-notify b/src/script/hydra-notify
index fbadf7ee..92776eaf 100755
--- a/src/script/hydra-notify
+++ b/src/script/hydra-notify
@@ -99,6 +99,7 @@ my $listener = Hydra::PostgresListener->new($dbh);
 $listener->subscribe("build_started");
 $listener->subscribe("build_finished");
 $listener->subscribe("step_finished");
+$listener->subscribe("hydra_notify_dump_metrics");
 
 sub runPluginsForEvent {
     my ($event) = @_;
@@ -145,6 +146,11 @@ while (!$queued_only) {
 
         $prom->inc("notify_event", { channel => $channelName });
 
+        if ($channelName eq "hydra_notify_dump_metrics") {
+            print STDERR "Dumping prometheus metrics:\n${\$prom->format}\n";
+            next;
+        }
+
         eval {
             my $event = Hydra::Event->new_event($channelName, $message->{"payload"});
             runPluginsForEvent($event);