From b3b01b08bd3c522655a174327551d044325ea57f Mon Sep 17 00:00:00 2001
From: Amnon Heiman <amnon@scylladb.com>
Date: Thu, 2 Feb 2023 10:44:53 +0200
Subject: [PATCH] metrics: Allows filtering by dynamic labels

The metrics relabel API allows the creation of new labels during run
time.  It would be helpful to add those labels to the set of all
existing labels so that Prometheus will be able to filter by those
labels.

This patch adds the labels to the label collection after performing
metric relabeling.

Signed-off-by: Amnon Heiman <amnon@scylladb.com>
---
 src/core/metrics.cc | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/core/metrics.cc b/src/core/metrics.cc
index c70c214ed27..fad19cc6749 100644
--- a/src/core/metrics.cc
+++ b/src/core/metrics.cc
@@ -436,9 +436,6 @@ void impl::add_registration(const metric_id& id, const metric_type& type, metric
             throw std::runtime_error("registering metrics " + name + " registered with different type.");
         }
         metric[rm->info().id.labels()] = rm;
-        for (auto&& i : rm->info().id.labels()) {
-            _labels.insert(i.first);
-        }
     } else {
         _value_map[name].info().type = type.base_type;
         _value_map[name].info().d = d;
@@ -447,6 +444,9 @@ void impl::add_registration(const metric_id& id, const metric_type& type, metric
         _value_map[name].info().aggregate_labels = aggregate_labels;
         _value_map[name][rm->info().id.labels()] = rm;
     }
+    for (auto&& i : rm->info().id.labels()) {
+        _labels.insert(i.first);
+    }
     dirty();
 }
 
@@ -488,7 +488,9 @@ future<metric_relabeling_result> impl::set_relabel_configs(const std::vector<rel
                 conflicts.metrics_relabeled_due_to_collision++;
                 rm->info().id.labels()["err"] = id;
             }
-
+            for (auto&& i : rm->info().id.labels()) {
+                _labels.insert(i.first);
+            }
             family.second[lb] = rm;
         }
     }