metrics: Add update_aggregate_labels()

include/seastar/core/metrics.hh

@@ -679,6 +679,13 @@ impl::metric_definition_impl make_total_operations(metric_name_type name,
     return make_counter(name, std::forward<T>(val), d, labels).set_type("total_operations");
 }
 
+/*!
+ * \brief Update the aggregation labels of a metric family
+ */
+void update_aggregate_labels(const group_name_type& group_name,
+                             const metric_name_type& metric_name,
+                             const std::vector<label>& aggregate_labels);
+
 /*! @} */
 }
 }

include/seastar/core/metrics_api.hh

@@ -369,6 +369,7 @@ public:
     }
 
     void add_registration(const metric_id& id, const metric_type& type, metric_function f, const description& d, bool enabled, skip_when_empty skip, const std::vector<std::string>& aggregate_labels);
+    void update_aggregate_labels(const metric_id& id, const std::vector<label>& aggregate_labels);
     void remove_registration(const metric_id& id);
     future<> stop() {
         return make_ready_future<>();

include/seastar/core/metrics_registration.hh

@@ -62,6 +62,7 @@ class metric_groups_impl;
 SEASTAR_MODULE_EXPORT_BEGIN
 
 using group_name_type = sstring; /*!< A group of logically related metrics */
+using metric_name_type = sstring; /*!< A single metric name */
 class metric_groups;
 
 class metric_definition {

src/core/metrics.cc

@@ -460,6 +460,19 @@ void impl::add_registration(const metric_id& id, const metric_type& type, metric
     dirty();
 }
 
+void impl::update_aggregate_labels(const metric_id& id,
+                                   const std::vector<label>& aggregate_labels) {
+    auto iter = _value_map.find(id.full_name());
+    if (iter != _value_map.end()) {
+        iter->second.info().aggregate_labels.clear();
+        std::transform(aggregate_labels.begin(), aggregate_labels.end(),
+            std::back_inserter(iter->second.info().aggregate_labels),
+            [] (const label& l) { return l.name(); });
+
+        dirty();
+    }
+}
+
 future<metric_relabeling_result> impl::set_relabel_configs(const std::vector<relabel_config>& relabel_configs) {
     _relabel_configs = relabel_configs;
     metric_relabeling_result conflicts{0};
@@ -556,5 +569,11 @@ histogram histogram::operator+(histogram&& c) const {
     return std::move(c);
 }
 
+void update_aggregate_labels(const group_name_type& group_name,
+                             const metric_name_type& metric_name,
+                             const std::vector<label>& aggregate_labels) {
+    impl::metric_id id(group_name, metric_name, {});
+    impl::get_local_impl()->update_aggregate_labels(id, aggregate_labels);
+}
 }
 }

tests/unit/metrics_test.cc

@@ -321,6 +321,50 @@ SEASTAR_THREAD_TEST_CASE(test_relabel_enable_disable_skip_when_empty) {
     sm::set_relabel_configs({}).get();
 }
 
+SEASTAR_THREAD_TEST_CASE(test_relabel_update_aggregate_labels) {
+    using namespace seastar::metrics;
+    namespace sm = seastar::metrics;
+    sm::metric_groups app_metrics;
+    std::string metrics_family_name = "update_aggregate_labels_test";
+    std::string metric_name = "metric";
+    sm::label label("label");
+
+    for (int i = 0; i < 3; ++i) {
+        app_metrics.add_group(metrics_family_name, {
+            sm::make_counter(metric_name, sm::description(""),
+            { sm::label_instance(label.name(), std::to_string(i))},
+            [] { return 0; }),
+        });
+    }
+
+    auto check_aggregate_labels = [&] (
+            std::vector<std::string> expected_labels, size_t expected_metrics_count) {
+        seastar::foreign_ptr<seastar::metrics::impl::values_reference> values = seastar::metrics::impl::get_values();
+        auto full_name = metrics_family_name + "_" + metric_name;
+        auto metadata = std::find_if(values->metadata->begin(), values->metadata->end(),
+            [&] (const auto& md) { return md.mf.name == full_name; });
+        BOOST_REQUIRE(metadata != values->metadata->end());
+        BOOST_REQUIRE_EQUAL(metadata->mf.aggregate_labels, expected_labels);
+        BOOST_REQUIRE_EQUAL(metadata->metrics.size(), expected_metrics_count);
+    };
+
+    check_aggregate_labels({}, 3);
+
+    // now add one with different aggregate labels which will be ignored
+    app_metrics.add_group(metrics_family_name, {
+        sm::make_counter(metric_name, sm::description(""),
+        { sm::label_instance(label.name(), 3)},
+        [] { return 0; }).aggregate({label}),
+    });
+
+    check_aggregate_labels({}, 4);
+
+    // properly update the aggregate labels
+    update_aggregate_labels(metrics_family_name, metric_name, {label});
+
+    check_aggregate_labels({label.name()}, 4);
+}
+
 SEASTAR_THREAD_TEST_CASE(test_estimated_histogram) {
     using namespace seastar::metrics;
     using namespace std::chrono_literals;