SERVER-114946: Add the MetricUnit enum. (#45140)

Co-authored-by: Cedric Sirianni <cedric.sirianni@mongodb.com>
GitOrigin-RevId: b45c6e1684f743daa882567841d3de01a29ca52d

src/mongo/otel/metrics/BUILD.bazel

@@ -110,3 +110,16 @@ mongo_cc_unit_test(
         "//src/third_party/opentelemetry-cpp/api",
     ],
 )
+
+mongo_cc_library(
+    name = "metric_units",
+    srcs = ["metric_units.cpp"],
+    deps = ["//src/mongo:base"],
+)
+
+mongo_cc_unit_test(
+    name = "metric_units_test",
+    srcs = ["metric_units_test.cpp"],
+    tags = ["mongo_unittest_second_group"],
+    deps = [":metric_units"],
+)

src/mongo/otel/metrics/metric_units.cpp

@@ -0,0 +1,64 @@
+/**
+ *    Copyright (C) 2025-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#include "mongo/otel/metrics/metric_units.h"
+
+#include "mongo/logv2/log.h"
+
+namespace mongo::otel::metrics {
+
+#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kDefault
+
+StringData toString(MetricUnit unit) {
+    switch (unit) {
+        // Time
+        case MetricUnit::kMicroseconds:
+            return "microseconds";
+        case MetricUnit::kMilliseconds:
+            return "milliseconds";
+        case MetricUnit::kSeconds:
+            return "seconds";
+
+        // Space
+        case MetricUnit::kBytes:
+            return "bytes";
+
+        // Database
+        case MetricUnit::kOperations:
+            return "operations";
+        case MetricUnit::kQueries:
+            return "queries";
+
+        // Networking
+        case MetricUnit::kConnections:
+            return "connections";
+    }
+    LOGV2_FATAL(11494600, "Unknown MetricUnit value", "value"_attr = unit);
+}
+}  // namespace mongo::otel::metrics

src/mongo/otel/metrics/metric_units.h

@@ -0,0 +1,57 @@
+/**
+ *    Copyright (C) 2025-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+#include "mongo/base/string_data.h"
+#include "mongo/util/modules.h"
+
+MONGO_MOD_PUBLIC;
+
+namespace mongo::otel::metrics {
+
+// Used to denote the unit of measurement in a metric.
+enum class MetricUnit {
+    // Time
+    kMicroseconds,
+    kMilliseconds,
+    kSeconds,
+
+    // Space
+    kBytes,
+
+    // Database
+    kOperations,
+    kQueries,
+
+    // Networking
+    kConnections,
+};
+
+// Converts any of the above units to a string.
+StringData toString(MetricUnit unit);
+
+}  // namespace mongo::otel::metrics

src/mongo/otel/metrics/metric_units_test.cpp

@@ -0,0 +1,42 @@
+/**
+ *    Copyright (C) 2025-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+#include "mongo/otel/metrics/metric_units.h"
+
+#include "mongo/unittest/death_test.h"
+#include "mongo/unittest/unittest.h"
+
+namespace mongo::otel::metrics {
+TEST(ToStringTest, Works) {
+    ASSERT_EQ(toString(MetricUnit::kSeconds), "seconds");
+}
+
+DEATH_TEST(ToStringDeathTest, DiesOnBadUnit, "11494600") {
+    toString(static_cast<MetricUnit>(-1));
+}
+}  // namespace mongo::otel::metrics