chore(instrumentation-mysql): update metric names to semconv METRIC_* exports (#3128)

Author: trentm

packages/instrumentation-mysql/src/instrumentation.ts

@@ -31,6 +31,7 @@ import {
   DB_SYSTEM_VALUE_MYSQL,
   ATTR_DB_STATEMENT,
   ATTR_DB_SYSTEM,
+  METRIC_DB_CLIENT_CONNECTIONS_USAGE,
 } from './semconv';
 import type * as mysqlTypes from 'mysql';
 import { AttributeNames } from './AttributeNames';
@@ -63,7 +64,7 @@ export class MySQLInstrumentation extends InstrumentationBase<MySQLInstrumentati
 
   protected override _updateMetricInstruments() {
     this._connectionsUsage = this.meter.createUpDownCounter(
-      'db.client.connections.usage', //TODO:: use semantic convention
+      METRIC_DB_CLIENT_CONNECTIONS_USAGE,
       {
         description:
           'The number of connections that are currently in state described by the state attribute.',

packages/instrumentation-mysql/src/semconv.ts

@@ -106,3 +106,13 @@ export const ATTR_NET_PEER_PORT = 'net.peer.port' as const;
  * @experimental This enum value is experimental and is subject to breaking changes in minor releases of `@opentelemetry/semantic-conventions`.
  */
 export const DB_SYSTEM_VALUE_MYSQL = 'mysql' as const;
+
+/**
+ * Deprecated, use `db.client.connection.count` instead.
+ *
+ * @experimental This metric is experimental and is subject to breaking changes in minor releases of `@opentelemetry/semantic-conventions`.
+ *
+ * @deprecated Replaced by `db.client.connection.count`.
+ */
+export const METRIC_DB_CLIENT_CONNECTIONS_USAGE =
+  'db.client.connections.usage' as const;