fix: gracefully close pool connections

lib/pool.js

@@ -127,7 +127,7 @@ class Pool extends EventEmitter {
     }
     for (let i = 0; i < this._allConnections.length; i++) {
       connection = this._allConnections.get(i);
-      connection._realEnd(endCB);
+      connection.end(endCB);
     }
   }
 
@@ -205,7 +205,7 @@ class Pool extends EventEmitter {
             Date.now() - this._freeConnections.get(0).lastActiveTime >
               this.config.idleTimeout)
         ) {
-          this._freeConnections.get(0).destroy();
+          this._freeConnections.get(0).end();
         }
       } finally {
         this._removeIdleTimeoutConnections();

lib/pool_connection.js

@@ -34,17 +34,9 @@ class PoolConnection extends Connection {
     return new PromisePoolConnection(this, promiseImpl);
   }
 
-  end() {
-    const err = new Error(
-      'Calling conn.end() to release a pooled connection is ' +
-        'deprecated. In next version calling conn.end() will be ' +
-        'restored to default conn.end() behavior. Use ' +
-        'conn.release() instead.'
-    );
-    this.emit('warn', err);
-    // eslint-disable-next-line no-console
-    console.warn(err.message);
-    this.release();
+  end(callback) {
+    this._removeFromPool();
+    super.end(callback);
   }
 
   destroy() {
@@ -64,6 +56,3 @@ class PoolConnection extends Connection {
 
 PoolConnection.statementKey = Connection.statementKey;
 module.exports = PoolConnection;
-
-// TODO: Remove this when we are removing PoolConnection#end
-PoolConnection.prototype._realEnd = Connection.prototype.end;

test/test-pool-releases-connections-gracefully.test.cjs

@@ -0,0 +1,41 @@
+'use strict';
+const createPool = require('../common.test.cjs').createPool;
+const { assert } = require('poku');
+
+/**
+ * This test case tests that the pool releases connections gracefully after the idle timeout has passed.
+ *
+ * @see https://github.com/sidorares/node-mysql2/issues/3148
+ */
+
+const pool = new createPool({
+  connectionLimit: 3,
+  maxIdle: 2,
+  idleTimeout: 1000,
+});
+
+let connection1Ended = false;
+let connection2Ended = false;
+let connection3Ended = false;
+
+pool.getConnection((_err1, connection1) => {
+  pool.getConnection((_err2, connection2) => {
+    pool.getConnection((_err3, connection3) => {
+      connection1.stream.on('end', () => (connection1Ended = true));
+      connection2.stream.on('end', () => (connection2Ended = true));
+      connection3.stream.on('end', () => (connection3Ended = true));
+
+      connection1.release();
+      connection2.release();
+      connection3.release();
+
+      setTimeout(() => {
+        assert(connection1Ended, 'connection1 should have ended');
+        assert(connection2Ended, 'connection2 should have ended');
+        assert(connection3Ended, 'connection3 should have ended');
+
+        pool.end();
+      }, 2000);
+    });
+  });
+});