handle connection close error message

A custom ERR_PACKET is sent by the server on MySQL 8.0.24 (and higher)
when the server disconnects inactive clients.

This causes some integration tests that destroy the socket connection to
fail due to packet number and order mismatch.

The patch introduces logic to handle this potential new and unexpected
packet and report the custom server message to the application.

Author: ruiquelhas

lib/connection.js

@@ -1,3 +1,8 @@
+// This file was modified by Oracle on June 1, 2021.
+// The changes involve new logic to handle an additional ERR Packet sent by
+// the MySQL server when the connection is closed unexpectedly.
+// Modifications copyright (c) 2021, Oracle and/or its affiliates.
+
 'use strict';
 
 const Net = require('net');
@@ -188,7 +193,7 @@ class Connection extends EventEmitter {
     if (this.connectTimeout) {
       Timers.clearTimeout(this.connectTimeout);
       this.connectTimeout = null;
-    }    
+    }
     // prevent from emitting 'PROTOCOL_CONNECTION_LOST' after EPIPE or ECONNRESET
     if (this._fatalError) {
       return;
@@ -368,6 +373,14 @@ class Connection extends EventEmitter {
   }
 
   protocolError(message, code) {
+    // Starting with MySQL 8.0.24, if the client closes the connection
+    // unexpectedly, the server will send a last ERR Packet, which we can
+    // safely ignore.
+    // https://dev.mysql.com/worklog/task/?id=12999
+    if (this._closing) {
+      return;
+    }
+
     const err = new Error(message);
     err.fatal = true;
     err.code = code || 'PROTOCOL_ERROR';
@@ -415,10 +428,18 @@ class Connection extends EventEmitter {
       }
     }
     if (!this._command) {
-      this.protocolError(
-        'Unexpected packet while no commands in the queue',
-        'PROTOCOL_UNEXPECTED_PACKET'
-      );
+      const marker = packet.peekByte();
+      // If it's an Err Packet, we should use it.
+      if (marker === 0xff) {
+        const error = Packets.Error.fromPacket(packet);
+        this.protocolError(error.message, error.code);
+      } else {
+        // Otherwise, it means it's some other unexpected packet.
+        this.protocolError(
+          'Unexpected packet while no commands in the queue',
+          'PROTOCOL_UNEXPECTED_PACKET'
+        );
+      }
       this.close();
       return;
     }

lib/constants/errors.js

@@ -1,3 +1,8 @@
+// This file was modified by Oracle on June 1, 2021.
+// An entry was created for a new error reported by the MySQL server due to
+// client inactivity.
+// Modifications copyright (c) 2021, Oracle and/or its affiliates.
+
 'use strict';
 
 // copy from https://raw.githubusercontent.com/mysqljs/mysql/7770ee5bb13260c56a160b91fe480d9165dbeeba/lib/protocol/constants/errors.js
@@ -994,6 +999,7 @@ exports.ER_INNODB_FT_AUX_NOT_HEX_ID = 1879;
 exports.ER_OLD_TEMPORALS_UPGRADED = 1880;
 exports.ER_INNODB_FORCED_RECOVERY = 1881;
 exports.ER_AES_INVALID_IV = 1882;
+exports.ER_CLIENT_INTERACTION_TIMEOUT = 4031;
 
 // Lookup-by-number table
 exports[1] = 'EE_CANTCREATEFILE';
@@ -1982,3 +1988,4 @@ exports[1879] = 'ER_INNODB_FT_AUX_NOT_HEX_ID';
 exports[1880] = 'ER_OLD_TEMPORALS_UPGRADED';
 exports[1881] = 'ER_INNODB_FORCED_RECOVERY';
 exports[1882] = 'ER_AES_INVALID_IV';
+exports[4031] = 'ER_CLIENT_INTERACTION_TIMEOUT';

lib/packets/index.js

@@ -1,3 +1,8 @@
+// This file was modified by Oracle on June 1, 2021.
+// A utility method was introduced to generate an Error instance from a
+// binary server packet.
+// Modifications copyright (c) 2021, Oracle and/or its affiliates.
+
 'use strict';
 
 const process = require('process');
@@ -122,6 +127,20 @@ class Error {
     packet._name = 'Error';
     return packet;
   }
+
+  static fromPacket(packet) {
+    packet.readInt8(); // marker
+    const code = packet.readInt16();
+    packet.readString(1, 'ascii'); // sql state marker
+    // The SQL state of the ERR_Packet which is always 5 bytes long.
+    // https://dev.mysql.com/doc/dev/mysql-server/8.0.11/page_protocol_basic_dt_strings.html#sect_protocol_basic_dt_string_fix
+    packet.readString(5, 'ascii'); // sql state (ignore for now)
+    const message = packet.readNullTerminatedString('utf8');
+    const error = new Error();
+    error.message = message;
+    error.code = code;
+    return error;
+  }
 }
 
 exports.Error = Error;

test/integration/test-server-close.js

@@ -0,0 +1,38 @@
+// Copyright (c) 2021, Oracle and/or its affiliates.
+
+'use strict';
+
+const errors = require('../../lib/constants/errors');
+const common = require('../common');
+const connection = common.createConnection();
+const assert = require('assert');
+
+const customWaitTimeout = 1; // seconds
+
+let error;
+
+connection.on('error', err => {
+  error = err;
+
+  connection.close();
+});
+
+connection.query(`set wait_timeout=${customWaitTimeout}`, () => {
+  setTimeout(() => {}, customWaitTimeout * 1000 * 2);
+});
+
+process.on('uncaughtException', err => {
+  // The ERR Packet is only sent by MySQL server 8.0.24 or higher, so we
+  // need to account for the fact it is not sent by older server versions.
+  if (err.code !== 'ERR_ASSERTION') {
+    throw err;
+  }
+
+  assert.equal(error.message, 'Connection lost: The server closed the connection.');
+  assert.equal(error.code, 'PROTOCOL_CONNECTION_LOST');
+});
+
+process.on('exit', () => {
+  assert.equal(error.message, 'The client was disconnected by the server because of inactivity. See wait_timeout and interactive_timeout for configuring this behavior.');
+  assert.equal(error.code, errors.ER_CLIENT_INTERACTION_TIMEOUT);
+});