node-mysql2: MaxListenersExceededWarning: Possible EventEmitter memory leak detected

Hi ,

i am using mysql2 with bluebird on nodejs 8.

const mysql = require('mysql2/promise');
const Promise = require("bluebird");
config.Promise = Promise;//plus database connection configuration
pool = mysql.createPool(config);

function  GetSqlConnection() {
    return  pool.getConnection().disposer(function(connection) {
        connection.release();
    });
};

after sometime i get hit by this warning, i get , 11 end listeners added. 11 drain listeners added etc …


at _addListener (events.js:281:19)
    at PoolConnection.addListener (events.js:298:10)
    at /home/test/servers/v6/project/node_modules/mysql2/promise.js:8:14
    at Array.forEach (native)
    at inheritEvents (/home/test/servers/v6/project/node_modules/mysql2/promise.js:7:6)
    at new PromiseConnection (/home/test/servers/v6/project/node_modules/mysql2/promise.js:37:3)
    at /home/test/servers/v6/project/node_modules/mysql2/promise.js:228:17
    at /home/test/servers/v6/project/node_modules/mysql2/lib/pool.js:36:14
    at _combinedTickCallback (internal/process/next_tick.js:95:7)
    at process._tickCallback (internal/process/next_tick.js:161:9)
---------------------------------------------
    at process.emitWarning (internal/process/warning.js:154:18)
    at _addListener (events.js:289:17)
    at PoolConnection.addListener (events.js:298:10)
    at /home/test/servers/v6/project/node_modules/mysql2/promise.js:8:14
    at Array.forEach (native)
    at inheritEvents (/home/test/servers/v6/project/node_modules/mysql2/promise.js:7:6)
    at new PromiseConnection (/home/test/servers/v6/project/node_modules/mysql2/promise.js:37:3)
    at /home/test/servers/v6/project/node_modules/mysql2/promise.js:228:17
    at /home/test/servers/v6/project/node_modules/mysql2/lib/pool.js:36:14
    at _combinedTickCallback (internal/process/next_tick.js:95:7)
    at process._tickCallback (internal/process/next_tick.js:161:9)
---------------------------------------------
    at Pool.getConnection (/home/test/servers/v6/project/node_modules/mysql2/lib/pool.js:35:20)
    at /home/test/servers/v6/project/node_modules/mysql2/promise.js:224:14
    at Promise._execute (/home/test/servers/v6/project/node_modules/bluebird/js/release/debuggability.js:300:9)
    at Promise._resolveFromExecutor (/home/test/servers/v6/project/node_modules/bluebird/js/release/promise.js:483:18)
    at new Promise (/home/test/servers/v6/project/node_modules/bluebird/js/release/promise.js:79:10)
    at PromisePool.getConnection (/home/test/servers/v6/project/node_modules/mysql2/promise.js:223:10)
    at Db.GetSqlConnection (/home/test/servers/v6/project/db.js:34:23)
    at Db.verify (/home/test/servers/v6/project/db.js:254:31)

About this issue

Original URL
State: closed
Created 7 years ago
Reactions: 3
Comments: 19 (7 by maintainers)

Commits related to this issue

Fix for #577, Remove listening to events after releasing the connection — committed to aankur/node-mysql2 by aankur 7 years ago
redo event delegation in promise wrappers to be lazy, self-cleaning fix sidorares/node-mysql2#577 — committed to rhendric/node-mysql2 by rhendric 7 years ago

Most upvoted comments

Same issue right here – any idea for a fix?

odino on Jul 16, 2017

@sidorares Well, meanwhile you can merge the fix, so we wont get spammed any errors anymore. You can still investigate the cause (just with removed fix).

ghost on Jun 23, 2017

i am able to reproduce it without bluebird disposer

Db.prototype.Verify= function Verify(email)
{
  
   const connection = await  this.pool.getConnection();
       try
       {
   		
          const [password] = await connection.execute("SELECT password from `user` where email=?",email);           
           connection.release();
           return password;
       }
       catch(ex)
       {
   	connection.release();
           return Promise.reject({exception : ex,error : new Error(ex)});
       }

   });

aankur on Jun 3, 2017