error after creating connection pool and being IDLE for a while

[MetaiR]

hi I am getting this error after creating a connection pool and put application IDLE for a while (I mean don't do anything with application) and it keeps coming

Uncaught (in promise) Error: (conn=1921, no: 45013, SQLState: 08S01) Cannot execute new commands: connection closed
sql: ROLLBACK
Uncaught (in promise) Error: (conn=1922, no: 45013, SQLState: 08S01) Cannot execute new commands: connection closed
sql: ROLLBACK
.
.
.

what's the problem?

btw: I am using mariadb 2.1.0 with a combination of Electronjs and angular to creating a desktop application and the error looks like is shown from zone.js file; here is the full stack trace:

zone.js:391 Uncaught (in promise) Error: (conn=1921, no: 45013, SQLState: 08S01) Cannot execute new commands: connection closed
sql: ROLLBACK
    at Object.module.exports.createError (F:\git\loan\node_modules\mariadb\lib\misc\errors.js:55)
    at _changeTransaction (F:\git\loan\node_modules\mariadb\lib\connection.js:945)
    at Connection.rollback (F:\git\loan\node_modules\mariadb\lib\connection.js:148)
    at Connection.conn.release (F:\git\loan\node_modules\mariadb\lib\pool-promise.js:74)
    at Connection.conn.releaseWithoutError (F:\git\loan\node_modules\mariadb\lib\pool-promise.js:50)
    at idleMaintainer (F:\git\loan\node_modules\mariadb\lib\pool-base.js:466)
    at ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invokeTask (zone.js:423)
    at Object.onInvokeTask (vendor.js:57205)
    at ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invokeTask (zone.js:422)
    at Zone.push../node_modules/zone.js/dist/zone.js.Zone.runTask (zone.js:195)

SQLError | @ | F:\git\loan\node_mod…ib\misc\errors.js:6
-- | -- | --
  | module.exports.createError | @ | F:\git\loan\node_mod…b\misc\errors.js:55
  | _changeTransaction | @ | F:\git\loan\node_mod…b\connection.js:945
  | Connection.rollback | @ | F:\git\loan\node_mod…b\connection.js:148
  | conn.release | @ | F:\git\loan\node_mod…\pool-promise.js:74
  | conn.releaseWithoutError | @ | F:\git\loan\node_mod…\pool-promise.js:50
  | idleMaintainer | @ | F:\git\loan\node_mod…ib\pool-base.js:466
  | push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invokeTask | @ | zone.js:423
  | onInvokeTask | @ | vendor.js:57205
  | push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invokeTask | @ | zone.js:422
  | push../node_modules/zone.js/dist/zone.js.Zone.runTask | @ | zone.js:195
  | push../node_modules/zone.js/dist/zone.js.ZoneTask.invokeTask | @ | zone.js:498
  | ZoneTask.invoke | @ | zone.js:487
  | timer | @ | zone.js:2281
  | Promise.then (async) |   |  
  | scheduleMicroTask | @ | zone.js:584
  | push../node_modules/zone.js/dist/zone.js.ZoneDelegate.scheduleTask | @ | zone.js:413
  | push../node_modules/zone.js/dist/zone.js.Zone.scheduleTask | @ | zone.js:238
  | push../node_modules/zone.js/dist/zone.js.Zone.scheduleMicroTask | @ | zone.js:258
  | scheduleResolveOrReject | @ | zone.js:879
  | ZoneAwarePromise.then | @ | zone.js:1012
  | setInterval (async) |   |  
  | scheduleTask | @ | zone.js:2302
  | push../node_modules/zone.js/dist/zone.js.ZoneDelegate.scheduleTask | @ | zone.js:410
  | onScheduleTask | @ | zone.js:301
  | push../node_modules/zone.js/dist/zone.js.ZoneDelegate.scheduleTask | @ | zone.js:404
  | push../node_modules/zone.js/dist/zone.js.Zone.scheduleTask | @ | zone.js:238
  | push../node_modules/zone.js/dist/zone.js.Zone.scheduleMacroTask | @ | zone.js:261
  | scheduleMacroTaskWithCurrentZone | @ | zone.js:1245
  | (anonymous) | @ | zone.js:2317
  | proto.(anonymous function) | @ | zone.js:1569
  | (anonymous) | @ | F:\git\loan\node_mod…ib\pool-base.js:147
  | push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invoke | @ | zone.js:391
  | onInvoke | @ | vendor.js:57214
  | push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invoke | @ | zone.js:390
  | push../node_modules/zone.js/dist/zone.js.Zone.run | @ | zone.js:150
  | (anonymous) | @ | zone.js:889
  | push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invokeTask | @ | zone.js:423
  | onInvokeTask | @ | vendor.js:57205
  | push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invokeTask | @ | zone.js:422
  | push../node_modules/zone.js/dist/zone.js.Zone.runTask | @ | zone.js:195
  | drainMicroTaskQueue | @ | zone.js:601
  | processTicksAndRejections | @ | internal/process/task_queues.js:86
  | Promise.then (async) |   |  
  | scheduleMicroTask | @ | zone.js:584
  | push../node_modules/zone.js/dist/zone.js.ZoneDelegate.scheduleTask | @ | zone.js:413
  | onScheduleTask | @ | zone.js:301
  | push../node_modules/zone.js/dist/zone.js.ZoneDelegate.scheduleTask | @ | zone.js:404
  | push../node_modules/zone.js/dist/zone.js.Zone.scheduleTask | @ | zone.js:238
  | push../node_modules/zone.js/dist/zone.js.Zone.scheduleMicroTask | @ | zone.js:258
  | scheduleResolveOrReject | @ | zone.js:879
  | resolvePromise | @ | zone.js:825
  | (anonymous) | @ | zone.js:741
  | processTicksAndRejections | @ | internal/process/task_queues.js:81

[rusher]

This seems to occur when a connection in pool close connection idle after reaching pool idleTimeout value (default to 30 minutes).

The problem here is that rollback command is normally done only if there is an existing transaction on connection but after pool.query or giving back a connection to pool, connection is reverted into a clean state, meaning that no rollback command is normally executed.

I can think only on initSql that change autocommit state or server equivalent (specifically autocommit query/ variables).
could you indicate pool configuration and server version and configuration relative to autocommit if changed ?

[MetaiR]

ommm, I didn't change any autocommit configurations. here is how I create the pool:

createPool() {
        this.pool = createPool({
            user: 'db-user',
            password: 'db-password',
            database: 'db',
            compress: true,
            charset: 'utf8mb4_persian_ci',
            resetAfterUse: false
        });
    }

I call this method at the very beginning of my application and then I get a new connection from pool by calling pool.getConnection();

---- update ----
I also added idleTimeout: 0 to my options and I am still getting the same error

[MetaiR]

@rusher any idea?

[rusher]

finally understood and reproduced. This won't have any incidence but having those ERRORs logged.
Will be in next corrective version (2.1.2)

[MetaiR]

hoooorrrraaaaayyyy
so it was a bug? what is the problem?

[rusher]

Correction corresponds to this commit . When a connection from pool is not used for some time (>idleTimeout ) connection is closed (a QUIT command is issued, followed by a ROLLBACK / COM_RESET command if using callback implementation. ).
These command has no use and will be removed, resulting in this console log error.