Hi,

We are developing an application and using mariadb connection pools to access our database. The project is on my laptop but the database server is on a different machine which is in the same LAN with my laptop.

I left the node process running for an hour or so and when I returned and tried to use the application (without restarting it) I saw some connection errors:

(node:10751) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'totalConnections' of undefined
at checkPoolSize (/home/mehmet/development/user-manager/node_modules/mariadb/lib/pool.js:502:39)
at conn.connect.then.catch.err (/home/mehmet/development/user-manager/node_modules/mariadb/lib/pool.js:378:23)
at <anonymous>
at process._tickCallback (internal/process/next_tick.js:189:7)
(node:10751) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was
not handled with .catch(). (rejection id: 3)
(node:10751) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
(node:10751) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'totalConnections' of undefined
at checkPoolSize (/home/mehmet/development/user-manager/node_modules/mariadb/lib/pool.js:502:39)
at conn.connect.then.catch.err (/home/mehmet/development/user-manager/node_modules/mariadb/lib/pool.js:378:23)
at <anonymous>
at process._tickCallback (internal/process/next_tick.js:189:7)
(node:10751) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was
not handled with .catch(). (rejection id: 5)
/home/mehmet/development/user-manager/node_modules/mariadb/lib/pool.js:502
if (!connectionInCreation && this.totalConnections() < opts.connectionLimit && !closed) {
^

TypeError: Cannot read property 'totalConnections' of undefined
at checkPoolSize (/home/mehmet/development/user-manager/node_modules/mariadb/lib/pool.js:502:39)
at Connection.conn.on.err (/home/mehmet/development/user-manager/node_modules/mariadb/lib/pool.js:490:21)
at emitOne (events.js:116:13)
at Connection.emit (events.js:211:7)
at /home/mehmet/development/user-manager/node_modules/mariadb/lib/connection.js:1128:16
at Connection._socketErrorHandler (/home/mehmet/development/user-manager/node_modules/mariadb/lib/connection.js:1093:9)
at emitOne (events.js:116:13)
at Socket.emit (events.js:211:7)
at emitErrorNT (internal/streams/destroy.js:66:8)
at _combinedTickCallback (internal/process/next_tick.js:139:11)

It seems somehow the internal pool variables are nullified, like garbage collected. Have you ever seen something like this before?