Cannot read property 'prev' of null

[berndartmueller]

Hey!

Lately we experience randomly this Cannot read property 'prev' of null while using sequelize@4.39.0 and node-pool@3.4.2. It just happens out of no where. But I noticed that whenever it happens, the current postgres connection count increases and reaches the pool limit of 5 per node.js instance.

TypeError: Cannot read property 'prev' of null,
at DoublyLinkedList.remove (/usr/src/app/node_modules/generic-pool/lib/DoublyLinkedList.js:69:14),
at Deque.shift (/usr/src/app/node_modules/generic-pool/lib/Deque.js:24:16),
at Pool._testOnBorrow (/usr/src/app/node_modules/generic-pool/lib/Pool.js:160:51),
at Pool._dispense (/usr/src/app/node_modules/generic-pool/lib/Pool.js:240:14),
at Pool.acquire (/usr/src/app/node_modules/generic-pool/lib/Pool.js:453:10),
at promise.then (/usr/src/app/node_modules/sequelize/lib/dialects/abstract/connection-manager.js:274:24),
at bound (domain.js:402:14),
at runBound (domain.js:415:12),
at tryCatcher (/usr/src/app/node_modules/bluebird/js/release/util.js:16:23),
at Promise._settlePromiseFromHandler (/usr/src/app/node_modules/bluebird/js/release/promise.js:512:31),
at Promise._settlePromise (/usr/src/app/node_modules/bluebird/js/release/promise.js:569:18),
at Promise._settlePromiseCtx (/usr/src/app/node_modules/bluebird/js/release/promise.js:606:10),
at _drainQueueStep (/usr/src/app/node_modules/bluebird/js/release/async.js:142:12),
at _drainQueue (/usr/src/app/node_modules/bluebird/js/release/async.js:131:9),
at Async._drainQueues (/usr/src/app/node_modules/bluebird/js/release/async.js:147:5),
at Immediate.Async.drainQueues [as _onImmediate] (/usr/src/app/node_modules/bluebird/js/release/async.js:17:14),
at runCallback (timers.js:705:18),
at tryOnImmediate (timers.js:676:5),
at processImmediate (timers.js:658:5),
at process.topLevelDomainCallback (domain.js:126:23)
]

Additionall, also following error happens:

TypeError: Cannot read property 'databaseVersion' of undefined,
at ConnectionManager.getConnection (/usr/src/app/node_modules/sequelize/lib/dialects/abstract/connection-manager.js:246:32),
at Promise.try (/usr/src/app/node_modules/sequelize/lib/sequelize.js:554:34),
at tryCatcher (/usr/src/app/node_modules/bluebird/js/release/util.js:16:23),
at Function.Promise.attempt.Promise.try (/usr/src/app/node_modules/bluebird/js/release/method.js:39:29),
at Promise.resolve.retryParameters (/usr/src/app/node_modules/sequelize/lib/sequelize.js:454:64),
at /usr/src/app/node_modules/retry-as-promised/index.js:39:21,
at Promise._execute (/usr/src/app/node_modules/bluebird/js/release/debuggability.js:313:9),
at Promise._resolveFromExecutor (/usr/src/app/node_modules/bluebird/js/release/promise.js:483:18),
at new Promise (/usr/src/app/node_modules/bluebird/js/release/promise.js:79:10),
at retryAsPromised (/usr/src/app/node_modules/retry-as-promised/index.js:29:10),
at Sequelize.query (/usr/src/app/node_modules/sequelize/lib/sequelize.js:454:28),
at QueryInterface.select (/usr/src/app/node_modules/sequelize/lib/query-interface.js:1104:27),
at Promise.try.then.then.then (/usr/src/app/node_modules/sequelize/lib/model.js:1604:34),
at bound (domain.js:402:14),
at runBound (domain.js:415:12),
at tryCatcher (/usr/src/app/node_modules/bluebird/js/release/util.js:16:23),
at Promise._settlePromiseFromHandler (/usr/src/app/node_modules/bluebird/js/release/promise.js:512:31),
at Promise._settlePromise (/usr/src/app/node_modules/bluebird/js/release/promise.js:569:18),
at Promise._settlePromise0 (/usr/src/app/node_modules/bluebird/js/release/promise.js:614:10),
at Promise._settlePromises (/usr/src/app/node_modules/bluebird/js/release/promise.js:694:18),
at _drainQueueStep (/usr/src/app/node_modules/bluebird/js/release/async.js:138:12),
at _drainQueue (/usr/src/app/node_modules/bluebird/js/release/async.js:131:9)
]
}

Does someone else also experience this behaviour? Any ideas how to fix it? Is it fixed in the latest version of node-pool?

Thanks!

PS: Similar issue is found in sequelize repo -> https://github.com/sequelize/sequelize/issues/10443