We run the nodejs mongo driver in the following environments

• fastify server
• docker lts-alpine image
• aws ecs fargate
• azure container instances

Our logs are constantly reporting the following error:

{{

{ "level": 30, "time": 1620059246339, "pid": 1, "hostname": "ip-10-0-34-147.ec2.internal", "type": "error", "message": "Pool with id [1] failed attempted illegal state transition from [disconnected] to [connected] only following state allowed [[ 'connecting', 'destroyed', 'disconnected' ]]", "className": "ReplSet", "date": 1620059246339, "msg": "[ERROR-ReplSet:1] 1620059246339 Pool with id [1] failed attempted illegal state transition from [disconnected] to [connected] only following state allowed [[ 'connecting', 'destroyed', 'disconnected' ]]" }

}}

 

Looking at the code i think i can eyeball the issue

https://github.com/mongodb/node-mongodb-native/blob/be269b1c537a091cbc97b8f06777860a8f27e828/lib/core/topologies/replset.js#L33-L40 

function stateTransition(self, newState) {
{{ var legalTransitions = {}}
  disconnected: [CONNECTING, DESTROYED, DISCONNECTED],
  connecting: [CONNECTING, DESTROYED, CONNECTED, DISCONNECTED],
  connected: [CONNECTED, DISCONNECTED, DESTROYED, UNREFERENCED],
  unreferenced: [UNREFERENCED, DESTROYED],
  destroyed: [DESTROYED]
{{ };}}

But there exists the following caller still

https://github.com/mongodb/node-mongodb-native/blob/be269b1c537a091cbc97b8f06777860a8f27e828/lib/core/topologies/replset.js#L555-L571

if (
{{ self.state === DISCONNECTED &&}}
{{ ((self.s.replicaSetState.hasSecondary() &&}}
{{ self.s.options.secondaryOnlyConnectionAllowed) ||}}
{{ self.s.replicaSetState.hasPrimary())}}
{{ ) {}}
  stateTransition(self, CONNECTED);// Rexecute any stalled operation
  rexecuteOperations(self);// Emit connected sign
  process.nextTick(function() {
  self.emit('reconnect', self);
{{ });}}
{{ }}}