MongoDB Connection Issues on macOS Catalina – Unable to Connect

mac-osxmongodb

After migrating my old MacBook Pro to a new machine via the Migration Assistant, I am unable to connect to MongoDB.

I re-installed it via Homebrew, and when I run:

brew services start mongodb-community

Terminal states that the service started, however, when I run: mongo

I get this error:

MongoDB shell version v3.4.9
connecting to: mongodb://127.0.0.1:27017
2020-04-09T09:20:02.419-0400 W NETWORK  [thread1] Failed to connect to 127.0.0.1:27017, in(checking socket for error after poll), reason: Connection refused
2020-04-09T09:20:02.419-0400 E QUERY    [thread1] Error: couldn't connect to server 127.0.0.1:27017, connection attempt failed :
connect@src/mongo/shell/mongo.js:237:13

I was following this guide on Medium: https://medium.com/better-programming/installing-mongodb-on-macos-catalina-aab1cbe0c836

to re-install MongoDB. Can anyone help me out?

Best Answer

Did you reinstall brew after migration? I had lots of problems after upgrade to Catalina. However on fresh Catalina (and brew default installation) I:

brew tap mongodb/brew
brew install mongodb-community
brew services start mongodb-community
==> Successfully startedmongodb-community`

You can try to:

download Xcode command line
restart
clear cellar folder and brew cache
brew tap mongodb/brew

or full brew reinstall and follow 1-4.

Related Solutions

Mongoid connection issue

Maybe your mongodb instance quited unexpectedly and you have stale locks and the database in inconsistent state.

As you already guessed start mongoDB with the --repair flag, but after that you need to restart it again without it.

Also make sure that all the processes are really terminated or you won't be able to bind the server on the same port. I would recommend to execute netstat -tulnp and double check if there is nothing listening on the 27017 port.

Mongodb in Kubernetes Timeouts when inserting large amount of data

I checked the logs and the kubernetes Dashboard with Boas Enkler.

In the Kubernetes dashboard regarding the status of the PODs there were the following hints:

Pod Name: kube-lego-*****-***     
Status: Evicted 
Reason: The node was low on resource: memory.

You could have retrieved the very same information through kubectl describe pod [podname]

Notice that quoting the documentation: "If the kubelet is unable to reclaim sufficient resources on the node, kubelet begins evicting Pods."

Therefore I believed that the error with Mongodb since it was working on premise without any issue, to doublecheck we went through the Kernel logs showed by the console serial output and we found:

Memory cgroup out of memory: Kill process 4**7 (mongod) score 1494 or sacrifice child
...
Memory cgroup out of memory: Kill process 1**8 (mongod) score 1538 or sacrifice child

We noticed as well that there was no Memory Request field in the YAML file of the deployment. This is an issue since it could happen that even if there are three nodes with no workload can happen that all the PODs are started on the very same node since they theoretically fit.

In order to mitigate this behaviour there are some possible solution:

Scale vertically the cluster and introduce memory request values
Instruct the mongodb process to consume an amount of memory smaller than the Requested one.
The introduction of memory limit is essential if you have more container running on the same node and you want to avoid that they are killed by it. Consider that in this way it will be killed sometimes even if there is still memory available on the node.

Best Answer

Related Solutions

Mongoid connection issue

Mongodb in Kubernetes Timeouts when inserting large amount of data

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