Cannot connect to Mongo SRV

[vanzhurov]

Bug Description

I try to create connection from this connection url (mocked data to hide my prod url)
mongodb+srv://user:password@mongo.com/?tls=false&readPreference=secondaryPreferred

I can connect via MongoCompass and other vscode extension

Expected Behavior

Connection created

Actual Behavior

Cannot connect. Gives error DNS: getaddrinfo ENOTFOUND mongo.host.com

Screenshots

other extension

[mikeburgh]

The URL you pasted has mongo.com but the error mentions mongo.host.com. I assume those are both mocked, but the structure of the names doesn't quite line up: SRV resolution looks up _mongodb._tcp. and gets back the actual cluster hostnames, so the failing host should be a sub-name of (or different domain from) the SRV host, not a longer version of it. Could you confirm:

The exact mongodb+srv://... prefix you pasted (just the hostname part — feel free to mock it consistently)

The exact ENOTFOUND from the error (mock it the same way)

[vanzhurov]

Hi @mikeburgh, thanks for the quick response — and good catch, the mocking in the original report was inconsistent. Sorry about that. Here are clean details (hostnames consistently mocked this time):
Connection string:
mongodb+srv://<user>:<password>@mongo-ml.example.com/?tls=false&readPreference=secondaryPreferred
Exact error from the extension: DNS: getaddrinfo ENOTFOUND mongo-ml.example.com
So the failing host is the SRV host itself, not a sub-name of it. The extension seems to be trying to resolve mongo-ml.example.com as a regular A record instead of doing the SRV lookup at _mongodb._tcp.mongo-ml.example.com.
DNS is healthy from my machine — both the system resolver and public DNS return the records correctly:

$ dig +short SRV _mongodb._tcp.mongo-ml.example.com
0 0 28928 mongo-0.mongo-ml.example.com.
0 0 28928 mongo-1.mongo-ml.example.com.
0 0 28928 mongo-2.mongo-ml.example.com.

$ dig +short TXT mongo-ml.example.com
"replicaSet=rs0&authSource=admin"

$ dig +short mongo-0.mongo-ml.example.com
<resolves to AWS ELB → public IP>

The same mongodb+srv:// URI works fine in MongoDB Compass and other VS Code Mongo extensions on the same machine, same network.

While debugging, I also tried the explicit multi-host URI as a workaround:
mongodb://<user>:<pass>@mongo-0.mongo-ml.example.com:28928,mongo-1.mongo-ml.example.com:28928,mongo-2.mongo-ml.example.com:28928/?replicaSet=rs0&authSource=admin&tls=false&readPreference=secondaryPreferred
This fails earlier with: Unable to parse connection string: Invalid URL.
This is a valid MongoDB connection string per the official spec

Happy to provide more diagnostics if useful.

[mikeburgh]

I just released 1.31.2, bumped the mongo driver version (still 1 major behind, but that's a bigger change).. and also cleaned up some issues around SRV and tls, and added support for parsing multi host connection urls..

Can you give it a try, it should work for multi host urls fine now, I also tested the SRV side with a Mongo Atlas cluster, and it worked there.. so hopefully fixed for you as well.