What is the correct MONGO_URL setting for replica sets on Meteor 1.4.1.1

Question

This morning I went to deploy my updated Meteor project onto Heroku.

I was upgrading from 1.1.0.3 to 1.4.1.1.

Using the Meteor Buildpack Horse everything installed correctly, but the application was erroring out with the error;

MongoError: seed list contains no mongos proxies, replicaset connections requires the parameter replicaSet to be supplied in the URI or options object, mongodb://server:port/db?replicaSet=name

My MONGO_URL was mongodb://u:p@url1:port,url2:port/db so I changed it to;

mongodb://u:p@url1:port,url2:port/db?replicaSet=set-name

If I made a mistake with the replicaSet param I would get this error;

MongoError: no primary found in replicaset

Which seems sensible, since the replicaset didn't exist, but when I put the correct value in I get that original error again saying the seed list contains no proxies.

My replica set has a dash in the name, I don't know if that is relevant.

What I've tried

I've tried using the URL that throws this error in a Mongo client and it allows me to connect to the instance fine, so I know all the details are correct.

I've also tried escaping the replicaSet, so ?replicaSet=set\-name this gave me the MongoError: no primary found in replicaset error.

I have an open ticket with my MongoDB provider, but I suspect this is a Meteor/me issue!

Alga

I don't think you're doing anything wrong which is really strange. I am currently using the following structure in an app I am working on: mongodb://username:[email protected]:PORT1,url2.com:PORT2/database?replicaSet=set-000000a0aaaa0000a00000a0 – Aspia

Also keep in mind your meteor settings file follows strict JSON requirements (no trailing commas for example). – Aspia

@AndrewHill can you elaborate on the strict JSON requirements? Where could I be running foul of that? (my settings.json is empty) – Alga

another suggestion, maybe there's issue with mongo package, in our production we use [email protected] – Pannonia

Where is your DB hosted? Did you update the MONGO_OPLOG_URL variable as well? Have you seen this issue? – Cuttlebone

@MasterAMthat OPLOG was exactly the issue! Thank you so much! My google-fu failed me there. Can you write up as an answer and I will send the bounty! – Alga

Answer 1

Meteor v1.4 uses a new version of the MongoDB driver.

While the MONGO_URL environment variable was in the correct form, the error was caused by MONGO_OPLOG_URL, which should be modified to include a replicaSet argument.

See this GitHub issue for more details and the following notes (regarding Compose.io).

From the oplog driver documentation:

Oplog tailing is automatically enabled in development mode with meteor run, and can be enabled in production with the MONGO_OPLOG_URL environment variable.

(...)

To use oplog tailing in your production Meteor app, your MongoDB servers must be configured as a replica set; a single-mongod database has no oplog. Your cluster may not use Mongo sharding.

And the migration guide:

As of 1.4, you must ensure your MONGO_OPLOG_URL contains a replicaSet argument (see the changelog and the oplog documentation).

NOTE: Some MongoDB hosting providers may have a deployment setup that doesn't require you to use a replicaSet argument. For example, Compose.io has two types of deployments, MongoDB Classic and MongoDB+. The new MongoDB+ offering is a sharded setup and not a true replica set (despite the shard being implemented as a replica set) so it does not require the replicaSet parameter and Meteor will throw an error if you add it to your connection strings.

Cuttlebone

What if you don't want to use Oplog? – Favianus

@Yeats, Simply don't set the MONGO_OPLOG_URL environment variable. But if you do, make sure it follows the requirements. – Cuttlebone