Mongo 3.6 DNS Seedlist Connection Format

[Brent Wilkins]

What are the plans, if any, to support the DNS seedlist connection format?

Thanks,

Brent

[Cédric Chantepie]

Could elaborate the feature request? So it could then be added to the github tracker?

[Brent Wilkins]

On Monday, June 4, 2018 at 12:41:48 PM UTC-6, Cédric Chantepie wrote:

Could elaborate the feature request? So it could then be added to the github tracker?

Here is the snippet from the mongo 3.6 documentation (https://docs.mongodb.com/manual/reference/connection-string/):

 

DNS Seedlist Connection Format

New in version 3.6.

In addition to the standard connection format, MongoDB supports a DNS-constructed seedlist. Using DNS to construct the available servers list allows more flexibility of deployment and the ability to change the servers in rotation without reconfiguring clients.

In order to leverage the DNS seedlist, use a connection string prefix of mongodb+srv: in place of the mongodb: string above.

The +srv indicates to the mongo client that the hostname that follows corresponds to a DNS SRV record. The client driver will then query the DNS for the record to determine the hosts that are running the mongod instances.

For example, to connect to a DNS-listed hostname:

mongodb+srv://server.example.com/

A typical DNS configuration for the connection string above might look something like this:

Record                            TTL   Class    Priority Weight Port  Target
_mongodb._tcp.server.example.com. 86400 IN SRV   0        5      27317 mongodb1.example.com.
_mongodb._tcp.server.example.com. 86400 IN SRV   0        5      27017 mongodb2.example.com.

NOTE

The hostnames returned in SRV records must share the same parent domain (in this example, example.com) as the given hostname.

The DNS seedlist connection string can also provide options as a query string, with a trailing “/?” as in the standard connection string above. However, the +srv appended to the standard connection string signals the driver to query the DNS for options as a configured TXT record.

Only two options are available for configuration via a TXT record – replicaSet and authSource, and only one TXT record is allowed per server. If multiple TXT records appear in the DNS and/or if the TXT record contains an option other than replicaSet or authSource, an error will be thrown by the driver.

An example of a properly configured TXT record:

Record              TTL   Class    Text
server.example.com. 86400 IN TXT   "replicaSet=mySet&authSource=authDB"

In this case, taking into account both the DNS SRV records and the options retrieved from the TXT records, the parsed string will look like:

mongodb://mongodb1.example.com:27317,mongodb2.example.com:27017/?replicaSet=mySet&authSource=authDB

Options set in a TXT record can be overridden by passing in a query string with the URI. In the example below, the query string has provided an override for the authSource option configured in the TXT record of the DNS entry above.

mongodb+srv://server.example.com/?connectTimeoutMS=300000&authSource=aDifferentAuthDB

The rest of the option string will remain, and we can expect that the resulting URI would look like this (after parse).

mongodb://mongodb1.example.com:27317,mongodb2.example.com:27017/?connectTimeoutMS=300000&replicaSet=mySet&authSource=aDifferentAuthDB

NOTE

The mongodb+srv option will fail if there is no available DNS with records that correspond to the hostname identified in the connection string. In addition, use of the +srv connection string modifier sets the ssl option to true automatically for the connection. This can be overridden by explicitly setting the ssl option to false with ssl=false in the query string.

[Cédric Chantepie]

Supported since 0.14

[Asma'u Shaheedah]

I have been trying to connect to an atlas cluster using the dns seed list connection string format but all i get is a: "MongoError['No primary node is available! (Supervisor-11/Connection-12)']"

On Tuesday, 26 June 2018 21:48:57 UTC+1, Cédric Chantepie wrote:

Supported since 0.14

[Cédric Chantepie]

Without more information, it's only possible to guess the configuration is wrong.

There is a tutorial for Atlas : http://reactivemongo.org/releases/0.1x/documentation/tutorial/mongodb-atlas.html

[Asma'u Shaheedah]

I followed the documentation to the letter from reactivemongo. my mongodb.uri in my application.conf is mongodb.uri = mongodb+srv://<username>:<password>@my-cluster.abo25.mongodb.net/my-db?retryWrites=true&w=majority All i received is "MongoError['No primary node is available! (Supervisor-13/Connection-14)']"

[Asma'u Shaheedah]

Also, i can access the db via mongo shell. Just not via my app

[Cédric Chantepie]

You can use to test your connection URI: https://github.com/cchantep/RM-SBT-Playground

Also the Atlas tutorial is up-to-date: http://reactivemongo.org/releases/1.0/documentation/tutorial/mongodb-atlas.html

[Carlos Saltos]

Sadly this is an old known bug for MongoDB 3.x ... at Talenteca we are using ReactiveMongo version 0.16.x until we are able to migrate to MongoDB 4.x

Best regards,

Carlos

Cédric Chantepie <chantep...@gmail.com> schrieb am Sa. 18. Juli 2020 um 23:24:

You can use to test your connection URI: https://github.com/cchantep/RM-SBT-Playground

Also the Atlas tutorial is up-to-date: http://reactivemongo.org/releases/1.0/documentation/tutorial/mongodb-atlas.html

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[Cédric Chantepie]

On Sunday, 19 July 2020 at 09:07:29:

Sadly this is an old known bug for MongoDB 3.x ... at Talenteca we are using ReactiveMongo version 0.16.x until we are able to migrate to MongoDB 4.x

I don't see your point.

ReactiveMongo 0.16.x can have issue now (as it's more than one year old), but later release are compatible with both MongoDB 3.x and MongoDB 4.x.