When creating an SSL connection to a mongos the documentation would get you to create it with...

MongoClient.connect("mongodb://dumper:dumper@example.1.dblayer.com:10900,example.0.dblayer.com:10901/dbname", {
mongos:

{ ssl: true, sslValidate: true, sslCA: ca, poolSize: 1, reconnectTries: 1 }

,
}, function(err, db) { ...

Which for other connections works, but with Mongos it will sit in a spin never connecting.

The reason to this is that mongodb-core uses `ca` for it's certificate array. Other connections when preparing options copy the value of sslCA to ca and continue down to making their mongodb-core connection. The MongoS code doesn't do that.

There is a workaround for anyone affected, and thats to add ca: value to the options map too like so:

MongoClient.connect("mongodb://dumper:dumper@example.1.dblayer.com:10900,example.0.dblayer.com:10901/dbname", {
mongos:

{ ssl: true, sslValidate: true, sslCA: ca, ca: ca, poolSize: 1, reconnectTries: 1 }

,
}, function(err, db) { ...

And the connection will then work.