MongoDB "no SNI name sent" error from heroku java application - mongodb

Question

I followed this tutorial to deploy a sample application to Heroku. I just added the below method in MyResource class and returned the result from it instead of "Hello World" from getIt() method. I'm connecting to an atlas free tier cluster:
static String getMessage() {
MongoClient mongoClient = new MongoClient(new MongoClientURI("mongodb://<USER>:<PASSWORD>#cluster0-shard-00-00-2lbue.mongodb.net:27017,cluster0-shard-00-01-2lbue.mongodb.net:27017,cluster0-shard-00-02-2lbue.mongodb.net:27017/test?ssl=true&replicaSet=Cluster0-shard-0&authSource=admin"));
DB database = mongoClient.getDB("mastery");
DBCollection collection = database.getCollection("summary");
DBObject query = new BasicDBObject("_id", new ObjectId("5c563fa2645d6b444c018dcb"));
DBCursor cursor = collection.find(query);
return (String)cursor.one().get("message");
}
This is the driver I'm using:
<dependency>
<groupId>org.mongodb</groupId>
<artifactId>mongodb-driver</artifactId>
<version>3.9.1</version>
</dependency>
This is my import:
import com.mongodb.*;
The application works fine from my local system. But I face the below error when I deploy the application to Heroku and hit the service:
INFO: Exception in monitor thread while connecting to server cluster0-shard-00-01-2lbue.mongodb.net:27017
com.mongodb.MongoCommandException: Command failed with error 8000 (AtlasError): 'no SNI name sent, make sure using a MongoDB 3.4+ driver/shell.' on server cluster0-shard-00-01-2lbue.mongodb.net:27017. The full response is { "ok" : 0, "errmsg" : "no SNI name sent, make sure using a MongoDB 3.4+ driver/shell.", "code" : 8000, "codeName" : "AtlasError" }
at com.mongodb.internal.connection.ProtocolHelper.getCommandFailureException(ProtocolHelper.java:179)
at com.mongodb.internal.connection.InternalStreamConnection.receiveCommandMessageResponse(InternalStreamConnection.java:299)
at com.mongodb.internal.connection.InternalStreamConnection.sendAndReceive(InternalStreamConnection.java:255)
at com.mongodb.internal.connection.CommandHelper.sendAndReceive(CommandHelper.java:83)
at com.mongodb.internal.connection.CommandHelper.executeCommand(CommandHelper.java:33)
at com.mongodb.internal.connection.InternalStreamConnectionInitializer.initializeConnectionDescription(InternalStreamConnectionInitializer.java:106)
at com.mongodb.internal.connection.InternalStreamConnectionInitializer.initialize(InternalStreamConnectionInitializer.java:63)
at com.mongodb.internal.connection.InternalStreamConnection.open(InternalStreamConnection.java:127)
at com.mongodb.internal.connection.DefaultServerMonitor$ServerMonitorRunnable.run(DefaultServerMonitor.java:117)
at java.lang.Thread.run(Thread.java:748)
What is this SNI name? I can understand that the drivers are able to pick it from my machine, but not from Heroku machine. But I'm clueless on how to go about solving this! Is there a way to configure Heroku to reveal the SNI name when the driver asks for it? Can we get this value manually from somewhere in Heroku and directly feed it to the MongoDB drivers? Any help is appreciated.
EDIT:
It turned out that the client mentions the SNI name of the server it wishes to connect to as part of TLS security. And there seems to be a way to manually indicate the name in python driver. Is there any way to do this from java? Still puzzled why this is not an issue when running the app locally.

Answer 1

The code I was using to connect to the cluster turned out to be wrong. I followed the directions from the docs and it mentioned this:
To connect to an Atlas M0 (Free Tier) cluster, you must use Java
version 8 or greater and use a Java driver version that supports
MongoDB 3.4.
So I changed the java version to 1.8 in system.properties file:
java.runtime.version=1.8
It was earlier set to 1.7. I was also getting a deprecation warning on one of the methods I had used. So I again followed the docs to use the latest code and it worked like a charm.
The real takeaway here is to refer to the official docs everytime :)