MongoDB replication not working

[Astro]

I am exploring the replication functionality in MongoDB, just wanted to clarify a simple scenario.

I have a java program which is inserting values in the db constantly in a three instance replica set, now if i shutdown the primary the java program just throws an ioexception and exits. Shouldn't it continue inserting in after the election when a new primary is selected whereas i can see using mongo shell that a new primary is selected and everything is fine.

Following is the code snippet:

MongoClient client = new MongoClient(Arrays.asList( new ServerAddress("myhost", 27017), 

                                  new ServerAddress("myhost", 27018), 

                                  new ServerAddress("myhost", 27019)));

MongoDatabase database = client.getDatabase("test"); 

MongoCollection<Document> collection = database.getCollection("recharge");

collection.drop(); for(int i=0;i<100000;i++){ Document doc = new Document("reference",""+i).append("owner", "a"+i); collection.insertOne(doc); 

Thread.sleep(5000); 

} }

at com.mongodb.connection.SocketStreamHelper.initialize(SocketStreamHelper.java:50) at com.mongodb.connection.SocketStream.open(SocketStream.java:58) ... 3 more May 06, 2016 10:13:27 AM com.mongodb.diagnostics.logging.JULLogger log INFO: Closed connection [connectionId{localValue:6}] to akhurraml2:27017 because there was a socket exception raised by this connection. Exception in thread "main" com.mongodb.MongoSocketOpenException: Exception opening socket at com.mongodb.connection.SocketStream.open(SocketStream.java:63) at com.mongodb.connection.InternalStreamConnection.open(InternalStreamConnection.java:114) at com.mongodb.connection.UsageTrackingInternalConnection.open(UsageTrackingInternalConnection.java:46) at com.mongodb.connection.DefaultConnectionPool$PooledConnection.open(DefaultConnectionPool.java:381) at com.mongodb.connection.DefaultConnectionPool.get(DefaultConnectionPool.java:96) at com.mongodb.connection.DefaultConnectionPool.get(DefaultConnectionPool.java:82) at com.mongodb.connection.DefaultServer.getConnection(DefaultServer.java:72) at com.mongodb.binding.ClusterBinding$ClusterBindingConnectionSource.getConnection(ClusterBinding.java:86) at com.mongodb.operation.OperationHelper.withConnectionSource(OperationHelper.java:228) at com.mongodb.operation.OperationHelper.withConnection(OperationHelper.java:221) at com.mongodb.operation.MixedBulkWriteOperation.execute(MixedBulkWriteOperation.java:168) at com.mongodb.operation.MixedBulkWriteOperation.execute(MixedBulkWriteOperation.java:74) at com.mongodb.Mongo.execute(Mongo.java:781) at com.mongodb.Mongo$2.execute(Mongo.java:764) at com.mongodb.MongoCollectionImpl.executeSingleWriteRequest(MongoCollectionImpl.java:515) at com.mongodb.MongoCollectionImpl.insertOne(MongoCollectionImpl.java:306) at com.mongodb.MongoCollectionImpl.insertOne(MongoCollectionImpl.java:297) at com.nextcontrols.App.main(App.java:33) Caused by: java.net.ConnectException: Connection refused: connect at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method) at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85) at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) at java.net.Socket.connect(Socket.java:589) at com.mongodb.connection.SocketStreamHelper.initialize(SocketStreamHelper.java:50) at com.mongodb.connection.SocketStream.open(SocketStream.java:58) ... 17 more

[Astro]

Update: 

mongodb version: 3.2.3

    mongodb java driver: 3.2.2 

[Astro]

Is there anything I am missing in the code to make it auto-reconnect when fail over happes?

Any help on this?

[William Hagan]

Hello Astro,

Can you confirm that the mongod server(s) and its ports are reachable from the application server?

Also ensure that "myhost" resolves to the server host name and not say "localhost" for example.

I tested your code using ReplSetTest to create a 3-node replica set and all is working fine. Of course, there is the period of the election where I get the ConnectException but it quickly resolves itself.

PS: mongod version is: 3.2.7

Cheers

[Astro]

The replica set is on the same machine.

All members are reachable. The app throws an exception app stops working when the primary goes down.

Thanks.

[William Hagan]

Hi Astro,

I couldn't replicate my successful test anymore. I am now experiencing a similar issue.

It will appear there is an issue with the Java driver.

Hopefully someone will help with this anomaly while I'll continue to see if I can identify a specific reason.

Cheers

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[Jeff Yemin]

Hi Astro,

The driver will automatically reconnect, but you still have to catch the exception thrown from the insert method.  Otherwise, your application will exit.

Have a look at this excellent blog post about retrying write operations with MongoDB.  While the examples are in Python, the lessons can reliably be applied to your Java application.

Regards,

Jeff

[William Hagan]

Thanks Jeff.

The explanation really does make things clear. My tests work as expected.

Cheers

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