Connection Troubleshooting

Security Certificate Errors

If you use Java version 8 or earlier, you might need to add a certificate to your trust store. You can either upgrade to a later version of the JDK or read the Security FAQ instructions in the Atlas documentation for information on how to add the certificate.

Timeout Errors

When you send messages through the driver to the server, sometimes the messages take a while to respond. When this happens, you might receive an error message similar to one of the following messages:

Timed out after 30000 ms while waiting for a server that matches ReadPreferenceServerSelector{readPreference=primary}.

No server chosen by ReadPreferenceServerSelector{readPreference=primary} from cluster description

If you receive one of these errors, try the following methods to resolve the issue.

Server Selection Timeout Exceptions

Your application might not be able to complete a request even when some servers are available, causing the driver to return a server selection timeout exception.

This exception is of type MongoTimeoutException. The following shows a sample of the exception that occurs if you attempt to send a request to a replica set in which the primary is not reachable:

com.mongodb.MongoTimeoutException:
Timed out while waiting for a server that matches ReadPreferenceServerSelector{readPreference=primary}.
Client view of cluster state is
{type=REPLICA_SET,
 servers=[
  {address=localhost:27017, type=UNKNOWN, state=CONNECTING, exception={com.mongodb.MongoSocketOpenException: Exception opening socket}, caused by {java.net.ConnectException: Connection refused}},
  {address=localhost:27018, type=UNKNOWN, state=CONNECTING, exception={com.mongodb.MongoSocketOpenException: Exception opening socket}, caused by {java.net.ConnectException: Connection refused}},
  {address=localhost:27019, type=REPLICA_SET_SECONDARY, roundTripTime=15.0 ms, state=CONNECTED}
 ]
}

The error includes a view of the cluster state that describes the connection state of each node, which can help you identify the source of your connection issue.

In the preceding error, the only connected server, localhost:27019, is a secondary node. Because of this, the request times out as the driver is unable to select a server that satisfies the read preference of primary. In this situation, you can still perform read operations against the connected secondary node if you set the read preference to secondary, secondaryPreferred, or nearest.

You can also specify the serverSelectionTimeoutMS connection option to adjust the amount of time in which the driver must select a server. To learn more, see the Connection Options guide.

Miscellaneous Errors

This section shows connection errors that do not fall into a broader category.

INFO: Exception in monitor thread while connecting to server ssc-cluster-01-shard-00-02.9cbnp.mongodb.net:27017

javax.net.ssl.SSLHandshakeException: extension (5) should not be presented in certificate_request

Debugging Tips

While not related to a specific error message, this section includes information that can help in the process of troubleshooting connection issues.