If incorrect credentials are supplied while setting up connection to replica-set, it results in stray monitor thread left behind. Since 'mongoClient' never got set, caller can not call close() to force driver to release resources.

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MongoCredential credential = MongoCredential.createCredential(dbUser, authDB, dbPassword.toCharArray()); // credentials supplied are incorrect

ServerAddress address = new ServerAddress(host, localPort);

MongoClientOptions options =
MongoClientOptions.builder()
.serverSelectionTimeout(serverSelectionTimeout)
.connectTimeout(connecTimeout)
.readPreference(ReadPreference.secondaryPreferred())
.sslEnabled(sslEnabled)
.sslInvalidHostNameAllowed(true)
.build();

try

{ MongoClient mongoClient = new MongoClient(address, credential, options); }

catch (MongoSecurityException mse)

{ // handle login error }

catch (MongoTimeoutException mte)

{ // handle timeout }

catch (Exception ex)

{ // handle other errors }