Why do I get a socket timeout the first time I hit the database after a recompile? - mongodb

Question

I am using playframework 2.0 and after every recompile I get a socket timeout the first time my app tries to go to the database. I am using the Mongo Driver directly. here is a typical stack trace:
play.core.ActionInvoker$$anonfun$receive$1$$anon$1: Execution exception [[Network: can't call something : ds031907.mongolab.com/107.21.99.26:31907/heroku_app4620908]]
at play.core.ActionInvoker$$anonfun$receive$1.apply(Invoker.scala:82) [play_2.9.1.jar:2.0]
at play.core.ActionInvoker$$anonfun$receive$1.apply(Invoker.scala:63) [play_2.9.1.jar:2.0]
at akka.actor.Actor$class.apply(Actor.scala:290) [akka-actor.jar:2.0]
at play.core.ActionInvoker.apply(Invoker.scala:61) [play_2.9.1.jar:2.0]
at akka.actor.ActorCell.invoke(ActorCell.scala:617) [akka-actor.jar:2.0]
at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:179) [akka-actor.jar:2.0]
Caused by: com.mongodb.MongoException$Network: can't call something : ds031907.mongolab.com/107.21.99.26:31907/heroku_app4620908
at com.mongodb.DBTCPConnector.call(DBTCPConnector.java:227) ~[mongo-java-driver-2.7.3.jar:na]
at com.mongodb.DBApiLayer$MyCollection.__find(DBApiLayer.java:305) ~[mongo-java-driver-2.7.3.jar:na]
at com.mongodb.DBCollection.findOne(DBCollection.java:647) ~[mongo-java-driver-2.7.3.jar:na]
at com.mongodb.DBCollection.findOne(DBCollection.java:626) ~[mongo-java-driver-2.7.3.jar:na]
at models.daos.ModuleDAO.findPublishedModuleById(ModuleDAO.java:445) ~[classes/:na]
at controllers.LearnController.viewModule(LearnController.java:31) ~[classes/:2.0]
Caused by: java.net.SocketException: Operation timed out
at java.net.SocketInputStream.socketRead0(Native Method) ~[na:1.6.0_31]
at java.net.SocketInputStream.read(SocketInputStream.java:129) ~[na:1.6.0_31]
at java.io.BufferedInputStream.fill(BufferedInputStream.java:218) ~[na:1.6.0_31]
at java.io.BufferedInputStream.read1(BufferedInputStream.java:258) ~[na:1.6.0_31]
at java.io.BufferedInputStream.read(BufferedInputStream.java:317) ~[na:1.6.0_31]
at org.bson.io.Bits.readFully(Bits.java:35) ~[mongo-java-driver-2.7.3.jar:na]
And here is my initialization code:
public static DB getDB(){
ensureMongo();
DB db = mongo.getDB(MOJULO_DB);
if(!db.isAuthenticated()){
db.authenticate(MONGO_USERNAME, MONGO_PASSWORD);
if(db.isAuthenticated())
System.out.println("authentication success on db:" + db.getName());
else
System.out.println("db authentication failure");
}
return db;
}
private static synchronized void ensureMongo(){
if(mongo == null){
try{
MongoURI mongoURI = new MongoURI(MONGO_URI);
mongo = new Mongo(mongoURI);
DB db = mongo.getDB(MOJULO_DB);
db.command("ping");
}catch(UnknownHostException ex){
mongo = null;
System.out.println("failed to connect to mongo");
ex.printStackTrace();
}
}
}
public static void disconnect(){
System.out.println("disconnecting from mongo");
if(mongo != null){
mongo.close();
mongo = null;
}
}
I use the getDB method from outside the class to get the db. The method is meant to create the mongo singleton if it does not exists. I always get the authentication success println, but then on the first hit to the database, I get the socket timeout exception.
In my Global class, I close the connection to the database when the application is closed.
#Override
public void onStop(Application app) {
System.out.println("stop");
Logger.info("Application shutdown...");
DBManager.disconnect();
}
Any Ideas?

Answer 1

I am not an expert on MongoDB but can see similarity with other DB connectivity.
How is your connection configured?
It looks (to me) like it may be attempting to load all mappings/DB and table definitions/everything else when you attempt to use DB connection (find method) for the first time.
It may be better to run a simple DB query in your ensureMongo() method to allow the system to re-initialise everything it needs (you may have to set longer time-out on this method).