MongoDB: get blocks forever?

alrunner4 commented 10 years ago

In my Yesod application, I've got the following implementation for YesodAuth's onLogin:

onLogin = do
    mAuth <- maybeAuthId
    case mAuth of
        Nothing -> error "logged in, but no AuthId!"
        Just authId -> do
            maybeUserId <- runDB $ selectKeys [
                Authenticators `multiEq` authId ] [] $$ await
            case maybeUserId of
                Nothing -> liftIO $ putStrLn "a new user needs to be created"
                Just userid -> do
                    setSession "userid" ( toPathPiece userid )
                    liftIO $ putStrLn $ "about to lookup user " ++ show userid
                    mUser <- runDB $ get userid
                    liftIO $ putStrLn $ "user logged in = " ++ show mUser

The relevant model in this case being:

User
    displayName      Text
    authenticators   [AppAuth]
    deriving         Read Show

And I'm using type AppAuth = Text since persistFileWith doesn't like it when I try to use AuthId App, which is also Text.

I'm not 100% sure this is a bug, but the selectKeys query does work when my MongoDB database is populated with some test data and I login with Google's OpenAuth (authGoogleEmail), but even though I know with 100% certainty that userid is a valid Key in my database (it just came back from the selectKeys query, after all), the get always blocks indefinitely. The last line of log the server generates is: about to lookup user Key {unKey = PersistObjectId "R\232\SO@\ESC\237\ESC9\192\&0_\228"} confirming that we're somewhere in runDB when the handler hangs.

My runDB is nothing special, either:

runDB action = do
    App{..} <- getYesod
    runMongoDBPoolDef action dbConnectionPool

Any ideas? Am I doing something stupid? persistent-mongoDB does do get, right? My mongod is version 2.4.9.

Thanks, Alex

alrunner4 commented 10 years ago

Okay. Playing around some more with this, I tried wiping my User collection and starting fresh: I think the problem may have been in the marshalling from the MongoDB document to my User data type. Is it expected behavior for queries to block indefinitely if a MongoDB document is malformed? I noticed that the User document I had been loading was missing a (required) field I added to the model after it was created, and deleting that field from other documents in the database causes the problem to occur. Documents matching the Yesod model schema load correctly without blocking.