Error: Callback was already called

[DundieWinner]

I am working through Chapter 8, page 177 where I am trying to get the photo album server to startup after implementing the very first steps in MongoDB integration, and I keep getting the same error sequence:

..\Node\Tutorial\photo_album_express\app\node_modules\mongodb\lib\mongo_client.js:350
throw err
^
Error: Callback was already called.
at ..\Node\Tutorial\photo_album_express\app\node_modules\async\dist\async.js:840:32
at Db.collection (..\Node\Tutorial\photo_album_express\app\node_modules\mongodb\lib\db.js:457:27)
at async.waterfall.exports.albums (..\Node\Tutorial\photo_album_express\app\data\db.js:33:16)
at nextTask (..\Node\Tutorial\photo_album_express\app\node_modules\async\dist\async.js:5070:14)
at ..\Node\Tutorial\photo_album_express\app\node_modules\async\dist\async.js:5064:13
at apply (..\Node\Tutorial\photo_album_express\app\node_modules\async\dist\async.js:21:25)
at ..\Node\Tutorial\photo_album_express\app\node_modules\async\dist\async.js:56:12
at ..\Node\Tutorial\photo_album_express\app\node_modules\async\dist\async.js:843:16
at MongoClient.connect (..\Node\Tutorial\photo_album_express\app\data\db.js:25:17)
at connectCallback (..\Node\Tutorial\photo_album_express\app\node_modules\mongodb\lib\mongo_client.js:428:5)

The "db.js:33:16" is referencing the db.collection("albums", cb); line and the "db.js:25:17" is referencing the cb(null) line within the MongoClient.connect function.

I even tried replacing my data/db.js file with exactly what you provide in repository (https://github.com/marcwan/LearningNodeJS/blob/master/Chapter08/02_create_album/app/data/db.js)

I've searched around but I can't seem to figure out this snag. What is happening?

[DundieWinner]

The problem is collection() function. Replacing it with createCollection() solves this issue for me. See my pull request: #29