'process.nextTick(function() { throw err; })&#

Question

I'm trying to connect to my mongodb using nodejs and socket.io. I am able to connect to the database because I get 'connection accepted' in my console but on the nodejs side, as soon as I - indeed - get

Connection to mongodb://localhost:27017 established through mongoose

it immediately fails next with

process.nextTick(function() { throw err; }) ^TypeError: undefined is not a function at showCollections**

And here goes showCollections:

var showCollections = function(db, callback) { 
    mongoose.connection.db.collectionNames(function(error, names) {
    if (error) {
      throw new Error(error);
    } else {
        console.log("=>Listening mongo collections:");
      names.map(function(cname) {
        mongoose.connection.db.dropCollection(cname.name);
        console.log("--»"+cname.name);
      });
    }
  });

}

And here is the content of my database folder:

_tmp (empty folder)
local.0
local.ns
mongod.lock

I run the mongodb by typing mongod --dbpath folder and it successfully 'awaits connections on port 27017'.

Also, my node_modules from package.json (npm)

"dependencies": {
    "express": "^4.9.6",
    "socket.io": "latest",
    "mongodb": "~2.0",
    "mongoose": "*"
  }

Thank you very much for your help...

StackTrace:

> TypeError: undefined is not a function
>     at showCollections (/usr/share/nginx/www/index.js:77:25)
>     at NativeConnection.callback (/usr/share/nginx/www/index.js:46:3)
>     at NativeConnection.g (events.js:199:16)
>     at NativeConnection.emit (events.js:104:17)
>     at open (/usr/share/nginx/www/node_modules/mongoose/lib/connection.js:485:10)
>     at NativeConnection.Connection.onOpen (/usr/share/nginx/www/node_modules/mongoose/lib/connection.js:494:5)
>     at /usr/share/nginx/www/node_modules/mongoose/lib/connection.js:453:10
>     at /usr/share/nginx/www/node_modules/mongoose/lib/drivers/node-mongodb-native/connection.js:59:5
>     at /usr/share/nginx/www/node_modules/mongoose/node_modules/mongodb/lib/db.js:200:5
>     at connectHandler (/usr/share/nginx/www/node_modules/mongoose/node_modules/mongodb/lib/server.js:272:7)

EDIT:

I'm as well having these problems when trying to run the nodejs instance:

{ [Error: Cannot find module '../build/Release/bson'] code: 'MODULE_NOT_FOUND' }
js-bson: Failed to load c++ bson extension, using pure JS version

I tried fixing them as other questions here would tell but nothing worked either...

Answer 1

From the provided information, it looks like you are using mongodb 2.0 driver. The db.collectionNames method was dropped. Check out the "Db Object" section of this page - https://github.com/mongodb/node-mongodb-native/blob/0642f18fd85037522acf2e7560148a8bc5429a8a/docs/content/tutorials/changes-from-1.0.md#L38

They've replaced it with listCollections. You should get the same effect with:

mongoose.connection.db.listCollections().toArray(function(err, names) {
    if (err) {
        console.log(err);
    }
    else {
        names.forEach(function(e,i,a) {
            mongoose.connection.db.dropCollection(e.name);
            console.log("--->>", e.name);
        });
    }
});

Answer 2

For me this error started popping up when i had to force shut down my pc as it became unresponsive. Next time i started my express server this error popped up. I solved it by running npm install mongoose@4.0 --save in the terminal. May be this error pops up when your server or database is force closed and some code is not save in mongod behind the scenes.

Answer 3

Shouldn't you specify the full path and have an export module?
...something like:

mongoose.connection.db.collectionNames(function (err, names)
{
        console.log(names); // [{ name: 'dbname.myCollection' }]
        module.exports.Collection = names;
}

If I'm wrong it's because I don't fancy moongodb :)