Remote MongoDB Example about examples

[kuashe]

I would like to upload this because I couldn't got mongoose to work until i explicitly call the function

db.close()

Otherwise , lambda continue to process the function , due to Node event loop never ending.

Is this specified anywhere in the documentation ?

[kuashe]

@leeeomaaax Thank you so much for this !

[DavidWells]

For sure! I'd love to see this

[leeeomaaax]

@kuashe , I've just been through this. I was trying to make mongoose work with lambda and everything was working well on local, both on invoke test (serverless-mocha-plugin) and invoke local. But on the lambda environment my function was timing out even though it was getting all the way through the code.

There is another way of solving this. Use this context property to prevent the lambda from executing the handler callback.

context.callbackWaitsForEmptyEventLoop = false;

This way you can keep your connection to mongo open and speed up the warm calls to your function.

[DavidWells]

merged #150

https://github.com/serverless/examples/tree/master/aws-node-rest-api-mongodb

[kvreem]

@kuashe I am using the following https://github.com/serverless/serverless-graphql as a boilerplate, but have integrated mongoDB instead of DynamoDB (using mongo atlas). Everything works fine offline using serverless-offline plugin. But when I sls log my lambda functions once i deploy i get the following error

2018-01-28 18:58:59.726 (-08:00)	59696d6e-04a0-11e8-82ec-8974eb6ffd47	MongoDB connection error. Please make sure MongoDb is running. { MongoError: failed to connect to server [undefined:27017] on first connect [MongoError: getaddrinfo ENOTFOUND undefined undefined:27017]
    at Pool.<anonymous> (/var/task/node_modules/mongodb-core/lib/topologies/server.js:336:35)
    at emitOne (events.js:96:13)
    at Pool.emit (events.js:188:7)
    at Connection.<anonymous> (/var/task/node_modules/mongodb-core/lib/connection/pool.js:280:12)
    at Connection.g (events.js:292:16)
    at emitTwo (events.js:106:13)
    at Connection.emit (events.js:191:7)
    at Socket.<anonymous> (/var/task/node_modules/mongodb-core/lib/connection/connection.js:189:49)
    at Socket.g (events.js:292:16)
    at emitOne (events.js:96:13)
    at Socket.emit (events.js:188:7)
    at connectErrorNT (net.js:1021:8)
    at _combinedTickCallback (internal/process/next_tick.js:80:11)
    at process._tickDomainCallback (internal/process/next_tick.js:128:9)
  name: 'MongoError',
  message: 'failed to connect to server [undefined:27017] on first connect [MongoError: getaddrinfo ENOTFOUND undefined undefined:27017]' }

In my handler.js I have similar code

exports.graphqlHandler = function graphqlHandler(event, context, callback) {
    context.callbackWaitsForEmptyEventLoop = false;

    function callbackFilter(error, output) {

        if (!output.headers) {
          output.headers = {};
        }
        // eslint-disable-next-line no-param-reassign
        output.headers['Access-Control-Allow-Origin'] = '*';
        output.headers['Access-Control-Allow-Credentials'] = true;
        output.headers['Content-Type'] = 'application/json';

        callback(error, output);
    }

    mongoose.connect(mongoString, {useMongoClient: true});

    mongoose.connection.on("error", (err) => {
        console.log("MongoDB connection error. Please make sure MongoDb is running.", err);
        process.exit();
    });

    const handler = server.graphqlLambda({ schema: myGraphQLSchema });
    return handler(event, context, callbackFilter);
};

The context.callbackWaitsForEmptyEventLoop = false; doesn't seem to be helping in my case.

Were you getting a similar error until you used db.close()?

[kuashe]

@kvreem The error seam pretty straight forward to me . It's your database connection .

Fork the repository , replace the mongo string at the top of the file to make sure you database is reachable from a lambda function.

Hence, make sure you are waiting in your graphql handler for the database connection to be open.

[kvreem]

@kuashe I am aware the connection is the problem, but since my application logic isn't exactly in the handler.js like the repo, I am a little bit confused how to refactor so that I make my handler wait for the database connection to be open. I also have 0.0.0.0 ip whitelisted since I am just testing development cluster with mongo atlas.

    const handler = server.graphqlLambda({ schema: myGraphQLSchema });
    return handler(event, context, callbackFilter);

Does the above snippet need to be moved in db.once('open' function?

Or does each query I make with graphql need to have the connection open then close it once it fetches the data? For example my query here:

export function getBookings() {
    return new Promise((resolve, reject) => {
        BookingModel
            .find()
            .then((bookings) => {
                let bookingMap = [];
                bookings = _.orderBy(bookings, ['updatedAt'], ['desc']);
                bookings.forEach((booking, index) => {
                    bookingMap[index] = booking;
                });
                resolve(bookingMap);
            })
            .catch((err) => {
                reject(err);
            });
        }
    );
}

[kuashe]

@kvreem Each individual query to Lambda needs to have the database connection open then closed.

The following code should the trick

db.once('open' , () => {
        return handler(event, context, callbackFilter);
  })

[kvreem]

@kuashe sorry to keep bugging you, here is my refactored handler, but i still get the same result in my logs when i deploy to lambda.

exports.graphqlHandler = function graphqlHandler(event, context, callback) {

    context.callbackWaitsForEmptyEventLoop = false;

    function callbackFilter(error, output) {

        if (!output.headers) {
          output.headers = {};
        }
        // eslint-disable-next-line no-param-reassign
        output.headers['Access-Control-Allow-Origin'] = '*';
        output.headers['Access-Control-Allow-Credentials'] = true;
        output.headers['Content-Type'] = 'application/json';

        callback(error, output);
    }

    mongoose.connect(mongoString, {useMongoClient: true});

    const db = mongoose.connection;
    const handler = server.graphqlLambda({ schema: myGraphQLSchema });

    db.on("error", (err) => {
        console.log("MongoDB connection error. Please make sure MongoDb is running.", err);
        process.exit();
    });

    db.once('open', () => {
       return handler(event, context, callbackFilter);
    })
};

I am trying to understand how I can keep the Lambda function from timing out, based on the logs it never connects to the database. When I deploy I do get a CORS issue,

No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'https://MY DOMAIN' is therefore not allowed access. The response had HTTP status code 502. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

But this shouldn't stop the database from connecting. Or is this whats causing the issue? I have the headers in my handler.

In my serverless.yml here is how I am defining my lambda functions. (Same as you are)

functions:
  graphql:
    handler: handler.graphqlHandler
    events:
    - http:
        path: graphql
        method: post
        cors: true

...

Again I appreciate all your help. Thanks a ton 👍

[DiptarkBose]

I am trying to connect to mlab from aws lambda, and am not keen to use serverless. Can someone please help me out? My query is posted in detail @ stackoverflow: https://stackoverflow.com/questions/50559243/not-being-able-to-connect-to-mongodb-from-aws-lambda