/serverless-evnt-trainee-repo

Slides:

https://docs.google.com/presentation/d/1ckFkQyszXuHJixhn8RP_PI8Lzoj7FK1lyKtsB7pPPYI/edit#slide=id.g74c57ff882_0_0

Goals structure:

  • 10 minutes describing the goal and giving some tips
  • 30 minutes of trainees attempting to solve it
  • 10 minutes of sharing the solution
  • 10 minutes rest

Goal 1: trigger a lambda to log something by posting an event via aws-cli.

  • Listening Lambda
  • Modify your lambda descriptor serverless.yml to be able to react to a published event (Define the event yourself).
  • Modify your handler.js function and make sure to simply log something. We'll need this to check if the event was received.
  • Deploy your newly created lambda.

How are you going to test it works (manually)?

Goal 2: trigger a lambda via GET message that sends an envent that triggers goal 1 lambda.

  • Publish Lambda
  • Create another lambda called publish_lambda and prepare it for modification.
  • Modify your lambda descriptior serverless.yml to be able to react to a get http event.
  • Don't forget to include iamRoleStatements to allow this function to put events
  • Modify your handler.js function to be able to publish an event of the type described in the Listening Lambda.
  • Deploy your modified lambda.

In order to check if both sides are properly working, you need to either trigger a local invocation of your Publish Lambda or remotely invoke it via http post invokation.

Expected result: Go to your each of your function definitions in AWS console, Monitoring Option and take a look at the logs, you should see the logs created on each handler.js file

Goal 3: change the goal 2 lambda to receive post messages and pipe the post payload throught the event bus so it gets logged the listening lambda

Now, we need you to make your Publish Lambda to react to a POST event instead of GET. This will act as a post (as an entity) creation.

In order to achieve this, you have to:

  • Modify your serverless.yml file and configure post http event
  • Modify your handler.js to be able to handle data sent to your function and forward it as part of the event
  • You can test locally your function, to check if it reacts to the post event, if you can read the data posted and if the data is forwarded as part of the event
  • Deploy your lambda and test it again. As this is a POST event, you will need to pass data. We recommend using a API testing tool like POSTMAN

After having done that, modify your Listening Lambda to be able to read data from the event

  • Modify your handler.js to be able to extract the data from the event and log it

Verify, as in Iteration 1, via Cloudwatch

Goal 4: have the listening lambda to store the post info in the database

In this stage we need you to modify the event to have all the required data that a post entity should have in order to persist a post

  • Modify the data you're passing in order to have the required data dateTime, postId, text and userId
  • Enable your handler.js function to access the database created in Get From Database exercise
  • Modify your function so it can create a new post from the data received (HINT: Use DynamoDB DocumentClient and update expression)
  • Verify that persistence is happening by checking logs and DynamoDB table

Example of a post


{
   "dateTime": 1549312452000,
   "postId": 102030,
   "text": "Fake post",
   "userId": 1234
}

Help:

  • Events get published but not received: check the amazon region where they are published

  • Hello world command: sls create --template aws-nodejs --path myService

  • you need a template for the json aws events put-events --generate-cli-skeleton

  • you need to send aws events put-events --entries file://firstEvent.json

  • you can call the lambda locally

    serverless invoke local -f publish

  • You can pass data to your local invokation

    serverless invoke local -f publish -d "testData.json" Where testData.json can have the following shape

{
  "body": {
    "dateTime": 1549312452000,
    "postId": 102030,
    "text": "Fake post done via CLI while backend is under construction"
  }
}

  • Event data comes inside ´detail´

  • Use DynamoDB.DocumentClient

var params = {
    TableName: 'posts',
    Key: {
      userId: "1234"
    },
    UpdateExpression: "SET #posts  = list_append(#posts, :post)",
    ExpressionAttributeNames: { "#posts" : "posts"},
    ExpressionAttributeValues: {":post": [event.detail]},
    ReturnValues : "UPDATED_NEW"

  }
...
...
docClient.update(params, function(err, data) { ... } );