如何创建自定义事件以在无服务器上触发 function

Question

I have a function that make a request each 5 minutes and get an array of result. I want to each item in this array call another lambda to process individually.

How can I create a custom trigger to call a function when this array is receive? I am using Nodejs with serverless framework.

PS: If I simply make a call http for each item in array, how can I get the url of the another function dinamically?

Thanks!

Answer 1

You should be able to use the AWS SDK to call the Lambda using the invoke method:

var params = {
  FunctionName: "my-function", 
  Payload: <Binary String>, 
  Qualifier: "1"
 };
 lambda.invoke(params, function(err, data) {
   if (err) console.log(err, err.stack); // an error occurred
   else     console.log(data);           // successful response
   /*
   data = {
    Payload: <Binary String>, 
    StatusCode: 200
   }
   */
 });

https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/Lambda.html#invoke-property

This lets you call as many Lambda functions as you need from within the current one. However, I would recommend a different technique since this does not handle errors very cleanly and assumes you will always use the one and only Lambnda to process a small number of items in a small array. A better method can help handle errors better as we as handle an increase in volume better.

In your serverless.yml file, have a function that process the items in your list get triggered by SNS (please name things correctly in your case):

functions:
  receiveItem:
    handler: fileName.receiveItem
    events:
      - sns: recieveItem

Then in the Lambda that has the array, add the item as a message into the SNS topic one at a time and you will then have Lambda functions spin up and process them.