Using gordon we can trigger our lambda function for the following services:

• API Gateway
• Scheduled CloudWatch Events
• CloudWatch Events
• Dynamodb Streams
• Kinesis Streams
• S3

Gordon Architecture:

Gordon consist of project and project apps, project consists of project apps and project wide settings file.

Each app has a lambda module which consists of lambda function and setting file which override project wide settings.

The following example will walkthrough creating lambda function which is triggered when an object is created in S3.

Setup Environment and Install Gordon:

mkdir gordon
cd gordon
virtualenv genv
source genv/bin/activate
pip install gordonclass="pretty-print"

Create Project:

Gordon startproject oscar_wilde

This will create a directory with name oscar_wilde and a settings.yml file

oscar_wilde
   └── settings.yml

Create Application:

Goto oscar_wilde project directory and run:

gordon startapp astrophe

This will create astrophe directory with settings.yml, helloworld directory which contains code.py.

Oscar_wilde
      settings.yml
      astrophe
          helloworld
              code.py
          settings.yml

You can rename helloworld directory to whatever name you desire but remember to change it in astrophe settings.yml file too.

S3 Integration:

Edit the oscar_wilde/settings.yml file with following content: ---

project: oscar_wilde
    default-region: us-east-1
    code-bucket: gordon-s3-0do9a8d
    apps:
      - gordon.contrib.helpers
      - gordon.contrib.lambdas
      - gordon.contrib.s3
      - astrophe
    s3:
     trigger_on_object_creation:
        bucket: us-east-1-oscarwilde
        notifications:
         run_lambda_on_object_create:
            lambda: astrophe.s3consumer
            events:
              - s3:ObjectCreated:*

We have included our app astrophe in apps and set to trigger our lambda function when an object is created to us-east-1-oscarwilde bucket in us-east-1 region.

Lambda Handler Code:

By default the handler just prints the output when the event happens, in our case when an object is created in S3 bucket.

#astrophe/helloworld/code.py file contents.

  import json
  def handler(event, context):
      data = "Hello World!"
      print(data)
      print("Received Event: " + json.dumps(event, indent=2))

Building CloudFormation Templates:

Configuring yaml files with appropriate actions is our part, building cloudformation templates is automatically done by gordon. Goto project root directory and run:

gordon build

This will create _build directory with contents:

0001_p.json         # creates s3 bucket and upload lambdas.
    0002_pr_r.json        # custom template.
    0003_r.json         # creates event sources.
    Code            # zipped files of our lambda code.
      Contrib_lambdas_version.zip
      firstapp_helloworld.zip

Deploy the Project:

Goto project root directory and run:

gordon apply

This will take a while, at the end you will have lambda handler that gets executed whenever you upload a file to s3 bucket.