Create lambda function and triggering actions is time taking and involves repetitive steps. We are going to use a simple application called Gordon.
Gordon creates CloudFormation templates based on our settings files, cloudformation is a configuration management tool for Amazon Web Services similar to chef, puppet, ansible etc.. but for AWS.
Gordon isolates all the processes, like it creates separate roles, separate bucket names etc..which enhance security and doesn’t mess up with other services already running.
Using gordon we can trigger our lambda function for the following services:
- API Gateway
- Scheduled CloudWatch Events
- CloudWatch Events
- Dynamodb Streams
- Kinesis Streams
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 gordon
Gordon startproject oscar_wilde
This will create a directory with name oscar_wilde and a settings.yml file
oscar_wilde └── settings.yml
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.
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:
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:
This will take a while, at the end you will have lambda handler that gets executed whenever you upload a file to s3 bucket.