Sunday, 28 June 2015

AWS-Lambdas - Automating function deploys

On this post, I talked about the ideas behind AWS-Lambdas computation service and how It works.The presented example shows how It can be be deployed and used. Even having an working example, there is an issue on the way I'm using It. All steps regarding the deploy process are manual. It just goes against agility. Manual deploys as such are error prone. More complex the application get, more expansive It will be to maintain.The side-effects when maintaining manual deploy steps are endless, so there should be an alternative to automate It and make AWS-Lambdas really cost effective as It promises to be.
Kappa seems to fill this gap. It is a command line tool that greatly simplifies the process of having lambdas deployed on the cloud. All steps described on the mentioned post can be automated. Now are talking!

Setup

Before start, be sure you have python (2.7.x)  and pip available on the command line.

Installing kappa: 

I strongly advice build It from sources as far there are important bug fixes that seems to be fixed recently:

git clone https://github.com/garnaat/kappa.git
cd kappa
pip install -r requirements.txt
python setup.py install

Instaling awscli:


sudo pip install awscli


Configuration:

First thing to do is create the the kappa configuration file. This is where I'm gonna tell It how to deploy my lambda function (config.yml).
---
profile: my-default-profile
region: us-west-2
iam:
  policy:
    name: AWSLambdaExecuteRole
  role:
    name: lambda_s3_exec_role
lambda:
  name: myLambdaFuncId
  zipfile_name: integrator.zip
  description: Somethhing that helps describe your lambda function
  path: src/
  handler: Integrator.handler
  runtime: nodejs
  memory_size: 128
  timeout: 3
  mode: event
  test_data: input.json
  event_sources:
    -
      arn: arn:aws:s3:::[set your bucket name]
      events:
        - s3:ObjectCreated:*


Lets see what is going on:

Line 2: There should be a profile that kappa will use to authenticate Itself on amazon and create the function in my behalf. We are gonna see it later on the awscli  configuration;
Line 4: The policies assigned to this lambda. In case they aren't there yet, kappa will create them for me.
Line 9 - 18: function Runtime configs.
Line 19: This is the file that contains an example request in order to test the function. It is useful once we want to be sure everything is working fine after the deploy is over.
Line 20: Here I'm setting from where events will come from. In this case, any changes on the given bucket, will trigger a call to my function.

Now It's time to configure aws-cli. The only configuration needed is the security profile. Kappa will use It as stated before:

Create the following file in case Isn't already there: ~/aws/credentials and put the following content
[my-default-profile]
aws_access_key_id=[YOUR KEY ID ]
aws_secret_access_key=[YOUR ACCESS KEY ]


Having it set, It's time to deploy it using kappa tasks:
kappa config.yml create
kappa config.yml add_event_source
kappa config.yml invoke
kappa config.yml status


It should be enough to see the function deployed on the aws-console. The previous commands in order did:

  • create the function on the amazon
  • Make it listen changes on a given bucket
  • Test the deployed function using fake data (simulating an event)
  • Check the status of the deployed function on amazon.


As far Kappa let me automate all deploy tasks,I'm able to create a smarter deploy process. I worked in an example about how could It be done here. I may forgot to mention some detail about the process of having It work, so in this case leave me message and I'll be glad to help.



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