Function as a Service
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This document discusses building a Slack bot using AWS Lambda and the Chalice framework. It describes how FaaS works, options for running functions through AWS Lambda including Python support. It then outlines how to build a Slack bot with Chalice that allows users to query Stack Overflow through natural language requests in Slack. Key steps include setting up the bot to handle requests, retrieving secrets securely, formatting responses, and deploying the code to AWS Lambda to be accessible through Slack. It also briefly discusses additional uses of FaaS beyond a basic bot including cron jobs and handling external events.
Function as a Service
- 1. Function as a Service Exploring slack bots with Chalice and AWS Lambda richiverse https://github.com/richiverse/slambda
- 2. What is a Function as a Service (FAAS)? Function as a Service (FaaS) is a category of cloud computing services that provides a platform allowing customers to develop, run, and manage application functionalities without the complexity of building and maintaining the infrastructure typically associated with developing and launching an app (Wikipedia)
- 3. Vendors ● AWS Lambda (node.js, java 8, python 2.7) ● Google Cloud Functions (node.js) ● Microsoft Azure Functions (JavaScript, C#, Python, PHP, Bash, Batch, and PowerShell) ● IBM Whisk (NodeJS, Swift and arbitrary binary programs encapsulated in Docker Containers)
- 4. Isn’t this Heroku (PaaS) all over again? You are given very few options as to how your environment is setup. You are given the freedom of choosing where/how your functions get called. Anywhere you are doing IO or responding to events or quick running jobs (< 5 minutes) is a good candidate for using FaaS. No provisioning servers, no complex deployments.
- 5. ...So I went with AWS Lambda One of the few that supports Python out of the box even though it is using python 2.7 (...not bad) ● Gateway drug to other AWS services. ● Relatively stable, inexpensive relative to newcomers. ● More binaries may be announced early December ● Supports arbitrary binary execution with certain deployment options.
- 6. Function Options The point and click and CLI options give a lot of options over how lambdas are run. ● Versioning ● Alias ● 1M free calls per month ● 4GB free compute memory per month
- 7. Frameworks to ease development I ended up using Chalice because of the slick python integration but if my project required tight integration with a lot of other events or required docker containers I would have gone with Gordon. https://github.com/awslabs/chalice https://github.com/jorgebastida/gordon https://github.com/anaibol/awesome-serverless#frameworks
- 8. How does Chalice work? Chalice takes your app.py as well as any dependencies in requirements.txt, zips them up, and deploys an AWS API Gateway endpoint to your function.
- 9. Requirements Need AWS credentials saved in your home directory Virtual environment and python 2.7 environment. I used yyuu’s pyenv for a project specific 2.7 interpreter which doesn’t interact with my system install of python 3.5 (also using yyuu’s pyenv tool). I created a user with the right policies for chalice to deploy correctly.
- 10. Building a slack bot for Stackoverflow I’m familiar with a python tool called howdoi which enables asking SO questions at the CLI. How do I bring this useful tool to my company? Ask them to pip install howdoi? That’s too much to ask in this busy world! Why not just bring the command line to them?! ;)
- 11. Hello World! I used Pertinent Serpent’s Magic the Gathering slackbot as a reference example of something pretty meaty over the traditional hello world. Things I did differently over this reference implementation was using credstash for KMS to encrypt and store the Slack token for authenticating users. http://pertinentserpent.tumblr.com/post/147568685382/deploy ing-a-slack-bot-on-amazon-lambda-with
- 12. Building a slackbot for Stackoverflow - Imports I used python’s standard logging module to log events to Amazon cloudwatch to track errors and log information about the slack user/request.
- 13. Building a slackbot for Stackoverflow - Routes Chalice has a similar syntax to Flask (Sinatra clone in Python) where you decorate the route to your function. Here I am using a built-in helper for query params.
- 14. Building a slackbot for Stackoverflow - secrets By default, you deploy to dev env. Chalice roadmap includes deploying to multiple stages. Here I also grab the keys that I’m going to use from credstash. I setup some additional contextual variables for retrieval in the credstash CLI.
- 15. Building a slackbot for Stackoverflow - Response Here I quickly greet the user to avoid the 3 second Slack timeout. I then process their query, format the response to look nice in slack, then modify the payload and post it back in the channel. After this, I run chalice deploy at the command line and my code is available to test in slack.
- 16. But wait… there’s more
- 17. Cron Jobs + Arbitrary executables While this is actually cool enough, it doesn’t tap into all the power of FaaS. AWS Lambdas can run on a schedule (using cron) AWS Lambdas can operate on arbitrary executables.
- 18. Event Driven development In reaction to an event, such as: ● S3 Bucket events ● DynamoDB event ● SNS/Kinesis events ● IOT, Alexa, Log events