[PYTHON] LoL ~ Lambda operate Lambda ~

Preface

It is a plan to create a Lambda function ** that updates the Lambda function group and challenge continuous Lambda update.

• The title is a story
• I think that it will be practical to some extent if the additional elements described below are carefully arranged.

AWS Lambda Review

Code running on AWS Lambda can be distributed in three ways.

• Inline code: Write and execute code directly
• Zip upload: Upload a code set that zips multiple codes
• S3 download: Get the zipped code set on the specified S3

What i want to do

Actually, when I first saw the options, I thought that the S3 download format would refer to the S3 file every time I started Lambda. With this, "If you distribute it to S3, you can deploy the code at that point, isn't it?"

As far as I can see the behavior, it seems that it is not so, so I made a mechanism to deploy locally while being a little disappointed, but based on the idea that "AWS SDK will also touch Lambda itself?"

0. Triggered by the POST of the codeset zip file to S3
1. Extract the Lambda configuration list included in the zip
2. Overwrite and update Lamda using AWS SDK

I wondered if I could make a mechanism like this, so I made a little code and tried it.

In addition, it is written in Python for personal convenience.

What to prepare

• Environmental system
• AWS account
• Codes
• Main code + Lambda list
• Lambda update Lambda

Advance

Lamda update Prepare Lambda function

Define a Lambda function with inline code upsert_lambda.py in this Gist.

I don't think the memory itself requires that much. However, depending on the contents, it will make a good API call, so it is better to keep the timeout seconds longer. (I set it to 30 seconds for the time being)

(Roughly explain in the comments while squeezing the contents)

upsert_lambda.py

# -*- coding:utf8 -*-
import boto3
from botocore.exceptions import ClientError
import zipfile
import json


class S3Object(object):
    #Class for simplification of delivery
    # <Abbreviated for each init>

def lambda_handler(event, context):
    #Function called by AWS Lambda
    records = event.get('Records', [])
    for record in records:
        s3_object = S3Object(record['awsRegion'], record['s3']['bucket']['name'], record['s3']['object']['key'])
        _update_functions('sharequiz', 'test', s3_object)


def _update_functions(project, env, s3_object):
    #Get the function list json from the uploaded zip
    with zipfile.ZipFile(project_zip_path) as zfp:
        handlers_json = zfp.read('functions.json')
    functions = json.loads(handlers_json)

    _lambda = boto3.client('lambda')
    for function in functions:
        try:
            #Try to create a Lambda function for the time being
            #Get at least at the time of writing this code_I remember that function was also an exception
            _lambda.create_function(
                # <Argument omitted>
            )
        except ClientError as err:
            #Overwrite settings and code if it already exists
            _lambda.update_function_configuration(**function)
            _lambda.update_function_code(
                # <Argument omitted>
            )

Prepare an S3 bucket

In S3, you can notify Lambda of events such as object creation and call specific Lambda functions. [^ 1] By using this mechanism, you can ** call the above Lambda function when the file is uploaded to the specified bucket folder **.

Make a zip with the code set of Lambda functions

Basically, there is no problem if you make this area according to the Lambda document. However, please include json to make lambda.create_function and lambda.update_function_code in boto3. (Named in functions.json)

Like ↓

functions.json

[{
	"Handler": "path/to/module.some_function",
	"Role": "arn:aws:iam::your-role",
	"FunctionName": "some_funtion",
	"Timeout": 3,
	"MemorySize": 128,
	"Description": "Easy processing"
}, {
	"Handler": "path/to/module.other_function",
	"Role": "arn:aws:iam::your-role",
	"FunctionName": "else_funtion",
	"Timeout": 30,
	"MemorySize": 1280,
	"Description": "Heavy processing"
}]

Upload

Please upload the created zip to the place where the notification goes to Lambda side.

I tried it

(If you have time after posting, paste the video or GIF)

Development (?)

• lambda update You can use Slack Webhook in lambda to let you know that you have updated
• If you prepare a mechanism that can create zip and upload S3 in CI environment, you can update automatically by pushing to master etc.
• If you combine the top two, you can make continuous delivery and announcements, which is wonderful.

This is the introduction of the code I made before I knew the existence of lambda-uploader.