Create a setting in terraform to send a message from AWS Lambda Python3.8 to Slack

[Personal memorandum] Simple setting to send a message from lambda to slack

Overview

• Regarding sending messages to Slack API

• Don't use slackweb library (it's annoying to install the library in your local environment).

• Use the Python standard library urllib.

• Set the information passed to the Slack API in the Lambda environment variable.

• Regarding Lambda creation with Terraform

• The version of aws provider is 2.48.0

• Lambda function code (python source code) should be zipped using the data source ** archive_file ** of ** terraform archive provider ** and then deployed.

• Send image

Terraform settings

• Terraform execution environment Local directory structure (MacOS)

├── .terraform
│   ├── plugins
│   │   └── darwin_amd64
│   │       └── terraform-provider-aws_v2.48.0_x4
├── post-slack.tf
└── source_code
    └── post-slack
        └── main.py

• A tf file that creates a Lambda function

post-slack.tf

data "archive_file" "post-slack" {
  type        = "zip"
  source_dir  = "./source_code/post-slack"
  output_path = "./source_code/post-slack.zip"
}
resource "aws_lambda_function" "post-slack" {
  filename         = "${data.archive_file.post-slack.output_path}"
  function_name    = "post-slack"
  role             = "arn:aws:iam::※※※※※※※※※※※※:role/service-role/lambda-basic-execution"
  handler          = "main.lambda_handler"
  source_code_hash = "${data.archive_file.post-slack.output_base64sha256}"
  runtime          = "python3.8"
  memory_size      = 128
  timeout          = 300
    environment {
    variables = {
      SLACK_CHANNEL = "#hogehoge"
      SLACK_TEXT = "Slack notification test"
      SLACK_USER_NAME = "Anonymous"
      SLACK_ICON_EMOJI = ":fearful:"
      SLACK_COLOR = "warning"
      SLACK_WEBHOOK_URL = "https://hooks.slack.com/services/※※※※※※※※※/※※※※※※※※※/※※※※※※※※※※※※※※※※※※※※※※※※"
    }
  }
}

• IAM role assigned to Lambda

lambda-basic-execution

data "aws_iam_policy_document" "lambda-assume-role-policy" {
  statement {
    actions = ["sts:AssumeRole"]
    principals {
      type        = "Service"
      identifiers = ["lambda.amazonaws.com"]
    }
  }
}
resource "aws_iam_role" "role_lambda-basic-execution" {
  name               = "lambda-basic-execution"
  assume_role_policy = data.aws_iam_policy_document.lambda-assume-role-policy.json
  path               = "/service-role/"
}
resource "aws_iam_role_policy_attachment" "AWSLambdaBasicExecutionRole" {
  role       = aws_iam_role.role_lambda-basic-execution.name
  policy_arn = "arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole"
}

• Python code to send a message to the Slack API

source_code/post-slack/main.py

import os
import json
from urllib.request import Request, urlopen

slackChannel = os.environ['SLACK_CHANNEL']
slackUserName = os.environ['SLACK_USER_NAME']
slackText = os.environ['SLACK_TEXT']
slackWebhookURL = os.environ['SLACK_WEBHOOK_URL']
slackIconEmoji = os.environ['SLACK_ICON_EMOJI']
slackColor = os.environ['SLACK_COLOR']

def lambda_handler(event, context):
    post_slack()

def post_slack():
    message = {
        'channel': slackChannel,
        'username': slackUserName,
        'text': slackText,
        'icon_emoji': slackIconEmoji,
        'attachments': [
            {
                "color": slackColor,
                "text": "what a day··"
            }
        ]
    }
    data = json.dumps(message).encode('utf-8')
    request = Request(slackWebhookURL, data)
    urlopen(request).read()

terraform plan

** If you get the following error when you run the terraform plan for the first time, **

$ terraform plan

Error: Could not satisfy plugin requirements
Plugin reinitialization required. Please run "terraform init".
Plugins are external binaries that Terraform uses to access and manipulate
resources. The configuration provided requires plugins which can't be located,
don't satisfy the version constraints, or are otherwise incompatible.
Terraform automatically discovers provider requirements from your
configuration, including providers used in child modules. To see the
requirements and constraints from each module, run "terraform providers".
Error: provider.archive: no suitable version installed
version requirements: "(any version)"
versions installed: none

** Run terraform init **

$ terraform init

Initializing the backend...

Initializing provider plugins...
- Checking for available provider plugins...
- Downloading plugin for provider "archive" (hashicorp/archive) 2.0.0...

The following providers do not have any version constraints in configuration,
so the latest version was installed.

To prevent automatic upgrades to new major versions that may contain breaking
changes, it is recommended to add version = "..." constraints to the
corresponding provider blocks in configuration, with the constraint strings
suggested below.

* provider.archive: version = "~> 2.0"

Terraform has been successfully initialized!

You may now begin working with Terraform. Try running "terraform plan" to see
any changes that are required for your infrastructure. All Terraform commands
should now work.

If you ever set or change modules or backend configuration for Terraform,
rerun this command to reinitialize your working directory. If you forget, other
commands will detect it and remind you to do so if necessary.

** terraform-provider-aws_v2.48.0_x4 has been downloaded to the plugins directory **

├── .terraform
│   ├── plugins
│   │   └── darwin_amd64
│   │       ├── terraform-provider-archive_v2.0.0_x5
│   │       └── terraform-provider-aws_v2.48.0_x4

terraform apply

$ terraform apply

** Post-slack.zip will be created in the source_code directory after execution **

└── source_code
    ├── post-slack
    │   └── main.py
    └── post-slack.zip

Check in the AWS Management Console

** Lambda function "post-slack" settings **

** Test run **

• Create test event
  

• Test run

• cloudwatch logs log group

• slack notification