Serverless.js

If you did not install before then install serverless.js framework:

npm install -g serverless

You should have finished basic slack setup and have your AWS credentials.

  1. In your terminal go to the sls_app directory you created before: cd sls_app.
  2. Install python requirements plugin: sls plugin install -n serverless-python-requirements
  3. Install AWS pseudo parameters plugin sls plugin install -n serverless-pseudo-parameters
  4. Set environment variables in your terminal (in case you do not know how, check How to set environment variables section:
AWS_ACCESS_KEY_ID=<your key ID>
AWS_SECRET_ACCESS_KEY=<your secret key>
AWS_REGION=eu-west-1
AWS_DEFAULT_REGION=eu-west-1
SLACK_TOKEN=<your BOT token>
SLACK_CHANNEL="<your slack channel ID>"

serverless.yml

We are going to briefly describe serverless.yml file, please visit official page with full description. Most common feature used in our serverless.yml is dynamic variable replacement (reference). Example syntax of variables:

yamlKeyXYZ: ${variableSource}
# this is an example of providing a default value as the second parameter
otherYamlKey: ${variableSource, defaultValue}

There are many variable sources, please see the official documentation for more details.

This file describes our environment (cloud provider), runtime, functions, plugins, other cloud resources and the final package.

serverless.yml
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service: user1

provider:
  name: aws
  runtime: python3.7
  region: eu-west-1
  tags:
    user: ${self:service}
  environment:  # global environment variables available to all functions within the service
    SLACK_CHANNEL: ${env:SLACK_CHANNEL}
    SLACK_TOKEN: ${env:SLACK_TOKEN}
    DYNAMODB_TABLE: ${self:service}
  iamManagedPolicies:
    - "arn:aws:iam::#{AWS::AccountId}:policy/${self:service}-serverless-workshop-policy"

  • service - Provides a namespace for our project

  • provider - Is the environment where are we going to deploy our application (in our case it’s AWS). Some attributes can be set at different scopes service, provider, function. Everything we set within provider scope is common for all functions.

  • provider.iamManagedPolicies - IAM service role with permissions our functions require to run.

    Note: if you are using this lab on your own account, you will need to define your own role similar to this one

serverless.yml
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package:
  exclude:
    - node_modules/**
    - tests/**
  • package - final zip file uploaded to S3 and deployed to AWS Lambda
serverless.yml
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functions:
  # Lambda function with Flask application to handle Slack communication
  slack-responses:
    handler: wsgi_handler.handler
    events:
      - http:
          path: actions
          method: post
  # Lambda function triggered by CloudWatch events
  scheduled-events:
    handler: standup_bot/scheduled.lambda_handler
    events:
      - schedule:
          description: 'Send questions'
#          rate: cron(0 8 ? * MON-FRI *)  # Mo-Fri 8:00
          rate: rate(5 minutes)  # For testing
          enabled: false
          inputTransformer:
            inputPathsMap:
              eventTime: "$.time"
              source: "$.source"
            inputTemplate: '{"source": <source>,"time": <eventTime>,"type": "send_questions"}'
      - schedule:
          description: 'Send report.'
#          rate: cron(0 10 ? * MON-FRI *)  # Mo-Fri 10:00
          rate: rate(5 minutes)  # For testing
          enabled: false
          inputTransformer:
            inputPathsMap:
              eventTime: "$.time"
              source: "$.source"
            inputTemplate: '{"source": <source>,"time": <eventTime>,"type": "send_report"}'
  • functions - Properties and settings for AWS Lambda functions.
  • functions.<fn-name>.handler - Path to python module containing lambda_handler function
  • functions.<fn-name>.events - AWS Lambda function triggers
serverless.yml
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plugins:
  - serverless-python-requirements
  - serverless-pseudo-parameters
  - serverless-wsgi
  • plugins - Serverless.js plugins (some are installed automatically, others must be installed with sls plugin install -n <plugin-name>
serverless.yml
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custom:
  wsgi:
    app: standup_bot.action_app.app
    pythonBin: python3
  pythonRequirements:
    slim: true
    slimPatternsAppendDefaults: true
    slimPatterns:
      - "**/*.egg-info*"
      - "**/*.dist-info*"
  • custom - Custom variables, which can be referenced as ${self:custom.<variableName>}
serverless.yml
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resources:
  Resources:
    StandupDynamoDbTable:
      Type: 'AWS::DynamoDB::Table'
      DeletionPolicy: Retain
      Properties:
        AttributeDefinitions:
          - AttributeName: report_id
            AttributeType: S
          - AttributeName: report_user_id
            AttributeType: S
        KeySchema:
          - AttributeName: report_id
            KeyType: HASH
          - AttributeName: report_user_id
            KeyType: RANGE
        ProvisionedThroughput:
          ReadCapacityUnits: 1
          WriteCapacityUnits: 1
        TableName: ${self:provider.environment.DYNAMODB_TABLE}