A CDK Stack defining a self-mutating Pipeline

cdk.pipeline_stack.py

from constructs import Construct
from aws_cdk import (
    Stack,
    pipelines as pipelines,
    aws_ssm as ssm,
    aws_secretsmanager as secretsmanager,
    aws_rds as rds,
)
from .deployment_stage import MyDjangoAppPipelineStage


class MyDjangoAppPipelineStack(Stack):
    def __init__(
            self,
            scope: Construct,
            construct_id: str,
            repository: str,
            branch: str,
            ssm_gh_connection_param: str,
            **kwargs
    ) -> None:
        super().__init__(scope, construct_id, **kwargs)
        self.repository = repository
        self.branch = branch
        self.ssm_gh_connection_param = ssm_gh_connection_param
        self.gh_connection_arn = ssm.StringParameter.value_for_string_parameter(
            self, ssm_gh_connection_param
        )
        aws_env = kwargs.get("env")
        pipeline = pipelines.CodePipeline(
            self,
            "Pipeline",
            docker_credentials=[
                pipelines.DockerCredential.docker_hub(
                    secretsmanager.Secret.from_secret_name_v2(
                        self,
                        "DockerHubSecret",
                        secret_name="/MyDjangoAppPipeline/DockerHubSecret"
                    )
                ),
            ],
            synth=pipelines.ShellStep(
                "Synth",
                input=pipelines.CodePipelineSource.connection(
                    self.repository,
                    self.branch,
                    connection_arn=self.gh_connection_arn,
                    trigger_on_push=True
                ),
                commands=[
                    "npm install -g aws-cdk",  # Installs the cdk cli on Codebuild
                    "pip install -r requirements.txt",  # Instructs Codebuild to install required packages
                    "npx cdk synth MyDjangoAppPipeline",
                ]
            ),
        )
        # Deploy to a staging environment
        self.staging_env = MyDjangoAppPipelineStage(
            self, "MyDjangoAppStaging",
            env=aws_env,  # AWS Account and Region
            django_settings_module="app.settings.stage",
            django_debug=True,
            domain_name="scalabledjango.com",
            subdomain="stage",
            # Limit scaling in staging to reduce costs
            db_min_capacity=rds.AuroraCapacityUnit.ACU_2,
            db_max_capacity=rds.AuroraCapacityUnit.ACU_2,
            db_auto_pause_minutes=5,
            app_task_min_scaling_capacity=1,
            app_task_max_scaling_capacity=2,
            worker_task_min_scaling_capacity=1,
            worker_task_max_scaling_capacity=2,
            worker_scaling_steps=[
                {"upper": 0, "change": 0},  # 0 msgs = 1 workers
                {"lower": 10, "change": +1},  # 10 msgs = 2 workers
            ]
        )
        pipeline.add_stage(self.staging_env)
        # Deploy to production after manual approval
        self.production_env = MyDjangoAppPipelineStage(
            self, "MyDjangoAppProduction",
            env=aws_env,  # AWS Account and Region
            django_settings_module="app.settings.prod",
            django_debug=False,
            domain_name="scalabledjango.com",
            db_auto_pause_minutes=0,  # Keep the database always up in production
            app_task_min_scaling_capacity=2,
            app_task_max_scaling_capacity=5,
            worker_task_min_scaling_capacity=2,
            worker_task_max_scaling_capacity=4,
            worker_scaling_steps=[
                {"upper": 0, "change": 0},     # 0 msgs = 1 workers
                {"lower": 100, "change": +1},  # > 100 msg = 2 worker
                {"lower": 200, "change": +1},  # > 200 msgs = 3 workers
                {"lower": 500, "change": +2},  # > 500 msgs = 5 workers
            ]
        )
        pipeline.add_stage(
            self.production_env,
            pre=[
                pipelines.ManualApprovalStep("PromoteToProduction")
            ]
        )