Container Properties

Configure CPU, memory, scaling, and other container-specific settings.

Overview

The WebAppContainerProperties dataclass allows you to customize the ECS Fargate container configuration, including:

• CPU and memory allocation
• Number of running tasks
• Container port
• Environment variables
• Health check endpoint

WebAppContainerProperties

gds_idea_cdk_constructs.web_app.props.WebAppContainerProperties dataclass

A structured class for default WebApp Container settings.

Source code in src/gds_idea_cdk_constructs/web_app/props.py

@dataclass
class WebAppContainerProperties:
    """A structured class for default WebApp Container settings."""

    # ECS Task settings
    cpu: int = 256
    """The number of CPU units to reserve for the container (256 = 0.25 vCPU)."""

    memory_limit_mib: int = 512
    """The amount of memory (in MiB) to reserve for the container."""

    desired_count: int = 1
    """The desired number of tasks for the service."""

    container_port: int = 8080
    """The port number on the container that is bound to the host port."""

    environment_variables: dict[str, str] = field(default_factory=dict)
    """A dictionary of environment variables to pass to the container."""

    # ALB Health Check settings
    health_check_path: str | None = None
    """The destination for the health check request."""

    health_check_grace_period: int = 60
    """Health check grace period in seconds"""

    min_healthy_percent: int = 50
    """Mininum healthy percentage """

cpu class-attribute instance-attribute

cpu: int = 256

The number of CPU units to reserve for the container (256 = 0.25 vCPU).

memory_limit_mib class-attribute instance-attribute

memory_limit_mib: int = 512

The amount of memory (in MiB) to reserve for the container.

desired_count class-attribute instance-attribute

desired_count: int = 1

The desired number of tasks for the service.

container_port class-attribute instance-attribute

container_port: int = 8080

The port number on the container that is bound to the host port.

environment_variables class-attribute instance-attribute

environment_variables: dict[str, str] = field(
    default_factory=dict
)

A dictionary of environment variables to pass to the container.

health_check_path class-attribute instance-attribute

health_check_path: str | None = None

The destination for the health check request.

health_check_grace_period class-attribute instance-attribute

health_check_grace_period: int = 60

Health check grace period in seconds

min_healthy_percent class-attribute instance-attribute

min_healthy_percent: int = 50

Mininum healthy percentage

Usage Examples

Default Configuration

from gds_idea_cdk_constructs.web_app import WebApp, AuthType

# Using defaults
WebApp(
    app,
    deployment_config=deployment_config,
    app_config=app_config,
    authentication=AuthType.NONE,
    # container_props not specified - uses defaults
)

# Equivalent to:
# cpu=256 (0.25 vCPU)
# memory_limit_mib=512 (512 MB)
# desired_count=1
# container_port=80
# environment_variables={}
# health_check_path=None (uses framework default)

Custom CPU and Memory

from gds_idea_cdk_constructs.web_app import WebAppContainerProperties

# High-performance configuration
props = WebAppContainerProperties(
    cpu=1024,              # 1 vCPU
    memory_limit_mib=2048, # 2 GB RAM
)

WebApp(
    app,
    deployment_config=deployment_config,
    app_config=app_config,
    container_props=props,
    # ... other parameters
)

Valid CPU and Memory Combinations

Fargate has specific valid combinations:

CPU (vCPU)	Memory (MB)
256	512, 1024, 2048
512	1024, 2048, 3072, 4096
1024	2048, 3072, 4096, 5120, 6144, 7168, 8192
2048	4096 to 16384 (1GB increments)
4096	8192 to 30720 (1GB increments)

Multiple Tasks (High Availability)

props = WebAppContainerProperties(
    desired_count=3,  # Run 3 tasks
    cpu=512,
    memory_limit_mib=1024,
)

WebApp(
    app,
    deployment_config=deployment_config,
    app_config=app_config,
    container_props=props,
    # ... other parameters
)

This creates 3 running containers with load balancing across them.

Custom Port

# For non-standard ports
props = WebAppContainerProperties(
    container_port=8080,  # Application listens on 8080
)

WebApp(
    app,
    deployment_config=deployment_config,
    app_config=app_config,
    container_props=props,
    # ... other parameters
)

Environment Variables

props = WebAppContainerProperties(
    environment_variables={
        "LOG_LEVEL": "INFO",
        "DATABASE_URL": "postgresql://db.example.com/mydb",
        "REDIS_HOST": "redis.example.com",
        "REDIS_PORT": "6379",
        "FEATURE_FLAG_NEW_UI": "true",
    },
)

WebApp(
    app,
    deployment_config=deployment_config,
    app_config=app_config,
    container_props=props,
    # ... other parameters
)

Note: Sensitive values (like database passwords) should be stored in AWS Secrets Manager or Systems Manager Parameter Store and accessed via IAM role, not passed as environment variables.

Custom Health Check

props = WebAppContainerProperties(
    health_check_path="/api/health",  # Override framework default
)

WebApp(
    app,
    deployment_config=deployment_config,
    app_config=app_config,
    container_props=props,
    # ... other parameters
)

Health checks are used by: - ALB Target Group - To determine if a task is healthy - ECS Service - To restart unhealthy tasks

Your application must respond with HTTP 200 at this endpoint.

Complete Example

from gds_idea_cdk_constructs.web_app import WebAppContainerProperties

# Production-ready configuration
props = WebAppContainerProperties(
    # Compute resources
    cpu=512,
    memory_limit_mib=1024,

    # High availability
    desired_count=2,

    # Network
    container_port=8501,

    # Health check
    health_check_path="/_stcore/health",

    # Application config
    environment_variables={
        "LOG_LEVEL": "INFO",
        "ENVIRONMENT": "production",
        "APP_VERSION": "1.2.3",
    },
)

WebApp(
    app,
    deployment_config=deployment_config,
    app_config=app_config,
    authentication=AuthType.COGNITO,
    container_props=props,
)