Amazon ECS Service Connect components - Amazon Elastic Container Service

Amazon ECS Service Connect components

When you use Amazon ECS Service Connect, you configure each Amazon ECS service to run a server application that receives network requests (client-server service) or to run a client application that makes the requests (client service).

When you prepare to start using Service Connect, start with a client-server service. You can add a Service Connect configuration to a new service or an existing service. Amazon ECS creates a Service Connect endpoint in the namespace. Additionally, Amazon ECS creates a new deployment in the service to replace the tasks that are currently running.

Existing tasks and other applications can continue to connect to existing endpoints, and external applications. If a client-server service adds tasks by scaling out, new connections from clients will be balanced between all of the tasks. If a client-server service is updated, new connections from clients will be balanced between the tasks of the new version .

Existing tasks can't resolve and connect to the new endpoint. Only new tasks with a Service Connect configuration in the same namespace and that start running after this deployment can resolve and connect to this endpoint.

This means that the operator of the client application determines when the configuration of their app changes, even though the operator of the server application can change their configuration at any time. The list of endpoints in the namespace can change every time that any service in the namespace is deployed. Existing tasks and replacement tasks continue to behave the same as they did after the most recent deployment.

Consider the following examples.

First, assume that you are creating an application that is available to the public internet in a single AWS CloudFormation template and single AWS CloudFormation stack. The public discovery and reachability should be created last by AWS CloudFormation, including the frontend client service. The services need to be created in this order to prevent an time period when the frontend client service is running and available the public, but a backend isn't. This eliminates error messages from being sent to the public during that time period. In AWS CloudFormation, you must use the dependsOn to indicate to AWS CloudFormation that multiple Amazon ECS services can't be made in parallel or simultaneously. You should add the dependsOn to the frontend client service for each backend client-server service that the client tasks connect to.

Second, assume that a frontend service exists without Service Connect configuration. The tasks are connecting to an existing backend service. Add a client-server Service Connect configuration to the backend service first, using the same name in the DNS or clientAlias that the frontend uses. This creates a new deployment, so all the deployment rollback detection or AWS Management Console, AWS CLI, AWS SDKs and other methods to roll back and revert the backend service to the previous deployment and configuration. If you are satisfied with the performance and behavior of the backend service, add a client or client-server Service Connect configuration to the frontend service. Only the tasks in the new deployment use the Service Connect proxy that is added to those new tasks. If you have issues with this configuration, you can roll back and revert to your previous configuration by using the deployment rollback detection or AWS Management Console, AWS CLI, AWS SDKs and other methods to roll back and revert the backend service to the previous deployment and configuration. If you use another service discovery system that is based on DNS instead of Service Connect, any frontend or client applications begin using new endpoints and changed endpoint configuration after the local DNS cache expires, commonly taking multiple hours.


By default, the Service Connect proxy listens on the containerPort from the task definition port mapping. Your security group rules must allow incoming (ingress) traffic to this port from the subnets where clients will run.

Even if you set a port number in the Service Connect service configuration, this doesn't change the port for the client-server service that the Service Connect proxy listens on. When you set this port number, Amazon ECS changes the port of the endpoint that the client services connect to, on the Service Connect proxy inside those tasks. The proxy in the client service connects to the proxy in the client-server service using the containerPort.

If you want to change the port that the Service Connect proxy listens on, change the ingressPortOverride in the Service Connect configuration of the client-server service. If you change this port number, you must allow inbound traffic on this port that is used by traffic to this service.

Traffic that your applications send to Amazon ECS services configured for Service Connect require that the Amazon VPC and subnets have route table rules and network ACL rules that allow the containerPort and ingressPortOverride port numbers that you are using.

You can use Service Connect to send traffic between VPCs. The same requirements for the route table rules, network ACLs, and security groups apply to both VPCs.

For example, two clusters create tasks in different VPCs. A service in each cluster is configured to use the same namespace. The applications in these two services can resolve every endpoint in the namespace without any VPC DNS configuration. However, the proxies can't connect unless the VPC peering, VPC, or subnet route tables, and VPC network ACLs allow the traffic on the containerPort and ingressPortOverride port numbers.

For tasks that use the bridge networking mode, you must create a security group with an inbound rule that allows traffic on the upper dynamic port range. Then, assign the security group to all the EC2 instances in the Service Connect cluster.

Service Connect proxy

If you create or update a service with Service Connect configuration, Amazon ECS adds a new container to each new task as it is started. This pattern of using a separate container is called a sidecar. This container isn't present in the task definition and you can't configure it. Amazon ECS manages the Container configuration in the service. This allows you to reuse the same task definitions between multiple services, namespaces, and tasks without Service Connect.

Proxy resources
  • For task definitions, you must set the CPU and memory parameters.

    We recommend adding 256 CPU units and at least 64 MiB of memory to your task CPU and memory for the Service Connect proxy container. On AWS Fargate, the lowest amount of memory that you can set is 512 MiB of memory. On Amazon EC2, task definition memory is required.

  • For the service, you set the log configuration in the Service Connect configuration.

  • If you expect tasks in this service to receive more than 500 requests per second at their peak load, we recommend adding 512 CPU units to your task CPU in this task definition for the Service Connect proxy container.

  • If you expect to create more than 100 Service Connect services in the namespace or 2000 tasks in total across all Amazon ECS services within the namespace, we recommend adding 128 MiB of memory to your task memory for the Service Connect proxy container. You should do this in every task definition that is used by all of the Amazon ECS services in the namespace.

Proxy configuration

Your applications connect to the proxy in the sidecar container in the same task as the application is in. Amazon ECS configures the task and containers so that applications only connect to the proxy when application is connects to the endpoint names in the same namespace. All other traffic doesn't use the proxy. The other traffic includes IP addresses in the same VPC, AWS service endpoints, and external traffic.

Load balancing

Service Connect configures the proxy to use the round-robin strategy for load balancing between the tasks in a Service Connect endpoint. The local proxy that is in the task where the connection comes from, picks one of the tasks in the client-server service that provides the endpoint.

For example, consider a task that runs WordPress in a service that is configured as a client service in a namespace called local. There is another service with 2 tasks that run the MySQL database. This service is configured to provide an endpoint called mysql through Service Connect in the same namespace. In the WordPress task, the WordPress application connects to the database using the endpoint name. Connections to this name go to the proxy that runs in a sidecar container in the same task. Then, the proxy can connect to either of the MySQL tasks using the round-robin strategy.

Load balancing strategies: round-robin

Outlier detection

This feature uses data that the proxy has about prior failed connections to avoid sending new connections to the hosts that had the failed connections. Service Connect configures the outlier detection feature of the proxy to provide passive health checks.

Using the previous example, the proxy can connect to either of the MySQL tasks. If the proxy made multiple connections to a specific MySQL task, and 5 or more of the connections failed in the last 30 seconds, then the proxy avoids that MySQL task for 30 to 300 seconds.


Service Connect configures the proxy to retry connection that pass through the proxy and fail, and the second attempt avoids using the host from the previous connection. This ensures that each connection through Service Connect doesn't fail for one-off reasons.

Number of retries: 2


Service Connect configures the proxy to wait a maximum time for your client-server applications to respond. The default timeout value is 15 seconds, but it can be updated.

Optional parameters:

idleTimeout ‐ The amount of time in seconds a connection stays active while idle. A value of 0 disables idleTimeout.

The idleTimeout default for HTTP/HTTP2/GRPC is 5 minutes.

The idleTimeout default for TCP is 1 hour.

perRequestTimeout ‐ The amount of time waiting for the upstream to respond with a complete response per request. A value of 0 turns off perRequestTimeout. This can only be set when the appProtocol for application container is HTTP/HTTP2/GRPC. The default is 15 seconds.


If idleTimeout is set to a time that is less than perRequestTimeout, the connection will close when the idleTimeout is reached and not the perRequestTimeout.


Consider the following when using Service Connect:

  • Tasks that run in Fargate must use the Fargate Linux platform version 1.4.0 or higher to use Service Connect.

  • The Amazon ECS agent version on the container instance must be 1.67.2 or higher.

  • Container instances must run the Amazon ECS-optimized Amazon Linux 2023 AMI version 20230428 or later, or Amazon ECS-optimized Amazon Linux 2 AMI version 2.0.20221115 to use Service Connect. These versions have the Service Connect agent in addition to the Amazon ECS container agent. For more information about the Service Connect agent, see Amazon ECS Service Connect Agent on GitHub.

  • Container instances must have the ecs:Poll permission for the resource arn:aws:ecs:region:0123456789012:task-set/cluster/*. If you are using the ecsInstanceRole, you don't need to add additional permissions. The AmazonEC2ContainerServiceforEC2Role managed policy has the necessary permissions. For more information, see Amazon ECS container instance IAM role.

  • Only services that use rolling deployments are supported with Service Connect.

  • Tasks that use the bridge network mode and use Service Connect don't support the hostname container definition parameter.

  • Task definitions must set the task memory limit to use Service Connect. For more information, see Service Connect proxy.

  • Task definitions that set container memory limits aren't supported.

    You can set container memory limits on your containers, but you must set the task memory limit to a number greater than the sum of the container memory limits. The additional CPU and memory in the task limits that aren't allocated in the container limits are used by the Service Connect proxy container and other containers that don't set container limits. For more information, see Service Connect proxy.

  • You can configure Service Connect to use any AWS Cloud Map namespace in the same Region in the same AWS account.

  • Each service can belong to only one namespace.

  • Only the tasks that services create are supported.

  • All endpoints must be unique within a namespace.

  • All discovery names must be unique within a namespace.

  • You must redeploy existing services before the applications can resolve new endpoints. New endpoints that are added to the namespace after the most recent deployment won't be added to the task configuration. For more information, see Amazon ECS Service Connect components.

  • Service Connect doesn't delete namespaces when clusters are deleted. You must delete namespaces in AWS Cloud Map.

  • Application Load Balancer traffic defaults to routing through the Service Connect agent in awsvpc network mode. If you want non-service traffic to bypass the Service Connect agent, use the ingressPortOverride parameter in your Service Connect service configuration.

Service Connect doesn't support the following:
  • Windows containers

  • HTTP 1.0

  • Standalone tasks

  • Services that use the blue/green and external deployment types

  • External container instance for Amazon ECS Anywhere aren't supported with Service Connect.

  • PPv2

Regions with Service Connect

Amazon ECS Service Connect is available in the following AWS Regions:

Region Name Region

US East (Ohio)


US East (N. Virginia)


US West (N. California)


US West (Oregon)


Africa (Cape Town)


Asia Pacific (Hong Kong)


Asia Pacific (Jakarta)


Asia Pacific (Mumbai)


Asia Pacific (Hyderabad)


Asia Pacific (Osaka)


Asia Pacific (Seoul)


Asia Pacific (Singapore)


Asia Pacific (Sydney)


Asia Pacific (Melbourne)


Asia Pacific (Tokyo)


Canada (Central)


Canada West (Calgary)


China (Beijing)

cn-north-1 (Note: TLS for Service Connect is not available in this region.)

China (Ningxia)

cn-northwest-1 (Note: TLS for Service Connect is not available in this region.)

Europe (Frankfurt)


Europe (Ireland)


Europe (London)


Europe (Paris)


Europe (Milan)


Europe (Spain)


Europe (Stockholm)


Europe (Zurich)


Israel (Tel Aviv)


Middle East (Bahrain)


Middle East (UAE)


South America (São Paulo)