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Yutaro Mori
Yutaro Mori

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Not documented App Runner specification


I plan to monitoring system with Datadog at office. At first, I prepared EC2 server for running Datadog Agent to monitor media servers and DB. However, I think that it's a waste of cost to run server just starting Datadog Agent. So I decided to migrate Datadog Agent from EC2 to ECS.


About App Runner

AWS App Runner is a fully managed container application service that lets you build, deploy, and run containerized web applications and API services without prior infrastructure or container experience.

I found it convenient that it is not need to set complex network configure and is able to implement fully managed container CI/CD infrastructure. But, I found something odd when I monitored the media server externally with Agent on App Runner.

Increase Response time

This is the graph of response time Datadog Agent obtained from our servers.


Response time increased rapidly immediately after migrating to App Runner. After a day had passed and it was not back to normal, I moved it to ECS on Fargate.

Curl inspection

I prepared curl container1 which obtains response time and measured ECS on Fargate and App Runner to compare the performance of each container

FROM  curlimages/curl:latest

CMD  curl -s -o /dev/null -w '%{time_starttransfer}' <URL>
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$ docker build -t curl-yuta .
$ docker run --rm curl-yuta
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There are two screenshots that Agent from ECS on Fargate or App Runner obtains response time.

ECS on Fargate


App Runner


It found that the response time is slower when retrieved via App Runner, even in curl.

Mystery Container

Datadog automatically registers containers with agents in their dashboards.

ECS on Fargate


App Runner


On Fargate, when Datadog Agent was installed into the container, one unit was registered. However, on App Runner, two units was registered.

Mystery container, aws-fargate-request-proxy was running, but I could not find details about this container in the App Runner documentation.

In my guess, deployed container on App Runner doesn't connect directly external and it takes a long time since the proxy container exists between App Runner container and Internet.



I built monitoring system with Datadog Agent on Fargate instead of App Runner. And in combination with GitHub Actions, I built a CI/CD infrastructure so that datadog configuration files can be pushed to GitHub repository and automatically run up to container deployments.



I tried App Runner for the first time except tutorial. Unfortunately, I can not make use of it on business, however I feel that it is so convenient for App Runner to be deployed container easily. I would like to take advantage of this on another occasion.



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