can you scale down desiredcount to 0 via same container in fargate

Question

I have a fargate service where a task running a container. So, my container is a custom made pipeline, which runs based on SQS count. So, if all the records are processed then I stop the pipeline from the container. So, what I'm wondering, instead of stopping the pipeline, can I set the desired count of the service to 0?(this service is the parent of this container's task)

Answer 1

Yes, you can set desire count to zero once the process complete, but there are few things that you need to consider.

• Your node process should exit once it complete operation
• Dockerfile should have a valid entrypoint, aws-cli
• Fargate service should have to ecs service update opertation

For example Dockerfile

FROM node:alpine
RUN apk add --no-cache python py-pip

RUN pip install awscli
RUN aws --version
WORKDIR /app
COPY app.js .
COPY entrypoint.sh /entrypoint.sh
RUN chmod +x /entrypoint.sh
ENTRYPOINT /entrypoint.sh

entrypoint that will deal with nodejs process and set service count to 0 when the nodejs process completed from SQS.

#!/bin/sh
# start the node process, but it should exit once it processes all SQS
node app.js
# once process is done, we are good to scale down the service
aws ecs update-service --cluster my-cluster --region us-west-2 --service my-http-service --desired-count 0

An example node process that will exit after 1 minute, app.js

function intervalFunc() {
  console.log('Container will stop  in 1 minutes');
}

setInterval(intervalFunc, 1500);
setTimeout((function() {
    return process.exit(0);
}), 60000);

So Docker image play an important role and the node process should exit otherwise it will keep running.