ECS Exec

In the previous section we showed you how to use sonic ssh to quickly ssh into an instance. Some of the identifiers used were ECS identifiers. As you can see sonic is ECS smart.

One of the additional things sonic can do is hop one more level and get you all the way to the running docker container via docker exec.

It does this with a variety of scripts and trickery and is covered in How It Works. Let’s go through examples of how sonic can help you get into an running ECS docker container quickly.

sonic ecs-exec

sonic ecs-exec [ECS_SERVICE] --cluster [ECS_CLUSTER]

Here’s a concrete example:

sonic ecs-exec hi-web-stag --cluster stag

You should see something like this:

$ sonic ecs-exec hi-web-stag --cluster stag
Running: scp -r /tmp/sonic ec2-user@34.211.195.71:/tmp/sonic  > /dev/null
Warning: Permanently added '34.211.195.71' (ECDSA) to the list of known hosts.
=> ssh -t ec2-user@34.211.195.71 bash /tmp/sonic/bash_scripts/docker-exec.sh
Warning: Permanently added '34.211.195.71' (ECDSA) to the list of known hosts.
root@fc4035f90bdc:/app#

What you see in the last line above is a bash prompt because you are in a bash shell within the docker container! Ultimately sonic runs runs a docker exec -ti ECS_SERVICE_CONTAINER bash after ssh-ing into the instance. With one command you have placed yourself into the running container 🎉

Possibilities

Here are examples to show what is possible:

$ sonic ecs-exec hi-web-stag bash
# You're in the docker container now
$ ls # check out some files to make sure you're the right place
$ ps auxxx | grep puma # is the web process up?
$ env # are the environment variables properly set?
$ bundle exec rails c # start up a rails console to debug

You can also pass in bundle exec rails console if you want to get to that as quickly as possible.

$ sonic ecs-exec hi-web-stag bundle exec rails console
# You're a rails console in the docker container now
> User.count

You can also use the container instance id or instance id in place of the service name:

sonic ecs-exec 9f1dadc7-4f67-41da-abec-ec08810bfbc9 bash
sonic ecs-exec i-006a097bb10643e20 bash

Settings - service_cluster mapping

As mentioned in the previous section and also in the Settings documentation you can configure a ~/.sonic/settings.yml file which shortens the command further. Let’s add this to your settings:

service_cluster:
  default: stag
  hi-web-stag: stag

This makes the command consise and memorable.

sonic ecs-exec hi-web-stag

The rest of this section assumes that you have the ~/.sonic/settings.yml set up.

You can also tack on a command at the end of the ecs-exec command to be run as a one off instead of starting a bash shell. Example:

$ sonic ecs-exec hi-web-stag uname -a
Running: scp -r /tmp/sonic ec2-user@34.211.195.71:/tmp/sonic  > /dev/null
Warning: Permanently added '34.211.195.71' (ECDSA) to the list of known hosts.
=> ssh -t ec2-user@34.211.195.71 bash /tmp/sonic/bash_scripts/docker-exec.sh uname -a
Warning: Permanently added '34.211.195.71' (ECDSA) to the list of known hosts.
Linux fc4035f90bdc 4.4.51-40.58.amzn1.x86_64 #1 SMP Tue Feb 28 21:57:17 UTC 2017 x86_64 GNU/Linux
Connection to 34.211.195.71 closed.
$

Remember the command runs within the running docker container.

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