This project provides a simple Golang CLI tool that binds to the Docker Swarm API to create an ad-hoc/one-shot Service and then poll until it exits. Service logs can also be retrieved if the experimental feature is enabled on the Docker daemon.

Motivation and context

For a blog post covering use-cases for JaaS and more on the portions of the Docker API used see below:

• Blog: One-shot containers on Docker Swarm

This is the contribution process for this repo.

• Raise a Github issue with the proposed change/idea
• I'll mark the issue as a feature/bug fix etc for the changelog
• This gives us a chance to discuss the idea
• If everything sounds good then go ahead and work on the PR
• Please link to the bug and explain how you tested the change
• I'll merge after reviewing/testing

Pre-requisites:

• Docker 1.13 or newer (experimental mode must be enabled if accessing service logs)
• Go 1.7.3 (or Golang container)
• Enable Swarm Mode (docker swarm init)

Run these commands

# export GOPATH=$HOME/go
# go get -d -v github.com/alexellis/jaas
# cd $GOPATH/src/github.com/alexellis/jaas
# go install
# export PATH=$PATH:$GOPATH/bin

Now test jaas with jaas --help

• Run your first one-shot container:

# jaas -rm -image alexellis2/cows:latest

The -rm flag removes the Swarm service that was used to run your container.

The exit code from your container will also be available, you can check it with echo $?

• Hiding logs

If you aren't interested in the output logs then run it with the --showlogs=false override:

# jaas -image alexellis2/cows:latest --showlogs=false

• Removing service after completion

To remove the service after it completes, run with the -rm flag:

# jaas -image alexellis2/href-counter:latest --env url=http://blog.alexellis.io/ --showlogs=true

Service created: peaceful_shirley (uva6bcqyubm1b4c80dghjhb44)
ID:  uva6bcqyubm1b4c80dghjhb44  Update at:  2017-03-14 22:19:54.381973142 +0000 UTC
...

Exit code: 0
State: complete


Printing service logs
?2017-03-14T22:19:55.660902727Z com.docker.swarm.node.id=b2dqydhfavwezorhkqi11f962,com.docker.swarm.service.id=uva6bcqyubm1b4c80dghjhb44,com.docker.swarm.task.id=yruxuawdipz2v5n0wvvm8ib0r {"internal":42,"external":2}

Removing service...

Notes on images

You can have a multi-node swarm but make sure whatever image you choose is available in an accessible registry.

A local image will not need to be pushed to a registry.

• Running jaas in a container

You can also run jaas in a container, but the syntax becomes slightly more verbose:

# docker run -ti -v /var/run/docker.sock:/var/run/docker.sock \
  alexellis2/jaas -image alexellis2/cows:latest

Here are several features / enhancements on the roadmap, please make additional suggestions through Github issues.

• Optionally delete service after fetching exit code/logs
• Support passing environmental variables
• Support private registry auth via -registryAuth flag

Todo:

• Support constraints on where to run tasks
• Support optional secrets through CLI flag
• Validation around images which are not in local library
• Extract stdout/stderr etc from logs in human readable format similar to docker logs

• When task logs are available in the API this will be used instead of service logs.
• When event streams are released they will prevent the need to poll continually