CLI for running jobs (ad-hoc containers/tasks) on Docker Swarm
Go Makefile
Clone or download
alexellis Update secret example
Secret example now uses Alpine to show how to access/cat a secret
for use in a script for example. Name of secret changed to
practical example and created via stdin. Tested on Swarm/MacOS.

Signed-off-by: Alex Ellis <>
Latest commit 4d19113 Jul 1, 2018

Jobs as a Service (JaaS)

A CLI for running jobs (ad-hoc containers/tasks) on Docker Swarm

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 Docker daemon API version is greater than 1.29 or if the experimental feature is enabled on the Docker daemon.

Build Status

Motivation and context

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

See also: Serverless

If you would like to build Serverless applications with Docker Swarm or Kubernetes checkout my write-up on OpenFaaS:

The OpenFaaS project has dozens of contributors and thousands of GitHub stars - if you're here because you want to run short-lived functions then I highly recommend checking out OpenFaaS now.

Contributions are welcome

See the contributing guide and do not raise a PR unless you've read it all.

Get started

Build and install the code


  • Docker 1.13 or newer (experimental mode must be enabled if accessing service logs with Docker versions >= 1.13 and < 1.29)
  • Go 1.9.2 (or Golang container)
  • Enable Swarm Mode (docker swarm init)

Run these commands

# export GOPATH=$HOME/go
# go get -d -v
# cd $GOPATH/src/
# go install
# export PATH=$PATH:$GOPATH/bin

Now test jaas with jaas --help

Running a task / batch job / one-shot container

  • Run your first one-shot container with jaas run:
# jaas run -r --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 --show-logs=false override:

# jaas run --image alexellis2/cows:latest --show-logs=false
  • Override the command of the container:
# jaas run -r --image alpine:3.6 --command "uname -a"

Printing service logs
w2018-02-06T13:40:00.131678932Z Linux f56d298c4ab9 4.9.75-linuxkit-aufs #1 SMP Tue Jan 9 10:58:17 UTC 2018 x86_64 Linux
  • Removing service after completion

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

# jaas run --image alexellis2/href-counter:latest --env url=

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,, {"internal":42,"external":2}

Removing service...
  • Docker authentication for registries

You can use jaas with Docker images in private registries or registries which require authentication.

Just run docker login then pass the --registry parameter and the encoded string you find in ~/.docker/config.json.

If you want to encode a string manually then do the following:

$ export auth='{
    "username" : "myUserName",
    "password" : "secret",
    "email" : "my@email",
    "serveraddress" : "my.reg.domain"
$ jaas run --registry="`echo $auth | base64`" --image my.reg.domain/hello-world:latest
  • Adding secret to service

To give the service access to an existing secret. run with the --secret or -s flag:

$ echo -n "S3_ACCESS_KEY_HERE" | docker secret create s3-access-key -
$ jaas run --image alpine:3.7 --secret s3-access-key --command "cat /run/secrets/s3-access-key"

Service created: priceless_tesla (f8gheat9f3b8cnnsjy9dth9y7)
ID:  f8gheat9f3b8cnnsjy9dth9y7  Update at:  2018-06-29 16:41:13.723257461 +0000 UTC

Exit code: 0
State: complete

Printing service logs
(2018-06-29T16:41:19.057738088Z S3_ACCESS_KEY_HERE

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 run --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
  • Move to cobra flags/args package for CLI
  • Support constraints on where to run tasks
  • Bind-mounting volumes
  • Overriding container command


  • 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