Sablier is an API that start containers for a given duration.

It provides an integrations with multiple reverse proxies and different loading strategies.

Which allows you to start your containers on demand and shut them down automatically as soon as there's no activity.

• Sablier
  • Quick start with Traefik
  • Reverse proxies integration plugins
    • Traefik
    • Nginx
  • Guides
    • Sablier Guide: Code-Server + Traefik + Kubernetes Ingress
  • Configuration
    • Configuration File
    • Environment Variables
    • Arguments
  • Install Sablier on its own
    • Use the Docker image
    • Use the binary distribution
    • Compile your binary from the sources
  • Loading with a waiting page
    • Dynamic Strategy Configuration
    • Creating your own loading theme
  • Blocking the loading until the session is ready
  • Saving the state to a file
  • Sablier Healthcheck
    • Using the /health route
    • Using the sablier health command
  • API
    • GET /api/strategies/dynamic
    • GET /api/strategies/blocking
  • Glossary
  • Versioning
  • Credits

You will see how to use Sablier with Traefik in order to start your container automatically when reaching it by its route.

git clone https://github.com/acouvreur/sablier
cd sablier
docker-compose up -d
docker-compose stop whoami

# Now you go to http://localhost:8080/whoami/dynamic with your browser
# Or you can call the blocking URL, this will wait until whoami is started
curl http://localhost:8080/whoami/blocking

Hostname: 1d034329b651
IP: 127.0.0.1
IP: 172.18.0.2
RemoteAddr: 172.18.0.4:33052
GET /whoami/blocking HTTP/1.1
Host: localhost:8080
User-Agent: curl/7.68.0
Accept: */*
Accept-Encoding: gzip
X-Forwarded-For: 172.18.0.1
X-Forwarded-Host: localhost:8080
X-Forwarded-Port: 8080
X-Forwarded-Proto: http
X-Forwarded-Server: 1aea141808c5
X-Real-Ip: 172.18.0.1

The reverse proxy integrations is probably what you're most interested about.

It leverage the API calls to Sablier to your reverse proxy middleware to wake up your instances on demand.

See Traefik Middleware Plugin

• Traefik Middleware Plugin with Docker classic
• Traefik Middleware Plugin with Docker Swarm
• Traefik Middleware Plugin with Kubernetes

See Nginx Middleware Plugin

See Sablier Guide: Code-Server + Traefik + Kubernetes Ingress

There are three different ways to define configuration options in Sablier:

1. In a configuration file
2. As environment variables
3. In the command-line arguments

These ways are evaluated in the order listed above.

If no value was provided for a given option, a default value applies.

At startup, Sablier searches for configuration in a file named sablier.yml (or sablier.yaml) in:

• /etc/sablier/
• $XDG_CONFIG_HOME/
• $HOME/.config/
• . (the working directory).

You can override this using the configFile argument.

sablier --configFile=path/to/myconfigfile.yml

provider:
  # Provider to use to manage containers (docker, swarm, kubernetes)
  name: docker 
server:
  # The server port to use
  port: 10000 
  # The base path for the API
  base-path: /
storage:
  # File path to save the state (default stateless)
  file:
sessions:
  # The default session duration (default 5m)
  default-duration: 5m
  # The expiration checking interval. 
  # Higher duration gives less stress on CPU. 
  # If you only use sessions of 1h, setting this to 5m is a good trade-off.
  expiration-interval: 20s
logging:
  level: trace
strategy:
  dynamic:
    # Custom themes folder, will load all .html files recursively (default empty)
    custom-themes-path:
    # Show instances details by default in waiting UI
    show-details-by-default: false
    # Default theme used for dynamic strategy (default "hacker-terminal")
    default-theme: hacker-terminal
    # Default refresh frequency in the HTML page for dynamic strategy
    default-refresh-frequency: 5s
  blocking:
    # Default timeout used for blocking strategy (default 1m)
    default-timeout: 1m

All environment variables can be used in the form of the config file such as

strategy:
  dynamic:
    custom-themes-path: /my/path

Becomes

STRATEGY_DYNAMIC_CUSTOM_THEMES_PATH=/my/path

To get the list of all available arguments:

sablier --help

# or

docker run acouvreur/sablier[:version] --help
# ex: docker run acouvreur/sablier:1.3.0 --help

All arguments can be used in the form of the config file such as

strategy:
  dynamic:
    custom-themes-path: /my/path

Becomes

sablier start --strategy.dynamic.custom-themes-path /my/path

You can install Sablier with the following flavors:

• Use the Docker image
• Use the binary distribution
• Compile your binary from the sources

• Docker Hub: acouvreur/sablier
• Github Container Registry: ghcr.io/acouvreur/sablier

Choose one of the Docker images and run it with one sample configuration file:

• sablier.yaml

docker run -d -p 10000:10000 \
    -v $PWD/sablier.yml:/etc/sablier/sablier.yml acouvreur/sablier:1.3.0

Grab the latest binary from the releases page.

And run it:

./sablier --help

git clone git@github.com:acouvreur/sablier.git
cd sablier
make
# Output will change depending on your distro
./sablier_draft_linux-amd64

The Dynamic Strategy provides a waiting UI with multiple themes. This is best suited when this interaction is made through a browser.

Name	Preview
ghost
shuffle
hacker-terminal
matrix

strategy:
  dynamic:
    # Custom themes folder, will load all .html files recursively (default empty)
    custom-themes-path:
    # Show instances details by default in waiting UI
    show-details-by-default: false
    # Default theme used for dynamic strategy (default "hacker-terminal")
    default-theme: hacker-terminal
    # Default refresh frequency in the HTML page for dynamic strategy
    default-refresh-frequency: 5s

See creating your own theme.

The Blocking Strategy waits for the instances to load before serving the request This is best suited when this interaction from an API.

strategy:
  blocking:
    # Default timeout used for blocking strategy (default 1m)
    default-timeout: 1m

You can save the state of the application in case of failure to resume your sessions.

For this you can use the storage configuration.

storage:
  file: /path/to/file.json

If the file doesn't exist it will be created, and it will be syned upon exit.

Loaded instances that expired during the restart won't be changed though, they will simply be ignored.

You can use the route /health to check for healthiness.

• Returns 200 OK when ready
• Returns 503 Service Unavailable when terminating

You can use the command sablier health to check for healthiness.

sablier health takes on argument --url which defaults to http://localhost:10000/health.

services:
  sablier:
    image: acouvreur/sablier:1.3.0
    healthcheck:
      test: ["sablier", "health"]
      interval: 1m30s

To run the following examples you can create two containers:

• docker create --name nginx nginx
• docker create --name apache httpd

Description: The /api/strategies/dynamic endpoint allows you to request a waiting page for multiple instances

Go to http://localhost:10000/api/strategies/dynamic?names=nginx&names=apache&session_duration=5m&show_details=true&display_name=example&theme=hacker-terminal&refresh_frequency=10s and you should see

A special header X-Sablier-Session-Status is returned and will have the value ready if all instances are ready. Or else not-ready.

Description: The /api/strategies/blocking endpoint allows you to wait until the instances are ready

A special header X-Sablier-Session-Status is returned and will have the value ready if all instances are ready. Or else not-ready.

Curl example

curl -X GET -v "http://localhost:10000/api/strategies/blocking?names=nginx&names=apache&session_duration=5m&timeout=5s"
*   Trying 127.0.0.1:10000...
* Connected to localhost (127.0.0.1) port 10000 (#0)
> GET /api/strategies/blocking?names=nginx&names=apache&session_duration=5m&timeout=30s HTTP/1.1
> Host: localhost:10000
> User-Agent: curl/7.74.0
> Accept: */*
> 
* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< Content-Type: application/json; charset=utf-8
< X-Sablier-Session-Status: ready
< Date: Mon, 14 Nov 2022 19:20:50 GMT
< Content-Length: 245
< 
{"session":
  {"instances":
    [
      {"instance":{"name":"nginx","currentReplicas":1,"desiredReplicas":1,"status":"ready"},"error":null},
      {"instance":{"name":"apache","currentReplicas":1,"desiredReplicas":1,"status":"ready"},"error":null}
    ],
    "status":"ready"
  }
}

I'll use these terms in order to be provider agnostic.

• Session: A Session is a set of instances
• Instance: An instance is either a docker container, docker swarm service, kubernetes deployment or kubernetes statefulset

Sablier follows the Semantic Versioning 2.0.0 Specification (SemVer).

Given a version number MAJOR.MINOR.PATCH, increment the:

1. MAJOR version when you make incompatible API changes
2. MINOR version when you add functionality in a backwards compatible manner
3. PATCH version when you make backwards compatible bug fixes

Additional labels for pre-release and build metadata are available as extensions to the MAJOR.MINOR.PATCH format.

This process is fully automated using Semantic Release.

The configuration is release.config.js.

• Hourglass icons created by Vectors Market - Flaticon
• tarampampam/error-pages for the themes