eremetic

Purpose

Eremetic is a Mesos Framework to run one-shot tasks. The vision is to provide a bridge between Applications that need to run tasks and Mesos. That way a developer creating an application that needs to schedule tasks (such as cron) wouldn't need to connect to Mesos directly.

Usage

Send a cURL to the eremetic framework with how much cpu and memory you need, what docker image to run and which command to run with that image.

curl -H "Content-Type: application/json" \
     -X POST \
     -d '{"task_mem":22.0, "task_cpus":1.0, "docker_image": "a_docker_container", "command": "rails"}' \
     http://eremetic_server:8080/task

These basic fields are required but you can also specify volumes, ports, environment variables, and URIs for the mesos fetcher to download. See examples.md for more examples on how to use eremetic.

JSON format:

{
  // Float64, fractions of a CPU to request
  "task_cpus":      1.0,
  // Float64, memory to use (MiB)
  "task_mem":       22.0,
  // String, full tag or hash of container to run
  "docker_image":   "busybox",
  // Boolean, if set to true, docker image will be pulled before each task launch.
  "force_pull_image": false,
  // String, command to run in the docker container
  "command": "echo date",
  // Array of Objects, volumes to mount in the container
  "volumes": [
    {
      "container_path": "/var/run/docker.sock",
      "host_path": "/var/run/docker.sock"
    }
  ],
  // Array of Objects, ports to forward to the container.
  // Assigned host ports are available as environment variables (e.g. PORT0, PORT1 and so on with PORT being an alias for PORT0).
  "ports": [
    {
      "container_port": 80,
      "protocol": "tcp"
    }
  ],
  // Object, Environment variables to pass to the container
  "env": {
    "KEY": "value"
  },
  // Object, Will be merged to `env` when passed to Mesos, but masked when doing a GET.
  // See Clarification of the Masked Env field below for more information
  "masked_env": {
    "KEY": "value"
  },
  // URIs of resource to download
  "uris": [
    "http://server.local/resource"
  ],
  // URIs and attributes of resource to download
  // Please note that `uris` auto-extract archive files based on their extension
  // with `fetch`, you need to explicitly define `"extract"` to unarchive files.
  "fetch": [
    {
      "uri" : "http://server.local/another_resource",
      "extract": false,
      "executable": false,
      "cache": false
    }
  ],
  // Constraints for which slave the task can run on (beyond cpu/memory).
  // Matching is strict and only attributes are currently supported. If
  // multiple constraints exist, they are evaluated using AND (ie: all or none).
  "slave_constraints": [
      {
          "attribute_name": "aws-region",
          "attribute_value": "us-west-2"
      }
  ],
  // String, URL to post a callback to. Callback message has format:
  // {"time":1451398320,"status":"TASK_FAILED","task_id":"eremetic-task.79feb50d-3d36-47cf-98ff-a52ef2bc0eb5"}
  "callback_uri": "http://callback.local"
}

Note

Most of this meta-data will not remain after a full restart of Eremetic.

Clarification of the Masked Env field

The purpose of the field is to provide a way to pass along environment variables that you don't want to have exposed in a subsequent GET call. It is not intended to provide full security, as someone with access to either the machine running Eremetic or the Mesos Slave that the task is being run on will still be able to view these values. These values are not encrypted, but simply masked when retrieved back via the API.

For security purposes, ensure TLS (https) is being used for the Eremetic communication and that access to any machines is properly restricted.

Configuration

create /etc/eremetic/eremetic.yml with:

address: 0.0.0.0
port: 8080
master: zk://<zookeeper_node1:port>,<zookeeper_node2:port>,(...)/mesos
messenger_address: <callback address for mesos>
messenger_port: <port for mesos to communicate on>
loglevel: DEBUG
logformat: json

Database

Eremetic uses a database to store task information. The driver can be configured by setting the database_driver value.

Allowed values are: zk, boltdb

The location of the database can be configured by setting the database value.

BoltDB

The default database that will be used unless anything is configured.

The default value of the database field is db/eremetic.db

ZooKeeper

If you use zk as a database driver, the database field must be provided as a complete zk-uri (zk://zk1:1234,zk2:1234/my/database).

Authentication

To enable mesos framework authentication add the location of credential file to your configuration:

credential_file: /var/mesos_secret

The file should contain the Principal to authenticate and the secret separated by white space like so:

principal    secret_key

Building

Environment

Clone the repository into $GOPATH/src/github.com/klarna/eremetic. This is needed because of internal package dependencies

Install dependencies

First you need to install dependencies. Parts of the eremetic code is auto-generated (assets and templates for the HTML view are compiled). In order for go generate to work, go-bindata and go-bindata-assetfs needs to be manually installed.

go get github.com/jteeuwen/go-bindata/...
go get github.com/elazarl/go-bindata-assetfs/...

All other dependencies are vendored, so it is recommended to run eremetic with Go >= 1.6 or with GO15VENDOREXPERIMENT=1

Creating the docker image

To build a docker image with eremetic, simply run

make docker

Compiling

Run make eremetic

Running on mesos

Eremetic can itself by run on mesos using e.g marathon. An example configuration for marathon is provided that is ready to be submitted through the api.

curl -X POST -H 'Content-Type: application/json' $MARATHON/v2/apps -d@misc/eremetic.json

Running tests

The default target of make builds and runs tests. Tests can also be run by running goconvey in the project root.

Running with minimesos

Using minimesos is a very simple way to test and play with eremetic.

docker run -e MASTER=$MINIMESOS_ZOOKEEPER -e HOST=0.0.0.0 -e DATABASE_DRIVER=zk -e DATABASE=$MINIMESOS_ZOOKEEPER/eremetic -e PORT=8000 -p 8000:8000 alde/eremetic:latest

hermit CLI

hermit is a command-line application to perform operations on a Eremetic server from the terminal.

Contributors

These are the fine folks who helped build eremetic

• Rickard Dybeck
• David Keijser
• Aidan McGinley
• William Strucke
• Charles G.
• Clément Laforet
• Marcus Olsson
• Rares Mirica

Acknowledgements

Thanks to Sebastian Norde for the awesome logo!

Licensing

Apache-2