Updater

A tiny update manager.

Purpose

Updater checks whether an app (specified by a small JSON file) has any pending updates (specified by a remote API). If there are updates pending, updater will download those updates, validate the download and install them into place.

Filesystem layout

Apps

updater expects apps to exist in the filesystem in a specific way.

A single invocation of updater check will check a specific directory on the filesystem, given by the --target argument.

Apps must exist in a subdirectory directoy below the target

An app must contain a releases directory containing a subdirectory for each release. A symlink named current points to the current release directory.

For example:

/opt/apps
  |
  +— magic-button
  |     |
  |     +— current -> ../releases/123451234
  |     |
  |     +— releases
  |         |
  |         +— 123451234
  |         |    |
  |         |    +- .deploy
  |         |
  |         +— 123451231
  |             |
  |             +- .deploy
  |
  +— not-a-valid-app
        |
        +— src
        +— bin

updater will ignore directories that do not match this layout.

.deploy file

Each release must contain a .deploy file containing the following JSON:

{
  "name": "radiodan/magic-button",
  "ref": "master",
  "commit": "d0ab003502b32510f8acd1c94b4b41664be6884"
}

Workspace

updater manages downloads in a workspace directory that you specify. This workspace should be the same on each invocation.

The workspace contains:

• downloads downloaded packages
• manifests JSON files specifying downloaded files
• status.json info about updater's workings

Remote API

updater compares the installed list of releases with a remote API.

The API should contain a single endpoint that returns JSON about the latest releases.

For example:

{
  "radiodan/magic-button": {
    "master": {
      "commit": "68200ec154d6dbdcc648e5706bb860c57b7fb621",
      "file": "http://example.com/radiodan/magic-button/magic-button-master-68200e.tar.gz",
      "sha1": "0e8ff998e905a2cfa5a4d15afe68622e3db24b72",
      "updated": "2014-10-29T19:30:54.095Z"
    },
    "radiotag": {
      "commit": "307c9c98dd229ba770ee3ad025ffa069bc860e61",
      "file": "http://example.com/radiodan/magic-button/magic-button-radiotag-307c9c.tar.gz",
      "sha1": "7f6566b8708a5f966cf6bfc9d125bd8365314bdb",
      "updated": "2014-10-09T14:14:17.322Z"
    }
  },
  "radiodan/physical-ui": {
    "master": {
      "commit": "d377b9a030c61ef803bc8ff8a5c8732b1d655427",
      "file": "http://example.com/radiodan/physical-ui/physical-ui-master-d377b9.tar.gz",
      "sha1": "6e149e6a098e30ce87adf87e36279637ccd42e2e",
      "updated": "2014-10-20T12:39:02.394Z"
    }
  }
}

This JSON represents two applications called radiodan/magic-button and radiodan/physical-ui. radiodan/magic-button contains two refs called master and radiotag.

Checking for updates

$ updater check --target=/opt/apps --workspace=/opt/updates

1. updater scans target directory for a list of apps with .deploy files
2. Requests the latest versions of apps from the remote API
3. Finds apps that have matching names and refs
4. Compares latest commits against deployed commits
5. If different, downloads the archive specified by file to the workspace
6. Terminates

Installing downloaded updates

$ updater install --target=/opt/apps --workspace=/opt/updates

1. updater scans workspace directory for downloaded updates
2. Validates each archive against it's SHA1
3. Installs as a new release in the app's directory
4. Symlinks the new release as current

Installation

updater is written in Go and must be compiled for each target platform. If you have a binary, just copy the single updater binary into /usr/local/bin.

License

See LICENSE

Copyright

Copyright 2014 British Broadcasting Corporation