weave-scope/examples/plugins/README.md

Scope Plugins

Protocol

All plugins should listen for HTTP connections on a unix socket in the /var/run/scope/plugins directory. The scope probe will recursively scan that directory every 5 seconds, to look for sockets being added (or removed). It is also valid to put the plugin unix socket in a sub-directory, in case you want to apply some permissions, or store other information with the socket.

When a new plugin is detected, the scope probe will begin requesting reports from it via GET /report.

All plugin endpoints are expected to respond within 500ms, and respond in the JSON format.

For more information see the example plugins.

Report

When the scope probe discovers a new plugin unix socket it will begin periodically making a GET request to the /report endpoint. The report data structure returned from this will be merged into the probe's report and sent to the app. An example of the report structure can be viewed at the /api/report endpoint of any scope app.

In addition to any data about the topology nodes, the report returned from the plugin must include some information about the plugin.

For example:

{
  "Processes: { ... },
  ...
  "Plugins": [
    {
      "id":          "iowait",
      "label":       "IOWait",
      "description": "Adds a graph of CPU IO Wait to hosts",
      "interfaces":  ["reporter"],
      "api_version": "1",
    }
  ]
}

Note that the "Plugins" section includes exactly one plugin description. The plugin description fields are: "interfaces" including "reporter".

The fields are:

• id is used to check for duplicate plugins. It is required.
• label is a human readable plugin label displayed in the UI. It is required.
• description is displayed in the UI
• interfaces is a list of interfaces which this plugin supports. It is required, and must equal ["reporter"].
• api_version is used to ensure both the plugin and the scope probe can speak to each other. It is required, and must match the probe.

Interfaces

Currently the only interface a plugin can fulfill is reporter.