Legion Capture

Legion-capture is a library and executable that captures statistical data from external sources. This package contains both the client and server components.

capture = require('legion-capture');

Reference

capture.client.loki

A loki.js implementation of a metrics database. Conforms to the same API as the capture.client.remote.

capture.client.remote

The client API.

capture.client.remote.create(endpoint)

Create a client.

• endpoint - the URL of the capture server

capture.client.remote.prototype.getMetrics(filter)

Get a statistical summary of all metrics that satisfy the given filter.

• filter - a query filter with the following fields:
  • project_key - the unique identifier for a project

Returns a promise containing:

• data - the blob of metrics
• metadata - various metadata, including:
  • project_key - the unique identifier for a project
  • min_timestamp - the starting timestamp of the metrics capture
  • max_timestamp - the ending timestamp of the metrics capture

capture.client.remote.prototype.postMetrics(blob)

Post a new metrics item to the capture server.

• blob - A JSON object containing:
  • data - the blob of metrics
  • metadata - various metadata, including:
    • project_key - the unique identifier for a project
    • min_timestamp - the starting timestamp of the metrics capture
    • max_timestamp - the ending timestamp of the metrics capture

capture.server

The server API.

capture.server.metrics()

Returns an Express.js middleware which responds to requests to 'metrics/'. This middleware requires body-parser.

capture.server.listen(...)

Starts the capture server. Accepts the same parameters as .listen() on any express app.

capture.Target

The capturing Target is an instance of the metrics Target from legion-metrics. It adds the behavior to push metrics to a capture server at regular intervals. As part of each push, the Target is 'clear()ed.' This means that such a Target will only contain the metrics for the current interval.

If you manually clear() a capturing Target, any metrics so cleared will not be pushed to the capture server. Likewise, if you get() the metrics from a capturing Target, you will only see the metrics captured so far during the current interval.

capture.Target.create(merge, endpoint, interval)

Create a capturing metrics Target.

Metrics will be streamed to the endpoint at regular intervals. Networking to the endpoint must be reliable, or data loss will occur.

• merge - the merge algorithm object, usually just require('legion-metrics').merge
• endpoint - the URL of the metrics collection endpoint
• interval - the collection interval in milliseconds