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');

Operation

Capture Server: ~/legion/legion-capture> npm start

Testcase Stats Collection: ~/legion/legion>node testcase.js -n 100 --capture-endpoint http://localhost:8000 --capture-interval 5

Reference

capture.client

The client API.

capture.client.create(endpoint)

Create a client.

• endpoint - the URL of the capture server

capture.client.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

capture.client.prototype.postMetrics(project_key, sample)

Post a new metrics item to the capture server. A metrics item is an object that supports the summarize() method, such as the objects created by sample() or problem() in the legion-metrics library.

• project_key - the unique identifier for a project
• sample - a summarizable metrics sample object

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 from a client 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