crow-metrics-viz

Viz is a small plugin for crow-metrics that exposes your server's metrics over HTTP using express. It collects snapshots over a rolling window (one hour, by default) and graphs this data on a web page.

Usage

There are two ways to construct the service:

• viz(metrics: Metrics, options: VizOptions = {}): express.Router

  Create an express router that will respond to a path with the viz interface. This is useful if your server is already using express for other requests.

  • express - the express module or a compatible one
  • metrics - a crow Metrics object
  • options - passed to the RingBuffer:
    • span: number - how many milliseconds to buffer (default is one hour, or 3600 * 1000)
    • prometheus: boolean - if true, a prometheus document will be hosted at /metrics

  For example:

  const express = require("express");
  const { Metrics } = require("crow-metrics");
  const { viz } = require("crow-metrics-viz");
  
  const app = express();
  const metrics = Metrics.create();
  app.use("/admin/viz", viz(express, metrics));

  This will add the viz paths under /admin/viz on your express server.

• startVizServer(metrics: Metrics, port: number = 8080, options: VizOptions = {})

  Start up the viz site on a devoted port with a new instance of express.

  For example:

  const { Metrics } = require("crow-metrics");
  const { startVizServer } = require("crow-metrics-viz");
  
  const metrics = Metrics.create();
  startVizServer(metrics, 9090);

  This will create a page at http://localhost:9090/.

Paths

• /

  A small webpage that loads the content from /history.json and draws an SVG graph for each one. This is meant to give a quick human-readable overview of the server instance's metrics.

• /current.json

  A JSON object where each key is the name of a metric, and each value is its current value.

• /history.json

  A JSON object where each key is the name of a metric, and each value is an array of the metric's values over the past hour (or whatever span you configured), in order from oldest to newest. A special key "@timestamp" gives an array of the corresponding timestamps for these values, in epoch seconds.

• /metrics

  A prometheus-formatted plaintext metrics snapshot, if requested in options.

License

Apache 2 (open-source) license, included in LICENSE.txt.

Authors

@robey - Robey Pointer robeypointer@gmail.com