Synthetics

Synthetic monitoring allows testing the availability and response time of a service from the perspective of an end user, including any latencies introduced by edge caching and API gateways. They're a good means of ensuring that a service is meeting performance targets. Synthetics Monitoring: Are You Cyber Monday Ready? offers a good introduction to the service.

Types

New Relic provides four types of synthetic monitors:

• Ping tests (SIMPLE) simply execute a HEAD (or GET) request for a given URL and check the response status, and optionally look a string in the response body. Redirects can be considered failures if desired. They can be used to verify the validity of an SSL certificate.
• Simple Browser (BROWSER) tests execute in Chrome, thus also fetch assets embedded in the response body and providing a more complete approximation of an end-user's experience.
• Scripted Browser (SCRIPT_BROWSWER) allows you to execute a more complex test against a Chrome browser instance via Selenium WebDriver, allowing you to simulate a series of requests.
• API Test (SCRIPT_API) execute tests against API endpoints, also against Chrome via WebDriver.

In all cases you're able to select the regions in which the synthetics clients should be located and a schedule with frequency between 1 minute and 1 day.

API

The API can be briefly summarised as:

• $browser, which exposes methods for driving the browser and working with the response data:
  • These methods return promises, which can be chained to perform requests in series:
    • get(url: string)
  • findElement()
• $driver
  • By:
    • className(className: string)
    • id(id: string)
    • name(name: string)
    • xpath(selector: string)
    • linkText(text: string)
    • partialLinkText(text: string)
• $env
• $secure