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diff --git a/python/mozperftest/perfdocs/writing.rst b/python/mozperftest/perfdocs/writing.rst new file mode 100644 index 0000000000..2281744852 --- /dev/null +++ b/python/mozperftest/perfdocs/writing.rst @@ -0,0 +1,176 @@ +Performance scripts +=================== + +Performance scripts are programs that drive the browser to run a specific +benchmark (like a page load or a lower level call) and produce metrics. + +We support two flavors right now in `perftest` (but it's easy to add +new ones): + +- **xpcshell** a classical xpcshell test, turned into a performance test +- **browsertime** a browsertime script, which runs a full browser and controls + it via a Selenium client. + +In order to qualify as performance tests, both flavors require metadata. + +For our supported flavors that are both Javascript modules, those are +provided in a `perfMetadata` mapping variable in the module, or in +the `module.exports` variable when using Node. + +This is the list of fields: + +- **owner**: name of the owner (person or team) [mandatory] +- **author**: author of the test +- **name**: name of the test [mandatory] +- **description**: short description [mandatory] +- **longDescription**: longer description +- **options**: options used to run the test +- **supportedBrowsers**: list of supported browsers (or "Any") +- **supportedPlatforms**: list of supported platforms (or "Any") +- **tags** a list of tags that describe the test + +Tests are registered using tests manifests and the **PERFTESTS_MANIFESTS** +variable in `moz.build` files - it's good practice to name this file +`perftest.ini`. + +Example of such a file: https://searchfox.org/mozilla-central/source/testing/performance/perftest.ini + + +xpcshell +-------- + +`xpcshell` tests are plain xpcshell tests, with two more things: + +- the `perfMetadata` variable, as described in the previous section +- calls to `info("perfMetrics", ...)` to send metrics to the `perftest` framework. + +Here's an example of such a metrics call:: + + # compute some speed metrics + let speed = 12345; + info("perfMetrics", { speed }); + + +Browsertime +----------- + +With the browsertime layer, performance scenarios are Node modules that +implement at least one async function that will be called by the framework once +the browser has started. The function gets a webdriver session and can interact +with the browser. + +You can write complex, interactive scenarios to simulate a user journey, +and collect various metrics. + +Full documentation is available `here <https://www.sitespeed.io/documentation/sitespeed.io/scripting/>`_ + +The mozilla-central repository has a few performance tests script in +`testing/performance` and more should be added in components in the future. + +By convention, a performance test is prefixed with **perftest_** to be +recognized by the `perftest` command. + +A performance test implements at least one async function published in node's +`module.exports` as `test`. The function receives two objects: + +- **context**, which contains: + + - **options** - All the options sent from the CLI to Browsertime + - **log** - an instance to the log system so you can log from your navigation script + - **index** - the index of the runs, so you can keep track of which run you are currently on + - **storageManager** - The Browsertime storage manager that can help you read/store files to disk + - **selenium.webdriver** - The Selenium WebDriver public API object + - **selenium.driver** - The instantiated version of the WebDriver driving the current version of the browser + +- **command** provides API to interact with the browser. It's a wrapper + around the selenium client `Full documentation here <https://www.sitespeed.io/documentation/sitespeed.io/scripting/#commands>`_ + + +Below is an example of a test that visits the BBC homepage and clicks on a link. + +.. sourcecode:: javascript + + "use strict"; + + async function setUp(context) { + context.log.info("setUp example!"); + } + + async function test(context, commands) { + await commands.navigate("https://www.bbc.com/"); + + // Wait for browser to settle + await commands.wait.byTime(10000); + + // Start the measurement + await commands.measure.start("pageload"); + + // Click on the link and wait for page complete check to finish. + await commands.click.byClassNameAndWait("block-link__overlay-link"); + + // Stop and collect the measurement + await commands.measure.stop(); + } + + async function tearDown(context) { + context.log.info("tearDown example!"); + } + + module.exports = { + setUp, + test, + tearDown, + owner: "Performance Team", + test_name: "BBC", + description: "Measures pageload performance when clicking on a link from the bbc.com", + supportedBrowsers: "Any", + supportePlatforms: "Any", + }; + + +Besides the `test` function, scripts can implement a `setUp` and a `tearDown` function to run +some code before and after the test. Those functions will be called just once, whereas +the `test` function might be called several times (through the `iterations` option) + + +Hooks +----- + +A Python module can be used to run functions during a run lifecycle. Available hooks are: + +- **before_iterations(args)** runs before everything is started. Gets the args, which + can be changed. The **args** argument also contains a **virtualenv** variable that + can be used for installing Python packages (e.g. through `install_package <https://searchfox.org/mozilla-central/source/python/mozperftest/mozperftest/utils.py#115-144>`_). +- **before_runs(env)** runs before the test is launched. Can be used to + change the running environment. +- **after_runs(env)** runs after the test is done. +- **on_exception(env, layer, exception)** called on any exception. Provides the + layer in which the exception occured, and the exception. If the hook returns `True` + the exception is ignored and the test resumes. If the hook returns `False`, the + exception is ignored and the test ends immediatly. The hook can also re-raise the + exception or raise its own exception. + +In the example below, the `before_runs` hook is setting the options on the fly, +so users don't have to provide them in the command line:: + + from mozperftest.browser.browsertime import add_options + + url = "'https://www.example.com'" + + common_options = [("processStartTime", "true"), + ("firefox.disableBrowsertimeExtension", "true"), + ("firefox.android.intentArgument", "'-a'"), + ("firefox.android.intentArgument", "'android.intent.action.VIEW'"), + ("firefox.android.intentArgument", "'-d'"), + ("firefox.android.intentArgument", url)] + + + def before_runs(env, **kw): + add_options(env, common_options) + + +To use this hook module, it can be passed to the `--hooks` option:: + + $ ./mach perftest --hooks hooks.py perftest_example.js + + |