Telemetry: Record a Page Set

We record page sets so we control network conditions and other changes in the live sites, leading to more stable benchmarks.

Write a page set

Before you can record a page set, you need to write it! If you want to record a pre-existing page set, you can skip this step.

Page sets are located in tools/perf/page_sets. A simple page set with one URL looks like:

from import page from import page_set class MyPageSet(page_set.PageSet): def __init__(self): super(MyPageSet, self).__init__( user_agent_type='desktop', archive_data_file='data/my_page_set.json', bucket=page_set.PUBLIC_BUCKET) self.AddPage(page.Page( name='example', url='', page_set=self))

Telemetry spoofs Chrome's User-Agent field, and user_agent_type tells it whether to use a desktop, mobile, or tablet user agent. We generally only use one recording for all platforms.

The archive_data_file contains metadata about which pages are stored in which archive files. You need to specify its location, and it will be generated when recording the page set.

Note that the naming convention of page set file is to lowercase & underscore class name, e.g. MyPageSet should be stored as

Choosing a bucket

Telemetry has three Cloud Storage buckets you can put page sets in.

  • page_set.PUBLIC_BUCKET == 'chromium-telemetry'
  • page_set.PARTNER_BUCKET == 'chrome-partner-telemetry'
  • page_set.INTERNAL_BUCKET == 'chrome-telemetry'

Google wants to avoid legal issues with distributing third-party content, so to be safe, most recordings of websites on the public web go in PARTNER_BUCKET, which is accessible by Googlers and whitelisted Google partners. Recordings of Google-properties on the public web can go in PUBLIC_BUCKET, and recordings of unreleased or internal Google websites go in INTERNAL_BUCKET.

Record a page set

Use the record_wpr script to record a page set. Your command will look something like this:

src$ tools/perf/record_wpr --browser=(release|system) <page_set_name>_page_set

For example, to record the page set, specify top25_smooth_page_set:

src$ tools/perf/record_wpr --browser=system top25_smooth_page_set

To update the recording for only some pages in the page set, use --page-filter. This command will record only Wikipedia pages:

src$ tools/perf/record_wpr --browser=system --page-filter=wikipedia top25_smooth_page_set

record_wpr generates a few files:

  • A .wpr file containing the recorded data. This file is hidden from git status, which we'll explain next.
  • A .wpr.sha1 file containing the SHA1 hash of the .wpr file.
  • A .json file containing metadata about which .wpr files store which URLs.

Upload the recording to Cloud Storage

To avoid bloating everyone's Chromium checkouts, we avoid committing the large .wpr files to source control. Instead, we upload them to Cloud Storage and download them as needed. If you just want to use your recording locally, you can skip this step.

If you haven't already, you may need to set up Cloud Storage.

To do this, check in only the .sha1 and .json files. When you run git cl upload, a PRESUBMIT script will upload the .wpr file to Google Storage.

To upload manually, use:

src$ depot_tools/ --bucket chromium-telemetry tools/perf/page_sets/data/my_page_set_000.wpr

Moving recordings between Cloud Storage buckets

Sometimes the addition or removal of pages changes the permission of the page set, or the page set archives are in the wrong bucket. To move files between buckets, use this command:

src$ tools/telemetry/cloud_storage mv tools/perf/page_sets/data/my_page_set_*.wpr (public|partner|google-only)

What is Web Page Replay?

Web Page Replay is a service that allows us to capture and store HTTP requests and responses.

Ethan Kuefner,
Feb 10, 2015, 11:21 AM