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910e62b5创建于 1月15日历史提交

Manifest Update Process

High level information: https://web.dev/manifest-updates/

The manifest update process is required whenever a new manifest is served to an existing web_app, which would mean that the database entries corresponding to that web application needs to be updated. To do this, the following steps are kicked off:

  • Whenever the tab has kicked off a navigation to an url for a web_app, a check is kicked off to determine if a manifest update is required or not. The update process is aborted if the following conditions are satisfied:

    • If the app is not installed.
    • If the installed app is a System Web App
    • If the installed app is a placeholder app
    • If there was an existing update already running for a specific app id.
    • If there has already been a manifest update within the past 24 hours. This is done to ensure similar behavior as on Android. This also helps prevent downloading megabytes of images every time a page with a valid manifest link is visited.

  • All pending updates are tracked in a map of update states keyed by app id by the ManifestUpdateManager. If a successful update needs to happen, the process goes ahead by executing the following steps:

    • Wait for the page to finish loading.
    • On successful page load, the ManifestUpdateCheckCommand takes over to perform the following tasks:
      • Fetching manifest data from the site.
      • Loading saved manifest data from disk.
      • Computing the differences between the site and on disk.
      • Resolving changes to identity sensitive fields (app icon and name) by either allowing, requesting user confirmation or reverting changes.
      • For any errors in the above steps or if there are no changes, the whole operation is aborted and the command gracefully exits.
    • Once all the data has been fetched, wait for all existing app windows for that app to close.
    • On all windows being closed, the ManifestUpdateFinalizeCommand runs to write the new data to the DB and verify that a successful write has completed.

Testing