When does a progressive web app update on making a change to its manifest file?

问题

I have a progressive web app and I wish to make changes to its manifest file like a change to its start_url, scope, icon, name and short_name. I wish to know, when is it that the updates to the progressive web app take place after making a change to its manifest? I tried the following to force update the web app on Chrome browser:

• Launch WebAPK
• Close the WebAPK
• Modify the Web Manifest
• Advance Android's system time by 3 days. On my device: Settings>System>Date & Time>Set date
• Launch WebAPK, wait a few seconds
• Run adb shell dumpsys jobscheduler | JOB.*91.*org.chromium.components.background_task_scheduler.BackgroundTaskJobService
• Check that the output is not empty
• Close the WebAPK
• Run adb shell cmd jobscheduler run -f com.android.chrome 91 to force an update

However, I wish to know what is the real criteria for update to the web app after a change to the manifest file is done? Please can someone attach a code snippet supporting the same, which may be specific to how Chrome implements it?

回答1:

I did a deep dive, to know what exactly is the criteria for update of web app on changes to manifest file and I was able to find the relevant source code in the chromium code base which had the update logic. According to the latest chromium source code changes https://chromium-review.googlesource.com/c/chromium/src/+/1635860 , the update interval is set to 1 day (99% cases, where the apps may update more frequently) and 30 days (1% cases where the apps may update less frequently). Previously, it was set to 3 days ( 99% cases) and 30 days ( 1% cases). Also, there is an official documentation by Google https://developers.google.com/web/fundamentals/integration/webapks#update-webapk which says :

Chrome will periodically compare the locally installed manifest against a copy of the manifest fetched from the network. If any of the properties in the manifest required to add the PWA to the home screen have changed in the network copy, Chrome will request an updated WebAPK, reflecting those new values. There are a number of rules that govern how these update checks are triggered:

• Update checks only happen when a WebAPK is launched. Launching Chrome directly will not a trigger an update check for a given WebAPK.
• Chrome checks for updates either every 1 day or every 30 days. Checking for updates every day happens the large majority of the time. It switches to the 30 day interval in unlikely cases where the update server cannot provide an update.
• Clearing Chrome's data (via "CLEAR ALL DATA" in Android settings) resets the update timer.
• Chrome will only update a WebAPK if the Web Manifest URL does not change. If you change the web page from referencing /manifest.json to reference /manifest2.json, the WebAPK will no longer update. (Don't do this!)
• Chrome will only update a WebAPK if the WebAPK is not running. Moving the WebAPK to the background is not sufficient if it keeps running.
• Only WebAPKs created by an official version of Chrome (Stable/Beta/Dev/Canary) will be updated. It does not work with Chromium (org.chromium.chrome).
• The update check may be delayed until the device is plugged in and has a WiFi connection.

Validated the same already.

The code flow responsible for this update is given by follows :

• Whenever, there is an update to the manifest file at the same origin, an update task is scheduled in the background service by the WebApkUpdateTask the link of which is given as follows : https://cs.chromium.org/chromium/src/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebApkUpdateTask.java .
• This update task is managed by the WebApkUpdateManager , the link of which is as follows : https://cs.chromium.org/chromium/src/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebApkUpdateManager.java?sq=package:chromium&dr=CSs&g=0
• The check for updates interval is done by the WebappDataStorage , the link of which is as follows : https://chromium.googlesource.com/chromium/src/+/652f0ba0d8d29ba7508654bf20172d3c83a784fb/chrome/ android/java/src/org/chromium/chrome/browser/webapps/WebappDataStorage.java (https://chromium.googlesource.com/chromium/src/+/652f0ba0d8d29ba7508654bf20172d3c83a784fb/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappDataStorage.java)

来源：https://stackoverflow.com/questions/59676685/when-does-a-progressive-web-app-update-on-making-a-change-to-its-manifest-file