The Web Site Assets are statically stored in the Browser. They are loaded into the

On each Page Refresh the Service Worker is polled for

Recognizing Service Worker Updates about plack-pwa-web HOT 5 CLOSED

bodo-hugo-barwich commented on August 11, 2024

Recognizing Service Worker Updates

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Comments (5)

bodo-hugo-barwich commented on August 11, 2024

On each Page Refresh the Service Worker Script is polled for Updates.

127.0.0.1 - - [16/May/2021:23:15:23 +0100] "GET /service-worker HTTP/1.1" 200 - "-" "Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0"

When the Browser finds that the script has changed it creates a new Instance of the Service Worker which is on hold for the Take Over.
When the Take Over is not executed the new Service Worker won't become active and the old version will continue to run forever.

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bodo-hugo-barwich commented on August 11, 2024

Introducing a ServiceWorker Version and the Version Check with doCheckVersion() it shows clearly that the Web Site is working with a different and outdated Version of the ServiceWorker:

{"version":"0.0.1","cache":"dev-coffee-site-0.0.1","client_id":"189695f1-6bc2-421e-89db-b23222511b96"}
Version: '0.0.1'

While when downloading the ServiceWorker Script it shows that the Version was already changed:

$ wget -S -O - http://localhost:3000/service-worker |grep -i sversion
--2021-05-23 13:12:24--  http://localhost:3000/service-worker
Resolviendo localhost (localhost)... ::1, 127.0.0.1
Conectando con localhost (localhost)[::1]:3000... falló: Conexión rehusada.
Conectando con localhost (localhost)[127.0.0.1]:3000... conectado.
Petición HTTP enviada, esperando respuesta... 
  HTTP/1.0 200 OK
  Content-Type: text/javascript
Longitud: no especificado [text/javascript]
Grabando a: “STDOUT”

-                            [<=>                                ]       0  --.-KB/s               var sversion = "0.0.2";
var staticDevCoffee = "dev-coffee-site-" + sversion;
            version: sversion
-                            [ <=>                               ]   2,82K  --.-KB/s    en 0,008s  

2021-05-23 13:12:24 (346 KB/s) - escritos a stdout [2890]

This becomes clear when looking on the ServiceWorkerRegistration Object that holds 2 different Instances of the ServiceWorker the old active ServiceWorker and the new waiting ServiceWorker

Service worker registration succeeded: 
ServiceWorkerRegistration { installing: null, waiting: ServiceWorker, active: ServiceWorker, scope: "http://localhost:3000/", updateViaCache: "imports", onupdatefound: null, pushManager: PushManager }
app.js:28:11
Service Worker installed 1: 
ServiceWorkerRegistration { installing: null, waiting: ServiceWorker, active: ServiceWorker, scope: "http://localhost:3000/", updateViaCache: "imports", onupdatefound: null, pushManager: PushManager }
app.js:37:11

The current ServiceWorker Version is polled from the active Instance:

doCheckVersion - go ... app.js:121:11
doCheckVersion - ServiceWorkerRegistration:  
ServiceWorkerRegistration { installing: null, waiting: ServiceWorker, active: ServiceWorker, scope: "http://localhost:3000/", updateViaCache: "imports", onupdatefound: null, pushManager: PushManager }
app.js:122:11
Version - registration.active (object):  
ServiceWorker { scriptURL: "http://localhost:3000/service-worker", state: "activated", onstatechange: null, onerror: null }
app.js:126:13
Version - registration.installing (object):  null app.js:127:13
doCheckVersion - Request posting ... app.js:139:13
Got Message:  
message { target: ServiceWorkerContainer, isTrusted: true, data: {…}, origin: "http://localhost:3000", lastEventId: "", source: ServiceWorker, ports: Restricted, srcElement: ServiceWorkerContainer, currentTarget: ServiceWorkerContainer, eventPhase: 2, … }
app.js:197:11
Message: Version Number '0.0.1' app.js:217:15

The OnUpdateFound Event is not triggered because it happens when the new instance is created.

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bodo-hugo-barwich commented on August 11, 2024

The ServiceWorkerRegistration state logged to the Browser Console shows that when there isn't a ServiceWorker registered in the System yet the active Property is still null.

Service worker registration succeeded: 
ServiceWorkerRegistration { installing: ServiceWorker, waiting: null, active: null, scope: "http://localhost:3000/", updateViaCache: "imports", onupdatefound: null, pushManager: PushManager }
app.js:28:11
Service Worker installed 1: 
ServiceWorkerRegistration { installing: ServiceWorker, waiting: null, active: null, scope: "http://localhost:3000/", updateViaCache: "imports", onupdatefound: null, pushManager: PushManager }
app.js:40:11

So the ServiceWorker in the installing Property will become the active ServiceWorker once the installation is completed.

It is also noticeable that the installing ServiceWorker is still unresponsive to any Message Posts:

doCheckVersion - go ... app.js:81:11
doCheckVersion - ServiceWorkerRegistration:  
ServiceWorkerRegistration { installing: ServiceWorker, waiting: null, active: null, scope: "http://localhost:3000/", updateViaCache: "imports", onupdatefound: null, pushManager: PushManager }
app.js:82:11
Version - registration.active (object):  null app.js:86:13
Version - registration.installing (object):  
ServiceWorker { scriptURL: "http://localhost:3000/service-worker", state: "installing", onstatechange: null, onerror: null }
app.js:87:13
doCheckVersion - Request posting ... app.js:99:13

So for the Update Detection a requirement must be that there is already an active ServiceWorker instance:

doCheckUpdate - go ... app.js:129:11
doCheckUpdate - ServiceWorkerRegistration:  
ServiceWorkerRegistration { installing: ServiceWorker, waiting: null, active: null, scope: "http://localhost:3000/", updateViaCache: "imports", onupdatefound: null, pushManager: PushManager }
app.js:130:11
Update - registration.installing (object):  
ServiceWorker { scriptURL: "http://localhost:3000/service-worker", state: "installing", onstatechange: null, onerror: null }
app.js:134:13
Update - registration.waiting (object):  null app.js:135:13
Service Worker Update detected! app.js:150:13

In the moment of installation the OnUpdateFound Event is triggered, but on a newly registered ServiceWorker the object was already moved ahead to the active Property of the ServiceWorkerRegistration

Got Update:  
updatefound { target: ServiceWorkerRegistration, isTrusted: true, srcElement: ServiceWorkerRegistration, currentTarget: ServiceWorkerRegistration, eventPhase: 2, bubbles: false, cancelable: false, returnValue: true, defaultPrevented: false, composed: false, … }
app.js:173:11
doCheckUpdate - go ... app.js:129:11
doCheckUpdate - ServiceWorkerRegistration:  
ServiceWorkerRegistration { installing: null, waiting: null, active: ServiceWorker, scope: "http://localhost:3000/", updateViaCache: "imports", onupdatefound: null, pushManager: PushManager }
app.js:130:11
Update - registration.installing (object):  null app.js:134:13
Update - registration.waiting (object):  null app.js:135:13
Update: No Update waiting. app.js:144:15

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bodo-hugo-barwich commented on August 11, 2024

This development introduces a Version Poll Logic which polls the ServiceWorker for it's Version and shows it on page.

In this Logic the Limitation was observed that when the ServiceWorker is still installing it is unresponsive and does not process the submitted messages.

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bodo-hugo-barwich commented on August 11, 2024

About the static assets there was a Limitation observed that the Browser does not request the Server when it populates the ServiceWorker Cache.
The Web Service Logs show that the assets were not requested from the Server only certain assets and the ServiceWoker Script.
The Browser Network Insights document that those assets were populated in the Browser from the Disc Cache.

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Recognizing Service Worker Updates about plack-pwa-web HOT 5 CLOSED

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