After a disconnect of the browser, commands from a VSCode extension do not work

[ariel-bentu]

Description

If the browser disconnects from the server, either briefly due to network error, or if the server restarted, VSCode extension commands stop working.
I also noticed that if the server restarted, the browser reconnects but the VSCode extension was not activated.

Maybe related to this:
#4590

in that case the whole extension may stop functioning and commands is just a special case.

Reproduction Steps

You may clone this vscode extension: https://github.com/ariel-bentu/theia-vscode-gaps.git
when you start the browser first time, you can see that it functions (right click on a node in the view that was added, click one of the commands and see that they work.

Now restart Theia server, and wait for the browser to reconnect - see that now these commands don't work.
Also, in the server log, you can see that the extension did not load (it prints:
console.log('Congratulations, your extension "bugs" is now active!');)

In addition, try disconnecting the network w/o restart and still these commands don't work after the reconnect. (for disconnecting technic, see #4590)

OS and Theia version:
MAC, latest version

Diagnostics:
See above

[akosyakov]

@benoitf I can have a look if you don't plan yet for someone else?

[amiramw]

@benoitf @akosyakov this issue is critical for us. Are you actively working on it or could we try to contribute? (with your help 😃 )

[akosyakov]

@amiramw try to contribute

[benoitf]

I was on PTO and at Red Hat Summi. @akosyakov you may have a look
about plans, up to @evidolob

[amiramw]

I also tried with language server extension.

When refreshing the browser connection is established fine.

When restarting the server I see this error:

Uncaught Error: no adapter found

Error: no adapter found
    at LanguagesExtImpl.withAdapter (C:\Users\i066470\repos\theia\packages\plugin-ext\lib\plugin\languages.js:109:35)
    at LanguagesExtImpl.$provideCompletionItems (C:\Users\i066470\repos\theia\packages\plugin-ext\lib\plugin\languages.js:139:21)
    at RPCProtocolImpl.doInvokeHandler (C:\Users\i066470\repos\theia\packages\plugin-ext\lib\api\rpc-protocol.js:207:23)
    at RPCProtocolImpl.invokeHandler (C:\Users\i066470\repos\theia\packages\plugin-ext\lib\api\rpc-protocol.js:192:41)
    at RPCProtocolImpl.receiveRequest (C:\Users\i066470\repos\theia\packages\plugin-ext\lib\api\rpc-protocol.js:154:45)
    at RPCProtocolImpl.receiveOneMessage (C:\Users\i066470\repos\theia\packages\plugin-ext\lib\api\rpc-protocol.js:123:22)
    at C:\Users\i066470\repos\theia\packages\plugin-ext\lib\api\rpc-protocol.js:55:89
    at C:\Users\i066470\repos\theia\packages\plugin-ext\lib\api\rpc-protocol.js:233:17
    at C:\Users\i066470\repos\theia\packages\core\lib\common\event.js:161:33
    at CallbackList.invoke (C:\Users\i066470\repos\theia\packages\core\lib\common\event.js:176:39)
    at http://localhost:3000/vs/editor/editor.main.js:12536:31

@benoitf @akosyakov does it give any hint where i should look for the problem? Also is there a nice way to debug the plugin host process code in plugin-ext extension code?

[benoitf]

@amiramw you can debug using

--hosted-plugin-inspect-brk=<port-number>

when you start Theia

it will break on first line when you'll access with your browser the ide

[amiramw]

@benoitf is there a way to unload plugin in the browser side? I am trying to trigger reload of all plugins on reconnect and there are duplicate configurations.

[amiramw]

@akosyakov @benoitf
It seems that there are two possible approaches to solve this:

• Browser listens to reconnects and reload the plugins. This will also work if the theia server is restarted. I tried it with no success. I think it is problematic as the plugins are already loaded in the browser. Is there a way to unload them?
• The hosted plugins child process can be kept for a while (1 minute?) and on reconnects the new client is linked with the same process. This will work on bad connectivity but not on restart of theia server. I did a working POC but there are questions:
  1. Is there a way to identify that the HostedPluginClient instance is coming from the same old client? Not from different browsers and not from after browser refresh.
  2. Is it ok to keep static fields on HostedPluginProcess for the child process caching? This class is reinstantiated on each connection from the client. Is there a better way to keep such cache?

Any thoughts?

[amiramw]

I created #5257 for keeping the host process alive for a while. This should solve the disconnections issue.

[akosyakov]

Browser listens to reconnects and reload the plugins. This will also work if the theia server is restarted. I tried it with no success. I think it is problematic as the plugins are already loaded in the browser. Is there a way to unload them?

It's a proper solution. We do it in the similar way for other services already (i.e. language servers, file watching, git watching and so on). On JSON-RPC connection you can be notified when connection is lost and recovered. If a connection is lost then a client plugin state should be cleaned up. If a connection is restored a client should deploy similarly as on first opening. See for file watching for example: https://github.com/theia-ide/theia/blob/78e1cb474e72ed7e641ba7df54ea62b2098684d6/packages/filesystem/src/common/filesystem-watcher-protocol.ts#L80-L84

Not sure that you need to implement the proper unloading of individual plugins. It would beneficial for dynamic plugin uninstallation, but can complicate things for now.

[amiramw]

@akosyakov do you plan to implement the proper solution here?
If not, what do you think about reflecting in the UI that plugins don't work anymore and refresh is required?

[akosyakov]

@amiramw I've started to work on it yesterday.