Support for server side rendering

[PKASHYAP-BEC]

Hello,
We are trying to use imodeljs libraries in Server side rendering and getting a lot of issues.
Can someone confirm,if imodeljs supports SSR or have any plan for enabling SSR in near future?

Thank you

[pmconne]

Please elaborate on "lots of issues" and provide details of your server environment.
The iModel.js frontend is designed to run in a browser or electron environment. Graphics capabilities are often constrained or unavailable in server contexts.

[hsanand61564]

@pmconne The basic issue that we are facing is when we try server-side rendering, global objects like a window, document are undefined so we are getting errors like

ReferenceError: document is not defined
at \node_modules@bentley\imodeljs-frontend\lib\IModeljs-css.js:111:19

do have any workaround for these kinds of issues

[pmconne]

window, document, etc are supplied by the browser (or electron); outside of that context they will be undefined.
Short of running a browser on your server, there isn't really a workaround.
Can I ask what you're trying to achieve by running the frontend on a server?

[PKASHYAP-BEC]

@pmconne we are trying to use our react based imodel viewer as a micro frontend using SSR.

The rest of our micro frontends are running great using SSR than client rendering, so we are trying to use SSR for our viewer also.

[pmconne]

Thanks. I don't think SSR can be made to work for an interactive iModel viewer.

[wgoehrig]

Just want to clarify, since I think there's been a bit of a miscommunication here regarding what kind of SSR we're talking about.

@pmconne is right that rendering viewports will always require an actual browser, but assuming you mean React Server Side Rendering - that should (at least in theory) be partially supported. We are working on fixing those document is not defined errors you're getting now.

However, I should also note that we are not doing any SSR of our frontends and have no plans to at this time, so there's a good chance it takes a bit more work to get SSR fully setup. We assume all iModel.js frontends are largely interactive single-page applications, so I wouldn't expect to see much immediate benefit to enabling SSR. In short, we've found SSR to be unnecessary, but YMMV.

[hsanand61564]

@calebmshafer We tried with version 2.10.0 and the issue for this still persists there. Have you guys released the solution for Server Side Rendering in the version?

It is still not able to find the document object

[calebmshafer]

@hsanand61564 The fix I made was in 2.10.0. Would you mind providing instructions on how you're setting up SSR or a repo with it reproducible? The testing I did must not have covered all cases.

[hsanand61564]

@calebmshafer I will try giving you the idea as to how we are trying to implement the same.

1. In the below code we are making the viewer
   

we are using the above viewer as a package in our MFE(Micro Frontends)

2. In the code below the App component is the viewer from 1st step
   

3. Below snippet is having component DataGrid which is the outcome from Step 2

4. Finally we are doing the below thing
   

After doing all the above steps we build the solution and then try to run the same and getting the following error

Hope the above details help us in some manner

[hsanand61564]

@calebmshafer any updates?

[calebmshafer]

@hsanand61564 just had a chance to take a look and judging by the error messages, there is most likely other assumptions that window exists in layers above the imodeljs-frontend package. This is most likely in the ui-* packages. I'm taking a pass through right now to identify them and open a pull request with a fix.

[hsanand61564]

@calebmshafer @pmconne Any updates on the reply

[calebmshafer]

@hsanand61564 just got back from Holiday today. I'll take a look at your response and provide an update later today.

[hsanand61564]

@calebmshafer Any updates?

[hsanand61564]

@pmconne @calebmshafer Any Updates?

[hsanand61564]

@calebmshafer @pmconne Any updates on the same?

[pmconne]

@calebmshafer was going to look through the UI packages for usage of browser-specific APIs like window and document. A quick grep through their code reveals many usages of window. This is unsurprising since the UI packages naturally assume they are executing in a browser context. I think we'll need input from @NancyMcCallB regarding whether and how the UI packages could be used in a server-side context.

[NancyMcCallB]

Hi, @hsanand61564,

The AppUi system for iTwin.js has some features and implementation details that make it unfriendly to SSR, including:
• Window event monitoring
• Dynamic calculation of overflow for containers like the Tool Settings and the Status Bar
• Save/restore for the user’s frontstage layout

Refactoring for AppUi for SSR might be possible, but not for a minor release. It would be helpful if you could tell us what you want to do with SSR and what parts of the UI you’re using.