refactor: Allow superset to be deployed under a prefixed URL

[martyngigg]

SUMMARY

Introduces changes in the front and backend to allow Superset to be deployed under a prefixed-URL path rather than the root of the domain. A new environment variable BASE_PATH has been introduced into webpack, alongside the existing ASSET_BASE_URL, to define the prefix.

The frontend has been updated to include the prefix in any resource links along with two new helper utilities, assetUrl & pathUtils, to help construct the paths. The SupersetClient has been update to remove the unused baseUrl field and rename it as basePath such that the object can be initialized with the base path and calling any endpoints through this class can use the same relative link as before. QUESTION: Have I broken an API here?

The backend has been refactored to avoid using hardcoded paths in redirects and instead uses Flask.url_for to construct reference. This requires that the proxy server set the X-Forwarded-Prefix header along with setting ENABLE_PROXY_FIX=True in superset_config.py

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[rusackas]

Thanks for tackling this... it's a popular request, no doubt about it. If you think it's relevant, we might also want to add an entry in the documentation somewhere.

[martyngigg]

Thanks for tackling this... it's a popular request, no doubt about it. If you think it's relevant, we might also want to add an entry in the documentation somewhere.

Yes agreed I definitely need to add some documentation for how to use this. I wanted to wait until I was more confident that the general approach was acceptable before working on describing how to use it. In terms of a review as part of #26319 is there anything I need to do at the moment?

[mistercrunch]

I think this may be quite an undertaking and might have to be tackled in phases. Would love to see this done :)

I remember giving it a shot early on in the project at least once, and never wrapped up the work. My main advice would be to avoid taking in side mission or bigger refactor while tackling this.

[mistercrunch]

there's a recent fix in master for this

[ravikantkml]

Thanks for tackling this... it's a popular request, no doubt about it. If you think it's relevant, we might also want to add an entry in the documentation somewhere.

Yes agreed I definitely need to add some documentation for how to use this. I wanted to wait until I was more confident that the general approach was acceptable before working on describing how to use it. In terms of a review as part of #26319 is there anything I need to do at the moment?

Thanks for these changes.
Can you please mention values for BASE_PATH and ASSET_BASE_URL. Just wanted to check these changes with superset and nginx.

[kasper-rutten]

For what it's worth, we've been running this fork to serve superset on a path prefix in a Kubernetes(K3S) + traefik context without any problems so far. Though testing has been limited.

Thanks for the work so far

[martyngigg]

Thanks for tackling this... it's a popular request, no doubt about it. If you think it's relevant, we might also want to add an entry in the documentation somewhere.

Yes agreed I definitely need to add some documentation for how to use this. I wanted to wait until I was more confident that the general approach was acceptable before working on describing how to use it. In terms of a review as part of #26319 is there anything I need to do at the moment?

Thanks for these changes. Can you please mention values for BASE_PATH and ASSET_BASE_URL. Just wanted to check these changes with superset and nginx.

Sorry for the delay in replying to this. I've had zero time to spend on this lately.

The latest commits rebase on the current master and I have also added some documentation to the configuring superset pages that describe the new variables with an example nginx.conf. Does that help?

[martyngigg]

@rusackas I think this is ready for review but in terms of it being related to SIP-112 is that the right thing to do in terms of the process?

[rusackas]

If you think it's ready for review, I'd say you can go ahead and move it from Draft to "Ready for Review" - though it looks like CI might need a little more love still.

As for the SIP, since @sfirke reopened the GitHub issue, I set the SIP itself back to "pre-discussion" state for its official consensus. Did you want to re-kindle that pre-existing SIP, or would it be easier to open a new one? I'm happy to help you carry that SIP through to fruition if you'd like. Feel free to DM me on slack if it's easier.