Add Header `X-Accel-Buffering: no` to server responses to improve buffering with clients

[sid8489]

# Summary We have been below facing workflows UI issues in production env, where ingress is enabled Note: our ingress controller -> KONG

• On submiting a new workflow:
  • initial steps in workflow Dag takes a lot of time to load
  • steps animation (like loader) does not work
  • delays in recieving workflow Progress updates, eg: step still in progress on UI, eventhough a it has completed
• For Workflows in Running state:
  • Sometimes DAG loads (after a long time) and sometimes it doesnot
  • Lot of lag and delay in recieving workflow Progress updates
• For Workflows in Completed state:
  • We get a empty screen.

Also we didn't see any error in network calls or web console. All of this was not happening when proxying the server over localhost.

After looking into github issues, we came across a bunch of issues where people reported same problem.

• https://github.com/argoproj/argo-workflows/issues/3080#issuecomment-648269107
• https://github.com/argoproj/argo-workflows/issues/8046
• https://github.com/argoproj/argo-workflows/issues/2272

Solution: In some of these issues people mentioned that they got it fixed by disabling proxy_buffering on the ingress-controller side. We tried the same workaround and were able to resolve all above mentioned issues.
We weren't allowed to disabling proxy_buffering on ingress-controller side, so we set "X-Accel-Buffering: no" headers to argo SSE responses.

We propose the same, argo-server should add header "X-Accel-Buffering: no" to responses to improve buffering b/w server and client, either by default or optional via cli param

What change needs making? PR

Use Cases

• improve SSE buffering b/w server and client, When would you use this?
• When ingress is enabled and user can't turn proxy_buffering off at ingress controller side

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[DavidConnack]

Im also experiencing this. I have my argo workflows deployed via helm behind a Kong ingress controller. Some calls are just pending. I cant set the disable the buffer as it will affect our other applications.

[DavidConnack]

I manged to solve this with the following kong annotation