doc: Integrate w/ AGIC

[draychev]

For folks using OSM on Azure (AKS or not) - the Application Gateway Ingress Controller would be a great option for Ingress. This is already available as an AKS addon and well documented.

This GitHub issue is for creating documentation on how to use AGIC and OSM together:

• Document the creation of Ingress resource and bringing in AGIC -- save the doc in ./docs/wip/ingress_agic.md (exact location is TBD - wip short term)

  • What traffic is currently working with v0.8 of OSM Controller? Would mTLS work? Would HTTPS work?

• Create a small demo with sample apps and SMI showing how this feature works

  • Create Ingress resource
  • Bring in AGIC (install via Helm or use AKS addon)

• List Common Issues

  • External traffic through Nginx shows an error (point to external docs where possible)
    • 503 - is there a service backing this? Is traffic from ingress to backends HTTP? Would any other traffic work?
    • 502 Bad Gateway - are there endpoints; Are they healthy? Are there custom health checks? Any health checks at all?
    • 404 - check Ingress spec's routes, backends
    • Point to external (AGIC) documentation on common ingress errors: 404, 502, 503

• Create Troubleshooting Guide

• Check Ingress resource for correctness and annotations (point to AGIC docs for this)

• Does the Ingress resource reference an existing Service?

• Does the Service referenced by the Ingress resource have Pods backing it - list the Endpoints

• Check Envoy configuration of one/all of the Endpoints referenced in the Ingress - to these Envoys have an HTTP ingress inbound opened?

• Automate Troubleshooting Guide in pkg/troubleshooter (create appropriate functions) - alternatively create a GitHub Issue with the stub of the function that could be eventually created within pkg/troubleshooter package to automatically troubleshoot this feature.

[draychev]

This will be helpful: https://docs.microsoft.com/en-us/azure/application-gateway/tutorial-ingress-controller-add-on-new

[zr-msft]

@draychev @phillipgibson this issue needs a demo to be completed

[zr-msft]

Integration with AGIC is covered here:
https://docs.microsoft.com/en-us/azure/aks/open-service-mesh-integrations#using-the-azure-gateway-ingress-controller-agic-with-the-osm-add-on-for-http-ingress