whereami app for GKE networking examples

[mark-church]

@theemadnes and I would like to submit https://github.com/theemadnes/gke-whereami to this repo so it can exist in gcr.io/google-samples and be referenced by GCP documentation as examples.

context

We are expanding our examples of GKE and Anthos Ingress, Service, and general networking example/recipes for reference from GKE documentation (similar to what was done for network policy). We have recipes for internal Ingress, external Ingress, internal L4 load balancing, custom HTTP headers, sticky sessions, weight-based load balancing, multi-cluster ingress, custom gRPC health checks .... and more.

challenge

We would like to use a common app for all examples. The challenge is that we require an app that replies with enough information about itself to demonstrate whatever key feature that's being focused on. The current apps in gcr.io/google-samples are either enourmously complex (looking at you hipster shop) or they don't provide enough response to be useful (hello-app).

whereami is a single Pod Flask app (easy to understand and deploy for the user) that provides the following as a response:

# easy to use
curl $VIP
{"cluster_name":"blog","node_name":"gke-blog-default-pool-9980a7d5-fihi.c.church-243723.internal","pod_ip":"10.4.1.8","pod_name":"whereami-64b9cc85b-g24tx","pod_name_emoji":"👨‍⚕️","pod_namespace":"default","pod_service_account":null,"project_id":"church-243723","timestamp":"2020-07-14T01:52:31","zone":"us-central1-c"}

# and easy to pull out just the info you need
curl -s $VIP | jq .pod_name_emoji -r
👨‍⚕️

This makes it easy for demos to show scaling, proximity-based load balancing between regions, sticky session etc and the simplicity of just a JSON response also makes it great for documentation example (no pictures required). Would it be possible to get whereami imported into this repo and pushed to google-samples so it can be referenced and used by GKE documentation?

cc @askmeegs

[theemadnes]

The fields have been updated a bit lately - a sample (current) response:

{"cluster_name":"ph-demo-01","host_header":"hello","node_name":"gke-ph-demo-01-default-pool-2259626e-qqxj.c.alexmattson-scratch.internal","pod_ip":"10.48.2.24","pod_name":"whereami-7566845f96-l5klw","pod_name_emoji":"💔","pod_namespace":"default","pod_service_account":"whereami-ksa","project_id":"alexmattson-scratch","timestamp":"2020-07-14T04:03:49","version":"1.0","zone":"us-central1-f"}

It uses a bunch of data sources in its response, like host headers, K8s downstream API, etc. Per a GOOG coworker's request, I added a feature flag to contact a downstream JSON service to include its response in the reply, which can be demo'ed using Kustomize via the overlay directory in the repo. As the name suggests, it's GKE-centric.

[theemadnes]

I added the emoji bit to hash the pod_name so you have a consistent visual representation of which pod you're talking to.

[mark-church]

The code is now pushed to this repo via #132 and #133. Once @theemadnes is able to get the image into the google-samples GCR we can close this issue. Thanks for all the help @askmeegs !

[theemadnes]

Pushed #134 to include header reflection.