This repo contains a sample application that uses Envoy as service proxy. It was meant to get familiar with Envoy and to experiment with an actual kubernetes setup (more specifically, I've used OpenShift as orchestrator).
+------+ +------+ +------+
| POD +--------+ | POD +--------+ | POD +--------+
,-----------------. ,-----------------. ,-----------------.
-->| envoy-sidecar |---->| envoy-sidecar |---->| envoy-sidecar |
`-----------------' `-----------------' `-----------------'
| ↓ ↑ | | ↓ ↑ | | ↓ ↑ |
| ,-----------. | | ,-----------. | | ,-----------. |
| | front-app | | | | passthr. | | | | h︎ttpbin | |
| `-----------' | | `-----------' | | `-----------' |
+-------------- + +---------------+ +---------------+
As the diagram above depicts there are three chained applications where httpbin, as the application whose endpoints we'd like to consume, is located at the very end of that chain.
As suggested in Christan Posta's blog series I've deployed Envoy as a sidecar to the actual application - by this means it's possible to equip even third party apps as httpbin with additional functionality like circuit breaker or in my case distributed tracing support using Zipkin.
Front as well as Passthrough are custom Spring Boot applications which only pass the given request along the chain to the next element, so nothing exciting here (actually, both times it's the same application realized as a Zuul Proxy - don't get confused with all the proxies, it's only meant to pass requests along the chain).
Finally, and this is not shown in the diagram above, I've also deployed a Zipkin Server so we can actually see who is calling what.
As I've said, I used OpenShift as container orchestrator - more specifically I've installed Minishift. Follow the installation instructions - the default setup is just fine. At least make sure you have a project named myproject.
For httpbin you don't have anything to do. The used Docker-Image is publicly available in Docker-Hub.
The Spring-Boot application although has to be build and packaged as a Docker container. So, change into the passthrough directory and execute:
mvn clean install && \
docker build -t $(minishift openshift registry)/myproject/passthrough . && \
docker push $(minishift openshift registry)/myproject/passthrough
This should build the java app, package it within a container and pushes it to minishifts Docker registry (assuming you've setup minishift accordingly).
If everything went fine so far switch back into the root-folder and apply all YAML-files (contained in k8s-folder).
oc apply -R -f ./k8s
Now, be patient ... all components should come up now and finally you should see something like this (your deployment numbers should vary):
Now you should be able to call httpbin-endpoints through the application-chain we've created, starting at front:
curl -s http://front-myproject.192.168.99.100.nip.io/api/get |jq
{
"args": {},
"headers": {
"Accept": "*/*",
"Accept-Encoding": "gzip",
"Content-Length": "0",
"Forwarded": "for=192.168.99.1;host=front-myproject.192.168.99.100.nip.io;proto=http",
"Host": "127.0.0.1",
"User-Agent": "curl/7.54.0",
"X-B3-Parentspanid": "eb9fd51a63d0bddd",
"X-B3-Sampled": "1",
"X-B3-Spanid": "0793010ac55a85b4",
"X-B3-Traceid": "3052706fbfe11d03",
"X-Forwarded-Host": "front-myproject.192.168.99.100.nip.io,127.0.0.1,127.0.0.1",
"X-Forwarded-Prefix": "/api/api",
"X-Ot-Span-Context": "3052706fbfe11d03;0793010ac55a85b4;eb9fd51a63d0bddd",
"X-Request-Id": "ade3dc66-92c6-9d29-9980-3b12e926d2de"
},
"origin": "192.168.99.1, 127.0.0.1",
"url": "http,http,http://front-myproject.192.168.99.100.nip.io/get"
}
You can see additional information like SpanId or TraceId which where added by Envoy to make distributed tracing possible.