Diagrams

+-------------------+          +----------+           +----------------------------+           +------------------+
|                   |          |          |           |                            |           |                  |
| downstream client +--------->+ listener +---------->+ filters (routing decision) +---------->+ upstream cluster |
|                   |          |          |           |                            |           |                  |
+-------------------+          +----------+           +----------------------------+           +------------------+

How is routing decision done?
+-------------+         +------------+          +--------------+           +---------------+          +----------------+
|             |         |            |          |              |           |               |          |                |
| TCP filters +-------->+ HCM filter +--------->+ http filters +---------->+ router filter +--------->+ host selection |
|             |         |            |          |              |           |               |          |                |
+-------------+         +------------+          +--------------+           +---------------+          +----------------+

Simple config

run the following:

fuser -k 8082/tcp
fuser -k 10000/tcp
fuser -k 10004/tcp

go run server_tcp.go&
envoy -c simple_tcp.yaml&
echo hi | nc localhost 10000

Http simple config:

fuser -k 8082/tcp
fuser -k 10000/tcp
fuser -k 10004/tcp

go run server.go&
envoy -c simple.yaml&
curl http://localhost:10000 -dhi

Let's use a filter!

cors

note: you can provide route level configuration for a filter

fuser -k 8082/tcp
fuser -k 10000/tcp
fuser -k 10004/tcp

go run server.go&
envoy -c cors.yaml&
curl -XOPTIONS http://localhost:10000 -H"Origin: solo.io" -v
curl -XOPTIONS http://localhost:10000 -H"Origin: example.com" -v

fault filter

remember: filter order matters.

fuser -k 8082/tcp
fuser -k 10000/tcp
fuser -k 10004/tcp

go run server.go&
envoy -c simple_fault.yaml -l debug&

for i in $(seq 10); do
curl http://localhost:10000 -s -o /dev/null -w "%{http_code}" 
echo
done

header manipulation

note: some route level configuration is handled by the router filter

fuser -k 8082/tcp
fuser -k 10000/tcp
fuser -k 10004/tcp

go run server.go&
envoy -c response-header.yaml&
curl http://localhost:10000 -v