9433da1a67
Traffic is a plugin that communicates via the xDS protocol to an Envoy control plane. Using the data from this control plane it hands out IP addresses. This allows you (via controlling the data in the control plane) to drain or send more traffic to specific endpoints. The plugin itself only acts upon this data; it doesn't do anything fancy by itself. Code used here is copied from grpc-go and other places, this is clearly marked in the source files. Signed-off-by: Miek Gieben <miek@miek.nl>
1.9 KiB
Hacking on traffic
Repos used:
- https://github.com/envoyproxy/go-control-plane
- implements control plane, has testing stuff in pkg/test/main (iirc).
- https://github.com/grpc/grpc-go/tree/master/xds/internal/client
- implements client for xDS - much of this code has been reused here.
I found these website useful while working on this.
- https://github.com/envoyproxy/envoy/blob/master/api/API_OVERVIEW.md
- https://github.com/envoyproxy/learnenvoy/blob/master/_articles/service-discovery.md
- This was really helpful: https://www.envoyproxy.io/docs/envoy/v1.11.2/api-docs/xds_protocol to show the flow of the protocol.
Testing
Assuming you have envoyproxy/go-control-plane checked out somewhere, then:
% cd ~/src/github.com/envoyproxy/go-control-plane/pkg/test/main
% go build
% ./main --xds=ads --runtimes=2 -debug
This runs a binary from pkg/test/main. Now we're testing aDS. Everything is using gRPC with TLS
disabled: grpc.WithInsecure(). The test binary runs on port 18000 on localhost; all these things
are currently hardcoded in the traffic plugin. This will be factored out into config as some
point. Another thing that is hardcoded is the use of the "example.org" domain.
Then for CoreDNS, check out the traffic branch, create a Corefile:
example.org {
traffic grpc://127.0.0.1:18000 {
id test-id
}
debug
}
Start CoreDNS (coredns -conf Corefile -dns.port=1053), and see logging/debugging flow by; the
test binary should also spew out a bunch of things. CoreDNS willl build up a list of cluster and
endpoints. Next you can query it:
% dig @localhost -p 1053 cluster-v0-0.example.org A
;; QUESTION SECTION:
;cluster-v0-0.example.org. IN A
;; ANSWER SECTION:
cluster-v0-0.example.org. 5 IN A 127.0.0.1
Note: the xds/test binary is a go-control-plane binary with added debugging that I'm using for testing.