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Readiness probe based on number of endpoints #590

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markmandel opened this issue Sep 10, 2022 · 0 comments · Fixed by #591
Closed

Readiness probe based on number of endpoints #590

markmandel opened this issue Sep 10, 2022 · 0 comments · Fixed by #591
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area/operations Installation, updating, metrics etc kind/feature New feature or request

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@markmandel
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Is your feature request related to a problem? Please describe.

Since we are putting Quilkin behind UDP Load Balancers in K8s, we should have a readiness endpoint, so that Services know if the proxy is ready to receive traffic or not.

This I feel is particularly true when scaling up a proxy that is connected to an xDS resource, but has yet to receive endpoint instructions yet.

Describe the solution you'd like

I think the easiest option is to have a /ready admin http probe that returns 200 when the proxy has 1 or more endpoints configured.

If the proxy has no endpoints, it will return StatusCode::INTERNAL_SERVER_ERROR.

That way new Proxies that have yet to receive their endpoints from the xDS server won't get sent data that won't go anywhere.

Also if no proxies have endpoints, there's no point for the Service to send data to a proxy anyway, since it's not going anywhere.

Describe alternatives you've considered

We could leave things as is, and rely on the eventual consistency, but I think that will potentially put unnecessary delays in UDP network streams / connections.

Additional context

quilkin/src/admin.rs

Lines 47 to 71 in 25d9360

fn handle_request(request: Request<Body>, config: Arc<Config>, health: Health) -> Response<Body> {
match (request.method(), request.uri().path()) {
(&Method::GET, "/metrics") => collect_metrics(),
(&Method::GET, "/live") => health.check_healthy(),
(&Method::GET, "/config") => match serde_json::to_string(&config) {
Ok(body) => Response::builder()
.status(StatusCode::OK)
.header(
"Content-Type",
hyper::header::HeaderValue::from_static("application/json"),
)
.body(Body::from(body))
.unwrap(),
Err(err) => Response::builder()
.status(StatusCode::INTERNAL_SERVER_ERROR)
.body(Body::from(format!("failed to create config dump: {err}")))
.unwrap(),
},
(_, _) => {
let mut response = Response::new(Body::empty());
*response.status_mut() = StatusCode::NOT_FOUND;
response
}
}
}

@markmandel markmandel added kind/feature New feature or request area/operations Installation, updating, metrics etc labels Sep 10, 2022
@XAMPPRocky XAMPPRocky mentioned this issue Sep 13, 2022
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Add ready probe endpoint googleforgames/quilkin
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@markmandel