Bug: uri metric label on gateway routes appears as "UNKNOWN" in prometheus export

[jrushto1]

http_server_requests metrics uri label shows up as "UNKNOWN" on gateway routes when using spring cloud gateway with spring boot release 2.1.3. This bug seems to have been introduced between spring boot 2.1.1 and 2.1.2 releases. Sample project here.

http_server_requests_seconds_count{exception="SSLHandshakeException",method="GET",outcome="SERVER_ERROR",status="500",uri="UNKNOWN",} 2.0
http_server_requests_seconds_sum{exception="SSLHandshakeException",method="GET",outcome="SERVER_ERROR",status="500",uri="UNKNOWN",} 1.022870125

Steps to reproduce:

1. Clone repo
2. Start Application
3. curL http://localhost:8080/test-service/200 a couple of times
4. Go to http://localhost:8080/actuator/prometheus

N.B. The curl command will result in 500 server errors due to separate https routing issue on gateway.

[tony-clarke-amdocs]

Maybe this is a change in Spring itself and not the Gateway. I would suggest you can debug by putting a break point in WebFluxTags#uri()

Note, this is not the Gateway metric but the Spring Web Flux one (http_server_requests).

[jrushto1]

Thanks for getting back to me. I've dug a little deeper and it does look to be a problem with the WebFluxTags#uri() method. In 2.1.1 the method is:

public static Tag uri(ServerWebExchange exchange) {
		PathPattern pathPattern = exchange
				.getAttribute(HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE);
		if (pathPattern != null) {
			return Tag.of("uri", pathPattern.getPatternString());
		}
		HttpStatus status = exchange.getResponse().getStatusCode();
		if (status != null) {
			if (status.is3xxRedirection()) {
				return URI_REDIRECTION;
			}
			if (status == HttpStatus.NOT_FOUND) {
				return URI_NOT_FOUND;
			}
		}
		String path = exchange.getRequest().getPath().value();
		if (path.isEmpty()) {
			return URI_ROOT;
		}
		return Tag.of("uri", path);
	}

where as in 2.1.3 the method is:

	public static Tag uri(ServerWebExchange exchange) {
		PathPattern pathPattern = exchange
				.getAttribute(HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE);
		if (pathPattern != null) {
			return Tag.of("uri", pathPattern.getPatternString());
		}
		HttpStatus status = exchange.getResponse().getStatusCode();
		if (status != null) {
			if (status.is3xxRedirection()) {
				return URI_REDIRECTION;
			}
			if (status == HttpStatus.NOT_FOUND) {
				return URI_NOT_FOUND;
			}
		}
		String path = getPathInfo(exchange);
		if (path.isEmpty()) {
			return URI_ROOT;
		}
		return URI_UNKNOWN;
	}

The default always returns URI_UNKNOWN despite path being not empty. You are correct it doesn't seem to be a gateway issue so I'll raise it in the spring boot repo. Thanks again!

[vladimirov001]

I have the same issue, is there any news?

[spencergibb]

@vladimirov001 it was determined this was a spring framework issue. Not sure if there was ever an issue opened there.

[sw-fox]

I just found a solution here that works for me: spring-projects/spring-boot#15609 (comment)

[danparisi]

For Spring Boot 3.X.X, you can find the solution I implemented here