RestTemplate instrumentation doesn't capture URI when calling restTemplate with a URI object instead of a URL string

[breun]

I was testing the client-side HTTP instrumentation for Spring's RestTemplate as described at http://micrometer.io/docs/prometheus#_client_side_http_instrumentation using this REST controller method:

@GetMapping
public String get() throws Exception {
    return restTemplate.getForObject(new URI("https://jsonplaceholder.typicode.com/posts/1"), String.class);
}

I get metrics for this, but the uri isn't being captured by Micrometer:

# HELP http_client_requests_duration_seconds  
# TYPE http_client_requests_duration_seconds summary
http_client_requests_duration_seconds_count{clientName="jsonplaceholder.typicode.com",method="GET",status="200",uri="none",} 1.0
http_client_requests_duration_seconds_sum{clientName="jsonplaceholder.typicode.com",method="GET",status="200",uri="none",} 0.164180339

I guess this is because io.micrometer.spring.RestTemplateUrlTemplateCapturingAspect only executes for RestOperations calls that have a String as their first argument, but calls using a URI object are also supported by RestTemplate (and RestOperations), so I guess those should also be intercepted?

[jkschneider]

Interesting, thanks!

[jkschneider]

I added support for capturing URI's for this signature, but I want to caution you that it should only be used when the URI is not parameterizable. What you have right now would cause dimensional explosion on the backend.

// BAD - will result in dimensional explosion with enough requests
restTemplate.getForObject(new URI("https://jsonplaceholder.typicode.com/posts/1"), String.class);

// GOOD - will result in one URI dimension regardless of the number of requests
restTemplate.getForObject("https://jsonplaceholder.typicode.com/posts/{id}", String.class, 1);