For Prometheus Default metrics, can we host value across all standard metrics

[ankittiwari-harness]

Issue Description

For all the standard Metrics, there are 3 labels present, However, the 4th Label host is available on one of the metrics

echo_request_size_bytes_count{code="200",method="POST",url="/v1/api"} 1200

echo_requests_total{code="200",host="localhost:9090",method="POST",url="/v1/api"} 104

Ideally we should add Host label as having host helps in differentiating the same API call across multiple service while scraping these metrics

Checklist

• Dependencies installed
• No typos
• Searched existing issues and docs

Expected behaviour

Actual behaviour

Steps to reproduce

Working code to debug

package main

func main() {
}

Version/commit

[aldas]

Probably these lines:

"host" needs to be added as arg

echo-contrib/prometheus/prometheus.go

Line 79 in 3020071

Args: []string{"code", "method", "url"},

and provided here

echo-contrib/prometheus/prometheus.go

Lines 442 to 447 in 3020071

	p.reqDur.WithLabelValues(statusStr, c.Request().Method, url).Observe(elapsed)
	p.reqCnt.WithLabelValues(statusStr, c.Request().Method, p.RequestCounterHostLabelMappingFunc(c), url).Inc()
	p.reqSz.WithLabelValues(statusStr, c.Request().Method, url).Observe(float64(reqSz))
	resSz := float64(c.Response().Size)
	p.resSz.WithLabelValues(statusStr, c.Request().Method, url).Observe(resSz)

[ankittiwari-harness]

Yeah, the changes would be exactly here.

Here is the PR for this from my fork

#89

[aldas]

NB: path is added to metrics this way:

echo-contrib/prometheus/prometheus.go

Lines 194 to 202 in b6855c2

	RequestCounterURLLabelMappingFunc: func(c echo.Context) string {
	p := c.Path() // contains route path ala `/users/:id`
	if p != "" {
	return p
	}
	// as of Echo v4.10.1 path is empty for 404 cases (when router did not find any matching routes)
	// in this case we use actual path from request to have some distinction in Prometheus
	return c.Request().URL.Path
	},