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metrics: Record request metrics on HTTP errors (#5979)
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@tgeoghegan
tgeoghegan authored Dec 15, 2023
1 parent b49ec05 commit 387545a
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Showing 2 changed files with 142 additions and 11 deletions.
34 changes: 23 additions & 11 deletions modules/caddyhttp/metrics.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@ package caddyhttp

import (
"context"
"errors"
"net/http"
"sync"
"time"
Expand Down Expand Up @@ -137,22 +138,33 @@ func (h *metricsInstrumentedHandler) ServeHTTP(w http.ResponseWriter, r *http.Re
err := h.mh.ServeHTTP(wrec, r, next)
dur := time.Since(start).Seconds()
httpMetrics.requestCount.With(labels).Inc()

observeRequest := func(status int) {
// If the code hasn't been set yet, and we didn't encounter an error, we're
// probably falling through with an empty handler.
if statusLabels["code"] == "" {
// we still sanitize it, even though it's likely to be 0. A 200 is
// returned on fallthrough so we want to reflect that.
statusLabels["code"] = metrics.SanitizeCode(status)
}

httpMetrics.requestDuration.With(statusLabels).Observe(dur)
httpMetrics.requestSize.With(statusLabels).Observe(float64(computeApproximateRequestSize(r)))
httpMetrics.responseSize.With(statusLabels).Observe(float64(wrec.Size()))
}

if err != nil {
var handlerErr HandlerError
if errors.As(err, &handlerErr) {
observeRequest(handlerErr.StatusCode)
}

httpMetrics.requestErrors.With(labels).Inc()
return err
}

// If the code hasn't been set yet, and we didn't encounter an error, we're
// probably falling through with an empty handler.
if statusLabels["code"] == "" {
// we still sanitize it, even though it's likely to be 0. A 200 is
// returned on fallthrough so we want to reflect that.
statusLabels["code"] = metrics.SanitizeCode(wrec.Status())
return err
}

httpMetrics.requestDuration.With(statusLabels).Observe(dur)
httpMetrics.requestSize.With(statusLabels).Observe(float64(computeApproximateRequestSize(r)))
httpMetrics.responseSize.With(statusLabels).Observe(float64(wrec.Size()))
observeRequest(wrec.Status())

return nil
}
Expand Down
119 changes: 119 additions & 0 deletions modules/caddyhttp/metrics_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,8 +5,10 @@ import (
"errors"
"net/http"
"net/http/httptest"
"strings"
"testing"

"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/testutil"
)

Expand Down Expand Up @@ -75,6 +77,123 @@ func TestMetricsInstrumentedHandler(t *testing.T) {
if actual := w.Result().Header; len(actual) != 0 {
t.Errorf("Not empty: expected headers to be empty, but got %#v", actual)
}

// handler returning an error with an HTTP status
mh = middlewareHandlerFunc(func(w http.ResponseWriter, r *http.Request, h Handler) error {
return Error(http.StatusTooManyRequests, nil)
})

ih = newMetricsInstrumentedHandler("foo", mh)

r = httptest.NewRequest("GET", "/", nil)
w = httptest.NewRecorder()

if err := ih.ServeHTTP(w, r, nil); err == nil {
t.Errorf("expected error to be propagated")
}

expected := `
# HELP caddy_http_request_duration_seconds Histogram of round-trip request durations.
# TYPE caddy_http_request_duration_seconds histogram
caddy_http_request_duration_seconds_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="0.005"} 1
caddy_http_request_duration_seconds_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="0.01"} 1
caddy_http_request_duration_seconds_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="0.025"} 1
caddy_http_request_duration_seconds_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="0.05"} 1
caddy_http_request_duration_seconds_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="0.1"} 1
caddy_http_request_duration_seconds_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="0.25"} 1
caddy_http_request_duration_seconds_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="0.5"} 1
caddy_http_request_duration_seconds_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="1"} 1
caddy_http_request_duration_seconds_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="2.5"} 1
caddy_http_request_duration_seconds_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="5"} 1
caddy_http_request_duration_seconds_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="10"} 1
caddy_http_request_duration_seconds_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="+Inf"} 1
caddy_http_request_duration_seconds_count{code="429",handler="foo",method="GET",server="UNKNOWN"} 1
# HELP caddy_http_request_size_bytes Total size of the request. Includes body
# TYPE caddy_http_request_size_bytes histogram
caddy_http_request_size_bytes_bucket{code="200",handler="bar",method="GET",server="UNKNOWN",le="256"} 1
caddy_http_request_size_bytes_bucket{code="200",handler="bar",method="GET",server="UNKNOWN",le="1024"} 1
caddy_http_request_size_bytes_bucket{code="200",handler="bar",method="GET",server="UNKNOWN",le="4096"} 1
caddy_http_request_size_bytes_bucket{code="200",handler="bar",method="GET",server="UNKNOWN",le="16384"} 1
caddy_http_request_size_bytes_bucket{code="200",handler="bar",method="GET",server="UNKNOWN",le="65536"} 1
caddy_http_request_size_bytes_bucket{code="200",handler="bar",method="GET",server="UNKNOWN",le="262144"} 1
caddy_http_request_size_bytes_bucket{code="200",handler="bar",method="GET",server="UNKNOWN",le="1.048576e+06"} 1
caddy_http_request_size_bytes_bucket{code="200",handler="bar",method="GET",server="UNKNOWN",le="4.194304e+06"} 1
caddy_http_request_size_bytes_bucket{code="200",handler="bar",method="GET",server="UNKNOWN",le="+Inf"} 1
caddy_http_request_size_bytes_sum{code="200",handler="bar",method="GET",server="UNKNOWN"} 23
caddy_http_request_size_bytes_count{code="200",handler="bar",method="GET",server="UNKNOWN"} 1
caddy_http_request_size_bytes_bucket{code="200",handler="empty",method="GET",server="UNKNOWN",le="256"} 1
caddy_http_request_size_bytes_bucket{code="200",handler="empty",method="GET",server="UNKNOWN",le="1024"} 1
caddy_http_request_size_bytes_bucket{code="200",handler="empty",method="GET",server="UNKNOWN",le="4096"} 1
caddy_http_request_size_bytes_bucket{code="200",handler="empty",method="GET",server="UNKNOWN",le="16384"} 1
caddy_http_request_size_bytes_bucket{code="200",handler="empty",method="GET",server="UNKNOWN",le="65536"} 1
caddy_http_request_size_bytes_bucket{code="200",handler="empty",method="GET",server="UNKNOWN",le="262144"} 1
caddy_http_request_size_bytes_bucket{code="200",handler="empty",method="GET",server="UNKNOWN",le="1.048576e+06"} 1
caddy_http_request_size_bytes_bucket{code="200",handler="empty",method="GET",server="UNKNOWN",le="4.194304e+06"} 1
caddy_http_request_size_bytes_bucket{code="200",handler="empty",method="GET",server="UNKNOWN",le="+Inf"} 1
caddy_http_request_size_bytes_sum{code="200",handler="empty",method="GET",server="UNKNOWN"} 23
caddy_http_request_size_bytes_count{code="200",handler="empty",method="GET",server="UNKNOWN"} 1
caddy_http_request_size_bytes_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="256"} 1
caddy_http_request_size_bytes_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="1024"} 1
caddy_http_request_size_bytes_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="4096"} 1
caddy_http_request_size_bytes_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="16384"} 1
caddy_http_request_size_bytes_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="65536"} 1
caddy_http_request_size_bytes_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="262144"} 1
caddy_http_request_size_bytes_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="1.048576e+06"} 1
caddy_http_request_size_bytes_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="4.194304e+06"} 1
caddy_http_request_size_bytes_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="+Inf"} 1
caddy_http_request_size_bytes_sum{code="429",handler="foo",method="GET",server="UNKNOWN"} 23
caddy_http_request_size_bytes_count{code="429",handler="foo",method="GET",server="UNKNOWN"} 1
# HELP caddy_http_response_size_bytes Size of the returned response.
# TYPE caddy_http_response_size_bytes histogram
caddy_http_response_size_bytes_bucket{code="200",handler="bar",method="GET",server="UNKNOWN",le="256"} 1
caddy_http_response_size_bytes_bucket{code="200",handler="bar",method="GET",server="UNKNOWN",le="1024"} 1
caddy_http_response_size_bytes_bucket{code="200",handler="bar",method="GET",server="UNKNOWN",le="4096"} 1
caddy_http_response_size_bytes_bucket{code="200",handler="bar",method="GET",server="UNKNOWN",le="16384"} 1
caddy_http_response_size_bytes_bucket{code="200",handler="bar",method="GET",server="UNKNOWN",le="65536"} 1
caddy_http_response_size_bytes_bucket{code="200",handler="bar",method="GET",server="UNKNOWN",le="262144"} 1
caddy_http_response_size_bytes_bucket{code="200",handler="bar",method="GET",server="UNKNOWN",le="1.048576e+06"} 1
caddy_http_response_size_bytes_bucket{code="200",handler="bar",method="GET",server="UNKNOWN",le="4.194304e+06"} 1
caddy_http_response_size_bytes_bucket{code="200",handler="bar",method="GET",server="UNKNOWN",le="+Inf"} 1
caddy_http_response_size_bytes_sum{code="200",handler="bar",method="GET",server="UNKNOWN"} 12
caddy_http_response_size_bytes_count{code="200",handler="bar",method="GET",server="UNKNOWN"} 1
caddy_http_response_size_bytes_bucket{code="200",handler="empty",method="GET",server="UNKNOWN",le="256"} 1
caddy_http_response_size_bytes_bucket{code="200",handler="empty",method="GET",server="UNKNOWN",le="1024"} 1
caddy_http_response_size_bytes_bucket{code="200",handler="empty",method="GET",server="UNKNOWN",le="4096"} 1
caddy_http_response_size_bytes_bucket{code="200",handler="empty",method="GET",server="UNKNOWN",le="16384"} 1
caddy_http_response_size_bytes_bucket{code="200",handler="empty",method="GET",server="UNKNOWN",le="65536"} 1
caddy_http_response_size_bytes_bucket{code="200",handler="empty",method="GET",server="UNKNOWN",le="262144"} 1
caddy_http_response_size_bytes_bucket{code="200",handler="empty",method="GET",server="UNKNOWN",le="1.048576e+06"} 1
caddy_http_response_size_bytes_bucket{code="200",handler="empty",method="GET",server="UNKNOWN",le="4.194304e+06"} 1
caddy_http_response_size_bytes_bucket{code="200",handler="empty",method="GET",server="UNKNOWN",le="+Inf"} 1
caddy_http_response_size_bytes_sum{code="200",handler="empty",method="GET",server="UNKNOWN"} 0
caddy_http_response_size_bytes_count{code="200",handler="empty",method="GET",server="UNKNOWN"} 1
caddy_http_response_size_bytes_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="256"} 1
caddy_http_response_size_bytes_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="1024"} 1
caddy_http_response_size_bytes_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="4096"} 1
caddy_http_response_size_bytes_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="16384"} 1
caddy_http_response_size_bytes_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="65536"} 1
caddy_http_response_size_bytes_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="262144"} 1
caddy_http_response_size_bytes_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="1.048576e+06"} 1
caddy_http_response_size_bytes_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="4.194304e+06"} 1
caddy_http_response_size_bytes_bucket{code="429",handler="foo",method="GET",server="UNKNOWN",le="+Inf"} 1
caddy_http_response_size_bytes_sum{code="429",handler="foo",method="GET",server="UNKNOWN"} 0
caddy_http_response_size_bytes_count{code="429",handler="foo",method="GET",server="UNKNOWN"} 1
# HELP caddy_http_request_errors_total Number of requests resulting in middleware errors.
# TYPE caddy_http_request_errors_total counter
caddy_http_request_errors_total{handler="bar",server="UNKNOWN"} 1
caddy_http_request_errors_total{handler="foo",server="UNKNOWN"} 1
`
if err := testutil.GatherAndCompare(prometheus.DefaultGatherer, strings.NewReader(expected),
"caddy_http_request_size_bytes",
"caddy_http_response_size_bytes",
// caddy_http_request_duration_seconds_sum will vary based on how long the test took to run,
// so we check just the _bucket and _count metrics
"caddy_http_request_duration_seconds_bucket",
"caddy_http_request_duration_seconds_count",
"caddy_http_request_errors_total",
); err != nil {
t.Errorf("received unexpected error: %s", err)
}
}

type middlewareHandlerFunc func(http.ResponseWriter, *http.Request, Handler) error
Expand Down

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