diff options
Diffstat (limited to 'microprom/handler.go')
| -rw-r--r-- | microprom/handler.go | 82 |
1 files changed, 72 insertions, 10 deletions
diff --git a/microprom/handler.go b/microprom/handler.go index db5e53f..a505df3 100644 --- a/microprom/handler.go +++ b/microprom/handler.go @@ -12,6 +12,8 @@ import ( "net/http" "slices" "strings" + + "go.xyrillian.de/gg/internal/accept" ) // Handler is an [http.Handler] rendering metrics in Prometheus exposition formats. @@ -42,29 +44,57 @@ var _ http.Handler = Handler{} // ServeHTTP implements the [http.Handler] interface. func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) { - ms := NewMetricSet(SyntaxOpenMetricsV1, h.Families) + acceptedFormat, ok := accept.ParseHeader(r.Header["Accept"]).Negotiate( + // The way that Prometheus handles `Accept` is insane. + // They put a billion parameters in there, with `escaping=` possibly depending on server configuration. + // (I have not read enough of the Prometheus source code to be sure.) + // The easiest way for us is to negotiate for all possible combinations. + // + // Note that it is fine for the client to request less specific formats, e.g. just "application/openmetrics-text", + // in which case the first match will be used. + // Each set of similar choices has `escaping=underscores` on top each time because that's the default escaping scheme in promhttp. + "text/plain; version=0.0.4; charset=utf-8; escaping=underscores", + "text/plain; version=0.0.4; charset=utf-8; escaping=allow-utf-8", + "text/plain; version=0.0.4; charset=utf-8; escaping=dots", + "text/plain; version=0.0.4; charset=utf-8; escaping=values", + "application/openmetrics-text; version=1.0.0; charset=utf-8; escaping=underscores", + "application/openmetrics-text; version=1.0.0; charset=utf-8; escaping=allow-utf-8", + "application/openmetrics-text; version=1.0.0; charset=utf-8; escaping=dots", + "application/openmetrics-text; version=1.0.0; charset=utf-8; escaping=values", + ).Unpack() + if !ok { + http.Error(w, "supported formats are text/plain and application/openmetrics-text", http.StatusNotAcceptable) + return + } + + w.Header().Set("Content-Type", acceptedFormat) + syntax := SyntaxPrometheusLegacy + if strings.HasPrefix(acceptedFormat, "application/openmetrics-text; version=1.0.0;") { + syntax = SyntaxOpenMetricsV1 + } + + ms := NewMetricSet(syntax, h.Families) err := h.Collect(r.Context(), ms) if err != nil { http.Error(w, err.Error(), http.StatusInternalServerError) return } - // TODO: add support for `Content-Type: application/openmetrics-text; version=1.0.0; charset=utf-8` if requested in `Accept` header - w.Header().Set("Content-Type", "text/plain; version=0.0.4; charset=utf-8; escaping=underscores") w.WriteHeader(http.StatusOK) - bw := bufio.NewWriter(w) if h.SortOutput { for _, familyName := range slices.Sorted(maps.Keys(h.Families)) { - h.printMetricFamily(bw, familyName, h.Families[familyName], ms.metrics[familyName]) + h.printMetricFamily(bw, syntax, familyName, h.Families[familyName], ms.metrics[familyName]) } } else { for familyName, familyInfo := range h.Families { - h.printMetricFamily(bw, familyName, familyInfo, ms.metrics[familyName]) + h.printMetricFamily(bw, syntax, familyName, familyInfo, ms.metrics[familyName]) } } - fmt.Fprint(bw, "# EOF\n") + if syntax != SyntaxPrometheusLegacy { + fmt.Fprint(bw, "# EOF\n") + } err = bw.Flush() if err != nil { // We do not have a way to log this because we do not know what log library the application uses, @@ -75,7 +105,7 @@ func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) { } } -func (h Handler) printMetricFamily(w io.Writer, familyName MetricFamilyName, info MetricFamilyInfo, metrics []metric) { +func (h Handler) printMetricFamily(w io.Writer, syntax Syntax, familyName MetricFamilyName, info MetricFamilyInfo, metrics []metric) { if len(metrics) == 0 { return } @@ -92,6 +122,11 @@ func (h Handler) printMetricFamily(w io.Writer, familyName MetricFamilyName, inf panic("unreachable") // NewMetricSet() should have rejected unknown MetricType values } + if syntax == SyntaxPrometheusLegacy { + // Prometheus Text Format does not distinguish between metric names and metric family names + familyName = MetricFamilyName(metricName) + } + fmt.Fprintf(w, "# HELP %s %s\n# TYPE %s %s\n", familyName, info.Help, familyName, metricTypeNames[info.Type]) if h.SortOutput { @@ -101,9 +136,36 @@ func (h Handler) printMetricFamily(w io.Writer, familyName MetricFamilyName, inf } for _, m := range metrics { if m.labels == "" { - fmt.Fprintf(w, "%s %g\n", metricName, m.value) + fmt.Fprintf(w, "%s ", metricName) + } else { + fmt.Fprintf(w, "%s{%s} ", metricName, m.labels) + } + if syntax == SyntaxPrometheusLegacy { + fmt.Fprintf(w, "%g\n", m.value) } else { - fmt.Fprintf(w, "%s{%s} %g\n", metricName, m.labels, m.value) + // TODO: ugly + fi := floatInspector{inner: w} + fmt.Fprintf(&fi, "%g", m.value) + if fi.clearlyFloat { + fmt.Fprintf(w, "\n") + } else { + fmt.Fprintf(w, ".0\n") + } } } } + +type floatInspector struct { + inner io.Writer + clearlyFloat bool +} + +func (fi *floatInspector) Write(buf []byte) (int, error) { + if slices.Contains(buf, '.') { + fi.clearlyFloat = true + } + if slices.Contains(buf, 'e') { + fi.clearlyFloat = true + } + return fi.inner.Write(buf) +} |