86 lines
2.2 KiB
Go
86 lines
2.2 KiB
Go
package main
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import (
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"github.com/fasthttp/router"
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"github.com/nspcc-dev/neofs-http-gw/response"
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"github.com/prometheus/client_golang/prometheus"
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"github.com/prometheus/common/expfmt"
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"github.com/valyala/fasthttp"
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"go.uber.org/zap"
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)
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func attachMetrics(r *router.Router, l *zap.Logger) {
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r.GET("/metrics/", metricsHandler(prometheus.DefaultGatherer, l))
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}
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func metricsHandler(reg prometheus.Gatherer, logger *zap.Logger) fasthttp.RequestHandler {
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var (
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inFlightSem chan struct{}
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errCnt = prometheus.NewCounterVec(
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prometheus.CounterOpts{
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Name: "promhttp_metric_handler_errors_total",
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Help: "Total number of internal errors encountered by the promhttp metric handler.",
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},
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[]string{"cause"},
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)
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)
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h := fasthttp.RequestHandler(func(c *fasthttp.RequestCtx) {
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if inFlightSem != nil {
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select {
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case inFlightSem <- struct{}{}: // All good, carry on.
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defer func() { <-inFlightSem }()
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default:
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response.Error(c, "Limit of concurrent requests reached, try again later.", fasthttp.StatusServiceUnavailable)
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return
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}
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}
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mfs, err := reg.Gather()
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if err != nil {
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if logger != nil {
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panic("error gathering metrics:" + err.Error())
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}
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errCnt.WithLabelValues("gathering").Inc()
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response.Error(c, err.Error(), fasthttp.StatusServiceUnavailable)
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return
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}
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contentType := expfmt.FmtText
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c.SetContentType(string(contentType))
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enc := expfmt.NewEncoder(c, contentType)
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var lastErr error
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// handleError handles the error according to opts.ErrorHandling
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// and returns true if we have to abort after the handling.
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handleError := func(err error) bool {
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if err == nil {
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return false
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}
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lastErr = err
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if logger != nil {
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logger.Error("encoding and sending metric family", zap.Error(err))
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}
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errCnt.WithLabelValues("encoding").Inc()
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response.Error(c, err.Error(), fasthttp.StatusServiceUnavailable)
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return true
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}
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for _, mf := range mfs {
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if handleError(enc.Encode(mf)) {
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return
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}
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}
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if closer, ok := enc.(expfmt.Closer); ok {
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// This in particular takes care of the final "# EOF\n" line for OpenMetrics.
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if handleError(closer.Close()) {
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return
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}
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}
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handleError(lastErr)
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})
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return h
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}
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