Use streaming encoding of metrics
Signed-off-by: beorn7 <beorn@soundcloud.com>
This commit is contained in:
parent
752f50d366
commit
62361fc0fb
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@ -32,7 +32,6 @@
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package promhttp
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import (
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"bytes"
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"compress/gzip"
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"fmt"
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"io"
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@ -59,12 +58,6 @@ var gzipPool = sync.Pool{
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},
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}
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var bufPool = sync.Pool{
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New: func() interface{} {
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return &bytes.Buffer{}
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},
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}
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// Handler returns an http.Handler for the prometheus.DefaultGatherer, using
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// default HandlerOpts, i.e. it reports the first error as an HTTP error, it has
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// no error logging, and it applies compression if requested by the client.
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@ -97,13 +90,13 @@ func HandlerFor(reg prometheus.Gatherer, opts HandlerOpts) http.Handler {
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inFlightSem = make(chan struct{}, opts.MaxRequestsInFlight)
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}
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h := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
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h := http.HandlerFunc(func(rsp http.ResponseWriter, req *http.Request) {
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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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http.Error(w, fmt.Sprintf(
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http.Error(rsp, fmt.Sprintf(
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"Limit of concurrent requests reached (%d), try again later.", opts.MaxRequestsInFlight,
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), http.StatusServiceUnavailable)
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return
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@ -119,49 +112,21 @@ func HandlerFor(reg prometheus.Gatherer, opts HandlerOpts) http.Handler {
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panic(err)
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case ContinueOnError:
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if len(mfs) == 0 {
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http.Error(w, "No metrics gathered, last error:\n\n"+err.Error(), http.StatusInternalServerError)
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// Still report the error if no metrics have been gathered.
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httpError(rsp, err)
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return
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}
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case HTTPErrorOnError:
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http.Error(w, "An error has occurred during metrics gathering:\n\n"+err.Error(), http.StatusInternalServerError)
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httpError(rsp, err)
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return
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}
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}
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contentType := expfmt.Negotiate(req.Header)
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buf := bufPool.Get().(*bytes.Buffer)
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buf.Reset()
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enc := expfmt.NewEncoder(buf, contentType)
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defer bufPool.Put(buf)
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var lastErr error
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for _, mf := range mfs {
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if err := enc.Encode(mf); err != nil {
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lastErr = err
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if opts.ErrorLog != nil {
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opts.ErrorLog.Println("error encoding metric family:", err)
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}
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switch opts.ErrorHandling {
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case PanicOnError:
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panic(err)
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case ContinueOnError:
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// Handled later.
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case HTTPErrorOnError:
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http.Error(w, "An error has occurred during metrics encoding:\n\n"+err.Error(), http.StatusInternalServerError)
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return
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}
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}
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}
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if lastErr != nil && buf.Len() == 0 {
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http.Error(w, "No metrics encoded, last error:\n\n"+lastErr.Error(), http.StatusInternalServerError)
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return
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}
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header := w.Header()
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header := rsp.Header()
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header.Set(contentTypeHeader, string(contentType))
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header.Set(contentLengthHeader, fmt.Sprint(buf.Len()))
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w := io.Writer(rsp)
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if !opts.DisableCompression && gzipAccepted(req.Header) {
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header.Set(contentEncodingHeader, "gzip")
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gz := gzipPool.Get().(*gzip.Writer)
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@ -170,12 +135,33 @@ func HandlerFor(reg prometheus.Gatherer, opts HandlerOpts) http.Handler {
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gz.Reset(w)
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defer gz.Close()
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zipWriter := gzipResponseWriter{gz, w}
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writeResult(zipWriter, buf, opts)
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return
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w = gz
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}
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enc := expfmt.NewEncoder(w, contentType)
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var lastErr error
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for _, mf := range mfs {
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if err := enc.Encode(mf); err != nil {
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lastErr = err
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if opts.ErrorLog != nil {
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opts.ErrorLog.Println("error encoding and sending metric family:", err)
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}
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switch opts.ErrorHandling {
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case PanicOnError:
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panic(err)
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case ContinueOnError:
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// Handled later.
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case HTTPErrorOnError:
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httpError(rsp, err)
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return
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}
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}
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}
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if lastErr != nil {
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httpError(rsp, lastErr)
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}
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writeResult(w, buf, opts)
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// TODO(beorn7): Consider streaming serving of metrics.
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})
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if opts.Timeout <= 0 {
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@ -296,29 +282,8 @@ type HandlerOpts struct {
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Timeout time.Duration
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}
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// gzipResponseWriter in charge of wrapping io.Writer and http.ReponseWriter
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// together, allowing to get a single struct which implements both interface.
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type gzipResponseWriter struct {
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io.Writer
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http.ResponseWriter
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}
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func (w gzipResponseWriter) Write(b []byte) (int, error) {
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return w.Writer.Write(b)
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}
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// writeResult to buf using http.ResponseWriter.
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// If ErrorLog is enabled, err is logged in.
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func writeResult(w http.ResponseWriter, buf *bytes.Buffer, opts HandlerOpts) {
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if _, err := w.Write(buf.Bytes()); err != nil && opts.ErrorLog != nil {
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opts.ErrorLog.Println("error while sending encoded metrics:", err)
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}
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}
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// gzipHandler return a http.HandlerFunc in charge of compressing the content
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// of the given http.HandlerFunc
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// gzipAccepted returns whether the client will accept gzip-encoded content.
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func gzipAccepted(header http.Header) bool {
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a := header.Get(acceptEncodingHeader)
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parts := strings.Split(a, ",")
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for _, part := range parts {
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@ -329,3 +294,18 @@ func gzipAccepted(header http.Header) bool {
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}
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return false
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}
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// httpError removes any content-encoding header and then calls http.Error with
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// the provided error and http.StatusInternalServerErrer. Error contents is
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// supposed to be uncompressed plain text. However, same as with a plain
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// http.Error, any header settings will be void if the header has already been
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// sent. The error message will still be written to the writer, but it will
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// probably be of limited use.
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func httpError(rsp http.ResponseWriter, err error) {
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rsp.Header().Del(contentEncodingHeader)
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http.Error(
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rsp,
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"An error has occurred while serving metrics:\n\n"+err.Error(),
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http.StatusInternalServerError,
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)
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}
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@ -103,7 +103,7 @@ func TestHandlerErrorHandling(t *testing.T) {
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})
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wantMsg := `error gathering metrics: error collecting metric Desc{fqName: "invalid_metric", help: "not helpful", constLabels: {}, variableLabels: []}: collect error
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`
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wantErrorBody := `An error has occurred during metrics gathering:
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wantErrorBody := `An error has occurred while serving metrics:
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error collecting metric Desc{fqName: "invalid_metric", help: "not helpful", constLabels: {}, variableLabels: []}: collect error
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`
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@ -250,7 +250,7 @@ metric: <
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},
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}
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expectedMetricFamilyInvalidLabelValueAsText := []byte(`An error has occurred during metrics gathering:
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expectedMetricFamilyInvalidLabelValueAsText := []byte(`An error has occurred while serving metrics:
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collected metric "name" { label:<name:"constname" value:"\377" > label:<name:"labelname" value:"different_val" > counter:<value:42 > } has a label named "constname" whose value is not utf8: "\xff"
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`)
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@ -299,15 +299,15 @@ complex_bucket 1
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},
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},
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}
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bucketCollisionMsg := []byte(`An error has occurred during metrics gathering:
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bucketCollisionMsg := []byte(`An error has occurred while serving metrics:
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collected metric named "complex_bucket" collides with previously collected histogram named "complex"
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`)
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summaryCountCollisionMsg := []byte(`An error has occurred during metrics gathering:
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summaryCountCollisionMsg := []byte(`An error has occurred while serving metrics:
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collected metric named "complex_count" collides with previously collected summary named "complex"
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`)
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histogramCountCollisionMsg := []byte(`An error has occurred during metrics gathering:
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histogramCountCollisionMsg := []byte(`An error has occurred while serving metrics:
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collected metric named "complex_count" collides with previously collected histogram named "complex"
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`)
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@ -333,7 +333,7 @@ collected metric named "complex_count" collides with previously collected histog
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},
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},
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}
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duplicateLabelMsg := []byte(`An error has occurred during metrics gathering:
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duplicateLabelMsg := []byte(`An error has occurred while serving metrics:
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collected metric "broken_metric" { label:<name:"foo" value:"bar" > label:<name:"foo" value:"baz" > counter:<value:2.7 > } has two or more labels with the same name: foo
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`)
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