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instrumentation.go
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instrumentation.go
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package tripperware
import (
"context"
"time"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promauto"
"github.com/weaveworks/common/instrument"
)
// InstrumentMiddleware can be inserted into the middleware chain to expose timing information.
func InstrumentMiddleware(name string, metrics *InstrumentMiddlewareMetrics) Middleware {
var durationCol instrument.Collector
// Support the case metrics shouldn't be tracked (ie. unit tests).
if metrics != nil {
durationCol = instrument.NewHistogramCollector(metrics.duration)
} else {
durationCol = &NoopCollector{}
}
return MiddlewareFunc(func(next Handler) Handler {
return HandlerFunc(func(ctx context.Context, req Request) (Response, error) {
var resp Response
err := instrument.CollectedRequest(ctx, name, durationCol, instrument.ErrorCode, func(ctx context.Context) error {
var err error
resp, err = next.Do(ctx, req)
return err
})
return resp, err
})
})
}
// InstrumentMiddlewareMetrics holds the metrics tracked by InstrumentMiddleware.
type InstrumentMiddlewareMetrics struct {
duration *prometheus.HistogramVec
}
// NewInstrumentMiddlewareMetrics makes a new InstrumentMiddlewareMetrics.
func NewInstrumentMiddlewareMetrics(registerer prometheus.Registerer) *InstrumentMiddlewareMetrics {
return &InstrumentMiddlewareMetrics{
duration: promauto.With(registerer).NewHistogramVec(prometheus.HistogramOpts{
Namespace: "cortex",
Name: "frontend_query_range_duration_seconds",
Help: "Total time spent in seconds doing query range requests.",
Buckets: prometheus.DefBuckets,
}, []string{"method", "status_code"}),
}
}
// NoopCollector is a noop collector that can be used as placeholder when no metric
// should tracked by the instrumentation.
type NoopCollector struct{}
// Register implements instrument.Collector.
func (c *NoopCollector) Register() {}
// Before implements instrument.Collector.
func (c *NoopCollector) Before(ctx context.Context, method string, start time.Time) {}
// After implements instrument.Collector.
func (c *NoopCollector) After(ctx context.Context, method, statusCode string, start time.Time) {}