[feature] Initial Prometheus metrics implementation (#2334)

* feat: Initial OTEL metrics

* docs: add metrics documentation

* fix: metrics endpoint conditional check

* feat: metrics endpoint basic auth

* fix: make metrics-auth-enabled default false

* fix: go fmt helpers.gen.go

* fix: add metric-related env vars to envparsing.sh

* fix: metrics docs

* fix: metrics related stuff in envparsing.sh

* fix: metrics docs

* chore: metrics docs wording

* fix: metrics stuff in envparsing?

* bump otel versions

---------

Co-authored-by: Tsuribori <user@acertaindebian>
Co-authored-by: Tsuribori <none@example.org>
Co-authored-by: tsmethurst <tobi.smethurst@protonmail.com>

1 files changed, 133 insertions, 0 deletions

diff --git a/vendor/go.opentelemetry.io/otel/sdk/metric/internal/aggregate/aggregate.go b/vendor/go.opentelemetry.io/otel/sdk/metric/internal/aggregate/aggregate.go
new file mode 100644
index 000000000..8dec14237
--- /dev/null
+++ b/vendor/go.opentelemetry.io/otel/sdk/metric/internal/aggregate/aggregate.go
@@ -0,0 +1,133 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package aggregate // import "go.opentelemetry.io/otel/sdk/metric/internal/aggregate"
+
+import (
+	"context"
+	"time"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/sdk/metric/metricdata"
+)
+
+// now is used to return the current local time while allowing tests to
+// override the default time.Now function.
+var now = time.Now
+
+// Measure receives measurements to be aggregated.
+type Measure[N int64 | float64] func(context.Context, N, attribute.Set)
+
+// ComputeAggregation stores the aggregate of measurements into dest and
+// returns the number of aggregate data-points output.
+type ComputeAggregation func(dest *metricdata.Aggregation) int
+
+// Builder builds an aggregate function.
+type Builder[N int64 | float64] struct {
+	// Temporality is the temporality used for the returned aggregate function.
+	//
+	// If this is not provided a default of cumulative will be used (except for
+	// the last-value aggregate function where delta is the only appropriate
+	// temporality).
+	Temporality metricdata.Temporality
+	// Filter is the attribute filter the aggregate function will use on the
+	// input of measurements.
+	Filter attribute.Filter
+}
+
+func (b Builder[N]) filter(f Measure[N]) Measure[N] {
+	if b.Filter != nil {
+		fltr := b.Filter // Copy to make it immutable after assignment.
+		return func(ctx context.Context, n N, a attribute.Set) {
+			fAttr, _ := a.Filter(fltr)
+			f(ctx, n, fAttr)
+		}
+	}
+	return f
+}
+
+// LastValue returns a last-value aggregate function input and output.
+//
+// The Builder.Temporality is ignored and delta is use always.
+func (b Builder[N]) LastValue() (Measure[N], ComputeAggregation) {
+	// Delta temporality is the only temporality that makes semantic sense for
+	// a last-value aggregate.
+	lv := newLastValue[N]()
+
+	return b.filter(lv.measure), func(dest *metricdata.Aggregation) int {
+		// Ignore if dest is not a metricdata.Gauge. The chance for memory
+		// reuse of the DataPoints is missed (better luck next time).
+		gData, _ := (*dest).(metricdata.Gauge[N])
+		lv.computeAggregation(&gData.DataPoints)
+		*dest = gData
+
+		return len(gData.DataPoints)
+	}
+}
+
+// PrecomputedSum returns a sum aggregate function input and output. The
+// arguments passed to the input are expected to be the precomputed sum values.
+func (b Builder[N]) PrecomputedSum(monotonic bool) (Measure[N], ComputeAggregation) {
+	s := newPrecomputedSum[N](monotonic)
+	switch b.Temporality {
+	case metricdata.DeltaTemporality:
+		return b.filter(s.measure), s.delta
+	default:
+		return b.filter(s.measure), s.cumulative
+	}
+}
+
+// Sum returns a sum aggregate function input and output.
+func (b Builder[N]) Sum(monotonic bool) (Measure[N], ComputeAggregation) {
+	s := newSum[N](monotonic)
+	switch b.Temporality {
+	case metricdata.DeltaTemporality:
+		return b.filter(s.measure), s.delta
+	default:
+		return b.filter(s.measure), s.cumulative
+	}
+}
+
+// ExplicitBucketHistogram returns a histogram aggregate function input and
+// output.
+func (b Builder[N]) ExplicitBucketHistogram(boundaries []float64, noMinMax, noSum bool) (Measure[N], ComputeAggregation) {
+	h := newHistogram[N](boundaries, noMinMax, noSum)
+	switch b.Temporality {
+	case metricdata.DeltaTemporality:
+		return b.filter(h.measure), h.delta
+	default:
+		return b.filter(h.measure), h.cumulative
+	}
+}
+
+// ExponentialBucketHistogram returns a histogram aggregate function input and
+// output.
+func (b Builder[N]) ExponentialBucketHistogram(maxSize, maxScale int32, noMinMax, noSum bool) (Measure[N], ComputeAggregation) {
+	h := newExponentialHistogram[N](maxSize, maxScale, noMinMax, noSum)
+	switch b.Temporality {
+	case metricdata.DeltaTemporality:
+		return b.filter(h.measure), h.delta
+	default:
+		return b.filter(h.measure), h.cumulative
+	}
+}
+
+// reset ensures s has capacity and sets it length. If the capacity of s too
+// small, a new slice is returned with the specified capacity and length.
+func reset[T any](s []T, length, capacity int) []T {
+	if cap(s) < capacity {
+		return make([]T, length, capacity)
+	}
+	return s[:length]
+}