[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>

6 files changed, 319 insertions, 0 deletions

diff --git a/vendor/github.com/technologize/otel-go-contrib/otelginmetrics/config.go b/vendor/github.com/technologize/otel-go-contrib/otelginmetrics/config.go
new file mode 100644
index 000000000..f33fe38ed
--- /dev/null
+++ b/vendor/github.com/technologize/otel-go-contrib/otelginmetrics/config.go
@@ -0,0 +1,45 @@
+package otelginmetrics
+
+import (
+	"net/http"
+
+	"go.opentelemetry.io/otel/attribute"
+	semconv "go.opentelemetry.io/otel/semconv/v1.7.0"
+)
+
+type config struct {
+	recordInFlight bool
+	recordSize     bool
+	recordDuration bool
+	groupedStatus  bool
+	recorder       Recorder
+	attributes     func(serverName, route string, request *http.Request) []attribute.KeyValue
+	shouldRecord   func(serverName, route string, request *http.Request) bool
+}
+
+func defaultConfig() *config {
+	return &config{
+		recordInFlight: true,
+		recordDuration: true,
+		recordSize:     true,
+		groupedStatus:  true,
+		attributes:     DefaultAttributes,
+		shouldRecord: func(_, _ string, _ *http.Request) bool {
+			return true
+		},
+	}
+}
+
+var DefaultAttributes = func(serverName, route string, request *http.Request) []attribute.KeyValue {
+	attrs := []attribute.KeyValue{
+		semconv.HTTPMethodKey.String(request.Method),
+	}
+
+	if serverName != "" {
+		attrs = append(attrs, semconv.HTTPServerNameKey.String(serverName))
+	}
+	if route != "" {
+		attrs = append(attrs, semconv.HTTPRouteKey.String(route))
+	}
+	return attrs
+}
diff --git a/vendor/github.com/technologize/otel-go-contrib/otelginmetrics/middleware.go b/vendor/github.com/technologize/otel-go-contrib/otelginmetrics/middleware.go
new file mode 100644
index 000000000..85479c7f1
--- /dev/null
+++ b/vendor/github.com/technologize/otel-go-contrib/otelginmetrics/middleware.go
@@ -0,0 +1,94 @@
+package otelginmetrics
+
+import (
+	"net/http"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	semconv "go.opentelemetry.io/otel/semconv/v1.7.0"
+)
+
+// Middleware returns middleware that will trace incoming requests.
+// The service parameter should describe the name of the (virtual)
+// server handling the request.
+func Middleware(service string, options ...Option) gin.HandlerFunc {
+	cfg := defaultConfig()
+	for _, option := range options {
+		option.apply(cfg)
+	}
+	recorder := cfg.recorder
+	if recorder == nil {
+		recorder = GetRecorder("")
+	}
+	return func(ginCtx *gin.Context) {
+
+		ctx := ginCtx.Request.Context()
+
+		route := ginCtx.FullPath()
+		if len(route) <= 0 {
+			route = "nonconfigured"
+		}
+		if !cfg.shouldRecord(service, route, ginCtx.Request) {
+			ginCtx.Next()
+			return
+		}
+
+		start := time.Now()
+		reqAttributes := cfg.attributes(service, route, ginCtx.Request)
+
+		if cfg.recordInFlight {
+			recorder.AddInflightRequests(ctx, 1, reqAttributes)
+			defer recorder.AddInflightRequests(ctx, -1, reqAttributes)
+		}
+
+		defer func() {
+
+			resAttributes := append(reqAttributes[0:0], reqAttributes...)
+
+			if cfg.groupedStatus {
+				code := int(ginCtx.Writer.Status()/100) * 100
+				resAttributes = append(resAttributes, semconv.HTTPStatusCodeKey.Int(code))
+			} else {
+				resAttributes = append(resAttributes, semconv.HTTPAttributesFromHTTPStatusCode(ginCtx.Writer.Status())...)
+			}
+
+			recorder.AddRequests(ctx, 1, resAttributes)
+
+			if cfg.recordSize {
+				requestSize := computeApproximateRequestSize(ginCtx.Request)
+				recorder.ObserveHTTPRequestSize(ctx, requestSize, resAttributes)
+				recorder.ObserveHTTPResponseSize(ctx, int64(ginCtx.Writer.Size()), resAttributes)
+			}
+
+			if cfg.recordDuration {
+				recorder.ObserveHTTPRequestDuration(ctx, time.Since(start), resAttributes)
+			}
+		}()
+
+		ginCtx.Next()
+	}
+}
+
+func computeApproximateRequestSize(r *http.Request) int64 {
+	s := 0
+	if r.URL != nil {
+		s = len(r.URL.Path)
+	}
+
+	s += len(r.Method)
+	s += len(r.Proto)
+	for name, values := range r.Header {
+		s += len(name)
+		for _, value := range values {
+			s += len(value)
+		}
+	}
+	s += len(r.Host)
+
+	// N.B. r.Form and r.MultipartForm are assumed to be included in r.URL.
+
+	if r.ContentLength != -1 {
+		s += int(r.ContentLength)
+	}
+	return int64(s)
+}
diff --git a/vendor/github.com/technologize/otel-go-contrib/otelginmetrics/option.go b/vendor/github.com/technologize/otel-go-contrib/otelginmetrics/option.go
new file mode 100644
index 000000000..144ef9378
--- /dev/null
+++ b/vendor/github.com/technologize/otel-go-contrib/otelginmetrics/option.go
@@ -0,0 +1,74 @@
+package otelginmetrics
+
+import (
+	"net/http"
+
+	"go.opentelemetry.io/otel/attribute"
+)
+
+// Option applies a configuration to the given config
+type Option interface {
+	apply(cfg *config)
+}
+
+type optionFunc func(cfg *config)
+
+func (fn optionFunc) apply(cfg *config) {
+	fn(cfg)
+}
+
+// WithAttributes sets a func using which what attributes to be recorded can be specified.
+// By default the DefaultAttributes is used
+func WithAttributes(attributes func(serverName, route string, request *http.Request) []attribute.KeyValue) Option {
+	return optionFunc(func(cfg *config) {
+		cfg.attributes = attributes
+	})
+}
+
+// WithRecordInFlight determines whether to record In Flight Requests or not
+// By default the recordInFlight is true
+func WithRecordInFlightDisabled() Option {
+	return optionFunc(func(cfg *config) {
+		cfg.recordInFlight = false
+	})
+}
+
+// WithRecordDuration determines whether to record Duration of Requests or not
+// By default the recordDuration is true
+func WithRecordDurationDisabled() Option {
+	return optionFunc(func(cfg *config) {
+		cfg.recordDuration = false
+	})
+}
+
+// WithRecordSize determines whether to record Size of Requests and Responses or not
+// By default the recordSize is true
+func WithRecordSizeDisabled() Option {
+	return optionFunc(func(cfg *config) {
+		cfg.recordSize = false
+	})
+}
+
+// WithGroupedStatus determines whether to group the response status codes or not. If true 2xx, 3xx will be stored
+// By default the groupedStatus is true
+func WithGroupedStatusDisabled() Option {
+	return optionFunc(func(cfg *config) {
+		cfg.groupedStatus = false
+	})
+}
+
+// WithRecorder sets a recorder for recording requests
+// By default the open telemetry recorder is used
+func WithRecorder(recorder Recorder) Option {
+	return optionFunc(func(cfg *config) {
+		cfg.recorder = recorder
+	})
+}
+
+// WithShouldRecordFunc sets a func using which whether a record should be recorded
+// By default the all api calls are recorded
+func WithShouldRecordFunc(shouldRecord func(serverName, route string, request *http.Request) bool) Option {
+	return optionFunc(func(cfg *config) {
+		cfg.shouldRecord = shouldRecord
+	})
+}
diff --git a/vendor/github.com/technologize/otel-go-contrib/otelginmetrics/otelrecorder.go b/vendor/github.com/technologize/otel-go-contrib/otelginmetrics/otelrecorder.go
new file mode 100644
index 000000000..efdc96ffd
--- /dev/null
+++ b/vendor/github.com/technologize/otel-go-contrib/otelginmetrics/otelrecorder.go
@@ -0,0 +1,70 @@
+package otelginmetrics
+
+import (
+	"context"
+	"time"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric"
+)
+
+const instrumentationName = "github.com/technologize/otel-go-contrib/otelginmetrics"
+
+// Recorder knows how to record and measure the metrics. This
+// has the required methods to be used with the HTTP
+// middlewares.
+type otelRecorder struct {
+	attemptsCounter       metric.Int64UpDownCounter
+	totalDuration         metric.Int64Histogram
+	activeRequestsCounter metric.Int64UpDownCounter
+	requestSize           metric.Int64Histogram
+	responseSize          metric.Int64Histogram
+}
+
+func GetRecorder(metricsPrefix string) Recorder {
+	metricName := func(metricName string) string {
+		if len(metricsPrefix) > 0 {
+			return metricsPrefix + "." + metricName
+		}
+		return metricName
+	}
+	meter := otel.Meter(instrumentationName, metric.WithInstrumentationVersion(SemVersion()))
+	attemptsCounter, _ := meter.Int64UpDownCounter(metricName("http.server.request_count"), metric.WithDescription("Number of Requests"), metric.WithUnit("Count"))
+	totalDuration, _ := meter.Int64Histogram(metricName("http.server.duration"), metric.WithDescription("Time Taken by request"), metric.WithUnit("Milliseconds"))
+	activeRequestsCounter, _ := meter.Int64UpDownCounter(metricName("http.server.active_requests"), metric.WithDescription("Number of requests inflight"), metric.WithUnit("Count"))
+	requestSize, _ := meter.Int64Histogram(metricName("http.server.request_content_length"), metric.WithDescription("Request Size"), metric.WithUnit("Bytes"))
+	responseSize, _ := meter.Int64Histogram(metricName("http.server.response_content_length"), metric.WithDescription("Response Size"), metric.WithUnit("Bytes"))
+	return &otelRecorder{
+		attemptsCounter:       attemptsCounter,
+		totalDuration:         totalDuration,
+		activeRequestsCounter: activeRequestsCounter,
+		requestSize:           requestSize,
+		responseSize:          responseSize,
+	}
+}
+
+// AddRequests increments the number of requests being processed.
+func (r *otelRecorder) AddRequests(ctx context.Context, quantity int64, attributes []attribute.KeyValue) {
+	r.attemptsCounter.Add(ctx, quantity, metric.WithAttributes(attributes...))
+}
+
+// ObserveHTTPRequestDuration measures the duration of an HTTP request.
+func (r *otelRecorder) ObserveHTTPRequestDuration(ctx context.Context, duration time.Duration, attributes []attribute.KeyValue) {
+	r.totalDuration.Record(ctx, int64(duration/time.Millisecond), metric.WithAttributes(attributes...))
+}
+
+// ObserveHTTPRequestSize measures the size of an HTTP request in bytes.
+func (r *otelRecorder) ObserveHTTPRequestSize(ctx context.Context, sizeBytes int64, attributes []attribute.KeyValue) {
+	r.requestSize.Record(ctx, sizeBytes, metric.WithAttributes(attributes...))
+}
+
+// ObserveHTTPResponseSize measures the size of an HTTP response in bytes.
+func (r *otelRecorder) ObserveHTTPResponseSize(ctx context.Context, sizeBytes int64, attributes []attribute.KeyValue) {
+	r.responseSize.Record(ctx, sizeBytes, metric.WithAttributes(attributes...))
+}
+
+// AddInflightRequests increments and decrements the number of inflight request being processed.
+func (r *otelRecorder) AddInflightRequests(ctx context.Context, quantity int64, attributes []attribute.KeyValue) {
+	r.activeRequestsCounter.Add(ctx, quantity, metric.WithAttributes(attributes...))
+}
diff --git a/vendor/github.com/technologize/otel-go-contrib/otelginmetrics/recorder.go b/vendor/github.com/technologize/otel-go-contrib/otelginmetrics/recorder.go
new file mode 100644
index 000000000..7fadeff38
--- /dev/null
+++ b/vendor/github.com/technologize/otel-go-contrib/otelginmetrics/recorder.go
@@ -0,0 +1,25 @@
+package otelginmetrics
+
+import (
+	"context"
+	"time"
+
+	"go.opentelemetry.io/otel/attribute"
+)
+
+type Recorder interface {
+	// AddRequests increments the number of requests being processed.
+	AddRequests(ctx context.Context, quantity int64, attributes []attribute.KeyValue)
+
+	// ObserveHTTPRequestDuration measures the duration of an HTTP request.
+	ObserveHTTPRequestDuration(ctx context.Context, duration time.Duration, attributes []attribute.KeyValue)
+
+	// ObserveHTTPRequestSize measures the size of an HTTP request in bytes.
+	ObserveHTTPRequestSize(ctx context.Context, sizeBytes int64, attributes []attribute.KeyValue)
+
+	// ObserveHTTPResponseSize measures the size of an HTTP response in bytes.
+	ObserveHTTPResponseSize(ctx context.Context, sizeBytes int64, attributes []attribute.KeyValue)
+
+	// AddInflightRequests increments and decrements the number of inflight request being processed.
+	AddInflightRequests(ctx context.Context, quantity int64, attributes []attribute.KeyValue)
+}
diff --git a/vendor/github.com/technologize/otel-go-contrib/otelginmetrics/version.go b/vendor/github.com/technologize/otel-go-contrib/otelginmetrics/version.go
new file mode 100644
index 000000000..323e1a4c1
--- /dev/null
+++ b/vendor/github.com/technologize/otel-go-contrib/otelginmetrics/version.go
@@ -0,0 +1,11 @@
+package otelginmetrics
+
+// Version is the current release version of the gin instrumentation.
+func Version() string {
+	return "1.0.0"
+}
+
+// SemVersion is the semantic version to be supplied to tracer/meter creation.
+func SemVersion() string {
+	return "semver:" + Version()
+}