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otel-meter.go
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otel-meter.go
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// Package otelmetric provides middleware to add opentelemetry metrics and Metrics exporter.
package echootelmetrics
import (
"errors"
"go.opentelemetry.io/otel/attribute"
"net"
"net/http"
"strconv"
"strings"
"time"
"go.opentelemetry.io/otel"
"go.opentelemetry.io/otel/exporters/prometheus"
"go.opentelemetry.io/otel/metric"
sdkmetric "go.opentelemetry.io/otel/sdk/metric"
"go.opentelemetry.io/otel/sdk/resource"
semconv "go.opentelemetry.io/otel/semconv/v1.24.0"
"github.com/labstack/echo/v4"
"github.com/labstack/echo/v4/middleware"
realprometheus "github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promhttp"
)
// Meter can be a global/package variable.
var meter = otel.GetMeterProvider().Meter("echo")
const (
_ = iota // ignore first value by assigning to blank identifier
_KB float64 = 1 << (10 * iota)
_MB
_GB
_TB
)
const (
unitDimensionless = "1"
unitBytes = "By"
unitMilliseconds = "ms"
)
// reqDurBucketsSeconds is the buckets for request duration. Here, we use the prometheus defaults
var reqDurBucketsSeconds = []float64{.005, .01, .025, .05, .1, .25, .5, 1, 2.5, 5, 10}
var longExecBucketsSeconds = []float64{0.5, 1.0, 1.5, 2.5, 5.0, 10.0, 15.0, 25.0, 40.0, 60, 90, 120, 150, 200, 250, 300}
// byteBuckets is the buckets for request/response size. Here we define a spectrom from 1KB thru 1NB up to 10MB.
var byteBuckets = []float64{1.0 * _KB, 2.0 * _KB, 5.0 * _KB, 10.0 * _KB, 100 * _KB, 500 * _KB, 1.0 * _MB, 2.5 * _MB, 5.0 * _MB, 10.0 * _MB}
/*
RequestCounterLabelMappingFunc is a function which can be supplied to the middleware to control
the cardinality of the request counter's "url" label, which might be required in some contexts.
For instance, if for a "/customer/:name" route you don't want to generate a time series for every
possible customer name, you could use this function:
func(c echo.Context) string {
url := c.Request.URL.Path
for _, p := range c.Params {
if p.Key == "name" {
url = strings.Replace(url, p.Value, ":name", 1)
break
}
}
return url
}
which would map "/customer/alice" and "/customer/bob" to their template "/customer/:name".
It can also be applied for the "Host" label
*/
type RequestCounterLabelMappingFunc func(c echo.Context) string
// MiddlewareConfig contains the configuration for creating prometheus middleware collecting several default metrics.
type MiddlewareConfig struct {
// Skipper defines a function to skip middleware.
Skipper middleware.Skipper
ServiceName string
ServiceVersion string
// Namespace is components of the fully-qualified name of the Metric (created by joining Namespace,Subsystem and Name components with "_")
// this will take from ServiceName if not set
// Optional
Namespace string
EnableServerAddrPort bool
RequestCounterURLLabelMappingFunc RequestCounterLabelMappingFunc
RequestCounterHostLabelMappingFunc func(c echo.Context) (string, int)
// if enabled, it will add the scope information (otel_scope_name="otelmetric-demo",otel_scope_version="") to every metrics
WithScopeInfo bool
// Registry is the prometheus registry that will be used as the default Registerer and
// Gatherer if these are not specified.
Registry *realprometheus.Registry
// Registerer sets the prometheus.Registerer instance the middleware will register these metrics with.
// Defaults to: prometheus.DefaultRegisterer
Registerer realprometheus.Registerer
// Gatherer is the prometheus gatherer to gather metrics with.
// If not specified the Registry will be used as default.
Gatherer realprometheus.Gatherer
}
// Metrics contains the metrics gathered by the instance and its path
type Metrics struct {
requests metric.Int64Counter
activeRequests metric.Int64UpDownCounter
reqDuration metric.Float64Histogram
reqSize metric.Int64Histogram
resSize metric.Int64Histogram
router *echo.Echo
*MiddlewareConfig
}
// New generates a new set of metrics with a certain subsystem name
func New(config MiddlewareConfig) *Metrics {
if config.Skipper == nil {
config.Skipper = middleware.DefaultSkipper
}
if config.Registry != nil {
config.Registerer = config.Registry
config.Gatherer = config.Registry
}
if config.Registerer == nil {
config.Registerer = realprometheus.DefaultRegisterer
}
if config.Gatherer == nil {
config.Gatherer = realprometheus.DefaultGatherer
}
if config.RequestCounterURLLabelMappingFunc == nil {
config.RequestCounterURLLabelMappingFunc = func(c echo.Context) string {
// contains route path ala `/users/:id`
// as of Echo v4.10.1 path is empty for 404 cases (when router did not find any matching routes)
return c.Path()
}
}
if config.RequestCounterHostLabelMappingFunc == nil {
config.RequestCounterHostLabelMappingFunc = func(c echo.Context) (string, int) {
if c.Request().Host == "" {
return "", 0
}
host, port, err := net.SplitHostPort(c.Request().Host)
if err != nil {
return c.Request().Host, 0
}
portInt, _ := strconv.Atoi(port)
return host, portInt
}
}
p := &Metrics{
MiddlewareConfig: &config,
}
var err error
// Standard default metrics
p.requests, err = meter.Int64Counter(
// the result name is `requests_total`
// https://github.com/open-telemetry/opentelemetry-go/blob/46f2ce5ca6adaa264c37cdbba251c9184a06ed7f/exporters/prometheus/exporter.go#L74
// the exporter will enforce the `_total` suffix for counter, so we do not need it here
"http.requests",
// see https://github.com/open-telemetry/opentelemetry-go/pull/3776
// The go.opentelemetry.io/otel/metric/unit package is deprecated. Setup the equivalent unit string instead. (#3776)
// Setup "1" instead of unit.Dimensionless
// Setup "By" instead of unit.Bytes
// Setup "ms" instead of unit.Milliseconds
// the exported metrics name will force suffix by unit, see
// https://github.com/open-telemetry/opentelemetry-go/blob/46f2ce5ca6adaa264c37cdbba251c9184a06ed7f/exporters/prometheus/exporter.go#L315
//
// var unitSuffixes = map[string]string{
// "1": "_ratio",
// "By": "_bytes",
// "ms": "_milliseconds",
// }
// disable this behaviour by using `prometheus.WithoutUnits()` option
// or hack: do not set unit for counter to avoid the `_ratio` suffix
metric.WithDescription("How many HTTP requests processed, partitioned by status code and HTTP method."),
)
if err != nil {
panic(err)
}
p.activeRequests, err = meter.Int64UpDownCounter(
MetricHTTPServerActiveRequests,
metric.WithDescription("Number of active HTTP server requests."),
)
p.reqDuration, err = meter.Float64Histogram(
MetricHTTPServerRequestDuration,
metric.WithUnit("s"),
metric.WithDescription("Duration of HTTP server requests in seconds."),
)
if err != nil {
panic(err)
}
p.reqSize, err = meter.Int64Histogram(
MetricHTTPServerRequestBodySize,
metric.WithUnit(unitBytes),
metric.WithDescription("Size of HTTP server request bodies."),
)
if err != nil {
panic(err)
}
p.resSize, err = meter.Int64Histogram(
MetricHTTPServerResponseBodySize,
metric.WithUnit(unitBytes),
metric.WithDescription("Size of HTTP server response bodies."),
)
if err != nil {
panic(err)
}
p.initMetricsMeterProvider()
return p
}
func (p *Metrics) Middleware() echo.MiddlewareFunc {
return p.handlerFunc
}
// HandlerFunc defines handler function for middleware
func (p *Metrics) handlerFunc(next echo.HandlerFunc) echo.HandlerFunc {
return func(c echo.Context) error {
if p.Skipper(c) {
return next(c)
}
start := time.Now()
reqSz := computeApproximateRequestSize(c.Request())
host, port := p.RequestCounterHostLabelMappingFunc(c)
p.activeRequests.Add(c.Request().Context(), 1,
metric.WithAttributes(HttpRequestMethod.String(c.Request().Method), ServerAddress.String(host), URLScheme.String(c.Scheme())))
err := next(c)
status := c.Response().Status
if err != nil {
var httpError *echo.HTTPError
if errors.As(err, &httpError) {
status = httpError.Code
}
if status == 0 || status == http.StatusOK {
status = http.StatusInternalServerError
}
}
elapsed := time.Since(start) / time.Millisecond
url := p.RequestCounterURLLabelMappingFunc(c)
elapsedSeconds := float64(elapsed) / float64(1000)
commonAttributes := []attribute.KeyValue{
URLScheme.String(c.Scheme()),
HttpResponseStatusCode.Int(status),
HttpRequestMethod.String(c.Request().Method),
HttpRoute.String(url),
}
if p.EnableServerAddrPort {
if host != "" {
commonAttributes = append(commonAttributes, ServerAddress.String(host))
}
if port != 0 {
commonAttributes = append(commonAttributes, ServerPort.Int(port))
}
}
p.reqDuration.Record(c.Request().Context(), elapsedSeconds, metric.WithAttributes(commonAttributes...))
p.requests.Add(c.Request().Context(), 1,
metric.WithAttributes(commonAttributes...))
p.reqSize.Record(c.Request().Context(), int64(reqSz),
metric.WithAttributes(commonAttributes...))
resSz := float64(c.Response().Size)
p.resSize.Record(c.Request().Context(), int64(resSz),
metric.WithAttributes(commonAttributes...))
p.activeRequests.Add(c.Request().Context(), -1,
metric.WithAttributes(HttpRequestMethod.String(c.Request().Method), ServerAddress.String(host), URLScheme.String(c.Scheme())))
return err
}
}
func (p *Metrics) initMetricsMeterProvider() *prometheus.Exporter {
namespace := p.Namespace
if namespace == "" {
namespace = p.ServiceName
}
namespace = strings.ReplaceAll(namespace, "-", "_")
opts := []prometheus.Option{
prometheus.WithRegisterer(p.Registerer),
}
res, err := resource.Merge(resource.Default(),
resource.NewSchemaless(
semconv.ServiceName(p.ServiceName),
semconv.ServiceVersion(p.ServiceVersion),
semconv.ServiceNamespace(namespace),
))
if err != nil {
panic(err)
}
if namespace != "" {
opts = append(opts, prometheus.WithNamespace(namespace))
}
if !p.WithScopeInfo {
opts = append(opts, prometheus.WithoutScopeInfo())
}
exporter, err := prometheus.New(opts...)
if err != nil {
panic(err)
}
durationBucketsView := sdkmetric.NewView(
// TODO: support more views like:
// request_duration_seconds
// processing_time_seconds
// latency_seconds
// server_handling_seconds
sdkmetric.Instrument{Name: "*request.duration"},
sdkmetric.Stream{Aggregation: sdkmetric.AggregationExplicitBucketHistogram{
Boundaries: reqDurBucketsSeconds,
}},
)
execBucketsView := sdkmetric.NewView(
sdkmetric.Instrument{Name: "*exec.cost"},
sdkmetric.Stream{Aggregation: sdkmetric.AggregationExplicitBucketHistogram{
Boundaries: reqDurBucketsSeconds,
}},
)
longExecBucketsView := sdkmetric.NewView(
sdkmetric.Instrument{Name: "*long_exec.cost"},
sdkmetric.Stream{Aggregation: sdkmetric.AggregationExplicitBucketHistogram{
Boundaries: longExecBucketsSeconds,
}},
)
bytesBucketsView := sdkmetric.NewView(
sdkmetric.Instrument{Name: "*body.size"},
sdkmetric.Stream{Aggregation: sdkmetric.AggregationExplicitBucketHistogram{
Boundaries: byteBuckets,
}},
)
defaultView := sdkmetric.NewView(sdkmetric.Instrument{Name: "*", Kind: sdkmetric.InstrumentKindCounter},
sdkmetric.Stream{})
provider := sdkmetric.NewMeterProvider(
sdkmetric.WithResource(res),
// view see https://github.com/open-telemetry/opentelemetry-go/blob/v1.11.2/exporters/prometheus/exporter_test.go#L291
sdkmetric.WithReader(exporter),
sdkmetric.WithView(longExecBucketsView, execBucketsView, durationBucketsView, bytesBucketsView, defaultView),
)
otel.SetMeterProvider(provider)
return exporter
}
func (p *Metrics) ExporterHandler() echo.HandlerFunc {
opts := promhttp.HandlerOpts{}
if p.Registry != nil {
opts.Registry = p.Registry
}
h := promhttp.HandlerFor(p.Gatherer, opts)
return func(c echo.Context) error {
h.ServeHTTP(c.Response(), c.Request())
return nil
}
}
func computeApproximateRequestSize(r *http.Request) int {
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 s
}