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example_test.go
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example_test.go
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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
package metric_test
import (
"context"
"database/sql"
"fmt"
"net/http"
"runtime"
"time"
"go.opentelemetry.io/otel"
"go.opentelemetry.io/otel/attribute"
"go.opentelemetry.io/otel/metric"
semconv "go.opentelemetry.io/otel/semconv/v1.26.0"
)
var meter = otel.Meter("my-service-meter")
func ExampleMeter_synchronous() {
// Create a histogram using the global MeterProvider.
workDuration, err := meter.Int64Histogram(
"workDuration",
metric.WithUnit("ms"))
if err != nil {
fmt.Println("Failed to register instrument")
panic(err)
}
startTime := time.Now()
ctx := context.Background()
// Do work
// ...
workDuration.Record(ctx, time.Since(startTime).Milliseconds())
}
func ExampleMeter_asynchronous_single() {
_, err := meter.Int64ObservableGauge(
"DiskUsage",
metric.WithUnit("By"),
metric.WithInt64Callback(func(_ context.Context, obsrv metric.Int64Observer) error {
// Do the real work here to get the real disk usage. For example,
//
// usage, err := GetDiskUsage(diskID)
// if err != nil {
// if retryable(err) {
// // Retry the usage measurement.
// } else {
// return err
// }
// }
//
// For demonstration purpose, a static value is used here.
usage := 75000
obsrv.Observe(int64(usage), metric.WithAttributes(attribute.Int("disk.id", 3)))
return nil
}),
)
if err != nil {
fmt.Println("failed to register instrument")
panic(err)
}
}
func ExampleMeter_asynchronous_multiple() {
// This is just a sample of memory stats to record from the Memstats
heapAlloc, err := meter.Int64ObservableUpDownCounter("heapAllocs")
if err != nil {
fmt.Println("failed to register updown counter for heapAllocs")
panic(err)
}
gcCount, err := meter.Int64ObservableCounter("gcCount")
if err != nil {
fmt.Println("failed to register counter for gcCount")
panic(err)
}
_, err = meter.RegisterCallback(
func(_ context.Context, o metric.Observer) error {
memStats := &runtime.MemStats{}
// This call does work
runtime.ReadMemStats(memStats)
o.ObserveInt64(heapAlloc, int64(memStats.HeapAlloc))
o.ObserveInt64(gcCount, int64(memStats.NumGC))
return nil
},
heapAlloc,
gcCount,
)
if err != nil {
fmt.Println("Failed to register callback")
panic(err)
}
}
// Counters can be used to measure a non-negative, increasing value.
//
// Here's how you might report the number of calls for an HTTP handler.
func ExampleMeter_counter() {
apiCounter, err := meter.Int64Counter(
"api.counter",
metric.WithDescription("Number of API calls."),
metric.WithUnit("{call}"),
)
if err != nil {
panic(err)
}
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
apiCounter.Add(r.Context(), 1)
// do some work in an API call
})
}
// UpDown counters can increment and decrement, allowing you to observe
// a cumulative value that goes up or down.
//
// Here's how you might report the number of items of some collection.
func ExampleMeter_upDownCounter() {
var err error
itemsCounter, err := meter.Int64UpDownCounter(
"items.counter",
metric.WithDescription("Number of items."),
metric.WithUnit("{item}"),
)
if err != nil {
panic(err)
}
_ = func() {
// code that adds an item to the collection
itemsCounter.Add(context.Background(), 1)
}
_ = func() {
// code that removes an item from the collection
itemsCounter.Add(context.Background(), -1)
}
}
// Histograms are used to measure a distribution of values over time.
//
// Here's how you might report a distribution of response times for an HTTP handler.
func ExampleMeter_histogram() {
histogram, err := meter.Float64Histogram(
"task.duration",
metric.WithDescription("The duration of task execution."),
metric.WithUnit("s"),
metric.WithExplicitBucketBoundaries(.005, .01, .025, .05, .075, .1, .25, .5, .75, 1, 2.5, 5, 7.5, 10),
)
if err != nil {
panic(err)
}
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
start := time.Now()
// do some work in an API call
duration := time.Since(start)
histogram.Record(r.Context(), duration.Seconds())
})
}
// Observable counters can be used to measure an additive, non-negative,
// monotonically increasing value.
//
// Here's how you might report time since the application started.
func ExampleMeter_observableCounter() {
start := time.Now()
if _, err := meter.Float64ObservableCounter(
"uptime",
metric.WithDescription("The duration since the application started."),
metric.WithUnit("s"),
metric.WithFloat64Callback(func(_ context.Context, o metric.Float64Observer) error {
o.Observe(float64(time.Since(start).Seconds()))
return nil
}),
); err != nil {
panic(err)
}
}
// Observable UpDown counters can increment and decrement, allowing you to measure
// an additive, non-negative, non-monotonically increasing cumulative value.
//
// Here's how you might report some database metrics.
func ExampleMeter_observableUpDownCounter() {
// The function registers asynchronous metrics for the provided db.
// Make sure to unregister metric.Registration before closing the provided db.
_ = func(db *sql.DB, meter metric.Meter, poolName string) (metric.Registration, error) {
max, err := meter.Int64ObservableUpDownCounter(
"db.client.connections.max",
metric.WithDescription("The maximum number of open connections allowed."),
metric.WithUnit("{connection}"),
)
if err != nil {
return nil, err
}
waitTime, err := meter.Int64ObservableUpDownCounter(
"db.client.connections.wait_time",
metric.WithDescription("The time it took to obtain an open connection from the pool."),
metric.WithUnit("ms"),
)
if err != nil {
return nil, err
}
reg, err := meter.RegisterCallback(
func(_ context.Context, o metric.Observer) error {
stats := db.Stats()
o.ObserveInt64(max, int64(stats.MaxOpenConnections))
o.ObserveInt64(waitTime, int64(stats.WaitDuration))
return nil
},
max,
waitTime,
)
if err != nil {
return nil, err
}
return reg, nil
}
}
// Observable Gauges should be used to measure non-additive values.
//
// Here's how you might report memory usage of the heap objects used
// in application.
func ExampleMeter_observableGauge() {
if _, err := meter.Int64ObservableGauge(
"memory.heap",
metric.WithDescription(
"Memory usage of the allocated heap objects.",
),
metric.WithUnit("By"),
metric.WithInt64Callback(func(_ context.Context, o metric.Int64Observer) error {
var m runtime.MemStats
runtime.ReadMemStats(&m)
o.Observe(int64(m.HeapAlloc))
return nil
}),
); err != nil {
panic(err)
}
}
// You can add Attributes by using the [WithAttributeSet] and [WithAttributes] options.
//
// Here's how you might add the HTTP status code attribute to your recordings.
func ExampleMeter_attributes() {
apiCounter, err := meter.Int64UpDownCounter(
"api.finished.counter",
metric.WithDescription("Number of finished API calls."),
metric.WithUnit("{call}"),
)
if err != nil {
panic(err)
}
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
// do some work in an API call and set the response HTTP status code
statusCode := http.StatusOK
apiCounter.Add(r.Context(), 1,
metric.WithAttributes(semconv.HTTPResponseStatusCode(statusCode)))
})
}