feat: add observer constructor (#251)

Author: nrwiersma

README.md

@@ -205,7 +205,13 @@ Here is an example of how one might use it:
 
 ```go
 func yourAction(c *cli.Context) error {
-     obsvr, err := newObserver(c)
+     obsvr, err := observe.NewFromCLI(c, "my-service", &observe.Options{
+        LogTimestamps: true,
+        StatsRuntime:  true,
+        TracingAttrs: []attribute.KeyValue{
+            semconv.ServiceVersionKey.String("1.0.0"),
+        },
+    })
     if err != nil {
         return err
     }
@@ -215,29 +221,6 @@ func yourAction(c *cli.Context) error {
 
 	return nil
 }
-
-func newObserver(c *cli.Context) (*observe.Observer, error) {
-    log, err := cmd.NewLogger(c)
-    if err != nil {
-        return nil, err
-    }
-
-    stats, err := cmd.NewStatter(c, log)
-    if err != nil {
-        return nil, err
-    }
-
-    tracer, err := cmd.NewTracer(c, log,
-        semconv.ServiceNameKey.String("my-service"),
-        semconv.ServiceVersionKey.String("1.0.0"),
-    )
-    if err != nil {
-        return nil, err
-    }
-    tracerCancel := func() { _ = tracer.Shutdown(context.Background()) }
-
-    return observe.New(log, stats, tracer, tracerCancel), nil
-}
 ```
 
 It also exposes `NewFake` which allows you to pass fake loggers, tracers and statters in your tests easily.

observe/doc.go

@@ -14,6 +14,15 @@ Example usage:
 		    	return nil, err
 		    }
 
+		    prof, err := cmd.NewProfiler(c, "my-service", log)
+		    if err != nil {
+		    	return nil, err
+		    }
+		    profStop := func() {}
+		    if prof != nil {
+		    	profStop = func() { _ = prof.Stop() }
+		    }
+
 		    tracer, err := cmd.NewTracer(c, log,
 		    	semconv.ServiceNameKey.String("my-service"),
 		    	semconv.ServiceVersionKey.String("1.0.0"),
@@ -23,7 +32,7 @@ Example usage:
 		    }
 		    tracerCancel := func() { _ = tracer.Shutdown(context.Background()) }
 
-		    return observe.New(log, stats, tracer, tracerCancel), nil
+		    return observe.New(log, stats, tracer, tracerCancel, profStop), nil
 	    }
 */
 package observe

observe/example_test.go

@@ -6,6 +6,7 @@ import (
 	"github.com/hamba/cmd/v2"
 	"github.com/hamba/cmd/v2/observe"
 	"github.com/urfave/cli/v2"
+	"go.opentelemetry.io/otel/attribute"
 	semconv "go.opentelemetry.io/otel/semconv/v1.17.0"
 )
 
@@ -24,6 +25,15 @@ func ExampleNew() {
 		return
 	}
 
+	prof, err := cmd.NewProfiler(c, "my-service", log)
+	if err != nil {
+		return
+	}
+	profStop := func() {}
+	if prof != nil {
+		profStop = func() { _ = prof.Stop() }
+	}
+
 	tracer, err := cmd.NewTracer(c, log,
 		semconv.ServiceNameKey.String("my-service"),
 		semconv.ServiceVersionKey.String("1.0.0"),
@@ -34,7 +44,25 @@ func ExampleNew() {
 	}
 	tracerCancel := func() { _ = tracer.Shutdown(context.Background()) }
 
-	obsrv := observe.New(log, stats, tracer, tracerCancel)
+	obsrv := observe.New(log, stats, tracer, tracerCancel, profStop)
+
+	_ = obsrv
+}
+
+func ExampleNewFromCLI() {
+	var c *cli.Context // Get this from your action.
+
+	obsrv, err := observe.NewFromCLI(c, "my-service", &observe.Options{
+		LogTimestamps: true,
+		StatsRuntime:  true,
+		TracingAttrs: []attribute.KeyValue{
+			semconv.ServiceVersionKey.String("1.0.0"),
+		},
+	})
+	if err != nil {
+		// Handle error.
+		return
+	}
 
 	_ = obsrv
 }

observe/observer.go

@@ -1,15 +1,36 @@
 package observe
 
 import (
+	"context"
 	"io"
 	"time"
 
+	otelpyroscope "github.com/grafana/otel-profiling-go"
+	"github.com/hamba/cmd/v2"
 	"github.com/hamba/logger/v2"
+	lctx "github.com/hamba/logger/v2/ctx"
 	"github.com/hamba/statter/v2"
+	"github.com/hamba/statter/v2/runtime"
+	"github.com/hamba/statter/v2/tags"
+	"github.com/urfave/cli/v2"
 	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	semconv "go.opentelemetry.io/otel/semconv/v1.17.0"
 	"go.opentelemetry.io/otel/trace"
 )
 
+// Options optionally configures an observer.
+type Options struct {
+	LogTimeFormat string
+	LogTimestamps bool
+	LogCtx        []logger.Field
+
+	StatsRuntime bool
+	StatsTags    []statter.Tag
+
+	TracingAttrs []attribute.KeyValue
+}
+
 // Observer contains observability primitives.
 type Observer struct {
 	Log       *logger.Logger
@@ -29,6 +50,81 @@ func New(log *logger.Logger, stats *statter.Statter, traceProv trace.TracerProvi
 	}
 }
 
+// NewFromCLI returns an observer with the given observability primitives.
+//
+//nolint:cyclop // Splitting this will not make it simpler.
+func NewFromCLI(cliCtx *cli.Context, svc string, opts *Options) (*Observer, error) {
+	var closeFns []func()
+
+	if opts == nil {
+		opts = &Options{}
+	}
+
+	// Logger.
+	log, err := cmd.NewLogger(cliCtx)
+	if err != nil {
+		return nil, err
+	}
+	if opts.LogTimeFormat != "" {
+		logger.TimeFormat = opts.LogTimeFormat
+	}
+	if opts.LogTimestamps {
+		closeFns = append(closeFns, log.WithTimestamp())
+	}
+	opts.LogCtx = append([]logger.Field{lctx.Str("svc", svc)}, opts.LogCtx...)
+	log = log.With(opts.LogCtx...)
+
+	// Statter.
+	stats, err := cmd.NewStatter(cliCtx, log)
+	if err != nil {
+		for _, fn := range closeFns {
+			fn()
+		}
+		return nil, err
+	}
+	closeFns = append(closeFns, func() { _ = stats.Close() })
+	if opts.StatsRuntime {
+		go runtime.Collect(stats)
+	}
+	opts.StatsTags = append([]statter.Tag{tags.Str("svc", svc)}, opts.StatsTags...)
+	stats = stats.With("", opts.StatsTags...)
+
+	// Profiler.
+	prof, err := cmd.NewProfiler(cliCtx, svc, log)
+	if err != nil {
+		for _, fn := range closeFns {
+			fn()
+		}
+		return nil, err
+	}
+	if prof != nil {
+		closeFns = append(closeFns, func() { _ = prof.Stop() })
+	}
+
+	// Tracer.
+	opts.TracingAttrs = append(opts.TracingAttrs, semconv.ServiceNameKey.String(svc))
+	tracer, err := cmd.NewTracer(cliCtx, log, opts.TracingAttrs...)
+	if err != nil {
+		for _, fn := range closeFns {
+			fn()
+		}
+		return nil, err
+	}
+	closeFns = append(closeFns, func() { _ = tracer.Shutdown(context.Background()) })
+
+	var tp trace.TracerProvider = tracer
+	if prof != nil && tracer != nil {
+		tp = otelpyroscope.NewTracerProvider(tp)
+	}
+
+	return &Observer{
+		Log:       log,
+		Stats:     stats,
+		TraceProv: tp,
+		closeFns:  closeFns,
+	}, nil
+}
+
 // Tracer returns a tracer with the given name and options.
 // If no trace provider has been set, this function will panic.
 func (o *Observer) Tracer(name string, opts ...trace.TracerOption) trace.Tracer {