Combine the Push and Pull metric controllers (#1378)

* Push->basic

* Repackage

* Rename away from push

* Make exporter optional; export from a separate goroutine

* Move pull_test into controller_test

* Precommit pass

* New OTLP/Prom example

* Precommit

* Fix the example

* Shorten the example

* Test starting controller w/o exporter

* Test export timeout

* Remove ancient example & lint

* go.mod revert & tidy

* Comments

* Tidy a diff

* Tidy a diff

* Move export kind selector in the new example

* Split this test into its original parts

* Reduce diff size

* Changelog

* Remove extra Add/Done pair

* Remove unused stopCh param; document the Stop behavior

* Typo

* Use ctx

* Missed v0.15

* Apply PR feedback

* Precommit pass

* 0.14 -> 0.15 in new file

* Remove diff chunk markers

* Fix OTLP example

* Upstream

* dashpole comments

* aneurysm9 feedback

* Tidy go.sum

.github/dependabot.yml

@@ -48,7 +48,7 @@ updates:
       interval: weekly
   -
     package-ecosystem: gomod
-    directory: /example/basic
+    directory: /example/prom-collector
     labels:
       - dependencies
       - go

.gitignore

@@ -10,10 +10,14 @@ coverage.*
 
 gen/
 
-/example/basic/basic
+/example/grpc/client/client
+/example/grpc/server/server
+/example/http/client/client
+/example/http/server/server
 /example/jaeger/jaeger
 /example/namedtracer/namedtracer
 /example/opencensus/opencensus
 /example/prometheus/prometheus
+/example/prom-collector/prom-collector
 /example/zipkin/zipkin
 /example/otel-collector/otel-collector

CHANGELOG.md

@@ -36,6 +36,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - `SamplingResult` now passed a `Tracestate` from the parent `SpanContext` (#1432)
 - Moved gRPC driver for OTLP exporter to `exporters/otlp/otlpgrpc`. (#1420)
 - The `TraceContext` propagator now correctly propagates `TraceState` through the `SpanContext`. (#1447)
+- Metric Push and Pull Controller components are combined into a single "basic" Controller:
+  - `WithExporter()` and `Start()` to configure Push behavior
+  - `Start()` is optional; use `Collect()` and `ForEach()` for Pull behavior
+  - `Start()` and `Stop()` accept Context. (#1378)
 
 ### Removed
 
@@ -58,7 +62,6 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Bump `github.com/google/go-cmp` from 0.5.3 to 0.5.4 (#1374)
 - Bump `github.com/golangci/golangci-lint` in `/internal/tools` (#1375)
 
-
 ### Fixed
 
 - Metric SDK `SumObserver` and `UpDownSumObserver` instruments correctness fixes. (#1381)

example/otel-collector/main.go

@@ -31,8 +31,8 @@ import (
 	"go.opentelemetry.io/otel/label"
 	"go.opentelemetry.io/otel/metric"
 	"go.opentelemetry.io/otel/propagation"
-	"go.opentelemetry.io/otel/sdk/metric/controller/push"
-	"go.opentelemetry.io/otel/sdk/metric/processor/basic"
+	controller "go.opentelemetry.io/otel/sdk/metric/controller/basic"
+	processor "go.opentelemetry.io/otel/sdk/metric/processor/basic"
 	"go.opentelemetry.io/otel/sdk/metric/selector/simple"
 	"go.opentelemetry.io/otel/sdk/resource"
 	sdktrace "go.opentelemetry.io/otel/sdk/trace"
@@ -73,28 +73,27 @@ func initProvider() func() {
 		sdktrace.WithSpanProcessor(bsp),
 	)
 
-	pusher := push.New(
-		basic.New(
+	cont := controller.New(
+		processor.New(
 			simple.NewWithExactDistribution(),
 			exp,
 		),
-		exp,
-		push.WithPeriod(2*time.Second),
+		controller.WithPusher(exp),
+		controller.WithCollectPeriod(2*time.Second),
 	)
 
 	// set global propagator to tracecontext (the default is no-op).
 	otel.SetTextMapPropagator(propagation.TraceContext{})
 	otel.SetTracerProvider(tracerProvider)
-	otel.SetMeterProvider(pusher.MeterProvider())
-	pusher.Start()
+	otel.SetMeterProvider(cont.MeterProvider())
+	handleErr(cont.Start(context.Background()), "failed to start controller")
 
 	return func() {
 		// Shutdown will flush any remaining spans.
 		handleErr(tracerProvider.Shutdown(ctx), "failed to shutdown TracerProvider")
 
 		// Push any last metric events to the exporter.
-		pusher.Stop()
-		handleErr(exp.Shutdown(ctx), "failed to stop exporter")
+		handleErr(cont.Stop(context.Background()), "failed to stop controller")
 	}
 }
 

example/prom-collector/README.md

@@ -0,0 +1,3 @@
+This example demonstrates a metrics export pipeline that supports
+Prometheus (pull) and simultaneously exports OTLP to an OpenTelemetry
+endpoint (push).

example/prom-collector/go.mod

@@ -0,0 +1,18 @@
+module go.opentelemetry.io/otel/example/prom-collector
+
+go 1.14
+
+replace (
+	go.opentelemetry.io/otel => ../..
+	go.opentelemetry.io/otel/exporters/metric/prometheus => ../../exporters/metric/prometheus
+	go.opentelemetry.io/otel/exporters/otlp => ../../exporters/otlp
+	go.opentelemetry.io/otel/sdk => ../../sdk
+)
+
+require (
+	go.opentelemetry.io/otel v0.15.0
+	go.opentelemetry.io/otel/exporters/metric/prometheus v0.15.0
+	go.opentelemetry.io/otel/exporters/otlp v0.15.0
+	go.opentelemetry.io/otel/sdk v0.15.0
+	google.golang.org/grpc v1.34.0
+)