WIP - Add remote sampling extension

defaults/defaults.go

@@ -27,6 +27,7 @@ import (
 	"github.com/open-telemetry/opentelemetry-collector/extension"
 	"github.com/open-telemetry/opentelemetry-collector/extension/healthcheckextension"
 	"github.com/open-telemetry/opentelemetry-collector/extension/pprofextension"
+	"github.com/open-telemetry/opentelemetry-collector/extension/remotesamplingextension"
 	"github.com/open-telemetry/opentelemetry-collector/extension/zpagesextension"
 	"github.com/open-telemetry/opentelemetry-collector/oterr"
 	"github.com/open-telemetry/opentelemetry-collector/processor"
@@ -55,6 +56,7 @@ func Components() (
 		&healthcheckextension.Factory{},
 		&pprofextension.Factory{},
 		&zpagesextension.Factory{},
+		&remotesamplingextension.Factory{},
 	)
 	if err != nil {
 		errs = append(errs, err)

defaults/defaults_test.go

@@ -32,6 +32,7 @@ import (
 	"github.com/open-telemetry/opentelemetry-collector/extension"
 	"github.com/open-telemetry/opentelemetry-collector/extension/healthcheckextension"
 	"github.com/open-telemetry/opentelemetry-collector/extension/pprofextension"
+	"github.com/open-telemetry/opentelemetry-collector/extension/remotesamplingextension"
 	"github.com/open-telemetry/opentelemetry-collector/extension/zpagesextension"
 	"github.com/open-telemetry/opentelemetry-collector/processor"
 	"github.com/open-telemetry/opentelemetry-collector/processor/attributesprocessor"
@@ -49,9 +50,10 @@ import (
 
 func TestDefaultComponents(t *testing.T) {
 	expectedExtensions := map[string]extension.Factory{
-		"health_check": &healthcheckextension.Factory{},
-		"pprof":        &pprofextension.Factory{},
-		"zpages":       &zpagesextension.Factory{},
+		"health_check":   &healthcheckextension.Factory{},
+		"pprof":          &pprofextension.Factory{},
+		"zpages":         &zpagesextension.Factory{},
+		"remotesampling": &remotesamplingextension.Factory{},
 	}
 	expectedReceivers := map[string]receiver.Factory{
 		"jaeger":     &jaegerreceiver.Factory{},

extension/remotesamplingextension/config.go

@@ -0,0 +1,35 @@
+// Copyright 2019, OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package remotesamplingextension
+
+import (
+	"github.com/open-telemetry/opentelemetry-collector/config/configmodels"
+)
+
+// Config has the configuration settings for the remote sampling extension,
+// used to fetch sampling configuration from the upstream Jaeger collector instance.
+//
+// It is an extension of configmodels.ExtensionSettings
+type Config struct {
+	configmodels.ExtensionSettings `mapstructure:",squash"`
+
+	// Port is the port used to publish the health check status.
+	// Default is `5778` (https://www.jaegertracing.io/docs/1.15/deployment/#agent).
+	Port uint16 `mapstructure:"port"`
+
+	// Addr is the upstream Jaeger collector address that can be used to fetch
+	// sampling configurations. The default value is `:14250`.
+	Addr string `mapstructure:"addr"`
+}

extension/remotesamplingextension/config_test.go

@@ -0,0 +1,56 @@
+// Copyright 2019, OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package remotesamplingextension
+
+import (
+	"path"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/open-telemetry/opentelemetry-collector/config"
+	"github.com/open-telemetry/opentelemetry-collector/config/configmodels"
+)
+
+func TestLoadConfig(t *testing.T) {
+	factories, err := config.ExampleComponents()
+	assert.Nil(t, err)
+
+	factory := &Factory{}
+	factories.Extensions[typeStr] = factory
+	cfg, err := config.LoadConfigFile(t, path.Join(".", "testdata", "config.yaml"), factories)
+
+	require.Nil(t, err)
+	require.NotNil(t, cfg)
+
+	ext0 := cfg.Extensions["remotesampling"]
+	assert.Equal(t, factory.CreateDefaultConfig(), ext0)
+
+	ext1 := cfg.Extensions["remotesampling/1"]
+	assert.Equal(t,
+		&Config{
+			ExtensionSettings: configmodels.ExtensionSettings{
+				TypeVal: "remotesampling",
+				NameVal: "remotesampling/1",
+			},
+			Port: 5779,
+			Addr: "0.0.0.0:14251",
+		},
+		ext1)
+
+	assert.Equal(t, 1, len(cfg.Service.Extensions))
+	assert.Equal(t, "remotesampling/1", cfg.Service.Extensions[0])
+}

extension/remotesamplingextension/doc.go

@@ -0,0 +1,17 @@
+// Copyright 2019, OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package remotesamplingextension implements an extension that serves as a proxy
+// and routes client requests for sampling config to the Jaeger collector.
+package remotesamplingextension

extension/remotesamplingextension/factory.go

@@ -0,0 +1,88 @@
+// Copyright 2019, OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package remotesamplingextension
+
+import (
+	"errors"
+	"sync/atomic"
+
+	"go.uber.org/zap"
+
+	"github.com/open-telemetry/opentelemetry-collector/config/configmodels"
+	"github.com/open-telemetry/opentelemetry-collector/extension"
+)
+
+const (
+	// The value of extension "type" in configuration.
+	typeStr = "remotesampling"
+)
+
+// Factory is the factory for the extension.
+type Factory struct {
+}
+
+var _ (extension.Factory) = (*Factory)(nil)
+
+// Type gets the type of the config created by this factory.
+func (f *Factory) Type() string {
+	return typeStr
+}
+
+// CreateDefaultConfig creates the default configuration for the extension.
+func (f *Factory) CreateDefaultConfig() configmodels.Extension {
+	return &Config{
+		ExtensionSettings: configmodels.ExtensionSettings{
+			TypeVal: typeStr,
+			NameVal: typeStr,
+		},
+		Port: 5778,
+		Addr: "0.0.0.0:14250",
+	}
+}
+
+// CreateExtension creates the extension based on this config.
+func (f *Factory) CreateExtension(
+	logger *zap.Logger,
+	cfg configmodels.Extension,
+) (extension.ServiceExtension, error) {
+	config := cfg.(*Config)
+	if config.Addr == "" {
+		return nil, errors.New("\"Addr\" is required when using the \"remotesampling\" extension")
+	}
+	if config.Port == 0 {
+		return nil, errors.New("\"Port\" is required when using the \"remotesampling\" extension")
+	}
+
+	// The runtime settings are global to the application, so while in principle it
+	// is possible to have more than one instance, running multiple will mean that
+	// the settings of the last started instance will prevail. In order to avoid
+	// this issue we will allow the creation of a single instance once per process
+	// while keeping the private function that allow the creation of multiple
+	// instances for unit tests. Summary: only a single instance can be created
+	// via the factory.
+	if !atomic.CompareAndSwapInt32(&instanceState, instanceNotCreated, instanceCreated) {
+		return nil, errors.New("only a single instance can be created per process")
+	}
+
+	return newServer(*config, logger)
+}
+
+// See comment in CreateExtension how these are used.
+var instanceState int32
+
+const (
+	instanceNotCreated int32 = 0
+	instanceCreated    int32 = 1
+)

extension/remotesamplingextension/factory_test.go

@@ -0,0 +1,83 @@
+// Copyright 2019, OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package remotesamplingextension
+
+import (
+	"sync/atomic"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/zap"
+
+	"github.com/open-telemetry/opentelemetry-collector/config/configcheck"
+	"github.com/open-telemetry/opentelemetry-collector/config/configmodels"
+)
+
+func TestFactory_Type(t *testing.T) {
+	factory := Factory{}
+	require.Equal(t, typeStr, factory.Type())
+}
+
+func TestFactory_CreateDefaultConfig(t *testing.T) {
+	factory := Factory{}
+	cfg := factory.CreateDefaultConfig()
+	assert.Equal(t, &Config{
+		ExtensionSettings: configmodels.ExtensionSettings{
+			NameVal: typeStr,
+			TypeVal: typeStr,
+		},
+		Port: 5778,
+		Addr: "0.0.0.0:14250",
+	},
+		cfg)
+
+	assert.NoError(t, configcheck.ValidateConfig(cfg))
+	ext, err := factory.CreateExtension(zap.NewNop(), cfg)
+	require.NoError(t, err)
+	require.NotNil(t, ext)
+
+	// Restore instance tracking from factory, for other tests.
+	atomic.StoreInt32(&instanceState, instanceNotCreated)
+}
+
+func TestFactory_CreateExtension(t *testing.T) {
+	factory := Factory{}
+	cfg := factory.CreateDefaultConfig().(*Config)
+
+	ext, err := factory.CreateExtension(zap.NewNop(), cfg)
+	require.NoError(t, err)
+	require.NotNil(t, ext)
+
+	// Restore instance tracking from factory, for other tests.
+	atomic.StoreInt32(&instanceState, instanceNotCreated)
+}
+
+func TestFactory_CreateExtensionOnlyOnce(t *testing.T) {
+	factory := Factory{}
+	cfg := factory.CreateDefaultConfig().(*Config)
+
+	logger := zap.NewNop()
+	ext, err := factory.CreateExtension(logger, cfg)
+	require.NoError(t, err)
+	require.NotNil(t, ext)
+
+	ext1, err := factory.CreateExtension(logger, cfg)
+	require.Error(t, err)
+	require.Nil(t, ext1)
+
+	// Restore instance tracking from factory, for other tests.
+	atomic.StoreInt32(&instanceState, instanceNotCreated)
+}