Add Jaeger remote sampler

samplers/jaeger_remote/README.md

@@ -0,0 +1,5 @@
+# Jaeger Remote Sampler
+
+This package implements a `"go.opentelemetry.io/otel/sdk".Sampler` that fetches its configuration from a Jaeger agent.
+
+The sampling strategy definition: [sampling.proto](https://github.com/jaegertracing/jaeger-idl/blob/master/proto/api_v2/sampling.proto).

samplers/jaeger_remote/config.go

@@ -0,0 +1,69 @@
+// Copyright The 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 jaeger_remote // import "go.opentelemetry.io/contrib/samplers/jaeger_remote"
+
+import "time"
+
+type config struct {
+	service             string
+	endpoint            string
+	pollingInterval     time.Duration
+	initialSamplingRate float64
+}
+
+func defaultConfig() *config {
+	return &config{
+		service:             "",
+		endpoint:            "localhost:5778",
+		pollingInterval:     defaultPollingInterval,
+		initialSamplingRate: defaultSamplingRate,
+	}
+}
+
+type Option interface {
+	apply(config *config)
+}
+
+type optionFunc func(config *config)
+
+var _ Option = optionFunc(nil)
+
+func (fn optionFunc) apply(config *config) {
+	fn(config)
+}
+
+func WithService(service string) Option {
+	return optionFunc(func(config *config) {
+		config.service = service
+	})
+}
+
+func WithEndpoint(endpoint string) Option {
+	return optionFunc(func(config *config) {
+		config.endpoint = endpoint
+	})
+}
+
+func WithPollingInterval(pollingInterval time.Duration) Option {
+	return optionFunc(func(config *config) {
+		config.pollingInterval = pollingInterval
+	})
+}
+
+func WithInitialSamplingRate(initialSamplingRate float64) Option {
+	return optionFunc(func(config *config) {
+		config.initialSamplingRate = initialSamplingRate
+	})
+}

samplers/jaeger_remote/doc.go

@@ -0,0 +1,16 @@
+// Copyright The 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 jaeger_remote implements the Jaeger Remote protocol.
+package jaeger_remote // import "go.opentelemetry.io/contrib/samplers/jaeger_remote"

samplers/jaeger_remote/fetcher.go

@@ -0,0 +1,59 @@
+// Copyright The 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 jaeger_remote // import "go.opentelemetry.io/contrib/samplers/jaeger_remote"
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+
+	jaeger_api_v2 "github.com/jaegertracing/jaeger/proto-gen/api_v2"
+)
+
+type samplingStrategyFetcher interface {
+	Fetch() (jaeger_api_v2.SamplingStrategyResponse, error)
+}
+
+type samplingStrategyFetcherImpl struct {
+	serviceName string
+	endpoint    string
+	httpClient  *http.Client
+}
+
+var _ samplingStrategyFetcher = samplingStrategyFetcherImpl{}
+
+func (f samplingStrategyFetcherImpl) Fetch() (s jaeger_api_v2.SamplingStrategyResponse, err error) {
+	uri := f.endpoint + "?service=" + url.QueryEscape(f.serviceName)
+
+	resp, err := f.httpClient.Get(uri)
+	if err != nil {
+		return
+	}
+	defer resp.Body.Close()
+
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return s, fmt.Errorf("request failed (%d): %s", resp.StatusCode, body)
+	}
+
+	err = json.Unmarshal(body, &s)
+	return
+}

samplers/jaeger_remote/fetcher_test.go

@@ -0,0 +1,75 @@
+package jaeger_remote
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	jaeger_api_v2 "github.com/jaegertracing/jaeger/proto-gen/api_v2"
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_samplingStrategyFetcher_Fetch(t *testing.T) {
+	tests := []struct {
+		name               string
+		responseStatusCode int
+		responseBody       string
+		expectedErr        string
+		expectedStrategy   jaeger_api_v2.SamplingStrategyResponse
+	}{
+		{
+			name:               "RequestOK",
+			responseStatusCode: http.StatusOK,
+			responseBody: `{
+  "strategyType": 0,
+  "probabilisticSampling": {
+    "samplingRate": 0.5
+  }
+}`,
+			expectedStrategy: jaeger_api_v2.SamplingStrategyResponse{
+				StrategyType: jaeger_api_v2.SamplingStrategyType_PROBABILISTIC,
+				ProbabilisticSampling: &jaeger_api_v2.ProbabilisticSamplingStrategy{
+					SamplingRate: 0.5,
+				},
+			},
+		},
+		{
+			name:               "RequestError",
+			responseStatusCode: http.StatusTooManyRequests,
+			responseBody:       "you are sending too many requests",
+			expectedErr:        "request failed (429): you are sending too many requests",
+		},
+		{
+			name:               "InvalidResponseData",
+			responseStatusCode: http.StatusOK,
+			responseBody:       `{"strategy`,
+			expectedErr:        "unexpected end of JSON input",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				assert.Equal(t, "/?service=foo", r.URL.RequestURI())
+
+				w.WriteHeader(tt.responseStatusCode)
+				_, err := w.Write([]byte(tt.responseBody))
+				assert.NoError(t, err)
+			}))
+			defer server.Close()
+
+			fetcher := samplingStrategyFetcherImpl{
+				serviceName: "foo",
+				endpoint:    server.URL,
+				httpClient:  http.DefaultClient,
+			}
+
+			strategyResponse, err := fetcher.Fetch()
+			if tt.expectedErr != "" {
+				assert.EqualError(t, err, tt.expectedErr)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.expectedStrategy, strategyResponse)
+			}
+		})
+	}
+}

samplers/jaeger_remote/go.mod

@@ -0,0 +1,10 @@
+module go.opentelemetry.io/contrib/samplers/jaeger_remote
+
+go 1.16
+
+require (
+	github.com/jaegertracing/jaeger v1.24.0
+	github.com/stretchr/testify v1.7.0
+	go.opentelemetry.io/otel v1.0.0-RC2
+	go.opentelemetry.io/otel/sdk v1.0.0-RC2
+)