Add Jaeger remote sampler

.github/dependabot.yml

@@ -465,6 +465,24 @@ updates:
     schedule:
       interval: "weekly"
       day: "sunday"
+  - package-ecosystem: "gomod"
+    directory: "/samplers/jaegerremote"
+    labels:
+      - dependencies
+      - go
+      - "Skip Changelog"
+    schedule:
+      interval: "weekly"
+      day: "sunday"
+  - package-ecosystem: "gomod"
+    directory: "/samplers/jaegerremote/example"
+    labels:
+      - dependencies
+      - go
+      - "Skip Changelog"
+    schedule:
+      interval: "weekly"
+      day: "sunday"
   - package-ecosystem: "gomod"
     directory: "/tools"
     labels:

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "samplers/jaegerremote/jaeger-idl"]
+	path = samplers/jaegerremote/jaeger-idl
+	url = https://github.com/jaegertracing/jaeger-idl

samplers/jaegerremote/Makefile

@@ -0,0 +1,9 @@
+PROTOC=docker run --rm -v${PWD}:${PWD} -w${PWD} otel/build-protobuf:latest --proto_path=${PWD}
+
+PROTO_INCLUDES=-I/usr/include/github.com/gogo/protobuf
+
+.PHONY: proto-gen
+proto-gen:
+	$(PROTOC) $(PROTO_INCLUDES) \
+	    --gogo_out=$(PWD)/internal/proto-gen \
+	    ${PWD}/jaeger-idl/proto/api_v2/sampling.proto

samplers/jaegerremote/README.md

@@ -0,0 +1,19 @@
+# Jaeger Remote Sampler
+
+This package implements [Jaeger remote sampler](https://www.jaegertracing.io/docs/latest/sampling/#collector-sampling-configuration).
+
+## Update generated Jaeger code
+
+Files generated from jaeger-idl are checked in and usually do not have to be regenerated.
+
+* Make sure the jaeger-idl submodule is synchronised.
+
+  ```
+  git submodule update --init jaeger-idl
+  ```
+
+*  Generate Go files from the .proto:
+
+  ```
+  make proto-gen
+  ```

samplers/jaegerremote/config.go

@@ -0,0 +1,80 @@
+// 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 jaegerremote // import "go.opentelemetry.io/contrib/samplers/jaeger_remote"
+
+import "time"
+
+const (
+	defaultPollingInterval = time.Minute
+	defaultSamplingRate    = 0.001
+)
+
+type config struct {
+	service             string
+	endpoint            string
+	pollingInterval     time.Duration
+	initialSamplingRate float64
+}
+
+func defaultConfig() *config {
+	return &config{
+		service:             "",
+		endpoint:            "http://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
+	})
+}
+
+// WithEndpoint sets the endpoint to retrieve the sampling strategy from.
+// Defaults to http://localhost:5778
+func WithEndpoint(endpoint string) Option {
+	return optionFunc(func(config *config) {
+		config.endpoint = endpoint
+	})
+}
+
+// WithPollingInterval sets the interval to poll for the sampling strategy
+// file. Defaults to 1 minute.
+func WithPollingInterval(pollingInterval time.Duration) Option {
+	return optionFunc(func(config *config) {
+		config.pollingInterval = pollingInterval
+	})
+}
+
+// WithInitialSamplingRate sets the sampling rate the sampler starts with,
+// before it has fetched the strategy file. Defaults to 0.001.
+func WithInitialSamplingRate(initialSamplingRate float64) Option {
+	return optionFunc(func(config *config) {
+		config.initialSamplingRate = initialSamplingRate
+	})
+}

samplers/jaegerremote/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 jaegerremote implements the Jaeger Remote protocol.
+package jaegerremote // import "go.opentelemetry.io/contrib/samplers/jaegerremote"

samplers/jaegerremote/example/docker-compose.yaml

@@ -0,0 +1,11 @@
+version: "3"
+services:
+
+  otel-collector:
+    image: otel/opentelemetry-collector:latest
+    command: [ "--config=/etc/otel-collector.yaml" ]
+    volumes:
+      - ./otel-collector.yaml:/etc/otel-collector.yaml
+      - ./strategies.json:/etc/strategies.json
+    ports:
+      - "5778:5778"  # default jaeger remote sampling port

samplers/jaegerremote/example/go.mod

@@ -0,0 +1,12 @@
+module go.opentelemetry.io/contrib/samplers/jaegerremote/example
+
+go 1.16
+
+require (
+	go.opentelemetry.io/contrib/samplers/jaegerremote v0.22.0
+	go.opentelemetry.io/otel v1.0.0-RC2
+	go.opentelemetry.io/otel/exporters/stdout/stdouttrace v1.0.0-RC2
+	go.opentelemetry.io/otel/sdk v1.0.0-RC2
+)
+
+replace go.opentelemetry.io/contrib/samplers/jaegerremote => ../