Add Jaeger remote sampler

.github/dependabot.yml

@@ -674,6 +674,24 @@ 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:

samplers/jaegerremote/Makefile

@@ -0,0 +1,11 @@
+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:
+	mkdir -p internal/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 +1,38 @@
+# Jaeger Remote Sampler
+
+This package implements [Jaeger remote sampler](https://www.jaegertracing.io/docs/latest/sampling/#collector-sampling-configuration).
+
+## Example
+
+[example/](./example) shows how to host remote sampling strategies using the OpenTelemetry Collector.
+The Collector uses the Jaeger receiver to host the strategy file. Note you do not need to run Jaeger to make use of the Jaeger remote sampling protocol. However, you do need Jaeger backend if you want to utilize its adaptive sampling engine that auto-calculates remote sampling strategies.
+
+Run the OpenTelemetry Collector using docker-compose:
+
+```shell
+$ docker-compose up -d
+```
+
+You can fetch the strategy file using curl:
+
+```shell
+$ curl 'localhost:5778/sampling?service=foo'
+$ curl 'localhost:5778/sampling?service=myService'
+```
+
+Run the Go program.
+This program will start with an initial sampling percentage of 50% and tries to fetch the sampling strategies from the OpenTelemetry Collector.
+It will print the entire Jaeger remote sampler structure every 10 seconds, this allows you to observe the internal sampler.
+
+```shell
+$ go run .
+```
+
+## Update generated Jaeger code
+
+Code is generated using the .proto files from [jaeger-idl](https://github.com/jaegertracing/jaeger-idl).
+In case [sampling.proto](./jaeger-idl/proto/api_v2/sampling.proto) is modified these have to be regenerated.
+
+```shell
+$ make proto-gen
+```

samplers/jaegerremote/constants.go

@@ -0,0 +1,31 @@
+// Copyright The OpenTelemetry Authors
+// Copyright (c) 2021 The Jaeger Authors.
+// Copyright (c) 2017 Uber Technologies, Inc.
+//
+// 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 (
+	"fmt"
+)
+
+const (
+	// defaultSamplingServerPort is the default port to fetch sampling config from, via http
+	defaultSamplingServerPort = 5778
+)
+
+var (
+	// defaultSamplingServerURL is the default url to fetch sampling config from, via http
+	defaultSamplingServerURL = fmt.Sprintf("http://127.0.0.1:%d/sampling", defaultSamplingServerPort)
+)

samplers/jaegerremote/doc.go

@@ -0,0 +1,19 @@
+// Copyright The OpenTelemetry Authors
+// Copyright (c) 2021 The Jaeger Authors.
+// Copyright (c) 2017 Uber Technologies, Inc.
+//
+// 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.
+// import "go.opentelemetry.io/contrib/samplers/jaegerremote"
+
+package 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 +1,13 @@
+module go.opentelemetry.io/contrib/samplers/jaegerremote/example
+
+go 1.16
+
+require (
+	github.com/davecgh/go-spew v1.1.1
+	go.opentelemetry.io/contrib/samplers/jaegerremote v0.22.0
+	go.opentelemetry.io/otel v1.1.0
+	go.opentelemetry.io/otel/exporters/stdout/stdouttrace v1.1.0
+	go.opentelemetry.io/otel/sdk v1.1.0
+)
+
+replace go.opentelemetry.io/contrib/samplers/jaegerremote => ../