Add support for OTEL_EXPORTER_JAEGER_AGENT_HOST and OTEL_EXPORTER_JAEGER_AGENT_PORT

src/OpenTelemetry.Exporter.Jaeger/CHANGELOG.md

@@ -2,6 +2,12 @@
 
 ## Unreleased
 
+* The `JaegerExporterOptions` defaults can be overridden using
+  `OTEL_EXPORTER_JAEGER_AGENT_HOST` and `OTEL_EXPORTER_JAEGER_AGENT_PORT`
+  envionmental variables as defined in the
+  [specification](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/sdk-environment-variables.md#jaeger-exporter).
+  ([#2123](https://github.com/open-telemetry/opentelemetry-dotnet/pull/2123))
+
 ## 1.1.0-rc1
 
 Released 2021-Jun-25

src/OpenTelemetry.Exporter.Jaeger/Implementation/JaegerExporterEventSource.cs

@@ -42,5 +42,11 @@ public void FailedExport(string exception)
         {
             this.WriteEvent(1, exception);
         }
+
+        [Event(2, Message = "Failed to parse environment variable: '{0}', value: '{1}'.", Level = EventLevel.Warning)]
+        public void FailedToParseEnvironmentVariable(string name, string value)
+        {
+            this.WriteEvent(2, name, value);
+        }
     }
 }

src/OpenTelemetry.Exporter.Jaeger/JaegerExporterOptions.cs

@@ -14,14 +14,41 @@
 // limitations under the License.
 // </copyright>
 
+using System;
 using System.Diagnostics;
+using OpenTelemetry.Exporter.Jaeger.Implementation;
 
 namespace OpenTelemetry.Exporter
 {
     public class JaegerExporterOptions
     {
         internal const int DefaultMaxPayloadSizeInBytes = 4096;
 
+        internal const string OTelAgentHostEnvVarKey = "OTEL_EXPORTER_JAEGER_AGENT_HOST";
+        internal const string OTelAgentPortEnvVarKey = "OTEL_EXPORTER_JAEGER_AGENT_PORT";
+
+        public JaegerExporterOptions()
+        {
+            string agentHostEnvVar = Environment.GetEnvironmentVariable(OTelAgentHostEnvVarKey);
+            if (!string.IsNullOrEmpty(agentHostEnvVar))
+            {
+                this.AgentHost = agentHostEnvVar;
+            }
+
+            string agentPortEnvVar = Environment.GetEnvironmentVariable(OTelAgentPortEnvVarKey);
+            if (!string.IsNullOrEmpty(agentPortEnvVar))
+            {
+                if (int.TryParse(agentPortEnvVar, out var agentPortValue))
+                {
+                    this.AgentPort = agentPortValue;
+                }
+                else
+                {
+                    JaegerExporterEventSource.Log.FailedToParseEnvironmentVariable(OTelAgentPortEnvVarKey, agentPortEnvVar);
+                }
+            }
+        }
+
         /// <summary>
         /// Gets or sets the Jaeger agent host. Default value: localhost.
         /// </summary>

test/OpenTelemetry.Exporter.Jaeger.Tests/JaegerExporterOptionsTests.cs

@@ -0,0 +1,80 @@
+// <copyright file="JaegerExporterOptionsTests.cs" company="OpenTelemetry Authors">
+// 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.
+// </copyright>
+
+using System;
+using Xunit;
+
+namespace OpenTelemetry.Exporter.Jaeger.Tests
+{
+    public class JaegerExporterOptionsTests : IDisposable
+    {
+        public JaegerExporterOptionsTests()
+        {
+            this.ClearEnvVars();
+        }
+
+        public void Dispose()
+        {
+            this.ClearEnvVars();
+        }
+
+        [Fact]
+        public void JaegerExporterOptions_Defaults()
+        {
+            var options = new JaegerExporterOptions();
+
+            Assert.Equal("localhost", options.AgentHost);
+            Assert.Equal(6831, options.AgentPort);
+            Assert.Equal(4096, options.MaxPayloadSizeInBytes);
+            Assert.Equal(ExportProcessorType.Batch, options.ExportProcessorType);
+        }
+
+        [Fact]
+        public void JaegerExporterOptions_EnvironmentVariableOverride()
+        {
+            Environment.SetEnvironmentVariable(JaegerExporterOptions.OTelAgentHostEnvVarKey, "jeager-host");
+            Environment.SetEnvironmentVariable(JaegerExporterOptions.OTelAgentPortEnvVarKey, "123");
+
+            var options = new JaegerExporterOptions();
+
+            Assert.Equal("jeager-host", options.AgentHost);
+            Assert.Equal(123, options.AgentPort);
+        }
+
+        [Fact]
+        public void JaegerExporterOptions_InvalidPortEnvironmentVariableOverride()
+        {
+            Environment.SetEnvironmentVariable(JaegerExporterOptions.OTelAgentPortEnvVarKey, "invalid");
+
+            var options = new JaegerExporterOptions();
+
+            Assert.Equal(6831, options.AgentPort); // use default
+        }
+
+        [Fact]
+        public void JaegerExporterOptions_EnvironmentVariableNames()
+        {
+            Assert.Equal("OTEL_EXPORTER_JAEGER_AGENT_HOST", JaegerExporterOptions.OTelAgentHostEnvVarKey);
+            Assert.Equal("OTEL_EXPORTER_JAEGER_AGENT_PORT", JaegerExporterOptions.OTelAgentPortEnvVarKey);
+        }
+
+        private void ClearEnvVars()
+        {
+            Environment.SetEnvironmentVariable(JaegerExporterOptions.OTelAgentHostEnvVarKey, null);
+            Environment.SetEnvironmentVariable(JaegerExporterOptions.OTelAgentPortEnvVarKey, null);
+        }
+    }
+}