Merge pull request #1157 from hughsimpson/OTEL_RESOURCE_ATTRIBUTES-support

Otel resource attributes support

Author: dpsoft

reporters/kamon-opentelemetry/src/main/resources/reference.conf

@@ -23,6 +23,10 @@ kamon.otel {
   protocol = "grpc"
   protocol = ${?OTEL_EXPORTER_OTLP_PROTOCOL}
 
+  # Support for OTEL_RESOURCE_ATTRIBUTES env var (cf https://opentelemetry.io/docs/reference/specification/resource/sdk/)
+  attributes = ""
+  attributes = ${?OTEL_RESOURCE_ATTRIBUTES}
+
   trace {
       endpoint = ${kamon.otel.endpoint}
       full-endpoint = ${?OTEL_EXPORTER_OTLP_TRACES_ENDPOINT}

reporters/kamon-opentelemetry/src/main/scala/kamon/otel/OpenTelemetryTraceReporter.scala

@@ -22,10 +22,11 @@ import kamon.Kamon
 import kamon.module.{Module, ModuleFactory, SpanReporter}
 import kamon.trace.Span
 import org.slf4j.LoggerFactory
+import java.net.URLDecoder
 import java.util.{Collection => JCollection}
 
 import scala.concurrent.ExecutionContext
-import scala.util.{Failure, Success}
+import scala.util.{Failure, Success, Try}
 
 import io.opentelemetry.sdk.common.InstrumentationLibraryInfo
 import io.opentelemetry.sdk.resources.Resource
@@ -73,7 +74,14 @@ class OpenTelemetryTraceReporter(traceServiceFactory: Config => TraceService)(im
     logger.info("Reconfigure OpenTelemetry Trace Reporter")
 
     //pre-generate the function for converting Kamon span to proto span
-    val resource: Resource = buildResource
+    val attributes: Map[String, String] =
+      newConfig.getString("kamon.otel.attributes").split(',').filter(_ contains '=').map(_.trim.split("=", 2)).map {
+        case Array(k, v) =>
+          val decoded = Try(URLDecoder.decode(v.trim, "UTF-8"))
+          decoded.failed.foreach(t => throw new IllegalArgumentException(s"value for attribute ${k.trim} is not a url-encoded string", t))
+          k.trim -> decoded.get
+      }.toMap
+    val resource: Resource = buildResource(attributes)
     this.spanConverterFunc = SpanConverter.convert(newConfig.getBoolean("kamon.otel.trace.include-error-event"), resource, kamonSettings.version)
 
     this.traceService = Option(traceServiceFactory.apply(newConfig))
@@ -90,7 +98,7 @@ class OpenTelemetryTraceReporter(traceServiceFactory: Config => TraceService)(im
     *
     * @return
     */
-  private def buildResource: Resource = {
+  private def buildResource(attributes: Map[String, String]): Resource = {
     val env = Kamon.environment
     val builder = Resource.builder()
       .put("host.name", kamonSettings.environment.host)
@@ -100,6 +108,7 @@ class OpenTelemetryTraceReporter(traceServiceFactory: Config => TraceService)(im
       .put("telemetry.sdk.language", "scala")
       .put("telemetry.sdk.version", kamonSettings.version)
 
+    attributes.foreach { case (k, v) => builder.put(k, v) }
     //add all kamon.environment.tags as KeyValues to the Resource object
     env.tags.iterator().foreach {
       case t: Tag.String => builder.put(t.key, t.value)

reporters/kamon-opentelemetry/src/test/resources/application.conf

@@ -12,4 +12,5 @@ kamon {
       env = "kamon-devint"
     }
   }
+  otel.attributes = "att1=v1, att2 = v2 ,att3=+a%3Db%2Cc%3Dd+"
 }

reporters/kamon-opentelemetry/src/test/scala/kamon/otel/OpenTelemetryTraceReporterSpec.scala

@@ -62,6 +62,9 @@ class OpenTelemetryTraceReporterSpec extends AnyWordSpec with Matchers with Opti
       spanData.getResource.getAttributes.asMap().asScala should contain(AttributeKey.stringKey("telemetry.sdk.version"), kamonVersion)
       spanData.getResource.getAttributes.asMap().asScala should contain(AttributeKey.stringKey("service.version"), "x.x.x")
       spanData.getResource.getAttributes.asMap().asScala should contain(AttributeKey.stringKey("env"), "kamon-devint")
+      spanData.getResource.getAttributes.asMap().asScala should contain(AttributeKey.stringKey("att1"), "v1")
+      spanData.getResource.getAttributes.asMap().asScala should contain(AttributeKey.stringKey("att2"), "v2")
+      spanData.getResource.getAttributes.asMap().asScala should contain(AttributeKey.stringKey("att3"), " a=b,c=d ")
       val host = spanData.getResource.getAttributes.asMap().asScala.get(AttributeKey.stringKey("host.name"))
       host shouldBe defined
       val instance = spanData.getResource.getAttributes.asMap().asScala.get(AttributeKey.stringKey("service.instance.id"))