expose text Content-Type in embedded http server

Author: xela85

reporters/kamon-prometheus/src/main/scala/kamon/prometheus/embeddedhttp/SunEmbeddedHttpServer.scala

@@ -41,6 +41,7 @@ class SunEmbeddedHttpServer(hostname: String, port: Int, path: String, scrapeSou
           val bytes = data.getBytes(StandardCharsets.UTF_8)
           var os: OutputStream = null
           try {
+            httpExchange.getResponseHeaders.set("Content-Type", "text/plain; charset=UTF-8")
             if (shouldUseCompression(httpExchange)) {
               httpExchange.getResponseHeaders.set("Content-Encoding", "gzip")
               httpExchange.sendResponseHeaders(200, 0)
@@ -51,7 +52,7 @@ class SunEmbeddedHttpServer(hostname: String, port: Int, path: String, scrapeSou
               httpExchange.sendResponseHeaders(200, bytes.length)
               os.write(bytes)
             }
-          } finally Option(os).map(_.close())
+          } finally Option(os).foreach(_.close())
         } else httpExchange.sendResponseHeaders(404, -1)
       }
     }

reporters/kamon-prometheus/src/test/scala/kamon/prometheus/EmbeddedHttpServerSpec.scala

@@ -7,8 +7,9 @@ import org.scalatest.matchers.should.Matchers
 import org.scalatest.wordspec.AnyWordSpec
 
 import java.io.FileNotFoundException
-import java.net.URL
+import java.net.{URL, URLConnection}
 import java.util.zip.GZIPInputStream
+import scala.jdk.CollectionConverters._
 
 class SunHttpServerSpecSuite extends EmbeddedHttpServerSpecSuite {
   override def testConfig: Config = ConfigFactory.load()
@@ -32,7 +33,7 @@ abstract class EmbeddedHttpServerSpecSuite extends AnyWordSpec
   "the embedded sun http server" should {
     "provide no data comment on GET to /metrics when no data loaded yet" in {
       // act
-      val metrics = httpGetMetrics("/metrics")
+      val metrics = httpGetMetrics("/metrics").content
       // assert
       metrics shouldBe "# The kamon-prometheus module didn't receive any data just yet.\n"
     }
@@ -41,7 +42,7 @@ abstract class EmbeddedHttpServerSpecSuite extends AnyWordSpec
       // arrange
       testee.reportPeriodSnapshot(emptyPeriodSnapshot)
       // act
-      val metrics = httpGetMetrics("/metrics")
+      val metrics = httpGetMetrics("/metrics").content
       // assert
       metrics shouldBe ""
     }
@@ -50,7 +51,7 @@ abstract class EmbeddedHttpServerSpecSuite extends AnyWordSpec
       // arrange
       testee.reportPeriodSnapshot(counter("jvm.mem"))
       // act
-      val metrics = httpGetMetrics("/metrics")
+      val metrics = httpGetMetrics("/metrics").content
       // assert
       metrics shouldBe "# TYPE jvm_mem_total counter\njvm_mem_total 1.0\n"
     }
@@ -60,8 +61,9 @@ abstract class EmbeddedHttpServerSpecSuite extends AnyWordSpec
       testee.reconfigure(testConfig)
       testee.reportPeriodSnapshot(counter("jvm.mem"))
       // act
-      val metrics = httpGetMetrics("/metrics")
+      val metrics = httpGetMetrics("/metrics").content
       // assert
+      println(metrics)
       metrics shouldBe "# TYPE jvm_mem_total counter\njvm_mem_total 2.0\n"
     }
 
@@ -70,42 +72,58 @@ abstract class EmbeddedHttpServerSpecSuite extends AnyWordSpec
       testee.reportPeriodSnapshot(counter("jvm.mem"))
       // act
       val metrics = httpGetMetrics("/metrics")
-      val gzippedMetrics = httpGetGzippedMetrics("/metrics")
+      val gzippedMetrics = httpGetMetrics("/metrics", useGzipEncoding = true)
+      // assert
+      metrics.contentLength should be > gzippedMetrics.contentLength
+    }
+
+    "property set Content-Type" in {
+      // arrange
+      testee.reportPeriodSnapshot(counter("jvm.mem"))
+      // act
+      val metrics = httpGetMetrics("/metrics")
+      val gzippedMetrics = httpGetMetrics("/metrics", useGzipEncoding = true)
       // assert
-      metrics.length should be > gzippedMetrics.length
+      metrics.headers("Content-type").head shouldBe "text/plain; charset=UTF-8"
+      gzippedMetrics.headers("Content-type").head shouldBe "text/plain; charset=UTF-8"
     }
 
     "respect the path configuration" in {
-      httpGetMetrics("/metrics") should not be empty
+      httpGetMetrics("/metrics").content should not be empty
       assertThrows[FileNotFoundException] {
         httpGetMetrics("/new-metrics")
       }
 
       testee.reconfigure(changeEndpoint("/new-metrics"))
-      httpGetMetrics("/new-metrics") should not be empty
+      httpGetMetrics("/new-metrics").content should not be empty
 
       assertThrows[FileNotFoundException] {
-        httpGetMetrics("/metrics")
+        httpGetMetrics("/metrics").content
       }
     }
   }
 
-  private def httpGetMetrics(endpoint: String): String = {
-    val url = new URL(s"http://127.0.0.1:$port$endpoint")
-    val src = scala.io.Source.fromURL(url)
-    try src.mkString
-    finally src.close()
-  }
+  private case class Result(content: String, headers: Map[String, List[String]], contentLength: Int)
 
-  private def httpGetGzippedMetrics(endpoint: String): String = {
+  private def httpGetMetrics(endpoint: String, useGzipEncoding: Boolean = false): Result = {
     val url = new URL(s"http://127.0.0.1:$port$endpoint")
     val connection = url.openConnection
-    connection.setRequestProperty("Accept-Encoding", "gzip")
-    val gzipStream = new GZIPInputStream(connection.getInputStream)
-    val src = scala.io.Source.fromInputStream(gzipStream)
-    connection.getRequestProperty("Accept-Encoding") shouldBe "gzip"
-    try src.getLines.mkString
-    finally gzipStream.close()
+    val stream = if (useGzipEncoding) {
+      connection.setRequestProperty("Accept-Encoding", "gzip")
+      new GZIPInputStream(connection.getInputStream)
+    } else connection.getInputStream
+    val src = scala.io.Source.fromInputStream(stream)
+    if (useGzipEncoding) {
+      connection.getRequestProperty("Accept-Encoding") shouldBe "gzip"
+    }
+    try {
+      val content = src.mkString
+      Result(
+        content,
+        connection.getHeaderFields.asScala.toMap.view.mapValues(_.asScala.toList).toMap,
+        connection.getContentLength
+      )
+    } finally stream.close()
   }
 
   private def changeEndpoint(path: String): Config = {