Expose prometheus metrics strictly on '/metrics'-endpoint

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

@@ -29,20 +29,24 @@ class SunEmbeddedHttpServer(hostname: String, port: Int, scrapeSource: ScrapeSou
     s.setExecutor(null)
     val handler = new HttpHandler {
       override def handle(httpExchange: HttpExchange): Unit = {
-        val data = scrapeSource.scrapeData()
-        val bytes = data.getBytes(StandardCharsets.UTF_8)
-        httpExchange.sendResponseHeaders(200, bytes.length)
-        val os = httpExchange.getResponseBody
-        try {
-          os.write(bytes)
+        if (httpExchange.getRequestURI.getPath == "/metrics") {
+          val data = scrapeSource.scrapeData()
+          val bytes = data.getBytes(StandardCharsets.UTF_8)
+          httpExchange.sendResponseHeaders(200, bytes.length)
+          val os = httpExchange.getResponseBody
+          try {
+            os.write(bytes)
+          }
+          finally
+            os.close()
+        }
+        else {
+          httpExchange.sendResponseHeaders(404, -1)
         }
-        finally
-          os.close()
       }
 
     }
     s.createContext("/metrics", handler)
-    s.createContext("/", handler)
     s.start()
     s
   }

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

@@ -1,5 +1,6 @@
 package kamon.prometheus
 
+import java.io.FileNotFoundException
 import java.net.URL
 
 import com.typesafe.config.{Config, ConfigFactory}
@@ -32,7 +33,7 @@ abstract class EmbeddedHttpServerSpecSuite extends WordSpec with Matchers with B
   "the embedded sun http server" should {
     "provide no data comment on GET to /metrics when no data loaded yet" in {
       //act
-      val metrics = httpGetMetrics()
+      val metrics = httpGetMetrics("/metrics")
       //assert
       metrics shouldBe "# The kamon-prometheus module didn't receive any data just yet.\n"
     }
@@ -41,7 +42,7 @@ abstract class EmbeddedHttpServerSpecSuite extends WordSpec with Matchers with B
       //arrange
       testee.reportPeriodSnapshot(emptyPeriodSnapshot)
       //act
-      val metrics = httpGetMetrics()
+      val metrics = httpGetMetrics("/metrics")
       //assert
       metrics shouldBe ""
     }
@@ -50,7 +51,7 @@ abstract class EmbeddedHttpServerSpecSuite extends WordSpec with Matchers with B
       //arrange
       testee.reportPeriodSnapshot(counter("jvm.mem"))
       //act
-      val metrics = httpGetMetrics()
+      val metrics = httpGetMetrics("/metrics")
       //assert
       metrics shouldBe "# TYPE jvm_mem_total counter\njvm_mem_total 1.0\n"
     }
@@ -60,18 +61,26 @@ abstract class EmbeddedHttpServerSpecSuite extends WordSpec with Matchers with B
       testee.reconfigure(testConfig)
       testee.reportPeriodSnapshot(counter("jvm.mem"))
       //act
-      val metrics = httpGetMetrics()
+      val metrics = httpGetMetrics("/metrics")
       //assert
       metrics shouldBe "# TYPE jvm_mem_total counter\njvm_mem_total 2.0\n"
     }
-  }
 
+    "provide the metrics strictly on /metrics endpoint" in {
+      assertThrows[FileNotFoundException] {
+        httpGetMetrics("")
+      }
+      assertThrows[FileNotFoundException] {
+        httpGetMetrics("/metricsss")
+      }
+    }
+  }
 
-  private def httpGetMetrics(): String = {
-    val src = scala.io.Source.fromURL(new URL(s"http://127.0.0.1:$port/metrics"))
+  private def httpGetMetrics(endpoint: String): String = {
+    val src = scala.io.Source.fromURL(new URL(s"http://127.0.0.1:$port$endpoint"))
     try
       src.mkString
     finally
       src.close()
   }
-}
+}