Add health check endpoint (#1016)

* add health check endpoint

* rewrite test to pekko http

README.md

@@ -627,6 +627,11 @@ ElasticMQ exposes `Queues` MBean. It contains three operations:
 * `NumberOfMessagesForAllQueues` - returns tabular data that contains information about number of messages per queue
 * `getNumberOfMessagesInQueue` - returns information about number of messages in specified queue
 
+# Health check endpoint
+
+When running the server in a container orchestration environment, it may be useful to have a health check endpoint.
+ElasticMQ provides a simple health check endpoint that can be used for this purpose. The endpoint is available at `/health`.
+
 # Technology
 
 * Core: [Scala](http://scala-lang.org) and [Pekko](https://pekko.apache.org/).

rest/rest-sqs-testing-amazon-java-sdk/src/test/scala/org/elasticmq/rest/sqs/HealthCheckTest.scala

@@ -0,0 +1,23 @@
+package org.elasticmq.rest.sqs
+import org.apache.pekko.http.scaladsl.Http
+import org.apache.pekko.http.scaladsl.model.{HttpRequest, HttpResponse, StatusCodes}
+import org.apache.pekko.http.scaladsl.testkit.ScalatestRouteTest
+import org.scalatest.matchers.should.Matchers
+
+import scala.concurrent.duration.DurationInt
+import scala.concurrent.{Await, Future}
+
+class HealthCheckTest extends SqsClientServerCommunication with ScalatestRouteTest with Matchers {
+
+  test("health check") {
+    val responseFuture: Future[HttpResponse] = Http().singleRequest(HttpRequest(uri = s"$ServiceEndpoint/health"))
+    val response = Await.result(responseFuture, 10.seconds)
+
+    response.status shouldBe StatusCodes.OK
+
+    val entityFuture = response.entity.dataBytes.runFold("")(_ ++ _.utf8String)
+    val entity = Await.result(entityFuture, 10.seconds)
+
+    entity shouldBe "OK"
+  }
+}

rest/rest-sqs/src/main/scala/org/elasticmq/rest/sqs/SQSRestServerBuilder.scala

@@ -11,12 +11,7 @@ import org.elasticmq.actor.QueueManagerActor
 import org.elasticmq.metrics.QueuesMetrics
 import org.elasticmq.rest.sqs.Constants._
 import org.elasticmq.rest.sqs.XmlNsVersion.extractXmlNs
-import org.elasticmq.rest.sqs.directives.{
-  AnyParamDirectives,
-  AWSProtocolDirectives,
-  ElasticMQDirectives,
-  UnmatchedActionRoutes
-}
+import org.elasticmq.rest.sqs.directives.{AWSProtocolDirectives, AnyParamDirectives, ElasticMQDirectives, UnmatchedActionRoutes}
 import org.elasticmq.rest.sqs.model.RequestPayload
 import org.elasticmq.util.{Logging, NowProvider}
 
@@ -29,10 +24,10 @@ import java.util.concurrent.atomic.AtomicReference
 import javax.management.ObjectName
 import scala.collection.immutable.TreeMap
 import scala.collection.mutable.ArrayBuffer
-import scala.concurrent.{Await, Future}
 import scala.concurrent.duration._
-import scala.util.{Failure, Success, Try}
+import scala.concurrent.{Await, Future}
 import scala.util.control.NonFatal
+import scala.util.{Failure, Success, Try}
 import scala.xml._
 
 /** By default: <li> <ul>for `socketAddress`: when started, the server will bind to `localhost:9324`</ul> <ul>for
@@ -222,7 +217,13 @@ case class TheSQSRestServerBuilder(
 
     val config = new ElasticMQConfig
 
-    val routes =
+    val healthCheckRoute = path("health") {
+      get {
+        complete("OK")
+      }
+    }
+
+    val sqsRoute =
       extractXmlNs { (_version: XmlNsVersion) =>
         implicit val version: XmlNsVersion = _version
         extractProtocol { (_protocol: AWSProtocol) =>
@@ -242,6 +243,8 @@ case class TheSQSRestServerBuilder(
         }
       }
 
+    val routes = concat(healthCheckRoute, sqsRoute)
+
     val appStartFuture = {
       // Scala 3 fix: implicit resolution conflict
       implicit val _implicitActorSystem: ActorSystem = implicitActorSystem