[async] Disable default timeout system for all async requests (javalin#1823)

Author: dzikoysk

javalin/src/main/java/io/javalin/http/servlet/JavalinServlet.kt

@@ -60,9 +60,11 @@ class JavalinServlet(val cfg: JavalinConfig) : HttpServlet() {
 
     private fun JavalinServletContext.handleUserFuture() {
         val userFutureSupplier = userFutureSupplier!!.also { userFutureSupplier = null } // nullcheck in handleSync
+        if (!isAsync()) startAsyncAndAddDefaultTimeoutListeners() // start async if not already started
+
         val userFuture = handleTask { userFutureSupplier.get() } ?: return handleSync() // get future from supplier or handle error
-        if (!isAsync()) startAsyncAndAddDefaultTimeoutListeners()
-        req().asyncContext.addListener(onTimeout = { userFuture.cancel(true) })
+        req().asyncContext.addListener(onTimeout = { userFuture.cancel(true) }) // cancel user's future if timeout occurs
+
         userFuture
             .thenApply { handleSync() }
             .exceptionally {

javalin/src/main/java/io/javalin/http/util/AsyncUtil.kt

@@ -1,5 +1,6 @@
 package io.javalin.http.util
 
+import io.javalin.config.HttpConfig
 import io.javalin.http.Context
 import io.javalin.util.ConcurrencyUtil
 import io.javalin.util.function.ThrowingRunnable
@@ -16,8 +17,15 @@ internal object AsyncUtil {
 
     val defaultExecutor = ConcurrencyUtil.executorService("JavalinDefaultAsyncThreadPool")
 
+    /**
+     * Utility method that executes [task] asynchronously using [executor] ([defaultExecutor] by default).
+     * It also provides custom timeout handling via [onTimeout] callback registered directly on underlying [CompletableFuture],
+     * so global [HttpConfig.asyncTimeout] does not affect this particular task.
+     */
     fun submitAsyncTask(context: Context, executor: ExecutorService?, timeout: Long, onTimeout: Runnable?, task: ThrowingRunnable<Exception>): Unit =
         context.future {
+            context.req().asyncContext.timeout = 0 // we're using cf timeouts below, so we need to disable default jetty timeout listener
+
             CompletableFuture.runAsync({ task.run() }, executor ?: defaultExecutor)
                 .let { if (timeout > 0) it.orTimeout(timeout, MILLISECONDS) else it }
                 .let { if (onTimeout == null) it else it.exceptionally { exception ->

javalin/src/test/java/io/javalin/TestFuture.kt

@@ -50,6 +50,16 @@ internal class TestFuture {
             assertThat(http.getBody("/")).isEqualTo("Success")
         }
 
+        @Test
+        fun `async context can be used in future supplier`() = TestUtil.test { app, http ->
+            app.get("/") { ctx ->
+                ctx.future {
+                    completedFuture(ctx.req().asyncContext.timeout).thenApply { ctx.result(it.toString()) }
+                }
+            }
+            assertThat(http.getBody("/")).isEqualTo(app.cfg.http.asyncTimeout.toString())
+        }
+
     }
 
     @Nested