[#3609] Improve error handling of custom mapper

The logic for invoking a custom mapper for upstream commands has been adapted
to consider the (failure) status code returned by the mapper when generating a corresponding
ServiceInvocationException to be sent back in the reply to the downstream sender.

fixes #3609

adapters/mqtt-base/src/main/java/org/eclipse/hono/adapter/mqtt/impl/HttpBasedMessageMapping.java

@@ -26,6 +26,7 @@
 import org.eclipse.hono.adapter.mqtt.MqttProtocolAdapterProperties;
 import org.eclipse.hono.client.ServerErrorException;
 import org.eclipse.hono.client.command.Command;
+import org.eclipse.hono.client.util.StatusCodeMapper;
 import org.eclipse.hono.util.MessageHelper;
 import org.eclipse.hono.util.RegistrationAssertion;
 import org.eclipse.hono.util.Strings;
@@ -199,7 +200,8 @@ private void mapUpstreamMessageRequest(
                         command.getDeviceId(),
                         mapperEndpoint.getHost(), mapperEndpoint.getPort(), mapperEndpoint.getUri(),
                         httpResponseAsyncResult.cause());
-                    result.fail(new ServerErrorException(HttpURLConnection.HTTP_UNAVAILABLE, httpResponseAsyncResult.cause()));
+                    final Throwable exception = mapException(command.getTenant(), httpResponseAsyncResult, null);
+                    result.fail(exception);
                 } else {
                     final HttpResponse<Buffer> httpResponse = httpResponseAsyncResult.result();
                     if (httpResponse.statusCode() == HttpURLConnection.HTTP_OK) {
@@ -208,8 +210,9 @@ private void mapUpstreamMessageRequest(
                         LOG.debug("mapping service [host: {}, port: {}, URI: {}] returned unexpected status code: {}",
                             mapperEndpoint.getHost(), mapperEndpoint.getPort(), mapperEndpoint.getUri(),
                             httpResponse.statusCode());
-                        result.fail(new ServerErrorException(HttpURLConnection.HTTP_UNAVAILABLE,
-                            "could not invoke configured mapping service"));
+                        final Throwable exception = mapException(command.getTenant(), httpResponseAsyncResult,
+                            "could not invoke configured mapping service");
+                        result.fail(exception);
                     }
                 }
                 resultHandler.handle(result.future());
@@ -279,4 +282,17 @@ private void mapDownstreamMessageRequest(
                 resultHandler.handle(result.future());
             });
     }
+
+    private Throwable mapException(final String tenantId, final AsyncResult<HttpResponse<Buffer>> httpResponseAsyncResult, final String message) {
+        final String detailMessage = Optional.ofNullable(message)
+                .orElse(Optional.ofNullable(httpResponseAsyncResult.cause()).map(Throwable::getMessage).orElse(null));
+        final Optional<HttpResponse<Buffer>> httpResponse = Optional.ofNullable(httpResponseAsyncResult.result());
+        final int statusCode = httpResponse.map(HttpResponse::statusCode).orElse(HttpURLConnection.HTTP_UNAVAILABLE);
+        return StatusCodeMapper.from(
+            tenantId,
+            statusCode,
+            detailMessage,
+            httpResponseAsyncResult.cause()
+        );
+    }
 }

adapters/mqtt-base/src/test/java/org/eclipse/hono/adapter/mqtt/impl/HttpBasedMessageMappingTest.java

@@ -34,6 +34,7 @@
 import org.eclipse.hono.adapter.MapperEndpoint;
 import org.eclipse.hono.adapter.mqtt.MqttContext;
 import org.eclipse.hono.adapter.mqtt.MqttProtocolAdapterProperties;
+import org.eclipse.hono.client.ClientErrorException;
 import org.eclipse.hono.client.ServerErrorException;
 import org.eclipse.hono.client.command.Command;
 import org.eclipse.hono.service.auth.DeviceUser;
@@ -353,7 +354,7 @@ public void testMapCommandSucceeds(final VertxTestContext ctx) {
     }
 
     /**
-     * Verifies that the upstream mapper returns a failed future with a ServerErrorException if the upstream mapper has been configured
+     * Verifies that the upstream mapper returns a failed future with a ClientErrorException if the upstream mapper has been configured
      * for an adapter but the remote service returns a 403 status code indicating that the device payload cannot be mapped.
      *
      * @param ctx   The Vert.x test context.
@@ -379,8 +380,8 @@ public void testMappingCommandFailsForWhenPayloadCannotMapped(final VertxTestCon
         messageMapping.mapUpstreamMessage(assertion, command)
             .onComplete(ctx.failing(t -> {
                 ctx.verify(() -> {
-                    assertThat(t).isInstanceOf(ServerErrorException.class);
-                    assertThat((((ServerErrorException) t).getErrorCode())).isEqualTo(HttpURLConnection.HTTP_UNAVAILABLE);
+                    assertThat(t).isInstanceOf(ClientErrorException.class);
+                    assertThat((((ClientErrorException) t).getErrorCode())).isEqualTo(HttpURLConnection.HTTP_FORBIDDEN);
                 });
                 ctx.completeNow();
             }));
@@ -389,4 +390,39 @@ public void testMappingCommandFailsForWhenPayloadCannotMapped(final VertxTestCon
         verify(httpRequest).sendBuffer(any(Buffer.class), handleCaptor.capture());
         handleCaptor.getValue().handle(Future.succeededFuture(httpResponse));
     }
+
+    /**
+     * Verifies that the upstream mapper returns a failed future with a ServerErrorException if the upstream mapper has been configured
+     * for an adapter but the remote service cannot be reached should return a 503.
+     *
+     * @param ctx   The Vert.x test context.
+     */
+    @Test
+    @SuppressWarnings("unchecked")
+    public void testMappingCommandFailsForWhenMapperCannotBeReached(final VertxTestContext ctx) {
+
+        config.setMapperEndpoints(Map.of("mapper", MapperEndpoint.from("host", 1234, "/uri", false)));
+        final HttpRequest<Buffer> httpRequest = mock(HttpRequest.class, withSettings().defaultAnswer(RETURNS_SELF));
+
+        final Buffer payload = Buffer.buffer("payload");
+
+        when(mapperWebClient.post(anyInt(), anyString(), anyString())).thenReturn(httpRequest);
+
+        final Command command = mock(Command.class);
+        when(command.getPayload()).thenReturn(payload);
+
+        final RegistrationAssertion assertion = new RegistrationAssertion("gateway").setUpstreamMessageMapper("mapper");
+        messageMapping.mapUpstreamMessage(assertion, command)
+                .onComplete(ctx.failing(t -> {
+                    ctx.verify(() -> {
+                        assertThat(t).isInstanceOf(ServerErrorException.class);
+                        assertThat((((ServerErrorException) t).getErrorCode())).isEqualTo(HttpURLConnection.HTTP_UNAVAILABLE);
+                    });
+                    ctx.completeNow();
+                }));
+
+        final ArgumentCaptor<Handler<AsyncResult<HttpResponse<Buffer>>>> handleCaptor = VertxMockSupport.argumentCaptorHandler();
+        verify(httpRequest).sendBuffer(any(Buffer.class), handleCaptor.capture());
+        handleCaptor.getValue().handle(Future.failedFuture(new RuntimeException("something went wrong")));
+    }
 }