feat(core): add config flag to disable the UI and run the webserver API-only (#16748)

Add kestra.webserver.ui.enabled (default true). Setting it to false
disables the bundled UI: the /ui/** static-resources route is turned
off via Micronaut's StaticResourceConfiguration.enabled, and the /
redirect and index.html rewriting filter are not registered. The API
(/api/v1/**, /ping) keeps working.

A positively-named flag lets the static route be disabled with pure
configuration (enabled = ${kestra.webserver.ui.enabled:true}), so no
short-circuiting filter is needed.

Closes #16747

Author: Ben8t

cli/src/main/resources/application.yml

@@ -12,6 +12,7 @@ micronaut:
       ui:
         paths: classpath:ui
         mapping: /ui/**
+        enabled: ${kestra.webserver.ui.enabled:true}
       static:
         paths: classpath:static
         mapping: /static/**

webserver/src/main/java/io/kestra/webserver/controllers/api/RedirectController.java

@@ -2,6 +2,7 @@
 
 import java.net.URI;
 
+import io.micronaut.context.annotation.Requires;
 import io.micronaut.context.annotation.Value;
 import io.micronaut.core.annotation.Nullable;
 import io.micronaut.http.HttpResponse;
@@ -12,6 +13,7 @@
 
 @Slf4j
 @Controller
+@Requires(property = "kestra.webserver.ui.enabled", notEquals = "false", defaultValue = "true")
 public class RedirectController {
     @Nullable
     @Value("${micronaut.server.context-path}")

webserver/src/main/java/io/kestra/webserver/controllers/api/StaticFilter.java

@@ -12,6 +12,7 @@
 
 import io.kestra.webserver.configuration.WebserverConfiguration;
 
+import io.micronaut.context.annotation.Requires;
 import io.micronaut.context.annotation.Value;
 import io.micronaut.core.annotation.Nullable;
 import jakarta.inject.Inject;
@@ -33,6 +34,7 @@
 import static io.kestra.core.utils.Rethrow.throwFunction;
 
 @Filter("/ui/**")
+@Requires(property = "kestra.webserver.ui.enabled", notEquals = "false", defaultValue = "true")
 public class StaticFilter implements HttpServerFilter {
     @Nullable
     @Value("${micronaut.server.context-path}")

webserver/src/test/java/io/kestra/webserver/controllers/api/UiDisabledWebserverTest.java

@@ -0,0 +1,62 @@
+package io.kestra.webserver.controllers.api;
+
+import org.junit.jupiter.api.Test;
+
+import io.kestra.core.junit.annotations.KestraTest;
+
+import io.micronaut.context.ApplicationContext;
+import io.micronaut.context.annotation.Property;
+import io.micronaut.http.HttpStatus;
+import io.micronaut.http.client.annotation.Client;
+import io.micronaut.http.client.exceptions.HttpClientResponseException;
+import io.micronaut.reactor.http.client.ReactorHttpClient;
+import jakarta.inject.Inject;
+
+import static io.micronaut.http.HttpRequest.GET;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+@KestraTest
+@Property(name = "kestra.webserver.ui.enabled", value = "false")
+class UiDisabledWebserverTest {
+    @Inject
+    @Client("/")
+    ReactorHttpClient client;
+
+    @Inject
+    ApplicationContext applicationContext;
+
+    @Test
+    void shouldNotServeUiWhenUiIsDisabled() {
+        // When / Then
+        assertThatThrownBy(() -> client.toBlocking().exchange(GET("/ui/")))
+            .isInstanceOf(HttpClientResponseException.class)
+            .extracting(e -> ((HttpClientResponseException) e).getStatus())
+            .isEqualTo(HttpStatus.NOT_FOUND);
+    }
+
+    @Test
+    void shouldNotRedirectRootToUiWhenUiIsDisabled() {
+        // When / Then
+        assertThatThrownBy(() -> client.toBlocking().exchange(GET("/")))
+            .isInstanceOf(HttpClientResponseException.class)
+            .extracting(e -> ((HttpClientResponseException) e).getStatus())
+            .isEqualTo(HttpStatus.NOT_FOUND);
+    }
+
+    @Test
+    void shouldKeepApiAvailableWhenUiIsDisabled() {
+        // When
+        String response = client.toBlocking().retrieve(GET("/ping"));
+
+        // Then
+        assertThat(response).isEqualTo("pong");
+    }
+
+    @Test
+    void shouldNotRegisterUiBeansWhenUiIsDisabled() {
+        // Then
+        assertThat(applicationContext.containsBean(RedirectController.class)).isFalse();
+        assertThat(applicationContext.containsBean(StaticFilter.class)).isFalse();
+    }
+}

webserver/src/test/java/io/kestra/webserver/controllers/api/UiEnabledWebserverTest.java

@@ -0,0 +1,48 @@
+package io.kestra.webserver.controllers.api;
+
+import org.junit.jupiter.api.Test;
+
+import io.kestra.core.junit.annotations.KestraTest;
+
+import io.micronaut.context.ApplicationContext;
+import io.micronaut.http.HttpResponse;
+import io.micronaut.http.HttpStatus;
+import io.micronaut.http.client.DefaultHttpClientConfiguration;
+import io.micronaut.http.client.HttpClient;
+import io.micronaut.runtime.server.EmbeddedServer;
+import jakarta.inject.Inject;
+
+import static io.micronaut.http.HttpRequest.GET;
+import static org.assertj.core.api.Assertions.assertThat;
+
+@KestraTest
+class UiEnabledWebserverTest {
+    @Inject
+    EmbeddedServer embeddedServer;
+
+    @Inject
+    ApplicationContext applicationContext;
+
+    @Test
+    void shouldRedirectRootToUiByDefault() {
+        // Given - a client that does not follow redirects
+        DefaultHttpClientConfiguration configuration = new DefaultHttpClientConfiguration();
+        configuration.setFollowRedirects(false);
+
+        try (HttpClient client = HttpClient.create(embeddedServer.getURL(), configuration)) {
+            // When
+            HttpResponse<?> response = client.toBlocking().exchange(GET("/"));
+
+            // Then
+            assertThat(response.getStatus().getCode()).isEqualTo(HttpStatus.TEMPORARY_REDIRECT.getCode());
+            assertThat(response.header("Location")).isEqualTo("/ui/");
+        }
+    }
+
+    @Test
+    void shouldRegisterUiBeansByDefault() {
+        // Then
+        assertThat(applicationContext.containsBean(RedirectController.class)).isTrue();
+        assertThat(applicationContext.containsBean(StaticFilter.class)).isTrue();
+    }
+}

webserver/src/test/resources/application-test.yml

@@ -11,6 +11,7 @@ micronaut:
       ui:
         paths: classpath:ui
         mapping: /ui/**
+        enabled: ${kestra.webserver.ui.enabled:true}
 
   http:
     client: