Update metrics with feedback from Ryan and Jon. Metrics are now reported before we send the response back to the client. Hence no need for sleeps in the client side test.

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/GatewayMetricsFilter.java

@@ -19,8 +19,6 @@ package org.springframework.cloud.gateway.filter;
 
 import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_ROUTE_ATTR;
 
-import java.util.Arrays;
-
 import org.springframework.cloud.gateway.route.Route;
 import org.springframework.core.Ordered;
 import org.springframework.http.HttpStatus;
@@ -29,7 +27,7 @@ import org.springframework.http.server.reactive.ServerHttpResponse;
 import org.springframework.web.server.ServerWebExchange;
 
 import io.micrometer.core.instrument.MeterRegistry;
-import io.micrometer.core.instrument.Tag;
+import io.micrometer.core.instrument.Tags;
 import io.micrometer.core.instrument.Timer;
 import io.micrometer.core.instrument.Timer.Sample;
 import reactor.core.publisher.Mono;
@@ -44,17 +42,18 @@ public class GatewayMetricsFilter implements GlobalFilter, Ordered {
 
 	@Override
 	public int getOrder() {
-		return NettyWriteResponseFilter.WRITE_RESPONSE_FILTER_ORDER - 1;
+		// start the timer as soon as possible and report the metric event before we write
+		// response to client
+		return NettyWriteResponseFilter.WRITE_RESPONSE_FILTER_ORDER + 1;
 	}
 
 	@Override
 	public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
 		Sample sample = Timer.start(meterRegistry);
-		return chain.filter(exchange).then(Mono.fromRunnable(() -> {
-			endTimerRespectingCommit(exchange, sample);
-		})).doOnError(t -> { // needed for example when netty routing filter times out
+
+		return chain.filter(exchange).doOnSuccessOrError((aVoid, ex) -> {
 			endTimerRespectingCommit(exchange, sample);
-		}).then();
+		});
 	}
 
 	private void endTimerRespectingCommit(ServerWebExchange exchange, Sample sample) {
@@ -69,7 +68,6 @@ public class GatewayMetricsFilter implements GlobalFilter, Ordered {
 				return Mono.empty();
 			});
 		}
-
 	}
 
 	private void endTimerInner(ServerWebExchange exchange, Sample sample) {
@@ -93,9 +91,8 @@ public class GatewayMetricsFilter implements GlobalFilter, Ordered {
 			}
 		}
 		Route route = exchange.getAttribute(GATEWAY_ROUTE_ATTR);
-		Iterable<Tag> iterableTags = Arrays.asList(Tag.of("outcome", outcome),
-				Tag.of("status", status), Tag.of("routeId", route.getId()),
-				Tag.of("routeUri", route.getUri().toString()));
-		sample.stop(meterRegistry.timer("gateway.requests", iterableTags));
+		Tags tags = Tags.of("outcome", outcome, "status", status, "routeId",
+				route.getId(), "routeUri", route.getUri().toString());
+		sample.stop(meterRegistry.timer("gateway.requests", tags));
 	}
 }

spring-cloud-gateway-core/src/test/java/org/springframework/cloud/gateway/filter/GatewayMetricFilterTests.java

@@ -18,7 +18,6 @@
 package org.springframework.cloud.gateway.filter;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.junit.Assert.assertEquals;
 import static org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT;
 
 import org.junit.Test;
@@ -29,7 +28,6 @@ import org.springframework.boot.SpringBootConfiguration;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.boot.test.web.client.TestRestTemplate;
-import org.springframework.cloud.gateway.config.GatewayProperties;
 import org.springframework.cloud.gateway.route.RouteLocator;
 import org.springframework.cloud.gateway.route.builder.RouteLocatorBuilder;
 import org.springframework.cloud.gateway.test.BaseWebClientTests;
@@ -44,7 +42,6 @@ import org.springframework.test.annotation.DirtiesContext;
 import org.springframework.test.context.junit4.SpringRunner;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
-import org.springframework.web.reactive.function.client.ClientResponse;
 
 import io.micrometer.core.instrument.MeterRegistry;
 
@@ -55,9 +52,6 @@ public class GatewayMetricFilterTests extends BaseWebClientTests {
 
 	private static final String REQUEST_METRICS_NAME = "gateway.requests";
 
-	@Autowired
-	private GatewayProperties properties;
-
 	@Autowired
 	private MeterRegistry meterRegistry;
 
@@ -66,11 +60,7 @@ public class GatewayMetricFilterTests extends BaseWebClientTests {
 
 	@Test
 	public void gatewayRequestsMeterFilterHasTags() throws InterruptedException {
-		assertThat(this.properties.getDefaultFilters()).isNotEmpty();
-		ClientResponse clientResponse = webClient.get().uri("/headers").exchange()
-				.block();
-		assertEquals(HttpStatus.OK, clientResponse.statusCode());
-		Thread.sleep(1000); // allow metrics to complete in the mono following the then
+		testClient.get().uri("/headers").exchange().expectStatus().isOk();
 		assertMetricsContainsTag("outcome", HttpStatus.Series.SUCCESSFUL.name());
 		assertMetricsContainsTag("status", HttpStatus.OK.name());
 		assertMetricsContainsTag("routeId", "default_path_to_httpbin");
@@ -80,12 +70,8 @@ public class GatewayMetricFilterTests extends BaseWebClientTests {
 	@Test
 	public void gatewayRequestsMeterFilterHasTagsForBadTargetUri()
 			throws InterruptedException {
-		assertThat(this.properties.getDefaultFilters()).isNotEmpty();
-		ClientResponse clientResponse = webClient.get().uri("/badtargeturi").exchange()
-				.block();
-		assertEquals("Expecting request to fail with http status internal server error",
-				HttpStatus.INTERNAL_SERVER_ERROR, clientResponse.statusCode());
-		Thread.sleep(1000); // allow metrics to complete in the mono following the then
+		testClient.get().uri("/badtargeturi").exchange().expectStatus()
+				.is5xxServerError();
 		assertMetricsContainsTag("outcome", HttpStatus.Series.SERVER_ERROR.name());
 		assertMetricsContainsTag("status", HttpStatus.INTERNAL_SERVER_ERROR.name());
 		assertMetricsContainsTag("routeId", "default_path_to_httpbin");
@@ -96,11 +82,11 @@ public class GatewayMetricFilterTests extends BaseWebClientTests {
 	public void hasMetricsForSetStatusFilter() throws InterruptedException {
 		HttpHeaders headers = new HttpHeaders();
 		headers.set(HttpHeaders.HOST, "www.setcustomstatus.org");
+		// cannot use netty client since we cannot read custom http status
 		ResponseEntity<String> response = new TestRestTemplate().exchange(
 				baseUri + "/headers", HttpMethod.GET, new HttpEntity<>(headers),
 				String.class);
 		assertThat(response.getStatusCodeValue()).isEqualTo(432);
-		Thread.sleep(1000); // allow metrics to complete in the mono following the then
 		assertMetricsContainsTag("outcome", "CUSTOM");
 		assertMetricsContainsTag("status", "432");
 		assertMetricsContainsTag("routeId", "test_custom_http_status");