Added an option to filter out outbound requests (#1048)

* Added an option to filter out outbound requests

without this change there's no way to filter outbound requests basing on the path via a property.
with this change we're introducing that

fixes gh-1047

spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/web/SleuthWebProperties.java

@@ -82,6 +82,10 @@ public class SleuthWebProperties {
 	}
 
 	public static class Client {
+		/**
+		 * Pattern for URLs that should be skipped in client side tracing
+		 */
+		private String skipPattern = "";
 
 		/**
 		 * Enable interceptor injecting into {@link org.springframework.web.client.RestTemplate}
@@ -95,6 +99,14 @@ public class SleuthWebProperties {
 		public void setEnabled(boolean enabled) {
 			this.enabled = enabled;
 		}
+
+		public String getSkipPattern() {
+			return this.skipPattern;
+		}
+
+		public void setSkipPattern(String skipPattern) {
+			this.skipPattern = skipPattern;
+		}
 	}
 
 	public static class Async {

spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/web/TraceHttpAutoConfiguration.java

@@ -111,8 +111,8 @@ public class TraceHttpAutoConfiguration {
 
 	@Bean
 	@ConditionalOnMissingBean(name = ClientSampler.NAME)
-	HttpSampler sleuthClientSampler() {
-		return HttpSampler.TRACE_ID;
+	HttpSampler sleuthClientSampler(SleuthWebProperties sleuthWebProperties) {
+		return new PathMatchingHttpSampler(sleuthWebProperties);
 	}
 }
 
@@ -138,3 +138,19 @@ class CompositeHttpSampler extends HttpSampler {
 		return leftDecision && rightDecision;
 	}
 }
+
+class PathMatchingHttpSampler extends HttpSampler {
+	private final SleuthWebProperties properties;
+
+	PathMatchingHttpSampler(SleuthWebProperties properties) {
+		this.properties = properties;
+	}
+
+	@Override public <Req> Boolean trySample(HttpAdapter<Req, ?> adapter, Req request) {
+		String path = adapter.path(request);
+		if (path == null) {
+			return null;
+		}
+		return path.matches(this.properties.getClient().getSkipPattern()) ? false : null;
+	}
+}

spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/instrument/web/client/RestTemplateTraceAspectIntegrationTests.java

@@ -62,19 +62,23 @@ import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.
 
 @RunWith(SpringJUnit4ClassRunner.class)
 @SpringBootTest(classes = RestTemplateTraceAspectIntegrationTests.Config.class,
-		webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT) @DirtiesContext
+		webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT,
+		properties = "spring.sleuth.web.client.skipPattern=/issue.*")
+@DirtiesContext
 public class RestTemplateTraceAspectIntegrationTests {
 
 	@Autowired WebApplicationContext context;
 	@Autowired AspectTestingController controller;
 	@Autowired Tracing tracer;
 	@Autowired ArrayListSpanReporter reporter;
+	@Autowired RestTemplate restTemplate;
 
 	private MockMvc mockMvc;
 
 	@Before public void init() {
 		this.mockMvc = MockMvcBuilders.webAppContextSetup(this.context).build();
 		this.controller.reset();
+		this.reporter.clear();
 	}
 
 	@Before @After public void verify() {
@@ -116,6 +120,16 @@ public class RestTemplateTraceAspectIntegrationTests {
 		thenClientKindIsReported();
 	}
 
+	// issue #1047
+	@Test
+	public void should_not_create_a_client_span_for_filtered_out_paths()
+			throws Exception {
+		whenARequestIsSentToASyncEndpointThatShouldBeFilteredOut();
+
+		then(Tracing.current().tracer().currentSpan()).isNull();
+		then(this.reporter.getSpans()).isEmpty();
+	}
+
 	private void whenARequestIsSentToAnAsyncRestTemplateEndpoint() throws Exception {
 		this.mockMvc.perform(MockMvcRequestBuilders.get("/asyncRestTemplate")
 				.accept(MediaType.TEXT_PLAIN)).andReturn();
@@ -127,6 +141,12 @@ public class RestTemplateTraceAspectIntegrationTests {
 				.andReturn();
 	}
 
+	private void whenARequestIsSentToASyncEndpointThatShouldBeFilteredOut() throws Exception {
+		this.mockMvc.perform(
+				MockMvcRequestBuilders.get("/issue1047_start").accept(MediaType.TEXT_PLAIN))
+				.andReturn();
+	}
+
 	private void thenTraceIdHasBeenSetOnARequestHeader() {
 		assertThat(this.controller.getTraceId()).matches("^(?!\\s*$).+");
 	}
@@ -183,6 +203,16 @@ public class RestTemplateTraceAspectIntegrationTests {
 			this.traceId = null;
 		}
 
+		@RequestMapping(value = "/issue1047_end", method = RequestMethod.GET,
+				produces = MediaType.TEXT_PLAIN_VALUE) public String issue1047() {
+			return "should_filter_out_this_endpoint";
+		}
+
+		@RequestMapping(value = "/issue1047_start", method = RequestMethod.GET,
+				produces = MediaType.TEXT_PLAIN_VALUE) public String issue1047Start() {
+			return callAndReturnIssue1047();
+		}
+
 		@RequestMapping(value = "/", method = RequestMethod.GET,
 				produces = MediaType.TEXT_PLAIN_VALUE) public String home(
 				@RequestHeader(value = "X-B3-SpanId", required = false) String traceId) {
@@ -228,7 +258,10 @@ public class RestTemplateTraceAspectIntegrationTests {
 			});
 		}
 
-		;
+		private String callAndReturnIssue1047() {
+			this.restTemplate.getForObject("http://localhost:" + port() + "/issue1047_end", String.class);
+			return "OK";
+		}
 
 		private String callAndReturnOk() {
 			this.restTemplate.getForObject("http://localhost:" + port(), String.class);