update TraceFilter to get TraceId from request

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

@@ -16,10 +16,10 @@
 package org.springframework.cloud.sleuth.web;
 
 import static org.springframework.cloud.sleuth.Trace.SPAN_ID_NAME;
+import static org.springframework.cloud.sleuth.Trace.TRACE_ID_NAME;
 import static org.springframework.util.StringUtils.hasText;
 
 import java.io.IOException;
-import java.lang.invoke.MethodHandles;
 import java.util.Collections;
 import java.util.regex.Pattern;
 
@@ -28,9 +28,6 @@ import javax.servlet.ServletException;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-import org.slf4j.MDC;
 import org.springframework.cloud.sleuth.MilliSpan;
 import org.springframework.cloud.sleuth.Span;
 import org.springframework.cloud.sleuth.Trace;
@@ -38,13 +35,11 @@ import org.springframework.cloud.sleuth.TraceScope;
 import org.springframework.web.filter.OncePerRequestFilter;
 
 /**
- * Filter that takes the value of the {@link CorrelationIdHolder#CORRELATION_ID_HEADER}
- * header from either request or response and sets it in the {@link CorrelationIdHolder}.
- * It also provides that value in {@link MDC} logging related class so that logger prints
- * the value of correlation id at each log.
+ * Filter that takes the value of the {@link Trace#SPAN_ID_NAME} and
+ * {@link Trace#TRACE_ID_NAME} header from either request or response and uses them to
+ * create a new span.
  *
  * @see Trace
- * @see MDC
  *
  * @author Jakub Nabrdalik, 4financeIT
  * @author Tomasz Nurkiewicz, 4financeIT
@@ -52,8 +47,7 @@ import org.springframework.web.filter.OncePerRequestFilter;
  * @author Spencer Gibb
  */
 public class TraceFilter extends OncePerRequestFilter {
-	private static final Logger log = LoggerFactory.getLogger(MethodHandles.lookup()
-			.lookupClass());
+
 	public static final Pattern DEFAULT_SKIP_PATTERN = Pattern
 			.compile("/api-docs.*|/autoconfig|/configprops|/dump|/info|/metrics.*|/mappings|/trace|/swagger.*|.*\\.png|.*\\.css|.*\\.js|.*\\.html");
 
@@ -74,44 +68,51 @@ public class TraceFilter extends OncePerRequestFilter {
 	protected void doFilterInternal(HttpServletRequest request,
 			HttpServletResponse response, FilterChain filterChain)
 			throws ServletException, IOException {
-		String spanIdFromRequest = getSpanIdFrom(request);
-		String spanId = (hasText(spanIdFromRequest)) ? spanIdFromRequest
-				: getSpanIdFrom(response);
+
+		String uri = hasText(request.getRequestURI()) ? request.getRequestURI() : "";
+		boolean skip = skipPattern.matcher(uri).matches();
 
 		TraceScope traceScope = null;
-		if (spanId != null) {
-			addCorrelationIdToResponseIfNotPresent(response, spanId);
+		if (!skip) {
+			String spanId = getHeader(request, response, SPAN_ID_NAME);
+			String traceId = getHeader(request, response, TRACE_ID_NAME);
+			if (hasText(spanId) && hasText(traceId)) {
 
-			Span span = MilliSpan.builder().traceId("") // FIXME get traceId from request
-					.parents(Collections.singletonList(spanId))
-					// TODO: use parent() when lombok plugin supports it
-					.build();
-			traceScope = trace.startSpan("traceFilter", span);
-		}
-		else {
-			traceScope = trace.startSpan("traceFilter");
+				Span span = MilliSpan.builder()
+						.traceId(traceId)
+						.parents(Collections.singletonList(spanId))
+						// TODO: use parent() when lombok plugin supports it
+						.build();
+				// Send new span id back
+				addToResponseIfNotPresent(response, SPAN_ID_NAME, span.getSpanId());
+
+				traceScope = trace.startSpan("traceFilter", span);
+			}
+			else {
+				traceScope = trace.startSpan("traceFilter");
+			}
 		}
 
 		try {
 			filterChain.doFilter(request, response);
 		}
 		finally {
-			traceScope.close();
+			if (traceScope != null) {
+				traceScope.close();
+			}
 		}
 	}
 
-	private String getSpanIdFrom(final HttpServletResponse response) {
-		return response.getHeader(SPAN_ID_NAME);
+	private String getHeader(HttpServletRequest request, HttpServletResponse response,
+			String name) {
+		String value = request.getHeader(name);
+		return hasText(value) ? value : response.getHeader(name);
 	}
 
-	private String getSpanIdFrom(final HttpServletRequest request) {
-		return request.getHeader(SPAN_ID_NAME);
-	}
-
-	private void addCorrelationIdToResponseIfNotPresent(HttpServletResponse response,
-			String spanId) {
-		if (!hasText(response.getHeader(SPAN_ID_NAME))) {
-			response.addHeader(SPAN_ID_NAME, spanId);
+	private void addToResponseIfNotPresent(HttpServletResponse response, String name,
+			String value) {
+		if (!hasText(response.getHeader(name))) {
+			response.addHeader(name, value);
 		}
 	}