Add fallback to W3C trace-id

When no X-CorrelationId header is found, the CorrelationIdFilter now searches
for a traceparent header. It will take the trace-id as correlation-id, if the header
value follows the W3C definition. This filter can be configured with customisable
http header configurations but keeps the old interface for compatibility.

Signed-off-by: Karsten Schnitter <k.schnitter@sap.com>

Author: KarstenSchnitter

cf-java-logging-support-servlet/src/main/java/com/sap/hcp/cf/logging/servlet/filter/CorrelationIdFilter.java

@@ -1,8 +1,11 @@
 package com.sap.hcp.cf.logging.servlet.filter;
 
 import static com.sap.hcp.cf.logging.common.customfields.CustomField.customField;
+import static com.sap.hcp.cf.logging.common.request.HttpHeaders.W3C_TRACEPARENT;
+import static java.util.Optional.ofNullable;
 
 import java.util.UUID;
+import java.util.function.Predicate;
 
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
@@ -25,13 +28,19 @@ public class CorrelationIdFilter extends AbstractLoggingFilter {
 
     private static final Logger LOG = LoggerFactory.getLogger(CorrelationIdFilter.class);
     private HttpHeader correlationHeader;
+    private HttpHeader traceparentHeader;
 
     public CorrelationIdFilter() {
         this(HttpHeaders.CORRELATION_ID);
     }
 
     public CorrelationIdFilter(HttpHeader correlationHeader) {
+        this(correlationHeader, W3C_TRACEPARENT);
+    }
+
+    public CorrelationIdFilter(HttpHeader correlationHeader, HttpHeader traceparentHeader) {
         this.correlationHeader = correlationHeader;
+        this.traceparentHeader = traceparentHeader;
     }
 
     @Override
@@ -43,7 +52,10 @@ protected void beforeFilter(HttpServletRequest request, HttpServletResponse resp
 
     private String determineCorrelationId(HttpServletRequest request) {
         String correlationId = HttpHeaderUtilities.getHeaderValue(request, correlationHeader);
-        if (correlationId == null || correlationId.isEmpty() || correlationId.equals(Defaults.UNKNOWN)) {
+        if (isBlankOrDefault(correlationId)) {
+            correlationId = getCorrelationIdFromTraceparent(request);
+        }
+        if (isBlankOrDefault(correlationId)) {
             correlationId = String.valueOf(UUID.randomUUID());
             // add correlation-id as custom field, since it is added to MDC only
             // in the next step
@@ -53,6 +65,25 @@ private String determineCorrelationId(HttpServletRequest request) {
         return correlationId;
     }
 
+    private boolean isBlankOrDefault(String value) {
+        return value == null || value.isEmpty() || value.equals(Defaults.UNKNOWN);
+    }
+
+    private String getCorrelationIdFromTraceparent(HttpServletRequest request) {
+        String traceparent = HttpHeaderUtilities.getHeaderValue(request, traceparentHeader);
+        return ofNullable(traceparent).filter(not(this::isBlankOrDefault)).map(this::parseTraceparent).orElse(
+                                                                                                                        null);
+    }
+
+    private <T> Predicate<T> not(Predicate<T> p) {
+        return p.negate();
+    }
+
+    private String parseTraceparent(String value) {
+        String[] tokens = value.split("-");
+        return tokens.length >= 2 ? tokens[1] : null;
+    }
+
     private void addCorrelationIdHeader(HttpServletResponse response, String correlationId) {
         if (!response.isCommitted() && response.getHeader(correlationHeader.getName()) == null) {
             response.setHeader(correlationHeader.getName(), correlationId);
@@ -63,5 +94,4 @@ private void addCorrelationIdHeader(HttpServletResponse response, String correla
     protected void cleanup(HttpServletRequest request, HttpServletResponse response) {
         LogContext.remove(correlationHeader.getField());
     }
-
 }

cf-java-logging-support-servlet/src/test/java/com/sap/hcp/cf/logging/servlet/filter/CorrelationIdFilterTest.java

@@ -29,7 +29,9 @@
 @RunWith(MockitoJUnitRunner.class)
 public class CorrelationIdFilterTest {
 
-    private static String KNOWN_CORRELATION_ID = UUID.randomUUID().toString();
+    private static final String KNOWN_CORRELATION_ID = UUID.randomUUID().toString();
+    private static final String KNOWN_TRACE_ID = "4bf92f3577b34da6a3ce929d0e0e4736";
+    private static final String KNOWN_TRACEPARENT = "00-" + KNOWN_TRACE_ID + "-00f067aa0ba902b7-01";
 
     @Mock
     private HttpServletRequest request;
@@ -108,13 +110,40 @@ public void doesNotOverwriteCorrelationIdInResponse() throws Exception {
     }
 
     @Test
-    public void usesCustomHeader() throws Exception {
-        HttpHeader myHeader = new HttpTestHeader("my-header", "my-field", null, false);
-        when(request.getHeader("my-header")).thenReturn(KNOWN_CORRELATION_ID);
+    public void usesCustomCorrelationIdHeader() throws Exception {
+        HttpHeader myCorrelationIdHeader = new HttpTestHeader("my-correlationId-header", "my-correlationId-field", null,
+                                                              false);
+        HttpHeader myTraceparentHeader = new HttpTestHeader("my-traceparent-header", "my-traceparent-field", null,
+                                                            false);
+        when(request.getHeader("my-correlationId-header")).thenReturn(KNOWN_CORRELATION_ID);
+        when(request.getHeader("my-traceparent-header")).thenReturn(KNOWN_TRACEPARENT);
+
+        new CorrelationIdFilter(myCorrelationIdHeader, myTraceparentHeader).doFilter(request, response, chain);
+
+        assertThat(mdcExtractor.getField("my-correlationId-field"), is(equalTo(KNOWN_CORRELATION_ID)));
+        verify(response).setHeader("my-correlationId-header", KNOWN_CORRELATION_ID);
+    }
+
+    @Test
+    public void usesCustomTraceparentHeader() throws Exception {
+        HttpHeader myCorrelationIdHeader = new HttpTestHeader("my-correlationId-header", "my-correlationId-field", null,
+                                                              false);
+        HttpHeader myTraceparentHeader = new HttpTestHeader("my-traceparent-header", "my-traceparent-field", null,
+                                                            false);
+        when(request.getHeader("my-traceparent-header")).thenReturn(KNOWN_TRACEPARENT);
 
-        new CorrelationIdFilter(myHeader).doFilter(request, response, chain);
+        new CorrelationIdFilter(myCorrelationIdHeader, myTraceparentHeader).doFilter(request, response, chain);
+
+        assertThat(mdcExtractor.getField("my-correlationId-field"), is(equalTo(KNOWN_TRACE_ID)));
+        verify(response).setHeader("my-correlationId-header", KNOWN_TRACE_ID);
+    }
+
+    @Test
+    public void usesTraceparentIfCorrelationIdHeaderNotPresent() throws Exception {
+        when(request.getHeader(HttpHeaders.W3C_TRACEPARENT.getName())).thenReturn(KNOWN_TRACEPARENT);
+
+        new CorrelationIdFilter().doFilter(request, response, chain);
 
-        assertThat(mdcExtractor.getField("my-field"), is(equalTo(KNOWN_CORRELATION_ID)));
-        verify(response).setHeader("my-header", KNOWN_CORRELATION_ID);
+        assertThat(getExtractedCorrelationId(), is(equalTo(KNOWN_TRACE_ID)));
     }
 }