ipc: extract content length from header (#1183)

If a `Content-Length` header is present and the payload
length hasn't already been explicitly set, then try to
extract from the header.

Author: brharrington

spectator-ext-ipc/src/main/java/com/netflix/spectator/ipc/IpcLogEntry.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2023 Netflix, Inc.
+ * Copyright 2014-2025 Netflix, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -40,6 +40,8 @@
 @SuppressWarnings({"PMD.ExcessiveClassLength", "PMD.AvoidStringBufferField"})
 public final class IpcLogEntry {
 
+  private static final String CONTENT_LENGTH = "Content-Length";
+
   private final Clock clock;
 
   private Registry registry;
@@ -526,6 +528,14 @@ public IpcLogEntry withUri(URI uri) {
     return withUri(uri.toString(), uri.getPath());
   }
 
+  private long parseContentLength(String value) {
+    try {
+      return Long.parseLong(value);
+    } catch (NumberFormatException e) {
+      return -1L;
+    }
+  }
+
   /**
    * Set the length for the request entity if it is known at the time of logging. If the size
    * is not known, e.g. a chunked HTTP entity, then a negative value can be used and the length
@@ -559,6 +569,8 @@ public IpcLogEntry addRequestHeader(String name, String value) {
       withClientNode(value);
     } else if (vip == null && name.equalsIgnoreCase(NetflixHeader.Vip.headerName())) {
       withVip(value);
+    } else if (requestContentLength < 0L && CONTENT_LENGTH.equalsIgnoreCase(name)) {
+      withRequestContentLength(parseContentLength(value));
     } else if (isMeshRequest(name, value)) {
       disableMetrics();
     }
@@ -584,6 +596,8 @@ public IpcLogEntry addResponseHeader(String name, String value) {
       withServerNode(value);
     } else if (endpoint == null && name.equalsIgnoreCase(NetflixHeader.Endpoint.headerName())) {
       withEndpoint(value);
+    } else if (responseContentLength < 0L && CONTENT_LENGTH.equalsIgnoreCase(name)) {
+      withResponseContentLength(parseContentLength(value));
     }
     this.responseHeaders.add(new Header(name, value));
     return this;

spectator-ext-ipc/src/test/java/com/netflix/spectator/ipc/IpcLogEntryTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2024 Netflix, Inc.
+ * Copyright 2014-2025 Netflix, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -394,6 +394,31 @@ public void addRequestAsgHeaderExplicitAsg() {
     Assertions.assertEquals("foo", map.get("clientAsg"));
   }
 
+  @Test
+  public void addRequestContentLengthHeader() {
+    Map<String, Object> map = entry
+        .addRequestHeader("Content-Length", "123")
+        .convert(this::toMap);
+    Assertions.assertEquals(123, map.get("requestContentLength"));
+  }
+
+  @Test
+  public void addRequestContentLengthHeaderExplicitPreferred() {
+    Map<String, Object> map = entry
+        .withRequestContentLength(456)
+        .addRequestHeader("Content-Length", "123")
+        .convert(this::toMap);
+    Assertions.assertEquals(456, map.get("requestContentLength"));
+  }
+
+  @Test
+  public void addRequestContentLengthHeaderInvalid() {
+    Map<String, Object> map = entry
+        .addRequestHeader("Content-Length", "foo")
+        .convert(this::toMap);
+    Assertions.assertNull(map.get("requestContentLength"));
+  }
+
   @Test
   public void addResponseAsgHeader() {
     Map<String, Object> map = entry
@@ -479,6 +504,31 @@ public void addResponseEndpointHeader() {
     Assertions.assertEquals("/api/v1/test", map.get("endpoint"));
   }
 
+  @Test
+  public void addResponseContentLengthHeader() {
+    Map<String, Object> map = entry
+        .addResponseHeader("Content-Length", "123")
+        .convert(this::toMap);
+    Assertions.assertEquals(123, map.get("responseContentLength"));
+  }
+
+  @Test
+  public void addResponseContentLengthHeaderExplicitPreferred() {
+    Map<String, Object> map = entry
+        .withResponseContentLength(456)
+        .addResponseHeader("Content-Length", "123")
+        .convert(this::toMap);
+    Assertions.assertEquals(456, map.get("responseContentLength"));
+  }
+
+  @Test
+  public void addResponseContentLengthHeaderInvalid() {
+    Map<String, Object> map = entry
+        .addResponseHeader("Content-Length", "foo")
+        .convert(this::toMap);
+    Assertions.assertNull(map.get("responseContentLength"));
+  }
+
   @Test
   public void source() {
     String expected = IpcSource.direct.value();