feat(request_id): set request id when it's set but empty (#38474)

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Commit Message: `feat(request_id): set request id when it's set but
empty`
Risk Level: Low
Testing: Yes
Docs Changes: N/A
Release Notes:
* `generate_request_id` will generate a request id on non-present and
empty `x-request-id` header.

Fixes #38445

---------

Signed-off-by: Nathanael DEMACON <quantumsheep@users.noreply.github.com>
Co-authored-by: Nathanael DEMACON <quantumsheep@users.noreply.github.com>

changelogs/current.yaml

@@ -25,6 +25,11 @@ minor_behavior_changes:
 - area: cel
   change: |
     Support extension regex fuctions(e.g. ``re.extract``, ``re.capture`, ``re.captureN``) in CEL.
+- area: http
+  change: |
+    :ref:`generate_request_id
+    <envoy_v3_api_field_extensions.filters.network.http_connection_manager.v3.HttpConnectionManager.generate_request_id>`
+    will generate a request id on non-present and now on empty ``x-request-id`` header.
 
 bug_fixes:
 # *Changes expected to improve the state of the world and are unlikely to have negative effects*

source/extensions/request_id/uuid/config.cc

@@ -16,7 +16,7 @@ void UUIDRequestIDExtension::set(Http::RequestHeaderMap& request_headers, bool e
   const Http::HeaderEntry* request_id_header = request_headers.RequestId();
 
   // No request ID then set new one anyway.
-  if (request_id_header == nullptr) {
+  if (request_id_header == nullptr || request_id_header->value().empty()) {
     request_headers.setRequestId(random_.uuid());
     return;
   }

test/extensions/request_id/uuid/config_test.cc

@@ -85,6 +85,51 @@ TEST(UUIDRequestIDExtensionTest, SetRequestID) {
   }
 }
 
+TEST(UUIDRequestIDExtensionTest, SetRequestIDWhenEmpty) {
+  testing::StrictMock<Random::MockRandomGenerator> random;
+  UUIDRequestIDExtension uuid_utils(envoy::extensions::request_id::uuid::v3::UuidRequestIdConfig(),
+                                    random);
+
+  {
+    // Request ID not set.
+
+    Http::TestRequestHeaderMapImpl request_headers;
+
+    // A new request ID will be set.
+    EXPECT_CALL(random, uuid()).WillOnce(Return("first-request-id"));
+    uuid_utils.set(request_headers, false, true);
+    EXPECT_EQ("first-request-id", request_headers.get_(Http::Headers::get().RequestId));
+  }
+
+  {
+    // Request ID is empty.
+
+    Http::TestRequestHeaderMapImpl request_headers{{
+        "x-request-id",
+        "",
+    }};
+
+    // A new request ID will be set.
+    EXPECT_CALL(random, uuid()).WillOnce(Return("first-request-id"));
+    uuid_utils.set(request_headers, false, true);
+    EXPECT_EQ("first-request-id", request_headers.get_(Http::Headers::get().RequestId));
+  }
+
+  {
+    // Request ID is not empty.
+
+    Http::TestRequestHeaderMapImpl request_headers{{
+        "x-request-id",
+        "some-request-id",
+    }};
+
+    // The request ID will be kept.
+    EXPECT_CALL(random, uuid()).Times(0);
+    uuid_utils.set(request_headers, false, true);
+    EXPECT_EQ("some-request-id", request_headers.get_(Http::Headers::get().RequestId));
+  }
+}
+
 TEST(UUIDRequestIDExtensionTest, ClearExternalTraceReason) {
   testing::NiceMock<Random::MockRandomGenerator> random;
   UUIDRequestIDExtension uuid_utils(envoy::extensions::request_id::uuid::v3::UuidRequestIdConfig(),