[service] allow follower ReportEvent queries

Author: charpty

kv_cache_manager/service/meta_service_impl.cc

@@ -964,8 +964,10 @@ void MetaServiceImpl::GetHostCacheState(RequestContext *request_context,
                                         const proto::meta::GetHostCacheStateRequest *request,
                                         proto::meta::GetHostCacheStateResponse *response) {
     SPAN_TRACER(request_context);
+    // This is a best-effort read of the node's local ReportEvent view. Followers may
+    // serve a stale view, while ReportEvent mutations remain leader-only.
     API_CALL_GUARD_WITH_DEBUG("GetHostCacheState",
-                              true,
+                              false,
                               BuildGetHostCacheStateRequestAccessLogSummary(request),
                               BuildGetHostCacheStateResponseAccessLogSummary(response));
     auto *header = response->mutable_header();

kv_cache_manager/service/test/BUILD

@@ -15,6 +15,21 @@ cc_test(
     ],
 )
 
+cc_test(
+    name = "MetaServiceImplTest",
+    srcs = [
+        "meta_service_impl_test.cc",
+    ],
+    copts = ["-fno-access-control"],
+    deps = [
+        "//kv_cache_manager/common:unittest",
+        "//kv_cache_manager/config",
+        "//kv_cache_manager/manager:cache_manager",
+        "//kv_cache_manager/metrics:metrics_registry",
+        "//kv_cache_manager/service:meta_service_impl",
+    ],
+)
+
 cc_test(
     name = "CommandLineTest",
     srcs = [

kv_cache_manager/service/test/meta_service_impl_test.cc

@@ -0,0 +1,51 @@
+#include <memory>
+
+#include "kv_cache_manager/common/request_context.h"
+#include "kv_cache_manager/common/unittest.h"
+#include "kv_cache_manager/config/registry_manager.h"
+#include "kv_cache_manager/manager/cache_manager.h"
+#include "kv_cache_manager/metrics/metrics_registry.h"
+#include "kv_cache_manager/protocol/protobuf/meta_service.pb.h"
+#include "kv_cache_manager/service/meta_service_impl.h"
+
+namespace kv_cache_manager {
+
+class MetaServiceImplTest : public TESTBASE {
+protected:
+    void SetUp() override {
+        metrics_registry_ = std::make_shared<MetricsRegistry>();
+        registry_manager_ = std::make_shared<RegistryManager>("", metrics_registry_);
+        cache_manager_ = std::make_shared<CacheManager>(metrics_registry_, registry_manager_);
+        service_ = std::make_unique<MetaServiceImpl>(cache_manager_, nullptr, nullptr);
+        service_->DisableLeaderOnlyRequests();
+    }
+
+    std::shared_ptr<MetricsRegistry> metrics_registry_;
+    std::shared_ptr<RegistryManager> registry_manager_;
+    std::shared_ptr<CacheManager> cache_manager_;
+    std::unique_ptr<MetaServiceImpl> service_;
+};
+
+TEST_F(MetaServiceImplTest, FollowerAllowsReportEventQueryButRejectsWrite) {
+    RequestContext query_context("follower-query");
+    proto::meta::GetHostCacheStateRequest query_request;
+    query_request.set_trace_id(query_context.trace_id());
+    proto::meta::GetHostCacheStateResponse query_response;
+
+    service_->GetHostCacheState(&query_context, &query_request, &query_response);
+
+    // INVALID_ARGUMENT proves the read passed the follower gate and reached
+    // normal request validation instead of being rejected as SERVER_NOT_LEADER.
+    EXPECT_EQ(proto::meta::INVALID_ARGUMENT, query_response.header().status().code());
+
+    RequestContext write_context("follower-write");
+    proto::meta::ReportEventRequest write_request;
+    write_request.set_trace_id(write_context.trace_id());
+    proto::meta::ReportEventResponse write_response;
+
+    service_->ReportEvent(&write_context, &write_request, &write_response);
+
+    EXPECT_EQ(proto::meta::SERVER_NOT_LEADER, write_response.header().status().code());
+}
+
+} // namespace kv_cache_manager