Add thread local cache of overload action states

include/envoy/server/overload_manager.h

@@ -1,6 +1,9 @@
 #pragma once
 
+#include <unordered_map>
+
 #include "envoy/common/pure.h"
+#include "envoy/thread_local/thread_local.h"
 
 namespace Envoy {
 namespace Server {
@@ -21,6 +24,22 @@ enum class OverloadActionState {
  */
 typedef std::function<void(OverloadActionState)> OverloadActionCb;
 
+/**
+ * Thread-local cache of the current state of each configured overload action.
+ */
+class OverloadActionStateCache : public ThreadLocal::ThreadLocalObject {
+public:
+  bool isActive(const std::string& action) const {
+    auto it = actions_.find(action);
+    return it != actions_.end() && it->second == OverloadActionState::Active;
+  }
+
+  void setState(const std::string& action, OverloadActionState state) { actions_[action] = state; }
+
+private:
+  std::unordered_map<std::string, OverloadActionState> actions_;
+};
+
 /**
  * The OverloadManager protects the Envoy instance from being overwhelmed by client
  * requests. It monitors a set of resources and notifies registered listeners if
@@ -46,6 +65,12 @@ class OverloadManager {
    */
   virtual void registerForAction(const std::string& action, Event::Dispatcher& dispatcher,
                                  OverloadActionCb callback) PURE;
+
+  /**
+   * Get the thread-local overload action state cache. Lookups in this cache can be used as
+   * an alternative to registering a callback for overload action state changes.
+   */
+  virtual const OverloadActionStateCache& getOverloadActionStateCache() PURE;
 };
 
 } // namespace Server

source/server/BUILD

@@ -167,6 +167,7 @@ envoy_cc_library(
     deps = [
         "//include/envoy/server:overload_manager_interface",
         "//include/envoy/stats:stats_interface",
+        "//include/envoy/thread_local:thread_local_interface",
         "//source/common/common:logger_lib",
         "//source/common/config:utility_lib",
         "//source/server:resource_monitor_config_lib",

source/server/overload_manager_impl.cc

@@ -84,8 +84,9 @@ bool OverloadAction::isActive() const { return !fired_triggers_.empty(); }
 
 OverloadManagerImpl::OverloadManagerImpl(
     Event::Dispatcher& dispatcher, Stats::Scope& stats_scope,
+    ThreadLocal::SlotAllocator& slot_allocator,
     const envoy::config::overload::v2alpha::OverloadManager& config)
-    : started_(false), dispatcher_(dispatcher),
+    : started_(false), dispatcher_(dispatcher), tls_(slot_allocator.allocateSlot()),
       refresh_interval_(
           std::chrono::milliseconds(PROTOBUF_GET_MS_OR_DEFAULT(config, refresh_interval, 1000))) {
   Configuration::ResourceMonitorFactoryContextImpl context(dispatcher);
@@ -125,6 +126,10 @@ OverloadManagerImpl::OverloadManagerImpl(
       resource_to_actions_.insert(std::make_pair(resource, name));
     }
   }
+
+  tls_->set([](Event::Dispatcher&) -> ThreadLocal::ThreadLocalObjectSharedPtr {
+    return std::make_shared<OverloadActionStateCache>();
+  });
 }
 
 void OverloadManagerImpl::start() {
@@ -157,6 +162,10 @@ void OverloadManagerImpl::registerForAction(const std::string& action,
                                std::forward_as_tuple(dispatcher, callback));
 }
 
+const OverloadActionStateCache& OverloadManagerImpl::getOverloadActionStateCache() {
+  return tls_->getTyped<OverloadActionStateCache>();
+}
+
 void OverloadManagerImpl::updateResourcePressure(const std::string& resource, double pressure) {
   auto action_range = resource_to_actions_.equal_range(resource);
   std::for_each(action_range.first, action_range.second,
@@ -170,6 +179,9 @@ void OverloadManagerImpl::updateResourcePressure(const std::string& resource, do
                         is_active ? OverloadActionState::Active : OverloadActionState::Inactive;
                     ENVOY_LOG(info, "Overload action {} has become {}", action,
                               is_active ? "active" : "inactive");
+                    tls_->runOnAllThreads([this, action, state] {
+                      tls_->getTyped<OverloadActionStateCache>().setState(action, state);
+                    });
                     auto callback_range = action_to_callbacks_.equal_range(action);
                     std::for_each(callback_range.first, callback_range.second,
                                   [&](ActionToCallbackMap::value_type& cb_entry) {

source/server/overload_manager_impl.h

@@ -11,6 +11,7 @@
 #include "envoy/server/resource_monitor.h"
 #include "envoy/stats/scope.h"
 #include "envoy/stats/stats.h"
+#include "envoy/thread_local/thread_local.h"
 
 #include "common/common/logger.h"
 
@@ -50,12 +51,14 @@ class OverloadAction {
 class OverloadManagerImpl : Logger::Loggable<Logger::Id::main>, public OverloadManager {
 public:
   OverloadManagerImpl(Event::Dispatcher& dispatcher, Stats::Scope& stats_scope,
+                      ThreadLocal::SlotAllocator& slot_allocator,
                       const envoy::config::overload::v2alpha::OverloadManager& config);
 
   // Server::OverloadManager
   void start() override;
   void registerForAction(const std::string& action, Event::Dispatcher& dispatcher,
                          OverloadActionCb callback) override;
+  const OverloadActionStateCache& getOverloadActionStateCache() override;
 
 private:
   class Resource : public ResourceMonitor::Callbacks {
@@ -90,6 +93,7 @@ class OverloadManagerImpl : Logger::Loggable<Logger::Id::main>, public OverloadM
 
   bool started_;
   Event::Dispatcher& dispatcher_;
+  ThreadLocal::SlotPtr tls_;
   const std::chrono::milliseconds refresh_interval_;
   Event::TimerPtr timer_;
   std::unordered_map<std::string, Resource> resources_;

source/server/server.cc

@@ -247,10 +247,6 @@ void InstanceImpl::initialize(Options& options,
 
   loadServerFlags(initial_config.flagsPath());
 
-  // Initialize the overload manager early so other modules can register for actions.
-  overload_manager_.reset(
-      new OverloadManagerImpl(dispatcher(), stats(), bootstrap_.overload_manager()));
-
   // Workers get created first so they register for thread local updates.
   listener_manager_.reset(new ListenerManagerImpl(
       *this, listener_component_factory_, worker_factory_, ProdSystemTimeSource::instance_));
@@ -259,6 +255,10 @@ void InstanceImpl::initialize(Options& options,
   // whether it runs on the main thread or on workers can still use TLS.
   thread_local_.registerThread(*dispatcher_, true);
 
+  // Initialize the overload manager early so other modules can register for actions.
+  overload_manager_.reset(
+      new OverloadManagerImpl(dispatcher(), stats(), threadLocal(), bootstrap_.overload_manager()));
+
   // We can now initialize stats for threading.
   stats_store_.initializeThreading(*dispatcher_, thread_local_);
 

test/mocks/server/mocks.h

@@ -282,6 +282,7 @@ class MockOverloadManager : public OverloadManager {
   MOCK_METHOD0(start, void());
   MOCK_METHOD3(registerForAction, void(const std::string& action, Event::Dispatcher& dispatcher,
                                        OverloadActionCb callback));
+  MOCK_METHOD0(getOverloadActionStateCache, const OverloadActionStateCache&());
 };
 
 class MockInstance : public Instance {

test/server/BUILD

@@ -122,6 +122,7 @@ envoy_cc_test(
         "//source/extensions/resource_monitors/common:factory_base_lib",
         "//source/server:overload_manager_lib",
         "//test/mocks/event:event_mocks",
+        "//test/mocks/thread_local:thread_local_mocks",
         "//test/test_common:registry_lib",
         "//test/test_common:utility_lib",
     ],

test/server/overload_manager_impl_test.cc

@@ -8,6 +8,7 @@
 #include "extensions/resource_monitors/common/factory_base.h"
 
 #include "test/mocks/event/mocks.h"
+#include "test/mocks/thread_local/mocks.h"
 #include "test/test_common/registry.h"
 #include "test/test_common/utility.h"
 
@@ -118,46 +119,55 @@ class OverloadManagerImplTest : public testing::Test {
     )EOF";
   }
 
+  std::unique_ptr<OverloadManagerImpl> createOverloadManager(const std::string& config) {
+    return std::make_unique<OverloadManagerImpl>(dispatcher_, stats_, thread_local_,
+                                                 parseConfig(config));
+  }
+
   FakeResourceMonitorFactory factory1_;
   FakeResourceMonitorFactory factory2_;
   Registry::InjectFactory<Configuration::ResourceMonitorFactory> register_factory1_;
   Registry::InjectFactory<Configuration::ResourceMonitorFactory> register_factory2_;
   NiceMock<Event::MockDispatcher> dispatcher_;
   Stats::IsolatedStoreImpl stats_;
+  NiceMock<ThreadLocal::MockInstance> thread_local_;
   Event::TimerCb timer_cb_;
 };
 
 TEST_F(OverloadManagerImplTest, CallbackOnlyFiresWhenStateChanges) {
   setDispatcherExpectation();
 
-  OverloadManagerImpl manager(dispatcher_, stats_, parseConfig(getConfig()));
+  auto manager(createOverloadManager(getConfig()));
   bool is_active = false;
   int cb_count = 0;
-  manager.registerForAction("envoy.overload_actions.dummy_action", dispatcher_,
-                            [&](OverloadActionState state) {
-                              is_active = state == OverloadActionState::Active;
-                              cb_count++;
-                            });
-  manager.registerForAction("envoy.overload_actions.unknown_action", dispatcher_,
-                            [&](OverloadActionState) { EXPECT_TRUE(false); });
-  manager.start();
+  manager->registerForAction("envoy.overload_actions.dummy_action", dispatcher_,
+                             [&](OverloadActionState state) {
+                               is_active = state == OverloadActionState::Active;
+                               cb_count++;
+                             });
+  manager->registerForAction("envoy.overload_actions.unknown_action", dispatcher_,
+                             [&](OverloadActionState) { EXPECT_TRUE(false); });
+  manager->start();
 
   Stats::Gauge& active_gauge = stats_.gauge("overload.envoy.overload_actions.dummy_action.active");
   Stats::Gauge& pressure_gauge1 =
       stats_.gauge("overload.envoy.resource_monitors.fake_resource1.pressure");
   Stats::Gauge& pressure_gauge2 =
       stats_.gauge("overload.envoy.resource_monitors.fake_resource2.pressure");
+  const OverloadActionStateCache& action_state = manager->getOverloadActionStateCache();
 
   factory1_.monitor_->setPressure(0.5);
   timer_cb_();
   EXPECT_FALSE(is_active);
+  EXPECT_FALSE(action_state.isActive("envoy.overload_actions.dummy_action"));
   EXPECT_EQ(0, cb_count);
   EXPECT_EQ(0, active_gauge.value());
   EXPECT_EQ(50, pressure_gauge1.value());
 
   factory1_.monitor_->setPressure(0.95);
   timer_cb_();
   EXPECT_TRUE(is_active);
+  EXPECT_TRUE(action_state.isActive("envoy.overload_actions.dummy_action"));
   EXPECT_EQ(1, cb_count);
   EXPECT_EQ(1, active_gauge.value());
   EXPECT_EQ(95, pressure_gauge1.value());
@@ -166,6 +176,7 @@ TEST_F(OverloadManagerImplTest, CallbackOnlyFiresWhenStateChanges) {
   factory1_.monitor_->setPressure(0.94);
   timer_cb_();
   EXPECT_TRUE(is_active);
+  EXPECT_TRUE(action_state.isActive("envoy.overload_actions.dummy_action"));
   EXPECT_EQ(1, cb_count);
   EXPECT_EQ(94, pressure_gauge1.value());
 
@@ -174,22 +185,24 @@ TEST_F(OverloadManagerImplTest, CallbackOnlyFiresWhenStateChanges) {
   factory2_.monitor_->setPressure(0.9);
   timer_cb_();
   EXPECT_TRUE(is_active);
+  EXPECT_TRUE(action_state.isActive("envoy.overload_actions.dummy_action"));
   EXPECT_EQ(1, cb_count);
   EXPECT_EQ(50, pressure_gauge1.value());
   EXPECT_EQ(90, pressure_gauge2.value());
 
   factory2_.monitor_->setPressure(0.4);
   timer_cb_();
   EXPECT_FALSE(is_active);
+  EXPECT_FALSE(action_state.isActive("envoy.overload_actions.dummy_action"));
   EXPECT_EQ(2, cb_count);
   EXPECT_EQ(0, active_gauge.value());
   EXPECT_EQ(40, pressure_gauge2.value());
 }
 
 TEST_F(OverloadManagerImplTest, FailedUpdates) {
   setDispatcherExpectation();
-  OverloadManagerImpl manager(dispatcher_, stats_, parseConfig(getConfig()));
-  manager.start();
+  auto manager(createOverloadManager(getConfig()));
+  manager->start();
   Stats::Counter& failed_updates =
       stats_.counter("overload.envoy.resource_monitors.fake_resource1.failed_updates");
 
@@ -207,8 +220,8 @@ TEST_F(OverloadManagerImplTest, SkippedUpdates) {
   Event::PostCb post_cb;
   ON_CALL(dispatcher_, post(_)).WillByDefault(Invoke([&](Event::PostCb cb) { post_cb = cb; }));
 
-  OverloadManagerImpl manager(dispatcher_, stats_, parseConfig(getConfig()));
-  manager.start();
+  auto manager(createOverloadManager(getConfig()));
+  manager->start();
   Stats::Counter& skipped_updates =
       stats_.counter("overload.envoy.resource_monitors.fake_resource1.skipped_updates");
 
@@ -233,8 +246,8 @@ TEST_F(OverloadManagerImplTest, DuplicateResourceMonitor) {
     }
   )EOF";
 
-  EXPECT_THROW_WITH_REGEX(OverloadManagerImpl(dispatcher_, stats_, parseConfig(config)),
-                          EnvoyException, "Duplicate resource monitor .*");
+  EXPECT_THROW_WITH_REGEX(createOverloadManager(config), EnvoyException,
+                          "Duplicate resource monitor .*");
 }
 
 TEST_F(OverloadManagerImplTest, DuplicateOverloadAction) {
@@ -247,8 +260,8 @@ TEST_F(OverloadManagerImplTest, DuplicateOverloadAction) {
     }
   )EOF";
 
-  EXPECT_THROW_WITH_REGEX(OverloadManagerImpl(dispatcher_, stats_, parseConfig(config)),
-                          EnvoyException, "Duplicate overload action .*");
+  EXPECT_THROW_WITH_REGEX(createOverloadManager(config), EnvoyException,
+                          "Duplicate overload action .*");
 }
 
 TEST_F(OverloadManagerImplTest, UnknownTrigger) {
@@ -264,8 +277,8 @@ TEST_F(OverloadManagerImplTest, UnknownTrigger) {
     }
   )EOF";
 
-  EXPECT_THROW_WITH_REGEX(OverloadManagerImpl(dispatcher_, stats_, parseConfig(config)),
-                          EnvoyException, "Unknown trigger resource .*");
+  EXPECT_THROW_WITH_REGEX(createOverloadManager(config), EnvoyException,
+                          "Unknown trigger resource .*");
 }
 
 TEST_F(OverloadManagerImplTest, DuplicateTrigger) {
@@ -290,8 +303,7 @@ TEST_F(OverloadManagerImplTest, DuplicateTrigger) {
     }
   )EOF";
 
-  EXPECT_THROW_WITH_REGEX(OverloadManagerImpl(dispatcher_, stats_, parseConfig(config)),
-                          EnvoyException, "Duplicate trigger .*");
+  EXPECT_THROW_WITH_REGEX(createOverloadManager(config), EnvoyException, "Duplicate trigger .*");
 }
 } // namespace
 } // namespace Server