dispatcher: split into multiple interfaces to improve functional scoping

envoy/event/dispatcher.h

@@ -63,6 +63,57 @@ class DispatcherBase {
 public:
   virtual ~DispatcherBase() = default;
 
+  /**
+   * Posts a functor to the dispatcher. This is safe cross thread. The functor runs in the context
+   * of the dispatcher event loop which may be on a different thread than the caller.
+   */
+  virtual void post(PostCb callback) PURE;
+
+  /**
+   * Validates that an operation is thread-safe with respect to this dispatcher; i.e. that the
+   * current thread of execution is on the same thread upon which the dispatcher loop is running.
+   */
+  virtual bool isThreadSafe() const PURE;
+};
+
+/**
+ * Minimal interface to support ScopeTrackedObjects.
+ */
+class ScopeTracker {
+public:
+  virtual ~ScopeTracker() = default;
+
+  /**
+   * Appends a tracked object to the current stack of tracked objects operating
+   * in the dispatcher.
+   *
+   * It's recommended to use ScopeTrackerScopeState to manage the object's tracking. If directly
+   * invoking, there needs to be a subsequent call to popTrackedObject().
+   */
+  virtual void pushTrackedObject(const ScopeTrackedObject* object) PURE;
+
+  /**
+   * Removes the top of the stack of tracked object and asserts that it was expected.
+   */
+  virtual void popTrackedObject(const ScopeTrackedObject* expected_object) PURE;
+
+  /**
+   * Whether the tracked object stack is empty.
+   */
+  virtual bool trackedObjectStackIsEmpty() const PURE;
+};
+
+/**
+ * Abstract event dispatching loop.
+ */
+class Dispatcher : public DispatcherBase, public ScopeTracker {
+public:
+  /**
+   * Returns the name that identifies this dispatcher, such as "worker_2" or "main_thread".
+   * @return const std::string& the name that identifies this dispatcher.
+   */
+  virtual const std::string& name() PURE;
+
   /**
    * Creates a file event that will signal when a file is readable or writable. On UNIX systems this
    * can be used for any file like interface (files, sockets, etc.).
@@ -103,48 +154,6 @@ class DispatcherBase {
    */
   virtual Event::SchedulableCallbackPtr createSchedulableCallback(std::function<void()> cb) PURE;
 
-  /**
-   * Appends a tracked object to the current stack of tracked objects operating
-   * in the dispatcher.
-   *
-   * It's recommended to use ScopeTrackerScopeState to manage the object's tracking. If directly
-   * invoking, there needs to be a subsequent call to popTrackedObject().
-   */
-  virtual void pushTrackedObject(const ScopeTrackedObject* object) PURE;
-
-  /**
-   * Removes the top of the stack of tracked object and asserts that it was expected.
-   */
-  virtual void popTrackedObject(const ScopeTrackedObject* expected_object) PURE;
-
-  /**
-   * Whether the tracked object stack is empty.
-   */
-  virtual bool trackedObjectStackIsEmpty() const PURE;
-
-  /**
-   * Validates that an operation is thread-safe with respect to this dispatcher; i.e. that the
-   * current thread of execution is on the same thread upon which the dispatcher loop is running.
-   */
-  virtual bool isThreadSafe() const PURE;
-
-  /**
-   * Returns a recently cached MonotonicTime value.
-   */
-  virtual MonotonicTime approximateMonotonicTime() const PURE;
-};
-
-/**
- * Abstract event dispatching loop.
- */
-class Dispatcher : public DispatcherBase {
-public:
-  /**
-   * Returns the name that identifies this dispatcher, such as "worker_2" or "main_thread".
-   * @return const std::string& the name that identifies this dispatcher.
-   */
-  virtual const std::string& name() PURE;
-
   /**
    * Register a watchdog for this dispatcher. The dispatcher is responsible for touching the
    * watchdog at least once per touch interval. Dispatcher implementations may choose to touch more
@@ -159,6 +168,11 @@ class Dispatcher : public DispatcherBase {
    */
   virtual TimeSource& timeSource() PURE;
 
+  /**
+   * Returns a recently cached MonotonicTime value.
+   */
+  virtual MonotonicTime approximateMonotonicTime() const PURE;
+
   /**
    * Initializes stats for this dispatcher. Note that this can't generally be done at construction
    * time, since the main and worker thread dispatchers are constructed before
@@ -264,12 +278,6 @@ class Dispatcher : public DispatcherBase {
    */
   virtual SignalEventPtr listenForSignal(signal_t signal_num, SignalCb cb) PURE;
 
-  /**
-   * Posts a functor to the dispatcher. This is safe cross thread. The functor runs in the context
-   * of the dispatcher event loop which may be on a different thread than the caller.
-   */
-  virtual void post(PostCb callback) PURE;
-
   /**
    * Post the deletable to this dispatcher. The deletable objects are guaranteed to be destroyed on
    * the dispatcher's thread before dispatcher destroy. This is safe cross thread.

source/common/common/scope_tracker.h

@@ -10,20 +10,20 @@ namespace Envoy {
 // A small class for managing the scope of a tracked object which is currently having
 // work done in this thread.
 //
-// When created, it appends the tracked object to the dispatcher's stack of tracked objects, and
-// when destroyed it pops the dispatcher's stack of tracked object, which should be the object it
+// When created, it appends the tracked object to the tracker's stack of tracked objects, and
+// when destroyed it pops the tracker's stack of tracked object, which should be the object it
 // registered.
 class ScopeTrackerScopeState {
 public:
-  ScopeTrackerScopeState(const ScopeTrackedObject* object, Event::Dispatcher& dispatcher)
-      : registered_object_(object), dispatcher_(dispatcher) {
-    dispatcher_.pushTrackedObject(registered_object_);
+  ScopeTrackerScopeState(const ScopeTrackedObject* object, Event::ScopeTracker& tracker)
+      : registered_object_(object), tracker_(tracker) {
+    tracker_.pushTrackedObject(registered_object_);
   }
 
   ~ScopeTrackerScopeState() {
     // If ScopeTrackerScopeState is always used for managing tracked objects,
     // then the object popped off should be the object we registered.
-    dispatcher_.popTrackedObject(registered_object_);
+    tracker_.popTrackedObject(registered_object_);
   }
 
   // Make this object stack-only, it doesn't make sense for it
@@ -32,7 +32,7 @@ class ScopeTrackerScopeState {
 
 private:
   const ScopeTrackedObject* registered_object_;
-  Event::Dispatcher& dispatcher_;
+  Event::ScopeTracker& tracker_;
 };
 
 } // namespace Envoy