Add client ready callback

client/include/loon/client.h

@@ -149,6 +149,17 @@ class IClient
      */
     virtual void wait_until_ready() = 0;
 
+    /**
+     * @brief Sets a callback for when the client is connected and ready.
+     *
+     * It is recommended to call this method before start(),
+     * to reliably detect client ready state.
+     * Do not call any client methods within the callback,
+     * as client locks are held when it is called,
+     * which would cause a deadlock.
+     */
+    virtual void on_ready(std::function<void()> callback) = 0;
+
     /**
      * @brief Sets a callback for when the client has unrecoverably failed.
      *
@@ -455,6 +466,11 @@ class Client : public IClient
         return m_impl->wait_until_ready(timeout);
     }
 
+    inline void on_ready(std::function<void()> callback) override
+    {
+        return m_impl->on_ready(callback);
+    }
+
     inline void on_failed(std::function<void()> callback) override
     {
         return m_impl->on_failed(callback);

client/src/client.cpp

@@ -326,13 +326,18 @@ void ClientImpl::on_hello(Hello const& hello)
         }
     }
 
-    m_cv_connection_ready.notify_all();
-    log(Info) << "ready" << var("base_url", m_hello->base_url());
-
     // The connection is idling if no content was registered yet.
     if (m_content.empty()) {
         set_idle(true);
     }
+
+    log(Info) << "ready" << var("base_url", m_hello->base_url());
+
+    // Call the callback before notifying that the connection is ready.
+    if (m_ready_callback) {
+        m_ready_callback();
+    }
+    m_cv_connection_ready.notify_all();
 }
 
 bool ClientImpl::check_request_limit(decltype(m_content)::iterator it)

client/src/client.h

@@ -57,6 +57,12 @@ class ClientImpl : public IClient
         wait_until_ready(lock, timeout);
     }
 
+    inline void on_ready(std::function<void()> callback) override
+    {
+        std::lock_guard<std::mutex> lock(m_mutex);
+        m_ready_callback = callback;
+    }
+
     inline void on_failed(std::function<void()> callback) override
     {
         std::lock_guard<std::mutex> lock(m_mutex);
@@ -315,6 +321,7 @@ class ClientImpl : public IClient
     const ClientOptions m_options{};
     std::deque<std::chrono::steady_clock::time_point>
         m_no_content_request_history{};
+    std::function<void()> m_ready_callback{};
     std::function<void()> m_failed_callback{};
 
     bool m_started{ false };

client/test/client_test.cpp

@@ -437,6 +437,15 @@ TEST(Client, FailsWhenMinCacheDurationIsSetAndServerDoesNotCacheResponses)
     EXPECT_THROW(client->wait_for_hello(), ClientNotConnectedException);
 }
 
+TEST(Client, ReadyWhenClientIsStarted)
+{
+    auto client = create_client(false);
+    ExpectCalled callback;
+    client->on_ready(callback.get());
+    client->start();
+    EXPECT_NO_THROW(client->wait_until_ready());
+}
+
 TEST(Client, FailsWhenMinCacheDurationIsSetButResponseIsNotCached)
 {
     uint32_t cache_duration = 10;