fix(connection): implement configurable connection timeout/backoff

Patric Stout
1 parent d502382e
Showing 5 changed files with 73 additions and 25 deletions
include/TrueMQTT.h
src/Client.cpp
src/ClientImpl.h
src/Connection.cpp
src/Connection.h
@@ -7,6 +7,7 @@
 #pragma once
+#include <chrono>
 #include <functional>
 #include <memory>
@@ -111,10 +112,17 @@ namespace TrueMQTT
          * @param port Port of the MQTT broker.
          * @param client_id Client ID to use when connecting to the broker.
          * @param connection_timeout Timeout in seconds for the connection to the broker.
+         * @param connection_backoff Backoff time when connection to the broker failed. This is doubled every time a connection fails, up till \ref connection_backoff_max.
          * @param connection_backoff_max Maximum time between backoff attempts in seconds.
          * @param keep_alive_interval Interval in seconds between keep-alive messages.
          */
-        Client(const std::string &host, int port, const std::string &client_id, int connection_timeout = 5, int connection_backoff_max = 30, int keep_alive_interval = 30);
+        Client(const std::string &host,
+               int port,
+               const std::string &client_id,
+               std::chrono::milliseconds connection_timeout = std::chrono::milliseconds(5000),
+               std::chrono::milliseconds connection_backoff = std::chrono::milliseconds(1000),
+               std::chrono::milliseconds connection_backoff_max = std::chrono::milliseconds(30000),
+               std::chrono::milliseconds keep_alive_interval = std::chrono::milliseconds(30000));
         /**
          * @brief Destructor of the MQTT client.
@@ -13,9 +13,15 @@
 #include <sstream>
-TrueMQTT::Client::Client(const std::string &host, int port, const std::string &client_id, int connection_timeout, int connection_backoff_max, int keep_alive_interval)
+TrueMQTT::Client::Client(const std::string &host,
+                         int port,
+                         const std::string &client_id,
+                         std::chrono::milliseconds connection_timeout,
+                         std::chrono::milliseconds connection_backoff,
+                         std::chrono::milliseconds connection_backoff_max,
+                         std::chrono::milliseconds keep_alive_interval)
 {
-    this->m_impl = std::make_unique<Client::Impl>(host, port, client_id, connection_timeout, connection_backoff_max, keep_alive_interval);
+    this->m_impl = std::make_unique<Client::Impl>(host, port, client_id, connection_timeout, connection_backoff, connection_backoff_max, keep_alive_interval);
     LOG_TRACE(this->m_impl, "Constructor of client called");
 }
@@ -27,11 +33,18 @@ TrueMQTT::Client::~Client()
     this->disconnect();
 }
-TrueMQTT::Client::Impl::Impl(const std::string &host, int port, const std::string &client_id, int connection_timeout, int connection_backoff_max, int keep_alive_interval)
+TrueMQTT::Client::Impl::Impl(const std::string &host,
+                             int port,
+                             const std::string &client_id,
+                             std::chrono::milliseconds connection_timeout,
+                             std::chrono::milliseconds connection_backoff,
+                             std::chrono::milliseconds connection_backoff_max,
+                             std::chrono::milliseconds keep_alive_interval)
     : host(host),
       port(port),
       client_id(client_id),
       connection_timeout(connection_timeout),
+      connection_backoff(connection_backoff),
       connection_backoff_max(connection_backoff_max),
       keep_alive_interval(keep_alive_interval)
 {
@@ -9,6 +9,7 @@
 #include "TrueMQTT.h"
+#include <chrono>
 #include <deque>
 #include <map>
 #include <mutex>
@@ -21,7 +22,13 @@
 class TrueMQTT::Client::Impl
 {
 public:
-    Impl(const std::string &host, int port, const std::string &client_id, int connection_timeout, int connection_backoff_max, int keep_alive_interval);
+    Impl(const std::string &host,
+         int port,
+         const std::string &client_id,
+         std::chrono::milliseconds connection_timeout,
+         std::chrono::milliseconds connection_backoff,
+         std::chrono::milliseconds connection_backoff_max,
+         std::chrono::milliseconds keep_alive_interval);
     ~Impl();
     enum State
@@ -52,12 +59,13 @@ public:
     State state = State::DISCONNECTED; ///< The current state of the client.
     std::mutex state_mutex;            ///< Mutex to protect state changes.
-    std::string host;           ///< Host of the broker.
-    int port;                   ///< Port of the broker.
-    std::string client_id;      ///< Client ID to use when connecting to the broker.
-    int connection_timeout;     ///< Timeout in seconds for the connection to the broker.
-    int connection_backoff_max; ///< Maximum time between backoff attempts in seconds.
-    int keep_alive_interval;    ///< Interval in seconds between keep-alive messages.
+    std::string host;                                 ///< Host of the broker.
+    int port;                                         ///< Port of the broker.
+    std::string client_id;                            ///< Client ID to use when connecting to the broker.
+    std::chrono::milliseconds connection_timeout;     ///< Timeout in seconds for the connection to the broker.
+    std::chrono::milliseconds connection_backoff;     ///< Backoff time when connection to the broker failed. This is doubled every time a connection fails, up till \ref connection_backoff_max.
+    std::chrono::milliseconds connection_backoff_max; ///< Maximum time between backoff attempts in seconds.
+    std::chrono::milliseconds keep_alive_interval;    ///< Interval in seconds between keep-alive messages.
     Client::LogLevel log_level = Client::LogLevel::NONE;                                                           ///< The log level to use.
     std::function<void(Client::LogLevel, std::string)> logger = [](Client::LogLevel, std::string) { /* empty */ }; ///< Logger callback.
@@ -18,7 +18,8 @@
 TrueMQTT::Client::Impl::Connection::Connection(Client::Impl &impl)
     : m_impl(impl),
-      m_thread(&Connection::run, this)
+      m_thread(&Connection::run, this),
+      m_backoff(impl.connection_backoff)
 {
 }
@@ -67,10 +68,16 @@ void TrueMQTT::Client::Impl::Connection::run()
             break;
         case State::BACKOFF:
-            LOG_WARNING(&m_impl, "Connection failed; will retry in NNN seconds");
+            LOG_WARNING(&m_impl, "Connection failed; will retry in " + std::to_string(m_backoff.count()) + "ms");
-            // TODO: use the configuration
-            std::this_thread::sleep_for(std::chrono::seconds(5));
+            std::this_thread::sleep_for(m_backoff);
+
+            // Calculate the next backoff time, slowly reducing how often we retry.
+            m_backoff *= 2;
+            if (m_backoff > m_impl.connection_backoff_max)
+            {
+                m_backoff = m_impl.connection_backoff_max;
+            }
             m_state = State::RESOLVING;
             break;
@@ -96,6 +103,11 @@ void TrueMQTT::Client::Impl::Connection::run()
         }
         case State::STOP:
+            if (m_socket != INVALID_SOCKET)
+            {
+                closesocket(m_socket);
+                m_socket = INVALID_SOCKET;
+            }
             return;
         }
     }
@@ -243,8 +255,7 @@ bool TrueMQTT::Client::Impl::Connection::connectToAny()
         }
         // Check if it is more than the timeout ago since we last tried a connection.
-        // TODO -- Used to configured value
-        if (std::chrono::steady_clock::now() < m_last_attempt + std::chrono::seconds(10))
+        if (std::chrono::steady_clock::now() < m_last_attempt + m_impl.connection_timeout)
         {
             return true;
         }
@@ -317,11 +328,13 @@ bool TrueMQTT::Client::Impl::Connection::connectToAny()
         LOG_WARNING(&m_impl, "Could not set socket to non-blocking; expect performance impact");
     }
+    m_backoff = m_impl.connection_backoff;
+    m_socket = socket_connected;
+
     // Only change the state if no disconnect() has been requested in the mean time.
     if (m_state != State::STOP)
     {
         m_state = State::AUTHENTICATING;
-        m_socket = socket_connected;
         sendConnect();
     }
     return true;
@@ -9,6 +9,7 @@
 #include "ClientImpl.h"
+#include <chrono>
 #include <string>
 #include <map>
 #include <netdb.h>
@@ -56,14 +57,19 @@ private:
     TrueMQTT::Client::Impl &m_impl;
-    State m_state = State::RESOLVING;
-    std::thread m_thread; ///< Current thread used to run this connection.
+    State m_state = State::RESOLVING; ///< Current state of the connection.
+    std::thread m_thread;             ///< Current thread used to run this connection.
+
+    std::chrono::milliseconds m_backoff; ///< Current backoff time.
+
+    addrinfo *m_host_resolved = nullptr;      ///< Address info of the hostname, once looked up.
+    std::vector<addrinfo *> m_addresses = {}; ///< List of addresses to try to connect to.
-    addrinfo *m_host_resolved = nullptr;                       ///< Address info of the hostname, once looked up.
-    std::vector<addrinfo *> m_addresses = {};                  ///< List of addresses to try to connect to.
     size_t m_address_current = 0;                              ///< Index of the address we are currently trying to connect to.
     std::chrono::steady_clock::time_point m_last_attempt = {}; ///< Time of the last attempt to connect to the current address.
-    std::vector<SOCKET> m_sockets = {};                        ///< List of sockets we are currently trying to connect to.
-    std::map<SOCKET, addrinfo *> m_socket_to_address = {};     ///< Map of sockets to the address they are trying to connect to.
-    SOCKET m_socket = INVALID_SOCKET;                          ///< The socket we are currently connected with, or INVALID_SOCKET if not connected.
+
+    std::vector<SOCKET> m_sockets = {};                    ///< List of sockets we are currently trying to connect to.
+    std::map<SOCKET, addrinfo *> m_socket_to_address = {}; ///< Map of sockets to the address they are trying to connect to.
+
+    SOCKET m_socket = INVALID_SOCKET; ///< The socket we are currently connected with, or INVALID_SOCKET if not connected.
 };