Merge pull request #871 from redboltz/add_auto_threads_per_ioc

Add auto threads per ioc

Author: redboltz

CHANGELOG.md

@@ -1,5 +1,9 @@
 ## 12.0.0
-* Added io_context and threads setting options for example broker (#866)
+* Improved exampless (#870)
+* Fixed example broker's invalid sync connack call (#869)
+* Added no CONNACK sending mode to the example broker (#869)
+* Added posting code to acceptors (#867)
+* Added io_context and threads setting options for example broker (#866, #871)
 * Fixed moved from object access (#865)
 * <<<< breaking change >>>> Removed ioc_con() and ioc_accept() (#866)
 * <<<< breaking change >>>> Unified automatic async/sync choosing flag. (#857, #862)
@@ -14,7 +18,7 @@
 * Added multi thread support for example broker (#842, #855, #866)
 * Replaced example broker's API call from sync to async (#842)
 * Replaced use_certificate_file() with use_certificate_chain_file() to support both server cert and server - intermediate CA cert (#841)
-* <<<< breaking change >>>> Added async_force_disconnect(). force_disconnect() is removed from async_client (#840)
+* <<<< breaking change >>>> Added async_force_disconnect(). force_disconnect() is removed from async_client (#840, #868)
 * Added will delay interval support (#839)
 * Fixed async_handler_t calling timing (#836)
 * Added BOOST_ASIO_NO_TS_EXECUTORS support (#830)

example/broker.cpp

@@ -10,6 +10,7 @@
 #include <boost/program_options.hpp>
 
 #include <fstream>
+#include <algorithm>
 
 namespace as = boost::asio;
 
@@ -349,8 +350,8 @@ void run_broker(boost::program_options::variables_map const& vm) {
                 return 1;
             } ();
         if (threads_per_ioc == 0) {
-            MQTT_LOG("mqtt_broker", error) << "threads per ioc must be greater than 0";
-            return;
+            threads_per_ioc = std::max(std::size_t(std::thread::hardware_concurrency()), std::size_t(4));
+            MQTT_LOG("mqtt_broker", info) << "threads_per_ioc set to auto decide (0). Automatically set to " << threads_per_ioc;
         }
 
         MQTT_LOG("mqtt_broker", info)