Introducing a dedicated cron.log file for logging cron related info, this reduces output in the system.log file.

Author: hostep

app/code/Magento/Cron/etc/di.xml

@@ -16,6 +16,18 @@
     <type name="Magento\Framework\App\Config\Initial\Converter">
         <plugin name="cron_system_config_initial_converter_plugin" type="Magento\Cron\Model\System\Config\Initial\Converter" />
     </type>
+    <virtualType name="Magento\Cron\Model\VirtualLoggerHandler" type="Magento\Framework\Logger\Handler\Base">
+        <arguments>
+            <argument name="fileName" xsi:type="string">/var/log/cron.log</argument>
+        </arguments>
+    </virtualType>
+    <virtualType name="Magento\Cron\Model\VirtualLogger" type="Magento\Framework\Logger\Monolog">
+        <arguments>
+            <argument name="handlers" xsi:type="array">
+                <item name="system" xsi:type="object">Magento\Cron\Model\VirtualLoggerHandler</item>
+            </argument>
+        </arguments>
+    </virtualType>
     <!-- @api -->
     <virtualType name="shellBackground" type="Magento\Framework\Shell">
         <arguments>
@@ -25,6 +37,7 @@
     <type name="Magento\Cron\Observer\ProcessCronQueueObserver">
         <arguments>
             <argument name="shell" xsi:type="object">shellBackground</argument>
+            <argument name="logger" xsi:type="object">Magento\Cron\Model\VirtualLogger</argument>
         </arguments>
     </type>
     <type name="Magento\Framework\Console\CommandListInterface">