svn commit - mysqldoc@docsrva: r2197 - trunk/refman-5.1

[jon]

Author: jstephens
Date: 2006-05-25 11:56:24 +0200 (Thu, 25 May 2006)
New Revision: 2197

Log:

Event scheduler thread and SHOW PROCESSLIST

You can't actually kill this thread (Andrey)



Modified:
   trunk/refman-5.1/events.xml

Modified: trunk/refman-5.1/events.xml
===================================================================
--- trunk/refman-5.1/events.xml	2006-05-24 19:26:47 UTC (rev 2196)
+++ trunk/refman-5.1/events.xml	2006-05-25 09:56:24 UTC (rev 2197)
@@ -199,6 +199,15 @@
       </listitem>
 
     </itemizedlist>
+    
+    <para>
+      Events are executed by a special <firstterm>event scheduler
+        thread</firstterm>; when we refer to the Event Scheduler, we
+      actually refer to this thread. When running, the event scheduler
+      thread and its current state can be seen by users having the
+      <literal>SUPER</literal> privilege in the output of <literal>SHOW
+        PROCESSLIST</literal>, as shown in the discussion that follows.
+    </para>
 
     <para>
       The global variable <literal>event_scheduler</literal> determines
@@ -219,23 +228,87 @@
           <literal><option>--event-scheduler</option>=0</literal> or
           <literal><option>--event-scheduler</option>=OFF</literal>. 
         </para>
+        
+        <para>
+          When the Event Scheduler is turned OFF, the event scheduler
+          thread does not run, and so cannot be seen listed in the
+          output of <literal>SHOW PROCESSLIST</literal>.
+        </para>
       </listitem>
       
       <listitem>
         <para>
-          <literal>1</literal>: The event scheduler is ON; the event
+          <literal>1</literal>: The Event Scheduler is ON; the event
           scheduler thread runs and executes all scheduled events.
         </para>
+        
+        <para>
+          When the Event Scheduler is in the ON state, it will appear to
+          be sleeping:
+        </para>
+        
+<programlisting>
+mysql&gt; <userinput>SHOW PROCESSLIST\G</userinput>
+*************************** 1. row ***************************
+     Id: 1
+   User: event_scheduler
+   Host: localhost
+     db: NULL
+Command: Connect
+   Time: 0
+  State: Sleeping
+   Info: NULL
+*************************** 2. row ***************************
+     Id: 52
+   User: root
+   Host: localhost
+     db: NULL
+Command: Query
+   Time: 0
+  State: NULL
+   Info: SHOW PROCESSLIST
+2 rows in set (0.00 sec)
+</programlisting>
       </listitem>
       
       <listitem>
         <para>
-          <literal>2</literal>: The event scheduler is SUSPENDED; the
+          <literal>2</literal>: The Event Scheduler is SUSPENDED; the
           event scheduler thread runs, but it does not execute any
           scheduled events. This is the default value for
           <literal>event_scheduler</literal>.
         </para>
-      </listitem>
+        
+        <para>
+          When the Event Scheduler is in the SUSPENDED state, this can
+          be seen from the <literal>State</literal> column in the output
+          of <literal>SHOW PROCESSLIST</literal> as shown here:
+        </para>
+        
+<programlisting>
+mysql&gt; <userinput>SHOW PROCESSLIST\G</userinput>
+*************************** 1. row ***************************
+     Id: 1
+   User: event_scheduler
+   Host: localhost
+     db: NULL
+Command: Connect
+   Time: 1
+  State: Suspended
+   Info: NULL
+*************************** 2. row ***************************
+     Id: 52
+   User: root
+   Host: localhost
+     db: NULL
+Command: Query
+   Time: 0
+  State: NULL
+   Info: SHOW PROCESSLIST
+2 rows in set (0.00 sec)
+</programlisting>
+      </listitem>      
+
     </itemizedlist>
     
     <para>
@@ -258,7 +331,7 @@
 </programlisting>
     
     <para>
-      If event scheduling is enabled, you can disable it by issuing
+      If event scheduling is enabled, you can suspend it by issuing
       either one of these two statements:
     </para>
 
@@ -310,6 +383,16 @@
       Since <literal>event_scheduler</literal> is a global variable, you
       must have the <literal>SUPER</literal> privilege to set its value.
     </para>
+    
+    <para>
+      The event scheduler thread cannot be killed. If you attempt to
+      <literal>KILL</literal> the event scheduler thread, the effect is
+      the same as suspending it. It can be re-enabled by setting the
+      global <literal>event_scheduler</literal> variable to
+      <literal>1</literal>, just as if you had previously set its value
+      to <literal>2</literal>. The only way to stop this thread is by
+      stopping the server.
+    </para>
 
     <para>
       <emphasis role="bold">Note</emphasis>: You can issue