Author: wyoung
Date: Wed Mar 19 14:13:43 2008
New Revision: 2251
URL: http://svn.gna.org/viewcvs/mysqlpp?rev=2251&view=rev
Log:
Small tweaks to userman chapter on threads
Modified:
trunk/doc/userman/threads.dbx
Modified: trunk/doc/userman/threads.dbx
URL:
http://svn.gna.org/viewcvs/mysqlpp/trunk/doc/userman/threads.dbx?rev=2251&r1=2250&r2=2251&view=diff
==============================================================================
--- trunk/doc/userman/threads.dbx (original)
+++ trunk/doc/userman/threads.dbx Wed Mar 19 14:13:43 2008
@@ -81,45 +81,47 @@
It’s a thornier problem when using threads, though.</para>
<para>The simple fix is to just create a separarate <ulink
- url="Connection" type="classref"/> object for each thread that needs
- to make database queries. This works well if you have a small number
- of threads that need to make queries, and each thread uses its
- connection often enough that the server doesn’t time out
- waiting for queries. (By default, current MySQL servers have an 8
- hour idle timeout on connections. It’s a configuration option,
- though, so your server may be set differently.)</para>
+ url="Connection" type="classref"/> object for each thread
+ that needs to make database queries. This works well if you
+ have a small number of threads that need to make queries, and
+ each thread uses its connection often enough that the server
+ doesn’t time out waiting for queries.<footnote><para>By
+ default, current MySQL servers have an 8 hour idle timeout on
+ connections. It’s a configuration option, though, so your
+ server may be set differently.</para></footnote></para>
<para>If you have lots of threads or the frequency of queries is
low, the connection management overhead will be excessive. To avoid
that, we created the <ulink url="ConnectionPool" type="classref"/>
- class. It manages a pool of <classname>Connection</classname>s like
- library books: a thread checks one out, uses it, and then returns it
- to the pool when it’s done with it. This keeps the number of
- active connections as low as possible.</para>
-
- <para><classname>ConnectionPool</classname> has three methods that
- you need to override in a subclass to make it concrete:
- <methodname>create()</methodname>,
+ class. It manages a pool of <classname>Connection</classname>
+ objects like library books: a thread checks one out, uses it,
+ and then returns it to the pool as soon as it’s done
+ with it. This keeps the number of active connections as low as
+ possible.</para>
+
+ <para><classname>ConnectionPool</classname> has three
+ methods that you need to override in a subclass to
+ make it concrete: <methodname>create()</methodname>,
<methodname>destroy()</methodname>, and
- <methodname>max_idle_time()</methodname>. These overrides let the
- base class delegate operations it can’t successfully do itself
- to its subclass. The <classname>ConnectionPool</classname>
- can’t know how to <methodname>create()</methodname> the
- <classname>Connection</classname> objects, because that depends on
- how your program gets login parameters, server information, etc.
- <classname>ConnectionPool</classname> also makes the subclass
- <methodname>destroy()</methodname> the
- <classname>Connection</classname> objects it created; it could
- assume that they’re simply allocated on the heap with
- <methodname>new</methodname>, but it can’t be sure, so the
- base class delegates destruction, too. Finally, the base class
- can’t know what the connection idle timeout policy in the
- client would make the most sense, so it asks its subclass via the
- <methodname>max_idle_time()</methodname> method.</para>
+ <methodname>max_idle_time()</methodname>. These overrides let
+ the base class delegate operations it can’t successfully do
+ itself to its subclass. The <classname>ConnectionPool</classname>
+ can’t know how to <methodname>create()</methodname>
+ the <classname>Connection</classname> objects, because that
+ depends on how your program gets login parameters, server
+ information, etc. <classname>ConnectionPool</classname>
+ also makes the subclass <methodname>destroy()</methodname>
+ the <classname>Connection</classname> objects it created; it
+ could assume that they’re simply allocated on the heap
+ with <methodname>new</methodname>, but it can’t be sure,
+ so the base class delegates destruction, too. Finally, the base
+ class can’t know what the connection idle timeout policy
+ in the client would make the most sense, so it asks its subclass
+ via the <methodname>max_idle_time()</methodname> method.</para>
<para>In designing your <classname>ConnectionPool</classname>
- derivative, you might consider making it a Singleton (see Gamma et
- al.), since there should only be one pool in a program.</para>
+ derivative, you might consider making it a Singleton (see Gamma
+ et al.), since there should only be one pool in a program.</para>
<para>Here is an example showing how to use connection pools with
threads:</para>
@@ -127,14 +129,15 @@
<programlisting><xi:include href="cpool.txt" parse="text"
xmlns:xi="http://www.w3.org/2001/XInclude"/></programlisting>
- <para>The example works with both Windows native threads and with
- POSIX threads. (The file <filename>examples/threads.h</filename>
- contains a few macros and such to abstract away the differences
- between the two threading models.) Because thread-enabled builds
- are only the default on Windows, it’s quite possible
- for this program to do nothing on other platforms. See your
- platform’s <filename>README-*.txt</filename> file for
- instructions on enabling a thread-aware build.</para>
+ <para>The example works with both Windows native
+ threads and with POSIX threads.<footnote><para>The file
+ <filename>examples/threads.h</filename> contains a few macros and
+ such to abstract away the differences between the two threading
+ models.</para></footnote> Because thread-enabled builds are only
+ the default on Windows, it’s quite possible for this program
+ to do nothing on other platforms. See your platform’s
+ <filename>README-*.txt</filename> file for instructions on enabling
+ a thread-aware build.</para>
<para>If you write your code without checks for thread support like
you see in the code above and link it to a build of MySQL++ that
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