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<HTML>
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<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
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<META NAME="Author" CONTENT="James CE Johnson">
<META NAME="Description" CONTENT="A first step towards using ACE productively">
<TITLE>ACE Tutorial 007</TITLE>
</HEAD>
<BODY TEXT="#000000" BGCOLOR="#FFFFFF" LINK="#000FFF" VLINK="#FF0F0F">
<CENTER><B><FONT SIZE=+2>ACE Tutorial 007</FONT></B></CENTER>
<CENTER><B><FONT SIZE=+2>Creating a thread-pool server</FONT></B></CENTER>
<P>
<HR WIDTH="100%">
<P><A HREF="client_handler.cpp">client_handler.cpp</A>
shows some of the changes due to the thread-pool. Just a few
though.
<P>
<HR WIDTH="100%">
<BR>
<BR><FONT FACE="Arial,Helvetica">// $Id: client_handler.cpp,v 1.1 1998/08/30
23:47:14 schmidt Exp $</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica">/*</FONT>
<BR><FONT FACE="Arial,Helvetica"> Since this is the third time
we've seen most of this, I'm going to strip out almost</FONT>
<BR><FONT FACE="Arial,Helvetica"> all of the comments that
you've already seen. That way, you can concentrate on the</FONT>
<BR><FONT FACE="Arial,Helvetica"> new items.</FONT>
<BR><FONT FACE="Arial,Helvetica"> */</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica">#include "client_acceptor.h"</FONT>
<BR><FONT FACE="Arial,Helvetica">#include "client_handler.h"</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica">/*</FONT>
<BR><FONT FACE="Arial,Helvetica"> We're going to be registering
and unregistering a couple of times. To make sure that</FONT>
<BR><FONT FACE="Arial,Helvetica"> we use the same flags every
time, I've created these handy macros.</FONT>
<BR><FONT FACE="Arial,Helvetica"> */</FONT>
<BR><FONT FACE="Arial,Helvetica">#define REGISTER_MASK
ACE_Event_Handler::READ_MASK</FONT>
<BR><FONT FACE="Arial,Helvetica">#define REMOVE_MASK
(ACE_Event_Handler::READ_MASK | ACE_Event_Handler::DONT_CALL)</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica">/*</FONT>
<BR><FONT FACE="Arial,Helvetica"> Our constructor still doesn't
really do anything. We simply initialize the acceptor</FONT>
<BR><FONT FACE="Arial,Helvetica"> pointer to "null" and get
our current thread id. The static self() method of ACE_Thread</FONT>
<BR><FONT FACE="Arial,Helvetica"> will return you a thread
id native to your platform.</FONT>
<BR><FONT FACE="Arial,Helvetica"> */</FONT>
<BR><FONT FACE="Arial,Helvetica">Client_Handler::Client_Handler (void)</FONT>
<BR><FONT FACE="Arial,Helvetica"> : client_acceptor_(0)</FONT>
<BR><FONT FACE="Arial,Helvetica"> ,creator_(ACE_Thread::self())</FONT>
<BR><FONT FACE="Arial,Helvetica">{</FONT>
<BR><FONT FACE="Arial,Helvetica">}</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica">Client_Handler::~Client_Handler (void)</FONT>
<BR><FONT FACE="Arial,Helvetica">{</FONT>
<BR><FONT FACE="Arial,Helvetica">}</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica">/*</FONT>
<BR><FONT FACE="Arial,Helvetica"> Query our acceptor for the
concurrency strategy. Notice that we don't bother</FONT>
<BR><FONT FACE="Arial,Helvetica"> to check that our acceptor
pointer is valid. That is proably a bad idea...</FONT>
<BR><FONT FACE="Arial,Helvetica"> */</FONT>
<BR><FONT FACE="Arial,Helvetica">int Client_Handler::concurrency(void)</FONT>
<BR><FONT FACE="Arial,Helvetica">{</FONT>
<BR><FONT FACE="Arial,Helvetica">
return this->client_acceptor()->concurrency();</FONT>
<BR><FONT FACE="Arial,Helvetica">}</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica">/*</FONT>
<BR><FONT FACE="Arial,Helvetica"> And here we ask the acceptor
about the thread pool.</FONT>
<BR><FONT FACE="Arial,Helvetica"> */</FONT>
<BR><FONT FACE="Arial,Helvetica">Thread_Pool * Client_Handler::thread_pool(void)</FONT>
<BR><FONT FACE="Arial,Helvetica">{</FONT>
<BR><FONT FACE="Arial,Helvetica">
return this->client_acceptor()->thread_pool();</FONT>
<BR><FONT FACE="Arial,Helvetica">}</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica">/*</FONT>
<BR><FONT FACE="Arial,Helvetica"> The destroy() method hasn't
changed since we wrote it back in Tutorial 5.</FONT>
<BR><FONT FACE="Arial,Helvetica"> */</FONT>
<BR><FONT FACE="Arial,Helvetica">void Client_Handler::destroy (void)</FONT>
<BR><FONT FACE="Arial,Helvetica">{</FONT>
<BR><FONT FACE="Arial,Helvetica"> this->peer ().close ();</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> this->reactor ()->remove_handler
(this, REMOVE_MASK );</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> delete this;</FONT>
<BR><FONT FACE="Arial,Helvetica">}</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica">/*</FONT>
<BR><FONT FACE="Arial,Helvetica"> Back to our open() method.
This is straight out of Tutorial 6. There's</FONT>
<BR><FONT FACE="Arial,Helvetica"> nothing additional here for
the thread-pool implementation.</FONT>
<BR><FONT FACE="Arial,Helvetica"> */</FONT>
<BR><FONT FACE="Arial,Helvetica">int Client_Handler::open (void *_acceptor)</FONT>
<BR><FONT FACE="Arial,Helvetica">{</FONT>
<BR><FONT FACE="Arial,Helvetica"> client_acceptor( (Client_Acceptor
*) _acceptor );</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> if( concurrency() == Client_Acceptor::thread_per_connection_
)</FONT>
<BR><FONT FACE="Arial,Helvetica"> {</FONT>
<BR><FONT FACE="Arial,Helvetica">
return this->activate();</FONT>
<BR><FONT FACE="Arial,Helvetica"> }</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> this->reactor (client_acceptor()->reactor
());</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> ACE_INET_Addr addr;</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> if (this->peer ().get_remote_addr
(addr) == -1)</FONT>
<BR><FONT FACE="Arial,Helvetica"> {</FONT>
<BR><FONT FACE="Arial,Helvetica"> return
-1;</FONT>
<BR><FONT FACE="Arial,Helvetica"> }</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> if (this->reactor ()->register_handler
(this, REGISTER_MASK) == -1)</FONT>
<BR><FONT FACE="Arial,Helvetica"> {</FONT>
<BR><FONT FACE="Arial,Helvetica"> ACE_ERROR_RETURN
((LM_ERROR, "(%P|%t) can't register with reactor\n"), -1);</FONT>
<BR><FONT FACE="Arial,Helvetica"> }</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> ACE_DEBUG ((LM_DEBUG, "(%P|%t) connected
with %s\n", addr.get_host_name ()));</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> return 0;</FONT>
<BR><FONT FACE="Arial,Helvetica">}</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica">/*</FONT>
<BR><FONT FACE="Arial,Helvetica"> As mentioned in the header,
the typical way to close an object in a threaded</FONT>
<BR><FONT FACE="Arial,Helvetica"> context is to invoke it's
close() method. Since we already have a handle_close()</FONT>
<BR><FONT FACE="Arial,Helvetica"> method built to cleanup after
us, we'll just forward the request on to that</FONT>
<BR><FONT FACE="Arial,Helvetica"> object.</FONT>
<BR><FONT FACE="Arial,Helvetica"> */</FONT>
<BR><FONT FACE="Arial,Helvetica">int Client_Handler::close(u_long flags)</FONT>
<BR><FONT FACE="Arial,Helvetica">{</FONT>
<BR><FONT FACE="Arial,Helvetica">
this->handle_close(ACE_INVALID_HANDLE,0);</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica">
/*</FONT>
<BR><FONT FACE="Arial,Helvetica">
After we've taken care of ourselves, call the baseclass method</FONT>
<BR><FONT FACE="Arial,Helvetica">
to do any other necessary cleanup.</FONT>
<BR><FONT FACE="Arial,Helvetica">
*/</FONT>
<BR><FONT FACE="Arial,Helvetica">
return inherited::close();</FONT>
<BR><FONT FACE="Arial,Helvetica">}</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica">/*</FONT>
<BR><FONT FACE="Arial,Helvetica"> In the open() method, we
registered with the reactor and requested to be</FONT>
<BR><FONT FACE="Arial,Helvetica"> notified when there is data
to be read. When the reactor sees that activity</FONT>
<BR><FONT FACE="Arial,Helvetica"> it will invoke this handle_input()
method on us. As I mentioned, the _handle</FONT>
<BR><FONT FACE="Arial,Helvetica"> parameter isn't useful to
us but it narrows the list of methods the reactor</FONT>
<BR><FONT FACE="Arial,Helvetica"> has to worry about and the
list of possible virtual functions we would have</FONT>
<BR><FONT FACE="Arial,Helvetica"> to override.</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> You've read that much before...
Now we have to do some extra stuff in case</FONT>
<BR><FONT FACE="Arial,Helvetica"> we're using the thread-pool
implementation. If we're called by our creator</FONT>
<BR><FONT FACE="Arial,Helvetica"> thread then we must be in
the reactor. In that case, we arrange to be put</FONT>
<BR><FONT FACE="Arial,Helvetica"> into the thread pool.
If we're not in the creator thread then we must be</FONT>
<BR><FONT FACE="Arial,Helvetica"> in the thread pool and we
can do some work.</FONT>
<BR><FONT FACE="Arial,Helvetica"> */</FONT>
<BR><FONT FACE="Arial,Helvetica">int Client_Handler::handle_input (ACE_HANDLE
_handle)</FONT>
<BR><FONT FACE="Arial,Helvetica">{</FONT>
<BR><FONT FACE="Arial,Helvetica"> ACE_UNUSED_ARG (_handle);</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> /*</FONT>
<BR><FONT FACE="Arial,Helvetica"> Check our strategy.
If we're using the thread pool and we're in the creation</FONT>
<BR><FONT FACE="Arial,Helvetica">
thread then we know we were called by the reactor.</FONT>
<BR><FONT FACE="Arial,Helvetica"> */</FONT>
<BR><FONT FACE="Arial,Helvetica"> if( concurrency() == Client_Acceptor::thread_pool_
)</FONT>
<BR><FONT FACE="Arial,Helvetica"> {</FONT>
<BR><FONT FACE="Arial,Helvetica">
if( ACE_Thread::self() == creator_ )</FONT>
<BR><FONT FACE="Arial,Helvetica">
{</FONT>
<BR><FONT FACE="Arial,Helvetica">
/*</FONT>
<BR><FONT FACE="Arial,Helvetica">
Remove ourselves from the reactor and ask to be put into the thread pool's</FONT>
<BR><FONT FACE="Arial,Helvetica">
queue of work. (You should be able to use suspend_handler() but I've
had</FONT>
<BR><FONT FACE="Arial,Helvetica">
problems with that.)</FONT>
<BR><FONT FACE="Arial,Helvetica">
*/</FONT>
<BR><FONT FACE="Arial,Helvetica">
this->reactor()->remove_handler( this, REMOVE_MASK );</FONT>
<BR><FONT FACE="Arial,Helvetica">
return this->thread_pool()->enqueue(this);</FONT>
<BR><FONT FACE="Arial,Helvetica">
}</FONT>
<BR><FONT FACE="Arial,Helvetica"> }</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> /*</FONT>
<BR><FONT FACE="Arial,Helvetica"> Any strategy
other than thread-per-connection will eventually get here. If we're
in the</FONT>
<BR><FONT FACE="Arial,Helvetica">
single-threaded implementation or the thread-pool, we still have to pass
this way.</FONT>
<BR><FONT FACE="Arial,Helvetica"> */</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> char buf[128];</FONT>
<BR><FONT FACE="Arial,Helvetica"> memset (buf, 0, sizeof (buf));</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> /*</FONT>
<BR><FONT FACE="Arial,Helvetica"> Invoke the process()
method to do the work but save it's return value instead</FONT>
<BR><FONT FACE="Arial,Helvetica">
of returning it immediately.</FONT>
<BR><FONT FACE="Arial,Helvetica"> */</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> int rval = this->process(buf,sizeof(buf));</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> /*</FONT>
<BR><FONT FACE="Arial,Helvetica"> Now, we look
again to see if we're in the thread-pool implementation. If so then
we</FONT>
<BR><FONT FACE="Arial,Helvetica">
need to re-register ourselves with the reactor so that we can get more
work when it</FONT>
<BR><FONT FACE="Arial,Helvetica">
is available. (If suspend_handler() worked then we would use resume_handler()
here.)</FONT>
<BR><FONT FACE="Arial,Helvetica"> */</FONT>
<BR><FONT FACE="Arial,Helvetica"> if( concurrency() == Client_Acceptor::thread_pool_
)</FONT>
<BR><FONT FACE="Arial,Helvetica"> {</FONT>
<BR><FONT FACE="Arial,Helvetica">
if( rval != -1 )</FONT>
<BR><FONT FACE="Arial,Helvetica">
{</FONT>
<BR><FONT FACE="Arial,Helvetica">
this->reactor()->register_handler( this, REGISTER_MASK );</FONT>
<BR><FONT FACE="Arial,Helvetica">
}</FONT>
<BR><FONT FACE="Arial,Helvetica"> }</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> /*</FONT>
<BR><FONT FACE="Arial,Helvetica"> Return the result
of process()</FONT>
<BR><FONT FACE="Arial,Helvetica"> */</FONT>
<BR><FONT FACE="Arial,Helvetica"> return(rval);</FONT>
<BR><FONT FACE="Arial,Helvetica">}</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica">int Client_Handler::handle_close (ACE_HANDLE
_handle, ACE_Reactor_Mask _mask)</FONT>
<BR><FONT FACE="Arial,Helvetica">{</FONT>
<BR><FONT FACE="Arial,Helvetica"> ACE_UNUSED_ARG (_handle);</FONT>
<BR><FONT FACE="Arial,Helvetica"> ACE_UNUSED_ARG (_mask);</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> this->destroy ();</FONT>
<BR><FONT FACE="Arial,Helvetica"> return 0;</FONT>
<BR><FONT FACE="Arial,Helvetica">}</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica">/*</FONT>
<BR><FONT FACE="Arial,Helvetica"> Remember that when we leave
our svc() method, the framework will take care</FONT>
<BR><FONT FACE="Arial,Helvetica"> of calling our close() method
so that we can cleanup after ourselves.</FONT>
<BR><FONT FACE="Arial,Helvetica"> */</FONT>
<BR><FONT FACE="Arial,Helvetica">int Client_Handler::svc(void)</FONT>
<BR><FONT FACE="Arial,Helvetica">{</FONT>
<BR><FONT FACE="Arial,Helvetica"> char buf[128];</FONT>
<BR><FONT FACE="Arial,Helvetica"> memset (buf, 0, sizeof (buf));</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> while( 1 )</FONT>
<BR><FONT FACE="Arial,Helvetica"> {</FONT>
<BR><FONT FACE="Arial,Helvetica"> if( this->process(buf,sizeof(buf))
== -1 )</FONT>
<BR><FONT FACE="Arial,Helvetica">
{</FONT>
<BR><FONT FACE="Arial,Helvetica">
return(-1);</FONT>
<BR><FONT FACE="Arial,Helvetica"> }</FONT>
<BR><FONT FACE="Arial,Helvetica"> }</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> return(0);</FONT>
<BR><FONT FACE="Arial,Helvetica">}</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica">/*</FONT>
<BR><FONT FACE="Arial,Helvetica"> Once again, we see that the
application-level logic has not been at all affected</FONT>
<BR><FONT FACE="Arial,Helvetica"> by our choice of threading
models. Of course, I'm not sharing data between threads</FONT>
<BR><FONT FACE="Arial,Helvetica"> or anything. We'll
leave locking issues for a later tutorial.</FONT>
<BR><FONT FACE="Arial,Helvetica"> */</FONT>
<BR><FONT FACE="Arial,Helvetica">int Client_Handler::process (char *_rdbuf,
int _rdbuf_len)</FONT>
<BR><FONT FACE="Arial,Helvetica">{</FONT>
<BR><FONT FACE="Arial,Helvetica"> switch (this->peer ().recv (_rdbuf,
_rdbuf_len))</FONT>
<BR><FONT FACE="Arial,Helvetica"> {</FONT>
<BR><FONT FACE="Arial,Helvetica"> case -1:</FONT>
<BR><FONT FACE="Arial,Helvetica"> ACE_ERROR_RETURN
((LM_ERROR, "(%P|%t) %p bad read\n", "client"), -1);</FONT>
<BR><FONT FACE="Arial,Helvetica"> case 0:</FONT>
<BR><FONT FACE="Arial,Helvetica"> ACE_ERROR_RETURN
((LM_ERROR, "(%P|%t) closing daemon (fd = %d)\n", this->get_handle ()),
-1);</FONT>
<BR><FONT FACE="Arial,Helvetica"> default:</FONT>
<BR><FONT FACE="Arial,Helvetica"> ACE_DEBUG
((LM_DEBUG, "(%P|%t) from client: %s", _rdbuf));</FONT>
<BR><FONT FACE="Arial,Helvetica"> }</FONT><FONT FACE="Arial,Helvetica"></FONT>
<P><FONT FACE="Arial,Helvetica"> return 0;</FONT>
<BR><FONT FACE="Arial,Helvetica">}</FONT>
<P>
<HR WIDTH="100%">
<P>Ok, now we've gone and changed handle_input() so that it knows when
to do work and when to enqueue itself. Beyond that, we're still about
the same.
<P>
<HR WIDTH="100%">
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