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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
<html>
<head>
<title>ORB & ORB Core Status</title>
</head>
<HR> <H3><A NAME="orb"></A>ORB & ORB Core</H3> Point of
contact: <A HREF="mailto:cleeland@cs.wustl.edu">Chris Cleeland</A>
<p>Last Update: 26 November 1997</P>
<P>Current status:
<UL>
<LI>Provides dynamically linked wholesale assignment of ORB
strategies for communication, concurrency, demultiplexing,
scheduling, and dispatching using the ACE Service Configurator
framework.</LI>
<LI>Supports several concurrency models out of the box:
Reactive, Thread-per-Connection, and ORB-per-thread. The
ORB-per-thread design is optimized for real-time I/O
subsystems.</LI>
</UL>
<p>Known problems:
<dl>
<dt><em>No <b>LOCATION_FORWARD</b> support.</em></dt>
<dd>The <b>LOCATION_FORWARD</b> capabilities as described in the
CORBA 2.0 Specification are currently not supported. They will
be supported in a future release of TAO.</dd>
<p><dt><em>Object references for objects dynamically created within a
server do not have proper host.</em></dt>
<dd>When an object is dynamically created and its object
reference returned, it simply has to "guess" at the host
information that is returned in the IIOP Profile. Currently, it
guesses using the host name, which is a good guess in most
cases.<p>
However, if there are multiple interfaces on a machine
<i>and</i> they have different host names, it is possible that
the desired effect will not be realized, i.e., the connection to
that new object may use a different interface from the original
object. Currently the only way to change this is to manually
specify that dynamically-created objects bind to a specific
interface so that their IIOP Profile has the desired hostname.
A more desirable fix is being investigated.</dd>
<p><dt><em>Server ORB does not appear to honor the
<b>-ORBhost</b> option.</em></dt>
<dd>Some recent change has made this option non-operational.</dd>
</dl>
Recently Completed Work:
<UL>
<li>Added support for <a
href="../Options.html#-ORBsndsock"><b>-ORBsndsock</b></a> and <a
href="../Options.html#-ORBrcvsock"><b>-ORBrcvsock</b></a> ORB
options. See <a href="../Options.html">options
documentation</a> for details.</li>
<li>Added support for pre-established connections using the <a
href="../Options.html#-ORBpreconnect"><b>-ORBpreconnect</b></a>
option. This allows connections to be esablished before any
CORBA requests are made. See <a href="../Options.html">options
documentation</a> for details.</li>
<li>Eliminated deprecated <b>-OAxxx</b> options parsed by the
Object Adapter <code>init</code> method but no longer used by
part of the ORB.</li>
<li>Made argument parsing within the ORB and POA consume the
arguments it parses.</li>
<li>Placed an optimization in IIOP::Profile that should speed up
invocations on the client side rather substantially. This was
done by caching an instance of <code>ACE_INET_Addr</code> in
the private portion of <code>Profile</code> because the cost
of constructing one for every invocation (in
<code>TAO_GIOP_Invocation::start</code>) was simply
enormous--the construction was something like 100 cycles on
Solaris. This is all because deep down this ends up calling
<code>gethostbyname()</code>, which can be very costly. Of
course, this is platform-dependent, so the improvements may
not be as great on a different platform.</li>
<li>Got rid of need to have compile in TSS ORB Core
(<code>-DTAO_HAS_TSS_ORBCORE</code>). This is accomplished by
having a Resource Factory (<code>TAO_Resource_Factory</code>)
singleton which the ORB Core consults in order to get pointers
to resources. The Resource Factory can be configured to
return pointers from thread-specific storage, or
process-global storage. By doing this, the ORB Core is
shielded from ever having to know whether or not its resources
are global or not.</li>
<li>Made all command-line like options look like the
standard-professed options, i.e., <b>-ORBxxx</b> or
<b>-OAxxxx</b>.</li>
<li>Moved ORB option parsing into
<code>TAO_ORB_Core::init()</code> rather than in
<code>ORB_init()</code>.</li>
<li>Define <code>_FAR</code> for all cases as an interim fix
for LynxOS.</li>
<li>Fixed TAO so that the default port of 5001 is defined in
<code>orb_core.h</code> config header somewhere rather than in
<code>orbobj.cpp</code>, and use <b>MAXHOSTNAMELEN</b> ACE
constant for the hostname buffer.</li>
<li>Eliminated need for <code>CORBA::Object</code> to keep a
pointer to its orb sitting around anywhere.</li>
<LI>Tested <code>CORBA_ORB::shutdown()</code> as a manner in
which a thread of control can request that
<code>CORBA_ORB::run()</code> should return and no longer
service requests. It only honors a
<em>wait_for_completion</em> argument of <b>FALSE</b> right
now because we haven't fully explored the issues which
surround doing all the completion.</li>
<li>Fixed bugs reported by Steven Wohlever, David Miron,
Manojkumar Acharya.</li>
<li>Created a brief section in <a
href="../../TAO-Install.html"><code>$TAO_ROOT/TAO-Install.html</code></a>
that <em>briefly</em> documents installation on Unix
platforms. There is also a brief section which documents
issues that apply across ALL platforms, such as the fact that
TAO and its application will likely not work well if your ACE
is linked through Orbix, VisiBroker, or another ORB. <a
href="../../ChangeLog">ChangeLog</a> discovery attribution for
this should go to <em>Steve Wohlever
<wohlever@mitre.org></em>.</li>
<LI>Implemented <code>CORBA_ORB::shutdown()</code> as a manner
in which a thread of control can request that
<code>CORBA_ORB::run()</code> should return and no longer
service requests.</li>
<LI>Validated movement of Strategy Connector into
ORB Core.</LI>
<li>Debated details of <code>Svc_Handler</code> modifications
with Irfan.</li>
<li>Tested and commited <code>Connector::connect_n</code>
changes to ACE</code>.</li>
<li>ACE & TAO compiling cleanly using Sun's CC on Solaris and
G++ on Linux. Also, the ACE tests run properly.</li>
<li>Use <code>truss</code> to verify for <a
href="mailto:PAUL.G.WEHLAGE@cdev.com">Paul Wehlage</a> that
TAO really uses <code>select</code> vs. <code>recv</code> for
<b>-R</b> vs. <b>-T</b>.</li>
<li>Renamed <code>boa.*</code> to <code>poa.*</code>.</li>
<LI>Renamed following files: Orb_Core.* ->orb_core.*
& orbobj.* -> corba_orb.*.</LI>
<LI>The lock used in <code>giop.cpp:626</code> originally
appeared in the IIOP-1.4 code base. Its purpose was to
protect access to the <code>fwd_profile</code> data member.
The original features are available, but they are currently
not used because none of our concurrency models present a
thread-unsafe condition. The <a
href="../../ChangeLog">ChangeLog</a> presents more details
on the subject.</li>
<li>Fixed problems seen by <a
href="mailto:brian.r.mendel@boeing.com">Brian Mendel</a> of
Boeing where the Cubit server application was crashing in
<code>TAO_OA_Connection_Handler::handle_message</code> when it
was trying to call <code>CORBA::POA::handle_request</code>
through a NULL <code>root_poa</code> pointer. The NULL
pointer resulted from the inadvertent use of the
Thread-per-Connection concurrency model, which is currently
incompatible with the ORB-per-thread model. It was not caught
because the change is normally done in configuration files
parsed by the Service Configurator, and VxWorks requires
special code in that area which was not tested until Boeing
got hold of the code.</li>
<li>Clean up build under g++. All 'function used before
declared inline' warnings have been eliminated. Also, all
other warnings (except for one that is nearly unavoidable)
have been eliminated.
</li>
<LI>Removed BOA and ROA names from the ORB.</LI>
<LI>Changed <code>CORBA_ORB::open()</code> to return an error
status (first cut at this already there--needs to be checked
out).</LI>
<LI>Added README file to multiCubit test.</li>
</UL> Ongoing Work:
<UL>
<LI>Verify ACE & TAO on Linux using g++, Solaris using CC, and
Solaris using g++.</LI>
<LI>Use Purify to eliminate straggling problems.</LI>
<LI>Clean up the internals and analyze for performance
bottlenecks using Quantify.</LI>
</UL> Current Work:
<UL>
<LI>
<p> Verify that, in the ORB-per-thread concurrency model,
it's possible to have a factory in each thread that creates
a client and returns an object reference to that client
within that thread. This is different from the model that
Sumedh originally had where the factory was trying to turn
out a client in a separate thread/ORB combination.</p> <p>
There is no application which attempts this at the moment,
so both a client and a server will need to be manufactured.
Using existing Cubit-like examples (that poor app is so
weary) should reduce development time to a couple of
hours.</p> <p> The real strategy/solution is to make
<code>CORBA::Object</code> not keep a pointer to its orb
sitting around anywhere. It should only get it when it
needs it. This should not be difficult to change.</p>
</LI>
</UL> Critical Work:
<UL>
<LI>Add pre-cached connection on client side. Clients will pass
in a comma-separated list of <em>host:port</em> destinations
using the <code>CORBA::ORB_init()</code> interface.</LI>
<LI>Support new concurrency models, e.g.,
Thread-per-Request.</LI>
</UL> Future work:
<UL>
<li>Implement <code>ORB::perform_work</code> and
<code>ORB::work_pending</code> so that <code>ORB::run</code>
<em>could</em> be implemented in terms of them.</li>
<li>Remove <code>_FAR</code> from all code.</li>
<li>Update ORB Patterns paper to reflect the latest TAO has to
offer. Specifically, sections on the Abstract Factory and
Concurrency strategies need to be updated, and the entire
paper needs to be reviewed for accuracy w.r.t the current
TAO.</li>
<li>Make the section in <a
href="../../TAO-Install.html"><code>$TAO_ROOT/TAO-Install.html</code></a> that documents installation on Unix platforms more complete.
</li>
<li>Improve the <code>Service Configurator</code> service
entry faking on VxWorks.</li>
<LI>Integrate the <A HREF="#poa">POA</A> implementation.</LI>
<LI>Add support for <TT>resolve_initial_references</TT> using
ACE support for UDP broadcast.</LI>
<LI>Assist in porting higher level services (e.g., <A
HREF="#eventchannel">Event Channel</A>) to TAO.</LI>
<li>Compile and verify ACE and TAO on Linux using the Kuck and
Associates, Inc. (KAI) compiler tools.</li>
<LI>Remove the CORBA_SEQUENCE structure which is not a true C++
mapping of sequences. This will affect the code that uses
OctetSequences and TC_opaque. </LI>
</UL>
</body>
</html>
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