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<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
<head>
<title>TAO Release Information and TODO List</title>
</head>
<body text="#000000" bgcolor="#FFFFFF">
<!-- $Id$ -->
<center>
<hr></center>
<center>
<h3>
Release Information for The ACE ORB (TAO)</h3></center>
Information is available on the following topics related to the <a href="http://www.cs.wustl.edu/~schmidt/ACE_wrappers/TAO/VERSION">current
release</a> of <a href="http://www.cs.wustl.edu/~schmidt/TAO.html">TAO</a>:
<ul>
<li>
<a href="#idl">IDL Compiler</a></li>
<li>
<a href="orbcore.html">ORB Core</a></li>
<li>
<a href="#pp">Pluggable Protocols</a></li>
<li>
<a href="#poa">Portable Object Adapter</a></li>
<li>
<a href="../implrepo/status.html">Implementation Repository</a></li>
<li>
<a href="#interfrepo">Interface Repository</a></li>
<li>
<a href="#nservices">CORBA Naming Service and Interoperable Naming Service</a></li>
<li>
<a href="#tservices">CORBA Trading Service</a></li>
<li>
<a href="#pservices">CORBA Property Service</a></li>
<li>
<a href="#cservices">CORBA Concurrency Service</a></li>
<li>
<a href="#av">CORBA Audio/Video Control Service</a></li>
<li>
<a href="#ts">CORBA Time Service</a></li>
<li>
<a href="#ec">CORBA Event Service</a></li>
<li>
<a href="ec.html">TAO's Real-time Event Service</a></li>
<li>
<a href="#scheduling">TAO's Scheduling Service</a></li>
<li>
<a href="#logging">TAO's Logging Service</a></li>
<li>
<a href="#apps">Test & Tests</a></li>
<li>
<a href="#ace">ORB-related ACE Changes</a></li>
<li>
<a href="#dove">The DOVE Demo</a></li>
<li>
<a href="#forwarding">Location Forwarding</a></li>
<li>
<a href="#leader">Global Resources and Leader-Follower Model</a></li>
<li>
<a href="#locate">Locate requests</a></li>
<li>
<a href="TODO.html">Our TODO list</a></li>
</ul>
A complete list of all modifications to TAO is available in the <a href="http://www.cs.wustl.edu/~schmidt/ACE_wrappers/TAO/ChangeLog">ChangeLog</a>.
<p>
<hr>
<h3>
<a NAME="idl"></a>IDL Compiler</h3>
Point of contact: <a href="mailto:gokhale@research.bell-labs.com">Aniruddha
Gokhale</a>
<p>Current status: (As of Jan 22, 1999.)
<ul>
<li>
Generated code closely follows the C++ Mapping specified in the latest
C++ mapping for CORBA 2.3 (Document ptc/98-09-03).</li>
<li>
Struct members of type strings and arrays of strings now use the managed
type instead of the _var type. This change was necessary to conform to
the IDL->C++ mapping.</li>
<li>
Fixed a large number of problems with anonymous arrays and sequences inside
structs and unions. The name of anonymous sequence needs to be fixed as
per latest C++ mapping spec.</li>
<li>
Compile problems with sequence of forward declared interfaces is fixed.
In addition, problems with sequence of CORBA::Objects is fixed. In this
specific case, we were not generating the _downcast and _upcast methods.</li>
<li>
Some more problems with the front-end have been fixed. In particular, oneway
operations with a "raises" clause or having an "inout", "out", or "return"
mode is flagged as an error.</li>
<li>
For platforms that support namespaces, we now allow reopening modules.</li>
<li>
Support for generating compiled marshaling code is added. Use the -Gc option.
However, this needs thorough testing before we can claim success. Unions
are still a problme with compiled marshaling.</li>
<li>
The problem of "#include"ing the relative path of the header files rather
than the paths of their corresponding IDL files has been fixed. tao_idl
now generates #include path names that are derived from the IDL files that
are #include'd in the main idl file.</li>
<li>
Added options to IDL compiler to specify file name endings for the IDL-generated
stubs, skeletons and the various header files. Please refer to the <a href="http://www.cs.wustl.edu/~schmidt/ACE_wrappers/TAO/docs/compiler.html">IDL
compiler options</a> for details.</li>
<li>
Added partial native C++ exception support:</li>
<ul>
<li>
The ORB can be configured to catch native C++ exceptions thrown on the
server side and transmit them to the client side. On the client side exceptions
received from the wire are thrown using native C++ exceptions also.</li>
<li>
To facilitate portability between the standard and alternative C++ mapping
the <tt>CORBA::Environment</tt> has a default value. The IDL compiler generates
code using that default value and the TAO library methods also have the
default.</li>
<li>
Some macros are provided to facilitate portability between platforms with
and without macros.</li>
</ul>
There is still some work to do, mainly provide complete support for the
standard mapping, i.e. remove the <tt>CORBA::Environment</tt> argument
completely.
<li>
Verified support for the "long long" and "unsigned long long" datatypes.
On platforms that do not support 64 bit longs we provided <i>partial</i>
emulation through ACE_U_LongLong.</li>
<li> Perfect Hashed Operation Lookup Strategy has been added to the
IDL Compiler. -P flag to <code>tao_idl</code> enables the perfect
hased lookup strategy. This strategy uses <a
href="http://www.cs.wustl.edu/~schmidt/gperf.ps.gz">GPERF</a>, the
GNU's Perfect Hash Function Generator written by Dr.Douglas
C. Schmidt. Right now, GPERF works only on Solaris. Any work on
porting GPERF to other platforms will be highly
appreciated.</L1></li>
<li>
Significantly improved the support for unions. The default case is yet
to be handled.</li>
<li>
Added support for TIE classes. If the interfaces are defined inside modules,
then the TIE class and its code gets generated inside a conditional macro.
For platforms that support namespaces, this macro will allow these TIE
classes else they get commented out. The reason to do this is because nested
templates have problems on most compilers.</li>
<li>
The <<= and >>= operators for user-defined types are now generated.</li>
<li> Completely redesigned the IDL compiler using the Visitor
patterns. Many incomplete issues have been resolved. These include
support for "sequence of typecodes", passing object references as in,
inout, and out parameters. Code generation for sequences is also
properly handled i.e., for a named sequence such as <CODE>typedef
sequence<char>CharSeq;</CODE>, we now generate a new class (and
hence a type) called "class CharSeq". Arrays are still being worked
out and will be done soon. An important difference in the generated
code is that the skeletons now use a table driven approach very
similar to the stubs.</li>
<li>
Support for the "native" keyword added.</li>
<li>
The problem of incorrect code generation for typedefs defined in an imported
file is resolved.</li>
<li>
Problems when interfaces use single or multiple inheritance solved. The
problem was with the demultiplexing code, the generated operation tables,
and the dispatching mechanism. We are currently testing this with the Event
Channel code.</li>
<li>
The problems arising due to public virtual inheritance when casting from
an interface class to CORBA::Object_ptr has been solved. We do this casting
inside the stubs/skeletons rather than first converting an interface class
pointer to a void*, storing it in an Any, and casting it to CORBA::Object_ptr
in the encode/decode methods. The casting inside the stubs/skeletons work
because the compiler has knowledge of both types.</li>
<li>
Include files are handled properly. So are the definitions used inside
the include files that are used in the currently parsed files.</li>
<li>
Generates C++ stubs and skeletons that use TAO's <a href="http://www.cs.wustl.edu/~schmidt/HICSS-97.ps.gz">interpretive
IIOP protocol engine</a>.</li>
<li>
Support dynamic libraries on NT, i.e., marking classes for DLL export was
added. Two backend options control the name of the export macro, and the
name of an extra include file were the macro is defined; the options are
<tt>-Wp,export_macro=MACRO_NAME-Wp,export_include=INCLUDE_NAME</tt>.</li>
<li>
The IDL compiler generates now source code for sequences. The user has
now the option to use these generated sequence classes or to use, as up
to now, the template instatiation. If TAO_LACKS_TEMPLATE_SPECIALIZATION
is defined, then template instantiation will be used, else not. The reason
for this was, that some C++ compilers did not support template instantiation
properly and sequences were based on templates. The generated source code
is mainly contained in the generated header file directly in the class
declaration.</li>
<li>
The IDL Compiler generates templates for servant implementations. The options
are -GI [ h | s | b | e | c ]</li>
</ul>
<p><br>Known bugs/unimplemented constructs:
<ul>
<li>
Generation of Managed types must somehow be moved to the ORB Core</li>
<li>
We need support for ``TIEs'' (i.e., the object form of the Adapter pattern).</li>
<li>
TypeCode generation for recursive types not implemented yet.</li>
<li>
Unions with default cases yet to be handled</li>
<li>
IDL is case-insensitive. However, it looks like our front-end is case-sensitive.
Thanks to Anil Gopinath (anil@ittc.ukans.edu) for pointing this out.</li>
</ul>
Future work:
<ul>
<li>
Need to relocate the various libraries used by the IDL compiler out of
the ACE directory. Having them here can cause problems when working with
multiple versions of TAO and a single version of ACE.</li>
<li>
Fix bugs in the SunSoft IDL front-end we've uncovered. These primarily
include support for Unions.</li>
<li>
Use <a href="http://www.cs.utah.edu/projects/flux/flick/">Flick</a> (from
the University of Utah) to generate compiled stubs.</li>
<p>Goal is to measure the code size of the interpretive stubs generated
by TAO IDL compiler <i>vs</i> code size of compiled stubs. Then compare
the performance of each. We want to prove the thesis that TAO IDL compiler
generated interpretive stubs have a small code size, yet are comparable
in performance (or slightly less) than compiled stubs. Hence, it will be
useful for small distributed equipment such as handsets, PDAs, etc.
<p>In doing the above, improvements to the IIOP protocol engine in terms
of size/performance/determinism will be made.
<li>
Tweak the IDL compiler to generate code that's more easily integrated back
into the ORB Core, e.g., POA, etc. This will depend largely on our ability
to generalize the changes necessary to generated code.</li>
<li>
The generated sequence classes should not be generated per sequence, but
per type and parent scope. Which means, that the overhead of having the
source code generated serveral times should be reduced. To do this, an
extra pass over the internal representation of the IDL file has to be done.<P>
</ul>
<hr></li>
<br><!--#include virtual="orbcore.html" -->
<hr>
<h3>
<a NAME="pp"></a>Pluggable Protocols</h3>
Point of contact: <a href="mailto:fredk@cs.wustl.edu">Fred Kuhns</a>
<p>The goal of the pluggable protocol effort is to (1) identify logical
communication layers in the ORB, (2) abstract out common features, (3)
define general interfaces, and (4) provide necessary mechanisms for implementing
different concrete ORB and transport protocols. TAO's pluggable protocol
framework will allow disparate communication mechanisms to be supported
transparently, each with its own set of requirements and strategies.
<p>For example, if the ORB is communicating over a system bus, such as
PCI or VME, and not all the features of GIOP/IIOP are necessary and a simpler,
optimized ORB and transport protocol can be defined and implemented. Similarly,
it should be straightforward to add support for new transport protocols
that use native ATM or shared memory as the underlying communication mechanism.
In all cases the ORB's interface to the application will remain compliant
with the OMG CORBA standard.
<p>There will be several stages of the development proccess: (1) basic
pluggable transport protocols framework, (2) support for multiple profiles,
(4) add example transport protocols, such as ATM and VME, and refine/optimize
the transport protocols framework, and (4) add support for pluggable ORB
protocols, e.g., replacements for GIOP. Each of these steps is outlined
below:
<ul>
<li>
<b>Basic pluggable transport protocols framework</b>: We're currently adding
several Bridge classes that decouple the transport-specific details from
the rest of TAO's ORB Core. This allows us to isolate the details of how
messages are communicated at the transport layer in a few classes. This
design has led us to restructure how TAO's ORB Core sends and receives
requests. For instance, there is now the concept of communication layers:
Objects (e.g., references, method invocations, etc.), ORB Messaging, Transport,
and Network. The Object layer is just the usual stubs and skeletons.</li>
<p>The common interfaces have been defined in the new abstract classes
that form the core of TAO's pluggable protocol framework, e.g.,
<tt>TAO_Connector</tt>,
<tt>TAO_Acceptor</tt>,
<tt>TAO_Profile</tt>
and <tt>TAO_Transport</tt>. Two new mechanisms for keeping track of supported
transport protocols are the
<tt>TAO_Connector_Registry</tt> and
<tt>TAO_Acceptor_Registry</tt>,
which are essentially Abstract Factories that produce the right types of
connector, acceptors, and transports. <p>
<li>
<b>Multiple Profile</b> - Support for more than one profile per object.
This is important since there may be several different ways to access an
object. Each profile for an object may encode information pertaining to
QoS, network and transport protocols, addresses or routes.<p>
<li>
<b>Example Transport protocols</b>- The first planned example aside from
IIOP will use UNIX domain sockets. Other interesting transport protocols
would be for ATM, Buses (VME or PCI), shared memory, TP4, GSMP, and
UDP/IP.</li> <p>
<li>
<b>Pluggable ORB protocols</b> - This step will add support for ORB protocols
besides GIOP. In particular, we will explore lightweight protocols using
shared memory and system buses like PCI or VME.</li>
</ul>
Current Status:
<ul>
<li>
The initial prototype of the basic framework to support pluggable transport
protocols has been compiled, linked and, tested against an older version
of TAO. The standard TAO regression tests
<tt>MT_Cubit</tt>, <tt>Multiple_Inheritance</tt>,
<tt>CDR</tt>
and <tt>EC_Throughput</tt> were run successfully.</li><P>
<li>
The basic framework does not include support for multiple profiles and
the Acceptor registry. What it does do is separate the transport specific
processing from the rest of the ORB.</li>
<p>
</ul>
Known Issues:
<ul>
<li>
The ORB Core's resource factory needs to be enhanced to support the dynamic
allocation of resources for different transport protocols.</li><p>
</ul>
Critical Work:
<ul>
<li>
Adding support for multiple profiles.</li><p>
<p>
</ul>
Future Work:
<ul>
<li>
Immediate plans are to bring my workspace up to date with the repository
and verify all of TAO's regression tests still work. This will be followed
by performing a suite of tests to compare performance of with the unmodified
TAO distribution. Also, we'll extensively retest TAO using purify and quantify.</li><p>
<li>
In parallel, we will add support for multiple profiles and an acceptor
registry class. The acceptor registry will both keep track of all acceptors
and be responsible for creating a list of profiles for new object references
(essentially the IOR).</li><p>
<li>
Long term work will include adding support for pluggable ORB protocols,
as well as transport protocols. This way we can develop optimal messaging
and transport protocols for a given platform.</li>
<p>
</ul>
<hr>
<h3>
<a NAME="poa"></a>Portable Object Adapter (POA)</h3>
Point of contact: <a href="mailto:irfan@cs.wustl.edu">Irfan Pyarali</a>
The POA associates servants with the ORB and demultiplexes incoming
requests to servants. <P>
<p>Current Status:
<ul>
<li>
TAO supports the POA spec. This section will carry updates as available.</li>
</ul>
Known issues:
<ul>
<li>
The synchronization in the POA is broken. For example, the locks are held
across the invocation on the servant. The locks are also held across the
invocation on the AdapterActivator. This forces the use of recursive locks
inside the POA. However, the problem with recursive locks is that multiple
threads cannot dispatch requests on the same POA simultaneous.</li><P>
<li>
Add the new RefCountServantBase class to TAO. This reference counted base
class was added to the CORBA specification to avoid race conditions for
servant deletion in threaded servers. <a href="ftp://ftp.omg.org/pub/docs/orbos/98-07-12.pdf">ftp://ftp.omg.org/pub/docs/orbos/98-07-12.pdf</a>
contains the relevant text.</li><P>
<li>
Currently, the complete POA name is used as the POA identity. This scheme
is inefficient in many ways including: (a) the complete POA name can be
significantly large in size, and therefore, ineffient to pass with every
method call from the client to the server; (b) it is varible in size, and
therefore, does not lend itself to smart and effective parsing; (c) the
searching based on the complete POA name is very ineffient.</li>
<p>The correct solution here is to use an active demux table, and flatten
the POA hierarchy. This will help in the searching since active demuxing
is fast and predictable. This will also help in the parsing since the demux
key will be fixed size.
<p>Note that for persistent ids, we have to pass the complete POA name
in addition to the demux key in order to handle POA creation on demand.<P>
<li>
Timestamps in persistent IORs are not required. They should be removed.</li> <P>
<li>
POA exceptions should be removed from the list of system
exceptions.</li> <P>
<li>
We need to separate out the POA functionality required to support the full
CORBA spec from the POA functionality required to support the Minimal CORBA
spec.</li> <P>
<li>
We need to investigate whether it feasible for us to provide active demuxing
for the USER_ID policy. Currently, the best we do with the USER_ID policy
is a hash table based demuxing.</li> <P>
Note that we have to pass the user id in addition to the demux key in
order to handle servant creation on demand. <P>
<li>
We can potentially add active demuxing for method name lookup. The benefit
of this optimization is questionable since the current perfect hashing
scheme provide very good and predictable behavior.</li> <P>
Also, note that this optimization will require many changes. We would
have to use the help of the IDL compiler to modify the object key that
is passed for every method call differently. Note that this scheme doesn't
work in the case of multiple inheritance or when the client stubs are not
TAO.<P>
<li>
There are some POA objects in a typical server that are not freed up properly,
resulting in a memory leak. This is not very significant since the leak
does not grow. However, it still needs a fix.</li> <P>
</UL>
Future work:
<ul>
<li>
Determine the degree to which we will support the full semantics of remote
objects on a collocated object. The spec mandates that collocated object
should behave <i>exactly</i> like remote objects, but that means that request
will have to be queued rather than calling a method directly, and this
could be hazardous to our quest for real-time ORB status.</li><P>
<li>
Provide extensions of the specification to ensure real-time delivery of
messages.</li> <P>
</ul>
Recently completed work:<P>
<ul>
<li>
Support for collocation should be much better now because the POA can tell
if we created the object reference.</li><P>
<li>
The POA now supports active demultiplexing of servants in the SYSTEM_ID
policy. This should make the POA faster and more predictable since there
is no hashing involved and the index of the slot where the servant is registered
is in the Object Key.</li> <P>
</UL>
<hr>
<h3>
<a NAME="interfrepo"></a>Interface Repository</h3>
Point of contact: <a href="mailto:parsons@cs.wustl.edu">Jeff Parsons</a><P>
The Interface Repository provides run-time information about IDL
interfaces. Using this information, it is possible for a program to
encounter an object whose interface was not known when the program was
compiled, yet, be able to determine what operations are valid on the
object and make invocations on it using the DII.
<p>Current Status: TDB
<p>Known Issues: TDB
<p>Recent Work: TDB
<p>Future Work: TDB
<p>
<hr>
<h3>
<a NAME="nservices"></a>CORBA Naming Service and Interoperable Naming Service</h3>
Points of contact: <a href="mailto:marina@cs.wustl.edu">Marina
Spivak</a> and <a href="mailto:vishal@cs.wustl.edu">Vishal Kachroo</a>
<p>
The CORBA <a href="ftp://www.omg.org/pub/docs/formal/97-07-12.pdf">The
Naming Service</a> supports a hierarchical mapping between sequences
of strings and object references. The CORBA <A
HREF="ftp://ftp.omg.org/pub/docs/orbos/98-10-11.pdf">Interoperable
Naming Service</A> defines a standard way for clients and servers to
locate the Naming Service. <P>
<p>Current status (as of 22nd Feb 1999):
<ul>
<li>
Implementation of the CORBA Naming Service spec is complete.</li>
</ul>
Recently completed work:
<ul>
<li>
The implementation of the Naming Service has been upgraded to use TAO's
exception macros, which allow it to work both with C++ exceptions and without.</li>
<li>
Destroy method has been updated.</li>
<li>
More test examples have been added to TAO/orbsvcs/tests/Simple_Naming.</li>
</ul>
Work in progress:
<ul>
<li>
Currently the bindings are stored as a table in memory. Work is under way
to provide persistance option for the Naming Service.</li>
<LI> Currently adding support for the Interoperable Naming Service,
which enables the ORB to support IORs in user-friendly URL formats
using the <CODE>iioploc</CODE> and <CODE>iiopname</CODE> formats.
These features allow the ORB to configured to return arbitrary object
references from <CODE>CORBA::ORB::resolve_initial_references</CODE>
for non-locality-constrained objects. In addition, two standard
<CODE>CORBA::ORB_init</CODE> arguments are being added to override the
TAO's initial reference configuration. The service provides an
extension to the existing Naming Service to include conversions to and
from URL-style IORs.
<LI>The Naming Service is being used as an agent to understand IIOP
request messages from clients and respond with reply messages with a
LOCATION_FORWARD status. Work is in progress for the client-side
lookup tables built through commandline arguments to the ORB,
<CODE>-ORBInitRef</CODE> and <CODE>-ORBDefaultInitRef</CODE>.<P>
</ul>
Future work:
<ul>
<li>
Replication of the bindings to other Naming Service's currently running.
It will probably be modeled after the LDAP Multi-Master Replication Protocol.</li>
</ul>
<p>
<hr>
<h3>
<a NAME="tservices"></a>CORBA Trading Service</h3>
Point of contact: <a href="mailto:sbw1@cs.wustl.edu">Seth Widoff</a>
<p>The <a href="http://www.omg.org/corba/sectrans.htm#trader"> Trading
Service</a> is an implementation of the COS Trading Service
speficiation that meets the Linked Trader conformance criteria --- it
implements the <tt>Lookup</tt>, <tt>Register</tt>, <tt>Admin</tt>, and
<tt>Link</tt> interfaces, but not the <tt>Proxy</tt>
interface. Notably, the TAO trader supports the following features:<P>
<ul> <li> Multithreaded operation;</li>
<li>
Trader federations and distributed queries;</li>
<li>
Dynamic properties;</li>
<li>
Modifiable properties;</li>
<li>
All policies described in the specification;</li>
<li>
Preference sorting;</li>
<li>
Service type inheritance hierarchies and subtype searching.</li>
</ul>
<a href="trader.html">Trading Service documentation</a> is also available.
<p>Future Work:
<ul>
<li>
The Proxy Interface.</li>
<li>
Persistent storage of service types and offers.</li>
</ul>
<p>
<hr>
<h3>
<a NAME="pservices"></a>CORBA Property Service</h3>
Point of contact: <a href="mailto:alex@cs.wustl.edu">Alexander Babu Arulanthu</a>
<p>Current status (as of May 2nd, 1998)
<p>All the interfaces of this service have been implemented. Please
go through the test examples at $TAO/orbsvcs/tests/CosPropertyService.
Property Service is now used by the AVStreams that is currently being
developed for TAO. More testing is being done.
<p>For general documentation of the Property Service, please read <a href="http://www.omg.org/corba/sectrans.htm#prop">The
Property Service Specification.</a>
<p>
<hr>
<h3>
<a NAME="cservices"></a>CORBA Concurrency Service</h3>
Point of contact: <a href="mailto:tworm@cs.wustl.edu">Torben Worm</a>
<p>Current status (as of May 3rd):
The <a href="http://www.omg.org/corba/sectrans.htm#concur">
Concurrency Service</a> provides a mechanism that allows clients to
acquire and release various types of locks in a distributed system.<P>
<ul>
<li>
A simple version of the Concurrency Service has been implemented, i.e.
a version without transactions. It is currently being tested.</li>
</ul>
Future Work:
<ul>
<li>
Implementation of the Concurrency Service with transactions</li>
</ul><P>
<hr WIDTH="100%">
<h3>
<a NAME="av"></a>CORBA Audio/Video Control Service</h3>
Point of contact: <a href="mailto:naga@cs.wustl.edu">Nagarajan Surendran</a>
<p>This is an implementation of the OMG spec addressing the <a href="http://www.cs.wustl.edu/~sumedh/research/corbaav.pdf">Control
and Management of Audio/Video Streams</a>.
<p>The audio/video streaming service has been implemented in the light
profile. An MPEG-1 application which streams mpeg-1 video and mpeg-1 audio
separately has been developed using the service. This application currently
works only for Unix platforms.
<p>Work in progress:
<ul>
<li>
Implementing the SFP protocol</li>
<li>
Integrating the mpeg-1 streaming application with the trading service.</li>
</ul>
<hr>
<p><a NAME="ts"></a><b>CORBA Time Service</b>
<p>Point of contact: <a href="mailto:vishal@cs.wustl.edu">Vishal Kachroo</a>
<p> The <a href="ftp://ftp.omg.org/pub/docs/formal/97-02-22.pdf">Time Service</a>
allows clients to connect to Time Service Clerks and obtain globally
synchronized time. This time is calculated from the time obtained from
one or more Time Servers running on multiple machines in the
network. The service uses the TAO Implementation Repository to
activate the time servers on demand.
<p>Current status (as of 10th Jan 1999):
<ul>
<li>
Implementation of a Distributed CORBA Time Service is complete.</li>
</ul>
Future work:
<ul>
<li>
Currently the average of the time obtained from the various servers is
considered the global notion of time. A better distributed time synchronization
algorithm can be used in the future.</li>
<li>
Implementation of the Timer Event Service.</li>
</ul>
<p>
<hr WIDTH="100%">
<h3>
<a NAME="ec"></a>CORBA Event Service</h3>
<h4>
Last updated: Fri Mar 5 20:38:26 CST 1999</h4>
Point of contact: <a href="mailto:pradeep@cs.wustl.edu">Pradeep Gore</a>
<p>The COS compliant Event Service implements the Event Service Specification:
<a href="http://www.omg.org/docs/formal/97-12-11.pdf">(.pdf)</a>,
<a href="http://www.omg.org/docs/formal/97-12-11.ps">(.ps)</a>
<br>This implementation is based on the Real Time Event service.
<h3>
Features in this release:</h3>
<ul>
<li>
The Event Channel (<tt>$TAO_ROOT/orbsvcs/orbsvcs/CosEvent</tt>) supports
the <tt>push </tt>style event communication.</li>
<li>
A simple test (<tt>$TAO_ROOT/orbsvcs/tests/CosEC_Basic</tt>) demonstrates
how to create and use the event channel.</li>
<li>
Event Service (<tt>$TAO_ROOT/orbsvcs/CosEvent_Service</tt>)The Event Service
creates a COS compliant event channel and registers it with the naming
service with the default name "CosEventChannel".</li>
<br>Please read the associated README for more details.
<li>
CosEC_Multiple: <tt>($TAO_ROOT/orbsvcs/tests/CosEC_Multiple)</tt>:
This test demonstrates how multiple CosEC's connect to one RtEC and how
multiple consumers and producers exchange events in this configuration.</li>
</ul>
<h3>
Known bugs:</h3>
<ul>
<li>
CosEC_Multiple: <tt>($TAO_ROOT/orbsvcs/tests/CosEC_Multiple)</tt>:
Once the tests are done, the control doesn't return to the shell,
you have to say CTRL-C to get back to the prompt.
</li>
</ul>
<hr WIDTH="100%">
<!--#include virtual="ec.html" -->
<p>
<hr>
<h3>
<a NAME="scheduling"></a>TAO's Scheduling Service</h3>
Point of contact: <a href="mailto:cdgill@cs.wustl.edu">Chris Gill</a>
and <a href="mailto:levine@cs.wustl.edu">David Levine</a>
<p>Currently Implemented Features:
<ul>
<li>
The scheduling service can be built to use either a null implementation
or a strategized implementation of the configuration scheduler.</li>
<li>
The null scheduler implementation, which is built by default, allows the
configuration scheduler to be used with applications that require a scheduling
service interface, but do not (at least in the current stage of their development,
in certain configurations, etc.) make use of the real-time scheduling features
it provides.</li>
<li>
The strategized scheduler implementation can be built by #defining TAO_USES_STRATEGY_SCHEDULER,
and the appropriate scheduling strategy macro (TAO_USES_RMS_SCHEDULING,
TAO_USES_EDF_SCHEDULING, TAO_USES_MUF_SCHEDULING, or TAO_USES_MUF_SCHEDULING)
in $ACE_ROOT/ace/config.h. This allows the configuration scheduler to be
used with applications that require a specific scheduling strategy. Each
scheduling strategy will produce a set of static scheduling priorities,
which it will assign to operations based on their RT_Infos. For each static
priority, a strategy will also determine the run-time (dynamic) scheduling
strategy to use for that priority level.</li>
</ul>
Future work:
<ul>
<li>
Implement heap-based dispatching queues.</li>
<li>
Add support for additional configurability, especially in the type
of dispatching strategy (list vs. heap) that will be used to dispatch operations
at a given static priority level.</li>
<li>
Benchmark the various alternative strategies to obtain performance
profiles across different operation loads and OS platforms.</li>
<li>
Add increased functionality. Requests and suggestions are welcome.</li>
</ul>
<hr>
<h3>
<a NAME="logging"></a>TAO's Logging Service</h3>
Point of contact: <a href="mailto:mjb2@cs.wustl.edu">Matt Braun</a>
<p>Current status (as of August 4'th):
<ul>
<li>
The basic logging service has been implemented. It can log basic messages
from multiple clients. It is currently in the testing stage.</li>
</ul>
Future work:
<ul>
<li>
Add increased functionality. Requests and suggestions are welcome.</li>
</ul>
<hr>
<h3>
<a NAME="apps"></a>Test & Performance Tests</h3>
Point of contact: <a href="mailto:naga@cs.wustl.edu">Nagarajan Surendran</a>
<p>Current Status:
<p>The TAO IDL_Cubit test application makes use of the Naming Service and
the server holds a TAO_Naming_Server component.Just running server and
client is enough to test the application.
<p>The various tests in the tests/POA test the different features of the
Portable Object Adapter interface like Explicit Activation, On Demand Activation,etc..
<p>MT_Cubit:
<p>Current status:
<p>The TAO MT_Cubit test application is meant to serve as a starting point
for real-time tests on the TAO system. It comprises the following parts:
<ul>
<li>
<i>Server.</i> The server creates multiple CORBA objects (servants), each
with different real-time priorities. This priority is implemented by using
real-time thread support provided by the operating system. Thus, requests
sent to a high-priority servant are handled by a high-priority real-time
thread, and those sent to a lower priority servant are handled by correspondingly
lower priority threads.</li>
<li>
<i>Client.</i> The client component binds to the servants, and sends a
stream of CORBA requests to the servants. It measures the response time,
i.e. the time taken for the request to complete successfully. In particular,
it measures the time taken for requests sent to the high priority servant
to complete. The volume of lower priority requests is configurable. The
client is thus able to measure the performance of the high-priority servant
in the presence of competition from several lower-priority servants.</li>
</ul>
Clearly, if the ORB endsystem handles the priorities of the various requests
correctly, increasing the volume of lower priority requests should not
affect the performance seen by the higher priority requests. The application
thus serves as a tool to measure and confirm this behavior.
<p>Future work:
<ul>
<li>
Study the impacts of scheduling & concurrency strategies on performance.</li>
<li>
Evolve into a testbed for discovering sources of performance non-determinism
& priority inversion.</li>
</ul>
<p>Pluggable:
<p>Current status:
<p>The TAO Pluggable test utilizes ACE Timeprobes to time the latency at
various points in the ORB, especially that incurred by the Pluggable Protocols
implementation. Comparisons can be made not only between different layers of the
ORB, but also between different protocols as they become available.
<p>Future work:
<ul>
<li>
Add options to redirect the output to a file.</li>
<li>
Script or otherwise automate the piping of the output to a spreadsheet.</li>
</ul>
<hr>
<h3>
<a NAME="ace"></a>ORB-related ACE Changes</h3>
Points of contact: <a href="mailto:nanbor@cs.wustl.edu">Nanbor Wang</a>
and <a href="mailto:irfan@cs.wustl.edu">Irfan Pyrarli</a>
<p>Recently Completed Work:
<ul>
<li>
Added special declaration to OS.h for <tt>inet_ntoa</tt> and other functions
because VxWorks doesn't provide full argument prototypes for these library
functions.</li>
<li>
The current caching connector behaves properly in the face of a non-blocking
connect request. The "fix" is simply to not support non-blocking connects
through the cache. When the <tt>connect()</tt> fails with <tt>EWOULDBLOCK</tt>,
morph the error to -1 and clean up the request.</li>
<li>
Service handlers obtained from the caching connector are now cleaned up.
The application needs to be able to signal that it's not using it any longer,
and, when the application encounters an error, needs to effectively close
down that connection for good so that a new connection can be initiated.</li>
<br>Added the ability for a Svc_Handler to recycle itself. idle() can be
called when the Svc_Handler is done serving a particular connection and
can how be recycled. The Svc_Handler now also has a pointer to a recycler
that is responsible for managing the connections. The recycler is usually
a Cached_Connector.
<br>Added new class ACE_Recycling_Strategy. It defines the interface (and
default implementation) for specifying a recycling strategy for a Svc_Handler.
This strategy acts as a consular to the Svc_Handler, preparing it for the
tough times ahead when the Svc_Handler will be recycled.
<br>Added new class ACE_NOOP_Concurrency_Strategy. It implements a no-op
activation strategy in order to avoid calling open on a recycled svc_handler
multiple times.
<br>ACE_Cached_Connect_Strategy now implements the ACE_Connection_Recycling_Strategy
interface. This allows Svc_Handlers to cache themselves with ACE_Cached_Connect_Strategy
when they become idle. It also allows them to purge themselves from the
connection cache when the Svc_Handlers close down.
<br>Also added ~ACE_Cached_Connect_Strategy that will cleanup up the connection
cache.</ul>
Future work:
<blockquote><i>None currently scheduled.</i></blockquote>
<hr>
<h3>
<a NAME="dove"></a>The DOVE Demo</h3>
Points of contact: <a href="mailto:mk1@cs.wustl.edu">Michael Kircher</a>
and <a href="mailto:cdgill@cs.wustl.edu">Chris Gill</a>.
<p><a href="http://www.cs.wustl.edu/~schmidt/dove.html">DOVE</a> is documented
in detail <a href="http://www.cs.wustl.edu/~schmidt/Dove.ps.gz">online</a>.
This discussion focuses on the following goals:
<ul>
<li>
Have a DOVE Browser running using Java Beans as vizualization components.</li>
<li>
Have the Event Channel as DOVE Agent running with an Event Consumer in
the DOVE Browser.</li>
<li>
Having a DOVE Management Information Base (MIB), which dumps all events
transfered on the Event Channel into a file on persistent storage for later
reuse.</li>
</ul>
The DOVE Browser uses independent visualization components (Java Beans)
and the Event Channel as DOVE Agent. Connections can be established between
monitored metrics and the visualization components.
<p>We have three major components: Observables (monitored metrics), Observers
(a Java Bean for displaying the metric) and a DataHandler (for demultiplexing
the monitored metrics to the appropriate Observables). Each component inherits
from a base class, so that a certain behavior of the components can be
assured for each component. Relationships between components are based
on these base classes.
<p>The used Java Beans are required to conform to some standards, as they
have to support a function called "getProperty" which allows the DOVE Browser
to determine if the vizualization capabilities of a specific Java Bean
are sufficient to display the metric. A JavaBean is for example a Java
Panel which shows a Graph of the delivered doubles. So all metrics can
be displayed by this visualization component which can be expressed by
a single double.
<p>The DataHandler is connected to the Event Push Consumer (PUSH, because
we use the push concept of the Event Service). The Event Push Consumer
does not know what kind of data is transported. The only component knowing
all the details about the dependencies of the metrics is the DataHandler.
This separation allows easy extension and change of the demo.
<p><a href="http://students.cec.wustl.edu/~mk1/dove.html">Object Diagrams</a>
are available about this new concept.
<p>Event Service events are used as communication between DOVE Applications
and the DOVE Browser. The DOVE MIB analyses the event data field of all
events and stores this information into a file. The event data filed is
of type CORBA::Any and the DOVE MIB has no notion of what is conveyed in
this field. So the DOVE MIB has to discover the content via the embedded
type code information. Future work includes:
<ul>
<li>
Enhancing MIB functionality</li>
<li>
Monitoring the AV Streaming Service</li>
</ul>
For more information on the DOVE demo, please refer to: $TAO_ROOT/orbsvcs/tests/Simulator/README.<P>
<hr>
<h3>
<a NAME="forwarding"></a>Location Forwarding</h3>
Point of contact: <a href="mailto:irfan@cs.wustl.edu">Irfan Pyarali</a>,
<a href="mailto:mk1@mk1.wustl.edu">Michael
Kircher</a>.
<p>For more information see <a href="../forwarding.html">Location forwarding</a>
<p>
<hr>
<h3>
<a NAME="leader"></a>Global Resources and Leader-Follower Model</h3>
Point of contact: <a href="mailto:irfan@cs.wustl.edu">Irfan Pyarali</a>,
<a href="mailto:mk1@mk1.wustl.edu">Michael
Kircher</a>.
<p>For more information see <a href="../leader_follower.html">Leader-follower
model</a>
<p>
<hr>
<h3>
<a NAME="locate"></a>Implementation of locate request</h3>
Point of contact: <a href="mailto:irfan@cs.wustl.edu">Irfan Pyarali</a>,
<a href="mailto:mk1@mk1.wustl.edu">Michael
Kircher</a>.
<p>For more information see <a href="../locate_request.html">Locate request</a>
<p>
<hr>
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