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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>
This document contains information 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>:
<TABLE cellpadding=10 cellspacing=0 border=0>
<TD>
<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="#rtcorba">Real-Time CORBA</a></li>
<li>
<a href="#poa">Portable Object Adapter (POA)</a></li>
<li>
<a HREF="../poa_migration.html">POA Migration Notes</a></li>
<li>
<a href="#ami">Asynchronous Method Invocation (AMI)</a></li>
<li>
<a href="#interceptor">Portable Interceptors</a></li>
<li>
<a href="../Smart_Proxies.html">Smart Proxies</a></li>
<li>
<a href="../implrepo/index.html">Implementation Repository</a></li>
<li>
<a href="#interfrepo">Interface Repository</a></li>
<li>
<a href="OBV.html">Object-by-Value</a></li>
</UL>
</TD>
<TD>
<UL>
<li>
<a href="#nservices">CORBA Naming Service </a>
<LI> <a href="../INS.html">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 Streaming Service</a></li>
<li>
<a href="#ts">CORBA Time Service</a></li>
<a href="#ec">CORBA Event Service</a></li>
<li>
<a href="#log">CORBA Telecom Log Service</a></li>
<li>
<a href="#notify">CORBA Notification 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>
</UL>
</TD>
<TD>
<UL>
<li>
<a href="#apps">Regression 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>
</TABLE>
</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:parsons@cs.wustl.edu">
Jeff Parsons</a>
<p>Current status: (As of August 2, 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>
IDL compiler is now able to generate code that support native C++
exceptions on the stubs and skeletons. With this strict mapping, the
CORBA::Environment parameter is no longer generated.
The default behavior is to generate code without the extra parameter
on plaforms with native exceptions and with the extra
parameter in platforms without native exceptions.
Use the -Ge flag to override the defaults.
</li>
<li>
We are now able to handle shared case labels and default label in
unions. In addition, whenever appropriate, we are also able to
generate the "default ()" operation.
</li>
<li>
We are now able to handle recursive types. We are also able to
generate optimized typecodes.
</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>
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>
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>
<li>
The IDL compiler generates source code for the management and (de)marshaling
of wide characters and wide strings, enabling the sending and receiving of
Unicode over the wire. However, wide character and wide string literals are
not yet portable to Unix platforms (see entry under Future Work below).</li>
<li>
Since the CORBA spec requires that all enums be 32 bits, and some compilers
will try to use less space if the enum values are small enough, the IDL
compiler now appends <enum name>_TAO_ENUM_32BIT_ENFORCER = 0xFFFFFFFF to
every enum. This appended enum value is not part of the IDL compiler's
internal representation of the enum, so unions that use the enum as a
discriminator will not have incorrect _default() code generated for them.</li>
<li>
The IDL compiler generates a C++ ostream operator for IDL exceptions. So
far only the repository ID is output, but this may be enhanced when
requirements and/or desires become clearer.</li>
<li>
The IDL compiler now has limited support for valuetypes (see release notes
for valuetypes for details). If the TAO library is built with
TAO_HAS_VALUETYPE defined, and IDL_HAS_VALUETYPE is also defined, then
the IDL compiler will enable OBV support with the command line option
-Gv, and disable it with the option -Sv (the default).</li>
<li>
As part of the implementation of interceptors, the TAO IDL compiler
now generates interception points in the client and server, as well
as the prepare_header method in the stubs.</li>
<li>
Scoping and name resolution rules have changed in CORBA with version
2.3. The IDL compiler now conforms to these new rules. </li>
<li>
IDL compiler now supports the CORBA AMI callback model, generating code
for reply handlers and reply stubs if the -GC command line option is
used. The TAO library must be compiled with TAO_HAS_CORBA_MESSAGING = 1.
If this is done, TAO_HAS_AMI_CALLBACK will automatically be defined to
1 as well. IDL_HAS_VALUETYPE is defined to 1 by default.
<li>
New command line option -Sc added to suppress generation of tie classes
and *S_T.* files. The default is still to generate them.
</ul>
<p><br>Known bugs/unimplemented constructs:
<ul>
<LI>At this point there are no known problems with the IDL compiler
</LI>
</ul>
Future work:
<ul>
<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.</li>
<li>
Unix's native wchar_t type is not compatible with Unicode. CORBA wide string
implementations are required to support Unicode, but are not restricted to
it, so the IDL compiler should ultimately support Unix's wchar_t as well.
</ul>
<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 have added
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 resulted in the restructuring of the ORB Core and how requests are
handled. 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> - Aside from IIOP, three additional
transport protocols have been implemented:
<ol>
<P><li>UIOP: GIOP over local IPC (UNIX domain sockets)</li>
<P><li>SHMIOP: GIOP over shared memory</li>
<P><li>SSLIOP: IIOP over SSL (Secure Socket Layer).
<FONT COLOR=RED>SSLIOP is not distributed with TAO due
to US cryptographic software export restrictions.
There are <STRONG>no</STRONG> security hooks in
TAO.</FONT></li>
</ol>
<P>
Other interesting transport protocols could be for ATM, Buses (VME or
PCI), TP4, GSMP, and UDP/IP. TAO users have also created their own
pluggable transport protocols, such as a ScramNet pluggable protocol.
</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 basic framework to support pluggable transport protocols has been
completed. The standard TAO regression tests <tt>MT_Cubit</tt>,
<tt>Multiple_Inheritance</tt>, <tt>CDR</tt> and <tt>EC_Throughput</tt>
can be used to verify performance using the new framework.</li>
<P><li>
Multiple endpoint support in the ORB has been added. A
list of TAO_Acceptors is kept in the Acceptor
Registry. When the ORB needs to create an IOR it iterates
over all the acceptors to do so. Using either multiple
<code>-ORBEndpoint</code> options or several endpoints
separated by semi-colons ';', the user can specify what
addresses the ORB should use. Each endpoint is specified
in URL format (ex: <code>iiop://foo.bar.com:0</code>),
this format can be extended to support different
protocols.
</li>
<P><li>
If the user does not specify a list of endpoints then the
ORB creates a default endpoint for each protocol
configured, unless the pluggable protocol explicitly
prevents that in an effort to prevent resource leaks.
</li>
<P><li>
Added support for multiple Connectors in the ORB, the ORB
finds the correct connector based on the tag for the
profile.
</li>
<P><li>
Added support for multiple profiles in the IORs, when the
ORB demarshals an IOR it queries the Connector Registry to
create the right kind of profile for the known protocols.
If one of the protocols is unknown we create a special
profile class that can only be used for marshaling and
demarshaling, not communication.
</li>
<P><li>
Enabled the UIOP protocol, this protocol uses local IPC
(aka UNIX domain sockets) as the transport mechanism. The
protocol is loaded by default.
</li>
<P><li>
Enabled the SHMIOP protocol, this protocol uses shared
memory as the transport mechanism. The protocol is loaded
by default.
</li>
<P><li>
An IIOP over SSL pluggable protocol called "SSLIOP" has
been implemented. It provides secure communication
between hosts that support IIOP over SSL, and is meant to
be a drop in replacement for the IIOP pluggable protocol.
TAO's SSLIOP pluggable protocol implementation supports
both the standard IIOP transport protocol and the secure
IIOP over SSL transport protocol.
<P>
SSLIOP is not distributed with TAO due to US
cryptographic laws. No changes were made to TAO to
provide this SSL support, nor does TAO contain any
security related hooks. TAO's SSLIOP implementation is
completely self-contained. This ensures that TAO
remains free of export restrictions.
</li>
<P><li>
Protocols can be dynamically loaded into the ORB: The
default resource factory reads the protocol "names" from
its list of arguments. These protocol names are used to
load an abstract factory via the service configurator.
This factory can create acceptors or connectors on demand.
By default only IIOP, UIOP (if supported by the platform)
and SHMIOP are loaded.
</li>
<P><li>
The service configurator is now used to load protocol factories.
</li>
<P><li>
The <code>-ORBHost</code> and <code>-ORBPort</code>
options are deprecated. The new <code>-ORBEndpoint</code>
option supercedes them. If the deprecated options are
used, the ORB issues a warning. The user should not
depend on the existence of these options in the future.
</li>
<P><li>
The <code>-ORBPreconnect</code> option supports multiple
protocols using the same URL formats that
<code>-ORBEndpoint</code> does. Note that the old
<em><code>host:port</code></em> format is supported for
backwards compatibility, but the user should not depend on
the existence of this old format since it is now deprecated.
</li>
<P><li>
The URL style object reference format has been updated to
conform with the format that <code>iioploc</code>
uses. The BNF specification for <code>iioploc</code> is:
<blockquote><code>
<iioploc> = "iioploc://"[<addr_list>]["/"<key_string>]<br>
<addr_list>= [<address> ","]* <address><br>
<address> = [<version> <host> [":" <port>]]<br>
<host> = DNS-style Host Name | ip_address<br>
<version> = <major> "." <minor> "@" | empty_string<br>
<port> = number<br>
<major> = number<br>
<minor> = number<br>
<key_string> = <string> | empty_string<br>
</code></blockquote>
In TAO, <code>iiop</code> URL style object references are
equivalent to <code>iioploc</code> URL style object
references. <code>uiop</code> URL style object references
have a similar syntax:
<blockquote><code>
<uioploc> = "uioploc://"[<addr_list>]["|"<key_string>]<br>
<addr_list>= [<address> ","]* <address><br>
<address> = [<version> <rendezvous point>]<br>
<rendezvous point> = Valid Filesystem Path<br>
<version> = <major> "." <minor> "@" |
empty_string<br>
<major> = number<br>
<minor> = number<br>
<key_string> = <string> | empty_string<br>
</code></blockquote>
Note that the key string delimiter for <b><code>uiop</code></b>
is a vertical bar `<b><code>|</code></b>' (the command line
"pipe" symbol) not a forward slash
`<code>/</code>'. A delimiter other than a
forward slash is needed to prevent ambiguities of
where the rendezvous point ends and where the key
string begins since both may contain forward
slashes in them.
</li>
<P><li>
The <i>rendezvous point</i> for <code>uiop</code> is
any valid path and filename that the ORB has permission to
read and write to. However, UIOP rendezvous points have
the same restrictions that local IPC has. The following
are some guidelines that will help ensure successful use
TAO's UIOP pluggable transport protocol:
<blockquote><li>
To guarantee portability, local IPC rendezvous
points (including the path and filename) should not
be longer than 99 characters long. Some platforms
may support longer rendezvous points, usually 108
characters including the null terminator, but
Posix.1g only requires that local IPC rendezvous
point arrays contain a maximum of <b>at least</b>
100 characters, including the null terminator.<P>
If an endpoint is longer than what the platform
supports then it will be truncated so that it fits,
and a warning will be issued.
</li>
<P><li>
Avoid using <em>relative</em> paths in your UIOP endpoints.
If possible, use <b><em>absolute</em></b> paths
instead. Imagine that the server is given an
endpoint to create using <code>-ORBEndpoint
uiop://foobar</code>. A local IPC rendezvous
point called <code>foobar</code> will be created
in the current working directory. If the client
is not started in the directory where the
<code>foobar</code> rendezvous point exists then
the client will not be able to communicate with
the server since its point of communication, the
rendezvous point, was not found. On the other
hand, if an absolute path was used, the client
would know exactly where to find the rendezvous
point.
<P>
It is up to the user to make sure that a given UIOP
endpoint is accessible by both the server and
the client.
</li>
<P><li>
It is important to be consistent in the use of
absolute paths and relative paths for rendezvous
points. The two types of paths should not be used
for the same endpoint. For example, if
<code>uiop:///tmp/foo</code> is specified as the
server endpoint and <code>uiop://foo</code> as a
preconnect for a client in <code>/tmp</code>, then
the preconnection may be established but it is
likely it won't be used since the endpoint and
preconnect are interpreted as different strings,
i.e. <code>/tmp/foo</code> and <code>foo</code> are
not the same, lexicographically. On the other
hand, if both the endpoint and the preconnect are
the same string then a preconnection will be
established and used successfully.<P>
</li></blockquote>
The <code>-ORBEndpoint</code> option uses a syntax similar
to that of the URL style object reference shown above.
The only difference is that the object key delimiter and
the object key string are not specified.
</li>
<P><li>
Added documentation that describes how to implement
pluggable transport protocols for TAO. The document is
available
<A HREF="../pluggable_protocols/index.html">here</A>.
</li>
<P><li>
TAO's IIOP pluggable protocol now supports automatic
creation of profiles for endpoints created on a host with
multiple network interfaces. It should no longer be
necessary to manually specify an endpoint for each network
interface.
<P>
This means that server IORs will contain profiles for
all of the default endpoints created on each network
interface the server is listening on, if no explicit
endpoints were specified.
</li>
</ul>
<P>
Known Issues:
<ul>
<li>
</ul>
Critical Work:
<ul>
<li>
None.
</li>
<p><p>
</ul>
Future Work:
<ul>
<li>
Complete support for multiple ORB messaging protocols.
<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>
</ul>
<p>
<hr>
<h3> <a NAME="rtcorba"></a>Real-Time CORBA </h3>
Point of contact: <a href="mailto:fredk@cs.wustl.edu">Fred Kuhns</a>
<P>
The Real-Time CORBA specification (RT-CORBA) defines a framework for
supporting end-to-end deterministic behavior for a fixed priority CORBA
system. This specification builds on the CORBA Architecture
Specification version 2.2 and the CORBA Messaging Specification.
Primarily, RT-CORBA adds to the Policy framework defined in the
Messaging specification and adds to GIOP/IIOP version 1.1 to support
these extensions. <P>
This effort will implement the RT-CORBA specification and required
parts of the Messaging specification. Our implementation of RT-CORBA
in TAO will occur in stages. Our initial focus will be the support of
statically configured, real-time embedded systems where it is possible
to eliminate many sources of unbounded priority inversion. This will
be followed by a more general implementation which supports more
dynamic environments and scheduling mechanisms. <P>
Support for statically configured applications requires a framework
which allows for explicit mappings between CORBA priorities,
connections (client side), endpoints (server side), threads, objects
and invocations. By supporting such mappings, applications will
realize a greater degree of control over end-to-end priority mappings.
Essentially, applications are able to assign priorities to connections
between server and client, then using the existing Policy framework
along with new Policy objects, requests are routed to the appropriate
connections. By assigning equivalent thread and object priorities,
applications are able to ensure end-to-end priority preservation. <P>
As a part of this initial effort we are also adding support for both
reliable and buffered oneway operations. Reliable oneway operations
are specified in the messaging specification. Reliable oneways is a
method for providing different levels of support for reliable message
delivery. Traditional oneway semantics are unacceptable in many
environments. For example, there is no guarantee that a particular
invocation will actually be delivered. Additionally, location
forwarding will not occur with traditional oneway invocations. <P>
<P>
The Messaging specification has defined four alternative
interpretations of the oneway interface. Two of these cases do provide
for both location forwarding and positive acknowledgment from the
server that a message was received. The <CODE>SyncScopePolicy</CODE>
Policy from the Messaging Specification is used to specify the level of
reliability required. The policy is set on the client side and uses a
new flags field in the GIOP 1.2 header. The server checks this flag to
determine if a reply is required for the oneway invocation. Four
different levels synchronization are defined in the RT specification:
<p>
<ul>
<li>
<CODE>SYNC_NONE</CODE><BR>
The ORB returns control to the client before passing the
request to the transport layer. Client is guaranteed not
to block. No location forward is done.
</li>
<li>
<CODE>SYNC_WITH_TRANSPORT</CODE><BR>
The ORB returns control to the client only after the
transport layer (e.g. TCP) has accepted the request.
Client can block. No location forwarding is done.
</li>
<li>
<CODE>SYNC_WITH_SERVER</CODE><BR>
The server sends a reply before invoking the target
implementation. A reply of NO_EXCEPTION implies that all
location forwarding has been performed and the ORB shall
return control to the client. Thus the client will block
for remote invocations. Server send reply after invoking
any ServantManager but before delivering request to
servant.
</li>
<li>
<CODE>SYNC_WITH_TARGET</CODE><BR>
Equivalent to a synchronous twoway operation in CORBA 2.2.
Server sends a reply only after the target has completed
the invoked operation. Any location forwarding will have
occurred and a SYSTEM_EXCEPTION reply may be sent. The
client is assured that the target has acted upon the
request.
</li>
</ul>
<P>
The underlying transport object will be enhanced to support different
oneway buffering strategies. This feature can be used to optimize
message throughput, possibly at the expense of latency. The One-Way
Buffer will be flushed under 5 conditions as specified by the
Buffering Constraint Policy:
<ul>
<li> Timeout value expires. </li>
<li> Max byte count is exceeded. </li>
<li> Explicit flush by the user. </li>
<li> Max message count is exceeded, or </li>
<li> ORB shutdown.</li>
</ul>
<p>Current Status:
<ul>
<li> SyncScopePolicy has been fully implemented. Setting a
SyncScope Policy value of SYNC_NONE will enable buffering of
oneway requests according to the current Buffering Constraint
Policy. </li>
<li> Buffering Constraint Policy is completely supported by TAO
providing flexible levels of flushing and queueing in the ORB. This
includes eager and delayed buffering and timed invocations.</li>
<li> ClientPriorityPolicy has been implemented. This TAO-specific
policy allows clients to specify priority to be used as a
selection criteria in choosing server endpoints for carrying out
consequent corba requests on objects. This client-side feature
together with the server-side capability to create multiple endpoints with
different priorities directly contributes to maintaining end-to-end
priority in a distributed system. Please see TAO/tao/TAO.pidl for
ClientPriorityPolicy interface, and TAO/tests/Endpoint_Per_Priority for
its use. Current implementation does not work properly in presence of
location forward messages. <P>
</ul>
Known issues:
<ul>
<li>
</ul>
Critial Work:
<ul>
<li>
</ul>
Future work:
<ul>
<li> Integrate SyncScope policy with DII deferred synchronous requests.
</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>
</UL>
Future work:
<ul>
</ul>
Recently completed work:<P>
<ul>
<li> ORB::shutdown now properly deactives all the POA
Managers. </li><P>
<li>
POA Managers in TAO were previously ignored in the request processing
path on the server. This is now fixed such that their state is checked
before dispatching the client request to the servant. Only if the
state is <CODE>ACTIVE</CODE>, is the request dispatched to the
servant. Otherwise, the request is rejected. Since POA Managers start
off in <CODE>HOLDING</CODE> state, make sure to
<CODE>activate()</CODE> them before falling into the event loop.
</li><P>
<li> TAO's POA now properly supports both the threading policies:
SINGLE_THREAD_MODEL and ORB_CTRL_MODEL. </li><P>
<li>The synchronization in the POA is now very optimal. For example,
the locks are not held across the invocation on the servant. The locks
are also not held across the invocation on the AdapterActivator and
ServantManagers. This allows us to use regular locks instead of
recursive locks inside the POA. This also allows multiple threads to
dispatch requests on the same POA simultaneous.</li><P>
<li>TAO now supports reference counting between POA and servants,
including the new RefCountServantBase and ServantBase_var
classes. RefCountServantBase is a reference counted base class that
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. Check <a
href="../poa_migration.html#Reference counting Servants">here</a> on
some hints to avoid trouble.</li><P>
<li> The POA now supports active demultiplexing of servants in the
SYSTEM_ID and the USER_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>
<li> Previously, the complete POA name was used as the POA
identity. This scheme was 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 new solution 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> There were some POA objects in a typical server that are not
freed up properly, resulting in a memory leak. This has now been
fixed.</li> <P>
<li> Timestamps in persistent IORs were not required and have been
removed.</li> <P>
<li> POA exceptions are not not system exceptions and have been
removed from the list of system exceptions.</li> <P>
<li> Vastly improved the ability of the POA to deal with user
exceptions, memory allocation failures, and constructor failures.</li>
<P>
<li> We now support a minimum POA for the minimum CORBA specification.
Recently, this feature was enchanced such that the minimum CORBA
footprint was further reduced. In addition, minimum POA can be
enabled/disable irrespective of the minimum CORBA setting.</li> <P>
<li> We have decided not to support active demuxing for method name
lookup. The benefit of this optimization was 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> Improved the parsing of object keys belonging to the
RootPOA. Since this is the default POA and is commonly used, we have
given it a reserved byte in the object key in order to quickly
identify it. With the reserved bit, the active demux key for the
RootPOA is not used, and no map lookups are required.</li> <P>
<li> POA name separator was changed from '/' to '\0'. Since POA names
are strings, this makes a better choice since there is no chance of a
conflict with the string specified by the user. </li> <P>
<li> We have support for reactivating servants with system generated
ids. </li> <P>
<li> The TAO specific synchronization POA policy has been
removed. </li> <P>
<li> New examples have been added to show how servants can be
dynamically loaded from DLLs on demand. </li> <P>
<li> Support for collocation should be much better now because the POA
can tell if we created the object reference.</li><P>
<li> After Nanbor's recent changes for collocation, we 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, which includes going through the POA, running the
Servant Managers, running the interceptors, and expecting the
reference counting behavior provided by the POA. Note that the old
scheme of direct call through to the servant is also still
available. </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>
<br><!--#include virtual="OBV.html" -->
<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">
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/99-09-01.pdf">Interoperable
Naming Service</A> defines a standard way for clients and servers to
locate the Naming Service. It allows the ORB to be administratively
configured for bootstrapping to services not set up with the orb at
install time. <P>
<p>Current status (as of 7th Apr 1999):
<ul>
<li>
Implementation of the CORBA Naming Service spec is complete. TAO's
Naming Service provides an optional persistence capability.</li>
<li>
Implementation of the CORBA InterOperable Naming Service is in
progress. </li>
</ul>
Recently completed work:
<ul>
<li>
Added support for Persistence (using memory-mapped files). Persistence
feature is optional, and is controlled by the command line argument.</li>
<li>
Updated the implementation of the Naming Service to use new ACE
exception macros.</li>
<li>
Added support for the InterOperable Naming Service, which enables the
ORB to support IORs in user-friendly <CODE>iioploc</CODE> format.
These features allow the ORB to be configured to return arbitrary object
references from <CODE>CORBA::ORB::resolve_initial_references</CODE>
for non-locality-constrained objects. Two options -ORBInitRef and
-ORBDefaultInitRef have been added to the orb for bootstrapping to
arbitrary services.
</li>
<li>Added support for the Naming service to act like an agent: to understand IIOP
request messages from clients and respond with reply messages with a
LOCATION_FORWARD/OBJECT_NOT_EXIST status. The Naming Service can be
configured through ORB options to register arbitrary services given
the URL-format IOR for the service. The resolve_initial_references ()
resolves a service in the following order :
<br>1. -ORBInitRef
<br>2. -ORBDefaultInitRef
<br>3. Multicast to service.
</li>
<li>
Added a test for the InterOperable Naming Service that works in
conjunction with the current TAO examples.
</li>
</ul>
Work in progress:
<ul>
<LI> Support for the iiopname format and conversions
to and from URL-style IORs.
</LI>
<LI>
A detailed InterOperable Naming Service test.
</LI>
</ul>
Future work:
<ul>
<li>
Support for a load balancing feature similar to the one present in ORBIX.
It will be possible to bind a group of objects under a single name, and when a client attempts to resolve the name in question, a preset policy (e.g., random, round robin, etc.) will determine which one of the object references from the group will be returned.
</li>
<li>
Support for the Naming Service to handle the IIOP
LocateRequest messages and respond with LocateReply messages with a
LOCATION_FORWARD/OBJECT_NOT_EXIST status.
</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 Mar 9th, 1999): All the interfaces of this
service have been implemented. Please
go through the test examples at $TAO/orbsvcs/tests/CosPropertyService.
Property Service is has been used by the TAO's <a href="#av">Audio Video Streaming
Service</a>developed for TAO. For general documentation of the
Property Service, please read <a
href="http://www.omg.org/corba/sectrans.html#prop">The Property Service
Specification.</a>
<P>Recent Work:
<ul>
<li>
Changed the PropertyException from Exception to struct, according
to the OMG's changes.
</li>
<li>
Changed the implementation to allocate storage for the Sequence
out parameters, eventhough their length is 0. This is according
to the CORBA specification.
</li>
</ul>
<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 Streaming Service</h3>
Point of contact: <a href="mailto:naga@cs.wustl.edu">Nagarajan
Surendran</a> and <a href="mailto:yamuna@cs.wustl.edu">Yamuna Krishnamurthy</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>.For more documentation on
TAO's A/V Service please have a look <A HREF="http://www.cs.wustl.edu/~naga/av.html">here</A>.
<p><h4>Current Status:</h4> (as of Sep 1st 1999)
<p>
<ul>
<li>
The audio/video streaming service has been implemented in the full
profile. The current implementation support all the flow related
components like flowEndpoint,FDev,FlowConnection,..,etc.
</li>
<li>
Point-to_Point and Point-to-MultiPoint streams have been
implemented.
</li>
<li>
A Pluggable protocols framework has been implemented to flexibly
add new flow protocols like SFP, RTP and new transports like
ATM. The current implementation has protoocol implementations
for SFP, RTP over UDP and Multicast UDP. Please look at this<A
HREF="http://www.cs.wustl.edu/~naga/pluggable_av.ps.gz"> paper
</A> for more documentation about the implementation.
</li>
<li>
A Videoconferencing application based on Vic, a MBONE tool, has
been implemented using the AV components. Please contact <A
HREF="mailto:yamuna@cs.wustl.edu"> yamuna or <A
HREF="mailto:naga@cs.wustl.edu"> Naga </A> if you're interested.
</li>
<li>
An MPEG-1 application which streams mpeg-1 video and mpeg-1 audio
separately has been developed using the service. The client side
of the mpeg player requires X windows support.Its available in
the release at $TAO_ROOT/orbsvcs/tests/AVStreams/mpeg/source.
</li>
<li>
An Integrated Video-on-demand application has been developed
using the Trading Service and the A/V Service. The demo uses a
Java FrontEnd and JNI to talk to the TAO C++ trader client. The
demo is available in the release at
$TAO_ROOT/orbsvcs/tests/AVStreams/server_discovery.
</li>
</ul>
<p>Work in progress:
<ul>
<li>
Adding more features to the VideoConferencing application
eg. porting vat, the audio counterpart of vic to use AV components.
</li>
<li>
Adding ATM AAL5 protocol support.
</li>
<li>
Adding QoS implementation.
</li>
</ul>
<hr>
<p><a NAME="ts"></a><b>CORBA Time Service</b>
<p>Point of contact: <a href="mailto:vishal@cs.wustl.edu">Vishal Kachroo</a>
<p> The <a href="ftp://ftp.omg.org/pub/docs/formal/97-02-22.pdf">Time Service</a>
allows clients to connect to Time Service Clerks and obtain globally
synchronized time. This time is calculated from the time obtained from
one or more Time Servers running on multiple machines in the
network. The service uses the TAO Implementation Repository to
activate the time servers on demand.
<p>Current status (as of 10th Jan 1999):
<ul>
<li>
Implementation of a Distributed CORBA Time Service is complete.</li>
</ul>
Future work:
<ul>
<li>
Currently the average of the time obtained from the various servers is
considered the global notion of time. A better distributed time synchronization
algorithm can be used in the future.</li>
<li>
Implementation of the Timer Event Service.</li>
</ul>
<p>
<hr WIDTH="100%">
<h3>
<a NAME="ec"></a>CORBA Event Service</h3>
<h4>
Last updated: Fri Mar 5 20:38:26 CST 1999</h4>
Point of contact: <a href="mailto:pradeep@cs.wustl.edu">Pradeep Gore</a>
<p>The COS compliant Event Service implements the Event Service Specification:
<a href="http://www.omg.org/docs/formal/97-12-11.pdf">(.pdf)</a>,
<a href="http://www.omg.org/docs/formal/97-12-11.ps">(.ps)</a>
<br>This implementation is based on the Real Time Event service.
<h3>
Features in this release:</h3>
<ul>
<li>
The Event Channel (<tt>$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%">
<h3><a NAME="log"></a>CORBA Telecom Log Service </h3>
<h4> Last updated: Sat Feb 19 16:58:42 CDT 2000 </h4>
Point of contact: <a href="mailto:krish@cs.wustl.edu">Krishnakumar Elakkara Pathayapura</a>
<p>The CORBA <a href="http://www.omg.org/cgi-bin/doc?telecom/99-05-01"> Telecom Log Service </a> prototype was released in TAO version 1.0.6.
<br>
<h3> Features supported in the first version:</h3>
<ul>
<li>
The Log Service implementation under <tt>$TAO_ROOT/orbsvcs/orbsvcs/Log</tt>
implements the <tt>DsLogAdmin </tt>module.
<br>
</li>
<li>
The Logging_Service (<tt>$TAO_ROOT/orbsvcs/Logging_Service</tt>) starts the Log
Service and registers the Log Service Factory with the Naming Service
as "BasicLogFactory".
<br>
</li>
<li>
The test <tt>$TAO_ROOT/orbsvcs/examples/Log/Client</tt> demonstrates
a simple use of the Log Service.
<br>
A thorough test <tt>$TAO_ROOT/orbsvcs/examples/Log/test/client</tt> tests
most of the features of the logging service.
</li>
<li>
The Query Language supported at present is "TCL".
The Log record id and Log record time are treated as properties
of the log and can be referenced in a query as "id" and "time"
respectively.
<br>
</li>
</ul>
<h3> Things to be done: </h3>
<ul>
<li>
Implement a few remaining methods - <br>
For the <tt>Log</tt> interface: copy.<br>
For the <tt>LogMgr</tt> interface: list_logs_by_id
<br>
</li>
</ul>
<h3> Future work and enhancements: </h3>
<ul>
<li>
Support the <tt>DsEventLogAdmin </tt> module, which uses
the <a href= "#ec">COS Event Service </a>
<br>
</li>
<li>
Support the <tt>DsLogNotification </tt> module after the
<tt>CORBA Notification Service</tt> is complete.
<br>
</li>
<li>
Currently all Log records are stored in memory, later we could add
support for persistant storage.
<br>
</li>
<li>
Support "Extended TCL" as the Query Language.
<br>
Support the record attributes as name-value pair properties.
<br>
</li>
<li>
Use Red-Black trees to optimize lookup on frequently used query keys -
namely record id's and time.
<br>
</li>
</ul>
<hr WIDTH="100%">
<h3><a NAME="notify"></a>CORBA Notification Service </h3>
<h4> Last updated: Fri Feb 4 00:19:08 CST 2000</h4>
Point of contact: <a href="mailto:pradeep@cs.wustl.edu">Pradeep Gore</a>
<p>Work is in progress to implement the CORBA <a href="ftp://ftp.omg.org/pub/docs/telecom/99-07-01.pdf">
Notification Service </a>.
The current implementation consists of the following (see the associated README's for more
information):
<ul>
<li>
The implementation of the interfaces in the Notification Service spec is in
<tt>$TAO_ROOT/orbsvcs/orbsvcs/Notify</tt>.
</li>
<li>
The service executable is implemented in <tt>$TAO_ROOT/orbsvcs/Notify</tt>.
</li>
<li>
The example in <tt>$TAO_ROOT/orbsvcs/examples/Notify/Filter</tt> shows a basic example
of using the Notification Service.
</li>
</ul>
<h3> Features supported thus far:</h3>
<ul>
<li>
Creating Event Channels. However, the Channel Factory does not assign ids as yet.
</li>
<li>
Creating ConsumerAdmins and Supplier Admins.
</li>
<li>
Creating ProxyConsumers and ProxySuppliers for "Any" events and Structured events.
</li>
<li>
Helper classes TAO_Notify_StructuredPushConsumer and TAO_Notify_StructuredPushSupplier
to write consumers and suppliers for Structured Events.
</li>
<li>
Support for Filters.The EventChannel's default Filter Factory can be used to create
filters. Note that for now we support "TCL" grammer from the Trading Service.
</li>
</ul>
<h3> Project Schedule </h3>
<ul>
<li>
Finish the remainder of the implementation of the Notification Service for the
TAO 1.1 release.This will include all administrative methods in all interfaces,
suspend/resume connections, Mapping Filters, Notify Publish,Subscribe interfaces.
This implementation will be backward compatible with the <a href="#ec">CORBA Event
Service</a>.
</li>
<li>
Address concurrency issues in the service - isolate the patterns identified in the
implementation of the <a href="ec.html"> RTEC </a> and reuse them. We hope to come up
with a collection of C++ template classes that capture these patterns so that they might
be used in other similar event communication senarios.
</li>
<li>
Come up with a rigorous test suite for this service to measure its performance.
</li>
<li>
Implement the parser engine for the <tt>Extended TCL</tt> grammer.
</li>
<li>
Implement the QoS features, especially the <i>Reliability</i> QoS property that requires
persistent events.
</li>
<li>
Implement event communication via reliable multicast.
</li>
</ul>
Note that we do not plan to support the following, anytime in the near future - Pull style and Typed
event style communication.
<P><HR><P>
<!--#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:krish@cs.wustl.edu">Krishnakumar Elakkara Pathayapura</a>
<p>Current status (Jan 23 2000):
<ul>
<li>
The basic logging service has been implemented. It can log basic messages
from multiple clients. The log scheduling is currently being tested.</li>
</ul>
Future work:
<ul>
<li>
Add persistence and then to add event notification</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: $TAO_ROOT/orbsvcs/tests/Simulator/README.<P>
<hr>
<h3>
<a NAME="forwarding"></a>Location Forwarding</h3>
Point of contact: <a href="mailto:irfan@cs.wustl.edu">Irfan Pyarali</a>,
<a href="mailto:mk1@mk1.wustl.edu">Michael
Kircher</a>.
<p>For more information see <a href="../forwarding.html">Location forwarding</a>
<p>
<hr>
<h3>
<a NAME="leader"></a>Global Resources and Leader-Follower Model</h3>
Point of contact: <a href="mailto:irfan@cs.wustl.edu">Irfan Pyarali</a>,
<a href="mailto:mk1@mk1.wustl.edu">Michael
Kircher</a>.
<p>For more information see <a href="../leader_follower.html">Leader-follower
model</a>
<p>
<hr>
<h3>
<a NAME="locate"></a>Implementation of locate request</h3>
Point of contact: <a href="mailto:irfan@cs.wustl.edu">Irfan Pyarali</a>,
<a href="mailto:mk1@mk1.wustl.edu">Michael
Kircher</a>.
<p>For more information see <a href="../locate_request.html">Locate request</a>
<p>
<hr>
<h3>
<a NAME="ami"></a>Asynchronous Method Invocation</h3>
Points of contact: <a href="mailto:alex@cs.wustl.edu">Alexander Arulanthu</a>
, <a href="mailto:Michael.Kircher@mchp.siemens.de">Michael Kircher</a> and
<a href="mailto:coryan@cs.wustl.edu">Carlos O'Ryan</a>
<p>Status:
<ul>
We've implemented the callback model of the <A
HREF="http://www.cs.wustl.edu/~schmidt/CORBA-docs/98-05-05.pdf.gz">Messaging
specification</a>. To activate the AMI for TAO and the TAO IDL
compiler define <tt>TAO_HAS_CORBA_MESSAGING</tt>,
<tt>TAO_HAS_AMI_CALLBACK</tt> in your config.h file. The TAO IDL
compiler can generate the AMI stubs, ReplyHandler und reply stubs
using the -GC switch.
<p>
For an example see <tt>$TAO_ROOT\tests\AMI</tt> and <tt>$TAO_ROOT\examples\AMI</tt>.
</ul>
<p> Finished work:
<ul>
<li> Redesign of the IDL compiler to make an addtional pass over
the AbstractSyntaxTree and generate the implied-IDL code in memory.
This reduced the amount of AMI specific IDL compiler code dramatically.</li>
<li>Support for exceptions</li>
<li>Support for attributes</li>
<li>Support for buffering and batching AMI calls. See <a
href="../../examples/Buffered_AMI">Buffered AMI</a> example for
details.</li>
<li>Support for deferred synchronous invocations.
<a href="mailto:parsons@cs.wustl.edu">Jeff Parsons</a></li>
</ul>
<p> Future Work:
<ul>
<li>Testing the current implementation</li>
<li>Implementation of the poller model.</li>
</ul>
<p>
<hr>
<h3> <a NAME="interceptor"></a>Portable Interceptors</h3>
Point of contact: <a href="mailto:nanbor@cs.wustl.edu">Nanbor Wang</a>,
<a href="mailto:kirthika@cs.wustl.edu">Kirthika Parameswaran</a>.
<p>For more information see <a href="../interceptors.html">Portable
Interceptors</a>
</p>
<hr>
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