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<HTML>
<HEAD>
<TITLE>TAO TODO List</TITLE>
</HEAD>
<BODY TEXT="#000000" BGCOLOR="#FFFFFF">
<!-- $Id$ -->
<CENTER><HR></CENTER>
<CENTER>
<H3>General TODO list for TAO</H3>
</CENTER>
<P>
This document presents a general TODO list for TAO,
the list is not very well organized or prioritized;
it started as a personal TODO list for Carlos so it is biased
towards the Event Service and related components.
Hopefully as more people gets involved it will become more
organized.
</P>
<P>
Last Updated: $Date$ $Revision$
</P>
<CENTER><HR></CENTER>
<CENTER>
<H4>Pending Tasks</H4>
</CENTER>
<OL>
<LI>Support native C++ exceptions.
This entails several subtasks:
<UL>
<LI>On the server side: catch any exceptions thrown by the
user or the system, and then transform that into the
proper <CODE>Reply</CODE> to the client side
</LI>
<LI>On the client side: when receiving an exception from the
server we need to create the object with the right dynamic
type. It is doable because the IDL compiler can give us a
list of the possible exceptions that we will receive,
it could augment this list with factory methods for the
exception objects. If the received exception is not on
the list we just throw a CORBA::UNKNOWN_EXCEPTION
exception.
</LI>
<LI>Add the _raise() method to the exceptions...
</LI>
<LI>Support the alternative mapping with an environment
variable, but with a default value (that <B>must</B> be
obtained from TSS).
</LI>
<LI>Support the standard mapping, without the environment
variable.
</LI>
<LI><P>I haven't looked into how would we support exceptions
with DII/DSI, the <CODE>ExceptionList</CODE> that is
received passed in the <CODE>Request</CODE> only contains
the <CODE>TypeCode</CODE> for each exception. Somehow the
ORB needs to map this into methods to create the Exception
objects with the right dynamic type.
</P>
<P>One possible solution is to register this methods with
the ORB when the stub is created, this will avoid the
use of statics that cause us so much pain</P>
</LI>
</UL>
</LI>
<LI>Add compiled marshalling
<BR>[STATUS] Andy is working on this.
</LI>
<LI>Add support for multiple Profiles in the ORB (completing the
IIOP 1.0 support)
</LI>
<LI>Support IIOP 1.1 in the ORB
</LI>
<LI>Support IIOP 1.2 in the ORB
</LI>
<LI>Support GIOP 1.1 in the ORB (fragments)
</LI>
<LI>Use the IIOP 1.1 profile info to pass QoS info and use it to
preserve end-to-end QoS.
</LI>
<LI>Use active demuxing in the POA
</LI>
<LI>Optimize twoways by delaying memory allocation for the
incoming data buffer, thus improving interleaving between the
client and server (the client does something useful before
starting to wait for the server).
</LI>
<LI>Further optimize memory allocation by using a memory pool
for the incoming CDR stream.
</LI>
<LI>Further optimize the outgoing memory allocation by adding
support for message blocks allocated from a pool (the
Message_Block class itself not the Data_Block or the buffer it
contains).
</LI>
<LI>The data blocks and their buffers could be allocated in a
single operation, using the beginning of a buffer to contain
the data block and the rest of it to contain the actual buffer
</LI>
<LI>The size of pre-allocated buffer for the outgoing CDR
streams is defined at compilation time; but if we use an
efficient enough allocator we could make its size configurable
via the svc.conf file. In any case the *second* (and
subsequent) buffers come out of the allocator, so their sizes
could be configured in the already mentioned file.
<BR>[NOTE] We have to be able to do this while minimizing the
number of calls to ORB_Core_instance()
</LI>
<LI>We need some TAO_TRY_* macro to encapsulate a common use of
the CORBA::Environment argument: checking if it contains an
exception and then returning.
</LI>
<LI>The TypeCode internal (private) state needs locking, double
checked locking is needed to avoid excessive overhead, there
is potential for memory leaks if this locking is not used.
</LI>
<LI>IDL compiler front-end should be case insensitive (actually
it should flag identifiers that only differ by case as a
conflict).
</LI>
<LI>The operation tables do not need to be statics, they could
be created on creation of the first servant of that type.
</LI>
<LI>Are nested upcalls in different concurrency models, like
thread-per-connection working?
</LI>
<LI>Add an option to the IDL-compiler (e.g. -rp) meaning
"generate relative include paths".
</LI>
<LI>The IDL compiler should generate the code locally (not in
the directory where the .idl resides) or at least give an
option to do so
</LI>
<LI>Support for unions with default cases (implicit or explicit)
in the IDL compiler is incomplete.
</LI>
<LI>It seems that some memory is leaked from the ORB cached
connector.
</LI>
<LI>Support for the fixed data type in the IDL compiler
</LI>
<LI>CDR stream support for wchar is flaky or at least untested.
</LI>
<LI>Add a corbafwd.h header file to eliminate the deep (and
recursive) header dependencies in TAO.
</LI>
<LI>Prepare the 1.0 release:
<UL>
<LI>Integrate the compiled marshalling approach.
</LI>
<LI>Verify the GPERF is working in all the relevant
platforms.
</LI>
<LI>Integrate active demux of operations?
</LI>
</UL>
</LI>
<LI>Support the Sun bootstrapping mechanism for the Naming
Service
</LI>
<LI>Add a -ORBlogfile flag so we can set the ACE_ERROR and
ACE_DEBUG output destination in all TAO applications
</LI>
<LI>Purify, purify, purify the EC
</LI>
<LI>Quantify the EC.
</LI>
<LI>Support several calls to ORB_init() on the same thread.
</LI>
<LI>Call ORB_init() in the EC threads?
[The dispatching threads for Boeing]
</LI>
<LI>Build an EC example that uses all the cool features
(multiple ORBs on each process, collocated EC and Scheduling
service, Naming, etc.)
</LI>
<LI>Extend the Concurrency Service (or create a new one) that
allow us to have global "barriers" to synchronize EC
startup/shutdown.
</LI>
<LI>Correlation in the EC has a bug [?]
Build regression tests for the EC features (filtering,
correlation, timers, etc).
</LI>
<LI>Build a COS Event Channel on top of the RTEC Event Service.
</LI>
<LI>Check what is failing in $TAO_ROOT/tests/CDR/tc.
</LI>
<LI>Debug interval computation in Linux (and NT?)
</LI>
<LI>Remove the uneeded methods from CORBA::Object
</LI>
<LI>Implement operation demuxing for clients.
</LI>
<LI>Study the CORBAlite spec and see how we could implement it
with TAO, considering dynamic and static configurations for
the full CORBA support
</LI>
<LI><P>The CORBAlite RFP is very interesting IMHO we just need to
remove features from TAO to make it a CORBAlite
implementation. The problem is how to keep the full blown
CORBA implementation also, this is an idea:
Write the TAOlite version of a class (example TypeCode):</P>
<PRE>
class TAO_CORBAlite_TypeCode {
// Just the CORBAlite methods are implemented.
};
</PRE>
<P>Derive the full blown implementation:</P>
<PRE>
class TAO_CORBA_TypeCode : public TAO_CORBAlite_TypeCode {
// Declare all the other methods.
};
</PRE>
<P>create two namespaces:</P>
<PRE>
// in tao/CORBAlite.h
class CORBA {
tyedef TAO_CORBAlite_TypeCode TypeCode;
};
// in tao/CORBAfull.h
class CORBA {
typedef TAO_CORBAfull_TypeCode TypeCode;
};
</PRE>
<P>then (at compile time) the users chooses between the CORBAlite
or CORBAfull implementations:</P>
<PRE>
// In $TAO_ROOT/tao/corba.h
#if USERS_WANTS_FAT_FREE_CORBA
#include "tao/CORBAlite.h"
#else
#include "tao/CORBAfull.h"
#endif
</PRE>
<P>We need to consider how to support even smaller profiles that
the CORBAlite RFP, like removing <any> or <fixed> support.
We also need to come out with a scheme to support
interpretive marshalling in the CORBAlite framework (where
TypeCodes don't have enough methods as to traverse them).
</P>
</LI>
<LI>Consider decompositions of the ORB that would allow
dynamically linked plug-ins, examples of things that would be
easy to implement as plugins:
<UL>
<LI>SSL support
</LI>
<LI>UNIX socket support
</LI>
</UL>
Things that would be really hard:
<UL>
<LI>Dynamically load the support for costly features, as the
ImplRepo or Location Forwarding.
</LI>
<LI>Dynamically configure POA with or without support for
holding state.
</LI>
</UL>
</LI>
<LI>Currently the IDL compiler creates an operation table that
includes all the base classes operations; this permits the
generation of efficient code that does not rely in
dynamic_cast or the _downcast() method for Servants (which
compare strings, hence it is slow).
It could be interesting to implement the alternative approach
were the class only looks its own operations and then tries
the parent. This will reduce code size, but will probably
decrease performance.
</LI>
<LI>Cleanup memory managment in some of the servers, for
instance: Naming still believes that controlling the memory
for a stub will control the servants, this is not true
anymore.
</LI>
<LI>The current scheme for the orbsvcs leaves the user without
control collocation of servants, we need to move to a scheme
similar to the one in $ACE_ROOT/netsvcs.
<BR>[STATUS] The user can control collocation, but we need a
dynamic way to do it (or an example) that exploits the Service
Configurator. We also may need to split the library.
</LI>
<LI>Cleanup the IDL structures for subscriptions, publications,
etc. (in the EC).
</LI>
<LI>Resolve the Typecode::equal dilemma: is it structural or
type equivalence? Or a mixin?
<BR>[STATUS] The correct interpretation seems to be:
<UL>
<LI>If the interface repository ID is not present and/or the
optional field name is not present then TypeCode::equal
should just test for structural equivalence.
</LI>
<LI>If the interface repository ID is present then type
structural equivalence is not enough
</LI>
<LI>The spec (2.2 or 2.3?) will add a
<CODE>equivalent</CODE> method to check for structural
equivalence modulo aliases
</LI>
</UL>
</LI>
<LI>Automate EC multicast group usage. This probably requires
some kind of server that mantains the realtion between event
type/source and the mcast groups.
</LI>
<LI>Improve configuration support in the EC, give an example of
a single threaded EC, support different dispatching
strategies, etc.
</LI>
<LI>Use the Service_Configurator to dynamically load the EC
Module_Factory thus making it really configurable.
</LI>
<LI>The current scheme for Typecode (keeping a CDR buffer with
their representation) is broken.
</LI>
<LI>We must support DynAny.
<BR>[STATUS] Jeff is working on this.
</LI>
<LI>We must support a IFR.
</LI>
<LI>Server_Request objects in TAO are magical, the _duplicate()
method returns 0 and release() does nothing.
The problem starts because Server_Request is allocated from the
stack (to speed up things), hence reference counting would be
useless. Adding a clone() method will work better, but the
Server_Request holds pointers to several positions in the CDR
stream, we could clone the CDR stream, but a normal
Server_Request does not own it.... In our opinion (Carlos and
Irfan) we need not worry about this until we find a use case for
it.
</LI>
<LI>
The current implementation of collocation is optimal for
hard-real-time
applications, but in some cases it may be desirable to follow
the normal execution path yet minize costs for collocated
calls.
An example would include an application that activates the
objects on demand.
It would be interesting to have a half-collocated stub
implementation, that will marshall the request and then
invokes the normal path on the "server" side, but without
crossing the kernel boundary. Ideally even the serialization
could be minimized or avoided.
</LI>
<LI>The IDL compiler could generate a static method to access
the interface repository ID of a class.
</LI>
</OL>
<CENTER>
<H4>Completed Tasks</H4>
</CENTER>
<UL>
<LI>Normalize the compiled marshalling interface: the IDL
compiler is going to generate a different interface than the
code I showed in the EC_Custom_Marshal example; we need to
make all the code consistent so users have easy access to it.
<BR>[DONE]
</LI>
<LI>Object references inside structures or sequences are not
decoded properly, the problem starts because the interpreter
expects a CORBA::Object_ptr, but the real type is a T_var;
virtual inheritance adds the last ingredient to the poison.
<BR>[STATUS] A possible solution is to use a T_manager_var that
has two fields a Object_ptr and a T_ptr....
<BR>[DONE] The solution was to use TAO_Object_Field_T<T>, that
behaves like the _var classes, but extends them to provide
virtual methods to _upcast() and _downcast() to and from
CORBA_Object_ptr.
Similar methods were added to sequences of objects.
</LI>
<LI>Add options to the IDL compiler to set the suffixes.
<BR>[DONE] Alex finished this.
</LI>
<LI>Support for 64bit longs in the IDL compiler
<BR>[DONE] They were supported already, but we had to test
them, I added a test to Param_Test.
</LI>
<LI>The do_static_call() and do_dynamic_call() methods should
use an array of void* (in the first case static and generated
by the IDL compiler);
this will remove the problems with g++ and probably work
faster.
<BR>[DONE]
</LI>
<LI>The IDL compiler gets confused with paths in NT, this may be
due to my changes to report errors correctly (coryan).
<BR>[STATUS] Creating a Win32 workspace to try it.
<BR>[DONE]
</LI>
<LI>The current implementation of octet sequences based on
message blocks has a few problems, it cannot marshall
chains of message blocks properly.
Notice that complete support for chains of message blocks will
complicate the sequence of octets implementation (like
operator[]) and will make others either hard or expensive
(like get_buffer ()).
<BR>[STATUS] It seems like the best tradeoff would be to
support the chain during marshalling, but disable or give no
warranties for operator[] and get_buffer().
<BR>[DONE]
</LI>
<LI>Debug Memory Pools in the EC there seem to be a problem when
sending multiple events in a row (a memory leak, limit or
corruption).
<BR>[DONE]
</LI>
<LI>Add suspend and resume operations to the PushConsumerProxy
and PushSupplierProxy interfaces, following the Notification
Service spec.
<BR>[DONE]
</LI>
<LI>Optimize connection lookup in the client side, using "hints"
from the previous lookup, or keeping smaller sets on each IIOP
profile or a combination of both.
<BR>[STATUS] Irfan is working on
this.
<BR>[DONE]
</LI>
<LI>Optimize the outgoing CDR streams by using TSS memory pools
for both the data blocks and the buffers.
<BR>[DONE] But we may consider strategizing the kind of allocator
we use (like using a free list instead of a generic
ACE_Malloc).
</LI>
<LI>Optimize Octet Sequences.
<BR>[DONE]
</LI>
<LI>Obtain results for the EC_Multiple test.
<UL>
<LI>Latency seems OK.
</LI>
<LI> Overhead: need lower priority for scavenger thread.
</LI>
</UL>
</LI>
<LI>Debug EC_Multiple.
</LI>
<LI>Your next assignment: Regenerate all methods in
_tao_collocated to avoid "inherit via dominance" warnings.
<BR>[STATUS] The IDL compiler was modified to generate a
suitable
<CODE>#pragma</CODE> that removes the warning, it reenables
the warning when leaving the file
</LI>
<LI>Remove the SOLARIS2 macro from the TAO_IDL compilation.
<BR>[DONE]
</LI>
<LI>Remove the preemption_prio message from Scheduling_Service.
</LI>
<LI>The ORB core should be able to choose the right port for us
(in other words -ORBport 0) should work.
<BR>[DONE]
</LI>
<LI>Client side optimization for Octet Sequences.
<BR>[DONE]
</LI>
<LI>Minimize memory allocation in TAO
<BR>[STATUS] Down to 3 on the client side and 4 on the server
side.
<BR>[STATUS] For oneways it is down to 0 (for the common case)
on the client side and 2 on the server side. For twoways it is
2 on both sides.
</LI>
<LI>Automate subscription and publication list generation in the
EC_Gateway.
[VERY important for Boeing]
<BR>[STATUS] Completed and debugged, but the EC is still
buggy.
</LI>
<LI>Debug EC shutdown and startup....
[Specially startup for Boeign, but shutdown is important for
Purify and Quantify]
<BR>[STATUS] Shutdown is clean and startup of threads can be
controlled by the user.
</LI>
<LI>Support a chain of Message Blocks in Output CDRs and use
writev() to write them.
<BR>[DONE]
</LI>
<LI>Memory managment in the demarshalling engine, it is not
clear that the current scheme works in all cases (like
sequences of unions of anys).
We also need to fix sequences of object references: how does
the demarshalling engine learn about the dynamic type of the
objects?
Closely related to this is the problem of memory alignment for
different architectures, we need to develop strategies for each
one (they should only be a few) and choose the right one.
<BR>[STATUS] This seems to be working for most of the cases, the
main idea is to delay demarshalling until enough information
is available, for instance, when decoding an Any just a
reference to the CDR stream is stored, decoding actually
happens when the user invokes >>= on the any (at that point
all the info is there).
</LI>
<LI>Add a new Profile type that includes the QoS info and using
for end-to-end QoS preservation.
[DEPRECATED] The IIOP 1.1 Profiles can handle that.
</LI>
<LI>Show an example of the sequence<octet> and CDR streams.
<BR>[DONE] But the example could also include the marshalling of
plain C++ types.
<BR>[DONE too]
</LI>
<LI>Test anys in the EC.
<BR>[DONE] Michael reported that they work OK on NT.
</LI>
<LI>UDP for event channel and Multicast support in the EC.
<BR>[STATUS] Manual configuration using Suppliers and Consumers is
possible, automation is under research.
</LI>
<LI>Unbind the EC and scheduling service from the Naming
Service.
<BR>[DONE] For the Event_Service and the examples.
</LI>
<LI>Optimize oneways by not allocating the memory for the return
buffers.
<BR>[DONE] Added different Invocation classes for each case.
</LI>
<LI>Fix the _non_existent call.
<BR>[DONE] The client side semantics match the new clarifications
of the C++ RTF, the server side is implemented by the IDL
compiler, though t could be a good idea to put that in the
POA.
</LI>
<LI>Simplify EC configuration, a Factory class must provide the
Dispatching, Supplier, Correlation and any other Modules that
are required.
This is the right spot to add trivial Dispatching or
Correlation Modules and to dynamically load and configure the
EC.
<BR>[DONE] A Factory class is used to create the modules, only the
default factory is implemented so far.
</LI>
<LI>Fix the ACE_Thread_Condition madness.
<BR>[DONE] We changed ACE so ACE_SYNCH_CONDITION expands to
ACE_Condition_Thread_Mutex
</LI>
<LI>Reference counting should have locks, but we should remove
all the QueryInterface madness to make that work. The policy
for references in multiple threads is: the reference count
must be >2 if that happens.
<BR>[STATUS] The QueryInterface method (all the COM stuff for that
matter) was removed...
<BR>[DONE]
</LI>
<LI>Reference counting for Typecodes is completely broken.
<BR>[DONE]
</LI>
<LI>Under g++(2.7.2) the use of multiple inheritance in IDL
triggers some compiler bug, if the IDL explictly generated the
copy constructor for the skeletons (the POA_ classes) the
problem would go away.
<BR>[DONE] Fixed, Seth is testing the fixes and will commit them
soon (Tue Jul 21 14:24:56 CDT 1998)
</LI>
<LI>The octet sequence optimization causes problems when Anys
get into the game.
<BR>[DONE] Seth reported that the problem was not real.
</LI>
<LI>The DEEP_FREE method is also broken, sometimes we need to
release the top-level memory, sometimes not.
<BR>[DONE] We always release the memory in the Any, it was failing
due to weird interactions between the Environment containing
an exception and the Any that also did.
</LI>
<LI>Improve error messages in the IDL compiler.
<BR>[DONE] At least the filename is correct now.
</LI>
<LI>Support for arrays in the IDL compiler is incomplete,
specially anonymous arrays.
<BR>[DONE] According to Andy this is properly supported by the IDL
compiler now.
</LI>
<LI>Prepare the 0.2 release:
<UL>
<LI>Execute all the tests in $TAO_ROOT/tests
</LI>
<LI>Run Param_Test (SII) and record what fails and what works.
</LI>
<LI>Run Param_test (DII) and record what fails and what works.
</LI>
<LI>Run Param_Test across Endian Borders.
</LI>
</UL>
<BR>[DONE] At last!
</LI>
<LI>Move this list to the release notes.
</LI>
</UL>
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