Release Information for The ACE ORB (TAO)
This document contains information on the following topics related to the
current release of TAO:
A complete list of all modifications to TAO is available in the
ChangeLog.
ACE Wrappers
Current status: (As of July 07, 2003.)
-
The following changes are related to improving memory management of Event
Handlers when they interact with Reactors (and Timer Queues). When a handler is
registered with the Reactor, the Reactor increments the reference count on the
handler. The Reactor also increments this reference count when making upcalls
on the handler. The reference count is decremented when an upcall completes or
when the handler is removed from the Reactor.
This mechanism is similar
to what happens between POAs and Servants and it allows for the safe deletion
of handlers. This mechanism is particularly need for multi-threaded
applications that can have multiple threads executing upcalls on a handler that
needs to be shutdown in a safe manner. The following illustrates an example of
how this mechanism works:
- When a handler is created, it reference count is one.
- After the handler is registered with the Reactor, it reference
count becomes two.
- At this point, the handler creator can let go of
the handler reference, bringing down the reference count to one.
- For each thread executing upcalls on the handler, the Reactor increments the
reference count by one. So if three threads were simultaneously making upcalls
on a handler, the reference count would be four.
- Assuming an external event (and thread) decides to close the handler. It
simply removes the handler
from the Reactor. This decreases the reference count to three.
- As each thread completes their upcall, the reference reduces.
- Once the final thread exits the upcall, the reference reaches zero, and the
handler is finally
deleted.
This mechanism ensures that the handler is not deleted
until the final upcall thread exits the handler. Reference counting on
handlers is optional and is disabled by default. To enable reference counting
on a handler, reset its reference counting policy to "ENABLED".
To
facilitate reference counting of handlers, an ACE_Event_Handler_var class was
added. This class is akin to the PortableServer::ServantBase_var class.
Similar
reference counting related changes were made to the Timer Queues so that
handlers can be used in a thread safe manner with the queues.
The Connector
implementation was completely revised to utilize the new memory management
mechanisms and remove existing concurrency bugs.
Several new examples/tests
were added: Reference_Counted_Event_Handler_Test,
MT_Reference_Counted_Event_Handler_Test, MT_Reference_Counted_Notify_Test,
Timer_Queue_Reference_Counting_Test, NonBlocking_Conn_Test,
Reactor_Registration_Test, WFMO_Reactor_Test, Timer_Cancellation_Test
Point of contact: Jeff Parsons
Current status: (As of November 19, 2003.)
-
Generated code closely follows the C++ Mapping specified in the latest
C++ mapping for CORBA 2.3 (Document ptc/98-09-03).
-
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.
-
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.
-
We are now able to handle recursive types. We are also able to
generate optimized typecodes.
-
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.
-
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.
-
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.
-
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.
-
For platforms that support namespaces, we now allow reopening modules.
-
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 problem with compiled marshaling.
-
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.
-
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
IDL compiler options for details.
-
Verified support for the "long long" and "unsigned long long" datatypes.
On platforms that do not support 64 bit longs we provided partial
emulation through ACE_U_LongLong.
-
Perfect Hashed Operation Lookup Strategy has been added to the
IDL Compiler. -P flag to
tao_idl
enables the perfect
hased lookup strategy. This strategy uses GPERF, 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.
-
The <<= and >>= operators for user-defined types are now generated.
-
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
typedef
sequence<char>CharSeq;
, 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.
-
Support for the "native" keyword added.
-
The problem of incorrect code generation for typedefs defined in an imported
file is resolved.
-
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.
-
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.
-
Include files are handled properly. So are the definitions used inside
the include files that are used in the currently parsed files.
-
Generates C++ stubs and skeletons that use TAO's interpretive
IIOP protocol engine.
-
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
-Wp,export_macro=MACRO_NAME-Wp,export_include=INCLUDE_NAME
.
-
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.
-
The IDL Compiler generates templates for servant implementations. The options
are
-GI [ h | s | b | e | c ]
-
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).
-
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
_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.
-
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.
-
The IDL compiler has support for valuetypes (see release notes
for valuetypes for details).
-
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.
-
Scoping and name resolution rules have changed in CORBA with version
2.3. The IDL compiler now conforms to these new rules.
-
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.
-
New command line option
-So
added to suppress generation of
ostream
operators for exceptions.
-
New command line option
-Sc
added to suppress generation of tie
classes
and *S_T.*
files. The default is still to generate them.
-
IDL compiler now handles escaped identifiers (CORBA 2.3.1). An identifier
appearing in an IDL file with a leading underscore will appear in
generated code without the underscore. This enables the use of identifiers
in generated code identical to IDL keywords, as specified in CORBA 2.3.1.
If the resulting identifier matches a C++ keyword, "_cxx_"
will be prepended in generated code as before.
-
The
-St
option to suppress generation of typecodes now also
suppresses the
generation of the Any insertion and extraction operators. The extraction
operators require the associated typecode, so the generated code for those
operators would not compile when the -St option was used.
-
Option
-Ge 2
added which generates 'throw' instead of
ACE_THROW_SPEC
, ACE_THROW
,
and ACE_RETHROW
. Since the expansion of
ACE_THROW_RETURN
is platform-dependent,
it was left as is. Same for TAO_INTERCEPTOR_THROW
, since it
sometimes
expands to ACE_THROW_RETURN
. Of course
ACE_HAS_EXCEPTIONS
must be defined for
this option to work.
-
Removed generation of ostream operators for user exceptions, along with the
command line option to suppress this generation. The ostream operator
defined in the base class
CORBA::Exception
works fine and produces
the same
output.
-
The TAO IDL compiler is no longer monolithic. It is composed of a top-level
executable, a front end library and a back end library. This will enable
different back ends to be plugged in for code generation in different
languages, and for IfR administration. Different back ends may require
a few changes to the executable (described below), but the front end
library can remain unchanged. The chain of dependencies is as follows:
FE : ACE
BE : FE
EXE : FE, BE
Executing the Makefile (or the TAO_IDL Compiler project in the MSVC 'tao_idl'
workspace) will build whatever is required in the proper order, as before.
Back end files, classes and functions required by the executable are as
follows:
be.h - file containing #includes of the major BE file headers.
TAO_Codegen - class, holds output stream references for the various generated
files.
TAO_CODEGEN - ACE_Singleton typedef of the above class.
tao_cg - pointer to instance of TAO_CODEGEN.
be_generator - class, inherits from AST_Generator in FE and generates AST
nodes.
void BE_produce (void) - global function, starts AST traversal for code
generation.
BE_GlobalData - class, holds default/command line arg settings specific to BE.
be_global - pointer to instance of above class.
All the code in the executable that may need to be modified for different back
ends in contained in the file drv_args.cpp. Code in this file processes the
command line arguments, outputs a usage message, and performs other
miscellaneous
BE initialization.
-
The IDL compiler can how handle interfaces forward declared in one IDL
file and defined in another. It will handle interfaces that are
mutually dependent across two IDL files, as long as code generated from both
IDL
files is included in the same C++ build.
-
Generation of template tie class declarations has been moved from the *S.h file
to the
*S_T.h file. The new SunCC 5.2 compiler does not require that template source
code
be included in the header file, but it does require that template declarations
and
implementations be in the same 'compilation unit' that is, the same
header/source
file combination. Generated ifdef guards prevent the compilation of tie class
code if the target platform does not support namespaces. For such platforms,
TAO
maps the IDL 'module' keyword to a class instead of to 'namespace', and C++
does
not allow template class declarations to occur inside another class.
-
IDL compiler can now process multiple IDL files per execution, on all
platforms.
A separate process is spawned for each file. IDL files and command line options
may appear in any order on the command line. Any option not starting with '-'
will
be treated as a filename.
-
Support for value types has been expanded to include forward declared value
types,
sequences of value types, and factory methods. Also, work to support Anys and
type
codes for value types is in progress.
-
Support for #pragma prefix has been revamped and improved to be compliant
(the prefix is now cleared when leaving the scope or the included IDL file
where it
was defined), and support for #pragma version and #pragma ID has been added.
-
Support for forward declared structs and unions has been added. In compliance
with
CORBA 2.6, such forward declarations must be fully defined in the same
compilation
unit, and may be used only in sequence declarations, which in turn may be used
in
the declaration of recursive structs and unions. Use of a forward declared
struct
or union as an aggregate type member or as an operation parameter will generat
an error message.
-
Support for enum constants has been added.
-
The IDL compiler can now handle concatenation of string literals, for example
const string foo = "hel" "lo " "the" "re";
-
Support for abstract interfaces has been added.
-
Support for valuetypes has been expanded.
- Forward declared valuetypes not defined in the same compilation unit
- Type codes for valuetypes
- Generation of Any insertion/extraction operators
- Abstract valuetypes
- Valuetype members of all IDL aggregate types
- Interface supports list
-
Support for the CCM extensions to IDL, which first appeared in CORBA 3.0 is
complete, with the exception of support for the 'import' keyword.
-
Generated code for constants defined in a module is now inlined (value is
assigned in the header file) by default, enabling such constants to be
referenced by name as array bounds, etc. either in subsequent generated
code or in application code. However, this inlining causes a problem with
some compilers when using pre-compiled headers, so the option -Guc has
been added to turn it off. NOTE: Constants defined at global scope (always
inlined) and constants defined inside an interface or a valuetype (never
inlined) are not affected by the option.
-
Generation of explicit template instantiations is now off by default. The
option -GT turns it on. If turned on, the generated explicit instantiations
are guarded by the same #ifdef preprocessor directives as before.
-
The mechanism for processing multiple IDL files in a single execution has
changed. Instead of spawning a separate process for each IDL file, the
IDL compiler now processes the files sequentially in a single process.
Note that, for each file, execution of the preprocessor spawns a new
process, as it always has.
-
Added command line option -Sm to suppress the action of CCM preprocessing
visitor, which is by default launched before the C++ generating visitors,
in order to add CCM equivalent IDL to the AST. There is a new tool in CIAO
which converts IDL files by replacing IDL3 constructs with equivalent IDL2
constructs, and if the IDL compiler is run on these files, we do not want
the CCM preprocessing to occur.
-
Changed the behavior of the -o option to create the specified directory
if it does not already exist. Only one level of directory can be created
with this option (any path prefix included must already exist).
If the specified directory already exists, no action is taken.
-
As part of the subsetting in TAO of Anys and TypeCodes, the generation of
these things in the IDL compiler has been further decoupled from other
code generation. Now the -GA option generates not only a *A.cpp file but
also a *A.h file, and in addition, the -oA option will create these files
in a directory different from that where the other generated files are
created.
-
Generation of explicit template instantiations has been completely
removed, it is no longer available via the command line option -GT.
-
Generation of Any insertion/extracion operators for local interfaces
has been enabled by default. An additional command line option -Sal
has also been added to suppress the generation of Any operators for
local interfaces only.
-
Added new command line option -oS to specify output directory for
all skeleton files, including TIE class files, if generated. Overrides
-o option value, if any.
Known Issues:
-
With Microsoft Visual C++, verison 6.0 and earlier, a problem has been
discovered
when the IDL compiler is built using the Release version of the MSVC project.
For
the Release version, the Optimizations box in the C/C++ tab has 'Maximize
Speed'
selected. This setting turned out to cause a problem when
const char *foo = ......
occurs in the source code. The variable foo is sometimes not allocated or
assigned
properly, and if foo is part of generated code, it will then display as garbage
or
as an empty string (or substring). Two workarounds have been found. One is to
change the declaration of foo to be
static const char *foo = ....
and this has been done in all cases we could find in the IDL compiler source
code.
Another way to avoid the problem is to change the Release project Optimization
setting to 'Minimize Size'. Reportedly the problem has been fixed in MSVC
version
7.0.
Future work:
ORB & ORB Core
Point of contact: Balchandran Natarajan
Last Update: $Date: 2006-08-21 16:13:08 $
Current status:
- We are compliant with OMG's CORBA 2.6 specification.
Known issues:
-
TAO's support for wstring as per GIOP 1.2 rules are not
perfect. There have been reported interoperability
problems.
-
The multi-profile parsing code in TAO hasnt been tested well
and we have been able to identify some issues with it. The
details are documented in our bug
tracking
system under id's
1237,
1238and1239
-
Applications using the distributed callback paradigm could
see crashes if they use multiple nested upcalls. The nested
upcalls sets of a stack growth and crashes when it runs out of
stack space. This happens when an upcall as a part of the
request leads to another request. The client thread waiting for
the reply in the reactor could in turn process yet another
request to build up the stack. The unbounded growth on the stack
leads to crash failures.
-
Support new concurrency models, e.g., Thread-per-Request,
etc..
-
Improvement to connection cache on the acceptor side so that
it will purge old connections when there are no more slots or
sockets are available. The connection cache does good job of
purging things on the connector side
-
Prevent unbounded stack growth that leads to a failure in
situations explained in known issues.
-
Performance bottlenecks:
-
Need to identify performance bottlenecks. Looks like
TAO has slowed down a bit over the past two betas. Need to
identify the bottlenecks before improving the performance.
-
Its a known fact that thread-per-connection is faster
than the reactive model, even for single threaded cases. Need
to identify portions of the reactor that slows down things and
fix them or create a fast path in the ORB just using plain
vanilla select for the server.
-
In the output data path, the CDR creates the message
block and all other associted things on TSS. If we could
change the CDR to first create them on the stack and then move
the data to TSS we could achieve better performance for small
messages.
-
Features:
-
Implement DP-CORBA specification
-
Implement TII specification.
-
Implemented a connection timeout policy in the ORB. This
is useful for applications to set a timeout value associated
with connection establishment. The name of the policy is
TAO::CONNECTION_TIMEOUT_POLICY_TYPE
and is
proprietary to TAO. It comes as a prt of the TAO_Messaging
library. Please see
$TAO_ROOT/tests/Connection_Timeout
for an example
of how to use this feature.
- Implemented non-blocking connects with three different strategies for
connection
establishment. The details of the strategies and the related documentation
can be found here.
-
Deprecated the option -ORBConnectionCachingStrategy. The
option -ORBConnectionPurgingStrategy fills in the role of the
deprecated strategy.
-
Deprecated the option -ORBResources.
-
The connectors have been moved to the lanes.
-
Fixed stack recursion problems that occurs, when a thread
flushing a reply by entering the reactor starts processing
incoming requests.
-
Fixed connection handling and connection closing problems,
when a write call to a remote host fails.
-
Moved the allocators used for allocating memory for the
incoming data path to the lanes. Only allocators on the
incoming data path are moved into the lanes. Allocators on the
outgoing data path are still on a per-orb basis. Since the
outgoing data path uses memory from the TSS, moving them to
the lanes is not necessary.
-
Added an option, -ORBSingleReadOptimization that allows
users to turn on or turn off the single read
optimization. This is useful for RTCORBA server threads to
avoid priority inversions. Buffering messages and sending
notifications to the reactor, that does not know or honour
priority could lead to priority inversions.
-
Several changes were made to utilize the new memory management mechanisms
of Event Handlers in TAO. Previously, both the connection handlers and
the transports had their own reference counting mechanism and
independent lifetimes. The reference counting was inadequate
since it was not originated at the Reactor and the independent
lifetimes unnecessarily completed protocol specific transport
code.
The changes couple the lifetime of the connection handler with
that of the transport and utilizes the reference count in the
base ACE_Event_Handler class. This allowed us to remove several
hacks throughout TAO code which were designed to prevent (or
delay) crashes. Several extra checks and unnecessary locks were
also removed.
All of the following protocols were updated: DIOP, IIOP,
SCIOP, SHMIOP, SSLIOP, UIOP, UIPMC.
- Support for the ORB methods create_value_tc, create_component_tc,
create_event_tc, create_home_tc and create_recursive_tc added.
Point of contact: Ossama Othman
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.
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.
There will be several stages of the development process: (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:
-
Basic pluggable transport protocols framework: 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.
The common interfaces have been defined in the new abstract classes
that form the core of TAO's pluggable protocol framework, e.g.,
TAO_Connector
,
TAO_Acceptor
,
TAO_Profile
and TAO_Transport
. Two new mechanisms for keeping track of
supported
transport protocols are the
TAO_Connector_Registry
and
TAO_Acceptor_Registry
,
which are essentially Abstract Factories that produce the right types of
connector, acceptors, and transports.
-
Multiple Profile - 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.
-
Example Transport protocols - Aside from IIOP, five additional
transport protocols are distributed with TAO:
- UIOP: GIOP over local IPC (UNIX domain sockets)
- SHMIOP: GIOP over shared memory
- SSLIOP: IIOP over SSL (Secure Socket Layer)
- DIOP: GIOP over UDP/IP
- MIOP: GIOP over unreliable multicast
Other interesting transport protocols could be for ATM, Buses (VME or
PCI), TP4, and GSMP. TAO users have also created their own
pluggable transport protocols, such as a ScramNet pluggable protocol.
-
Pluggable ORB protocols - 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.
Current Status:
-
The basic framework to support pluggable transport protocols has been
completed. The standard TAO regression tests
Latency
,
MT_Cubit
, Multiple_Inheritance
, CDR
and
EC_Throughput
can be used to verify performance using the new
framework.
-
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
-ORBEndpoint
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:
iiop://foo.bar.com:0
), this format can be
extended to support different protocols.
-
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.
-
Added support for multiple Connectors in the ORB, the ORB
finds the correct connector based on the tag for the
profile.
-
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.
-
Enabled the UIOP protocol. This protocol uses local IPC
(aka UNIX domain sockets) as the transport mechanism. The
protocol is loaded by default.
-
Enabled the SHMIOP protocol. This protocol uses shared
memory as the transport mechanism. The protocol is loaded
by default.
-
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.
No changes were made to the core TAO sources to provide
to this SSL support, nor does TAO contain any security
related hooks. TAO's SSLIOP implementation is
completely self-contained. This ensures that the core
TAO sources remains free of export restrictions.
-
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 is loaded.
-
The service configurator is now used to load protocol factories.
-
Support for the
-ORBHost
and
-ORBPort
has been removed. The new
-ORBEndpoint
option supersedes them, and provides the same
functionality in a protocol-neutral way. If the
deprecated options are used, the ORB exits with a
CORBA::BAD_PARAM
exception, indicating an
unknown -ORB
option.
-
The
-ORBPreconnect
ORB option has been
deprecated in favor of the standard
validate_connection
run-time feature.
Support for this option will be removed from future
releases.
-
The URL style object reference format has been updated to
conform with the format that
corbaloc
uses. The BNF specification for corbaloc
is:
<corbaloc> =
"corbaloc:/"[<obj_addr_list>]["/"<key_string>]
<obj_addr_list>= [<obj_addr> ","]* <obj_addr>
<obj_addr>= <prot_addr> | <future_prot_addr>
<prot_addr>= <rir_prot_addr> | <iiop_prot_addr>
<rir_prot_addr>= <rir_prot_token>":"
<iiop_prot_addr>= <iiop_id><iiop_addr>
<iiop_id>= ":" | <iiop_prot_token>":"
<iiop_prot_token> = "iiop"
<iiop_add> = [<version> <host> [":" <port>]]
<host> = DNS-style Host Name | ip_address
<version> = <major> "." <minor> "@" | empty_string
<port> = number
<major> = number
<minor> = number
<future_prot_addr> = <future_prot_id><future_prot_addr>
<future_prot_id> = <future_prot_token>":"
<future_prot_token> = possible examples: "atm" | "dce"
<future_prot_addr> = protocol specific address
<key_string> = <string> | empty_string
The uiop
URL style object references syntax
is:
<uioploc> = "uioploc://"[<addr_list>]["|"<key_string>]
<addr_list>= [<address> ","]* <address>
<address> = [<version> <rendezvous point>]
<rendezvous point> = Valid Filesystem Path
<version> = <major> "." <minor> "@" | empty_string
<major> = number
<minor> = number
<key_string> = <string> | empty_string
Note that the key string delimiter for uiop
is a vertical bar `|
' (the command line
"pipe" symbol) not a forward slash
`/
'. 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. The new corbaloc:uiop
URL
format may also be used.
It should be noted that these formats have been superseded
by the new corbaloc
Interoperable Naming Service
support.
-
The rendezvous point for
uiop
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:
-
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 at least
100 characters, including the null terminator.
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.
-
Avoid using relative paths in your UIOP endpoints.
If possible, use absolute paths
instead. Imagine that the server is given an
endpoint to create using
-ORBEndpoint
uiop://foobar
. A local IPC rendezvous
point called foobar
will be created
in the current working directory. If the client
is not started in the directory where the
foobar
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.
It is up to the user to make sure that a given UIOP
endpoint is accessible by both the server and
the client.
-
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
uiop:///tmp/foo
is specified as the
server endpoint and uiop://foo
as a
preconnect for a client in /tmp
, 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. /tmp/foo
and foo
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.
The -ORBEndpoint
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.
-
Added documentation that describes how to implement
pluggable transport protocols for TAO. The document is
available
here.
-
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.
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.
Known Issues:
Critical Work:
Future Work:
-
Complete support for multiple ORB messaging protocols.
-
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.
Point of contact: Irfan Pyarali
The POA associates servants with the ORB and demultiplexes incoming
requests to servants.
Current Status:
-
TAO supports the POA spec. This section will carry updates as available.
Known issues:
Future work:
Recently completed work:
-
ORB::shutdown now properly deactives all the POA
Managers.
-
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
ACTIVE
, is the request dispatched to the
servant. Otherwise, the request is rejected. Since POA Managers start
off in HOLDING
state, make sure to
activate()
them before falling into the event loop.
-
TAO's POA now properly supports both the threading policies:
SINGLE_THREAD_MODEL and ORB_CTRL_MODEL.
-
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.
-
Before 1.4.6 TAO 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. ftp://ftp.omg.org/pub/docs/orbos/98-07-12.pdf
contains the relevant text. Check here
on some hints to avoid trouble. From TAO 1.4.6 reference counting is always
enabled for servants and RefCountServantBase is a noop struct you don't
need anymore.
-
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.
-
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.
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.
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.
-
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.
-
Timestamps in persistent IORs were not required and have been
removed.
-
POA exceptions are not not system exceptions and have been
removed from the list of system exceptions.
-
Vastly improved the ability of the POA to deal with user
exceptions, memory allocation failures, and constructor failures.
-
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.
-
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.
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.
-
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.
-
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.
-
We have support for reactivating servants with system generated ids.
-
The TAO specific synchronization POA policy has been removed.
-
New examples have been added to show how servants can be
dynamically loaded from DLLs on demand.
-
Support for collocation should be much better now because the POA
can tell if we created the object reference.
-
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 exactly 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.
Objects-by-Value
Points of contact: Jeff Parsons
Boris Kolpackov
George Edwards
Last Update: 2004/08/24
Objects-by-Value (OBV) describes the new type, valuetype
, introduced in CORBA 2.3
(Core:
formal/02-12-06.pdf; Mapping to C++:
formal/03-06-03.pdf).
The original TAO implementation was contributed by
Torsten Kuepper, and has subsequently been enhanced and corrected by Jeff Parsons and George Edwards.
Valuetype
s are similar to IDL struct
s extended with
these features:
Encapsulate both state information and operations in an implementation that is guaranteed to be local.
Can be declared abstract
, in which case no state members are defined.
Can inherit from a single concrete valuetype
and multiple abstract valuetype
s.
Can support a single concrete interface
, allowing them to be manipulated as either a valuetype or an object reference.
Can support multiple abstract interface
s, allowing them to be substituted for those interfaces in operation invocations.
Can hold references to other valuetype
s, with the
possibility of NULL references or shared (aliased) references.
Valuetypes have the following uses:
Implement abstract datatypes (ADTs) that can be copied to another process.
Represent eventtype
s in the Event Service.
Ensure operations are executed locally for increased performance.
Current status:
Valuetype
s work only in conjunction with
compiled marshaling (-Gc
, currently default for
tao_idl
).
No support for sharing (aliasing).
No support for valuebox
es
-
No support for valuetype
s with cyclic references.
No support for fragmentation (chunking) of the marshalled
valuetype
object. Hence no support for truncation or
custom marshalling.
The marshal engine accesses the state members directly and
does not utilize the accessor/modifier functions. This is different
from the CORBA specs and needs to be changed. But the
optimized mode (-Wb,obv_opt_accessor
) should be
unaffected by that.
The map of valuetype
factories needs some
revision to provide proper locking. Currently the
registration of factories is best completed before
unmarshalling valuetype
s.
There is one map of factories for the whole process. This
will once be changed to conform to the specs, which
suggests one per ORB.
Points of contact: Marina
Spivak and Vishal Kachroo
OMG defined CORBA Naming Service (spec here)
to provide a basic service location mechanism for CORBA systems.
CosNaming manages a hierarchy of name-to-object-reference mappings.
Anything, but typically the server process hosting an object, may bind
an object reference with a name in the Naming Service by providing the
name and object reference. Interested parties (typically clients) can
then use the Naming Service to resolve a name to an object reference.
More recently, CORBA Naming Service was subsumed/extended by the CORBA
Interoperable Naming Service, a.k.a. INS. INS
inherits all the functionality from the original Naming Service
specification in addition to addressing some its shortcomings. In
particular, INS defines a standard way for clients and servers to
locate the Naming Service itself. It also allows the ORB to be
administratively configured for bootstrapping to services not set up
with the orb at install time. This page
provides a brief description of additional features INS provides, and
how they are implemented in TAO.
Current status (as of 18 May 2001):
-
The Naming Service now does not do listen for multicast
discovery as the default. Use
-m1
option to turn it on.
Recent work:
-
Changed default for multicast discovery to
Features:
-
Added support for Persistence (using memory-mapped files). Persistence
feature is optional, and is controlled by the command line argument.
-
Updated the implementation of the Naming Service to use new ACE
exception macros.
-
Added support for the InterOperable Naming Service, which enables the
ORB to support IORs in user-friendly
corbaloc
format.
These features allow the ORB to be configured to return arbitrary object
references from CORBA::ORB::resolve_initial_references
for non-locality-constrained objects. Two options -ORBInitRef and
-ORBDefaultInitRef have been added to the orb for bootstrapping to
arbitrary services.
-
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 :
-ORBInitRef
-ORBDefaultInitRef
- Multicast discovery
-
Added a test for the InterOperable Naming Service that works in
conjunction with the current TAO examples.
-
Implementation of the CORBA INS spec is completed. The
following features are now supported:
- corbaname format
- NamingServiceExt interface
Future work:
-
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.
-
Support for the Naming Service to handle the IIOP LocateRequest
messages and respond with LocateReply messages with a
LOCATION_FORWARD/OBJECT_NOT_EXIST
status.
Point of contact: Ossama Othman
Additional information is available
here.
Security Service Overview
TAO's current Security Service support implements the core functionality of the
CORBA Security Service v1.8.
In particular, it implements the most of the CORBA
SecurityLevel1 API, in addition to some of
SecurityLevel2. Of the transport protocols described in the above
specification, only SSLIOP is supported.Documentation for TAO's SSLIOP
pluggable protocol is available
here.
The 1.8 specification defines the Common Secure Interoperability version 1
(CSIv1) protocol that is currently implemented in TAO.
There are basically two ways to use security in TAO:
-
Use TAO's SSLIOP pluggable transport in TAO alone. This allows one to secure
application requests without modifying the application code. This is the
easiest approach but is also the least flexible.
-
Use the Security Service API implemented by TAO in conjunction with TAO's
SSLIOP pluggable transport. This provides the benefits of secured application
requests with the flexibility of disabling security in some requests, if so
desired. This approach also allows one to choose at run-time which X.509
certificates will be associated with application requests, as opposed to
setting configuring only one SSL certificate at application start-up-time.
These things are basically configured using the SecurityLevel2 defined
policies:
SecurityLevel2::QOPPolicy
SecurityLevel2::EstablishTrustPolicy
SecurityLevel3::ContextEstablishmentPolicy
Implemented Features:
IIOP over SSL integration via TAO's
SSLIOP
pluggable protocol.
- Added an
SSLIOP::Current
implementation that can be used to
obtain the SSL session state for the current execution context. This is useful
for obtaining the SSL peer certificate chain associated with the current
request, for example.
- TAO's SSLIOP pluggable protocol now registers a secure invocation server
request interceptor. It enforces secure invocation by rejecting requests coming
in on the insecure port if the server is configured to do so (default
behavior).
- Implemented
SecurityLevel1
for the SSLIOP security mechanism.
- The
SecurityLevel2::QOPPolicy
policy has been implemented. This
policy is used to set the desired invocation Quality-of-Protection (QoP). It
can be created using ORB::create_policy()
, and used in conjunction
with the standard policy manipulation CORBA features (e.g. PolicyManager
,
PolicyCurrent
), meaning that this policy can be set on a per-ORB,
per-thread or per-object basis.
This policy makes it possible to, for example, make both secure
and insecure invocations within the same client process.
- TAO's SSLIOP pluggable protocol implementation is now thread-safe.
- The
SecurityLevel2::EstablishTrustPolicy
policy
has been implemented. This policy is used to set the desired invocation
level of establishment of trust. It can be created using ORB::create_policy()
,
and used in conjunction with the standard policy manipulation CORBA
features (e.g. PolicyManager
, PolicyCurrent
),
meaning that this policy can be set on a per-ORB, per-thread or
per-object basis.
This policy makes it possible to, for example, make authenticated
and non-authenticated invocations within the same client process.
- Implemented
SecurityLevel2::PrincipalAuthenticator
support for SSLIOP. In particular, a SSLIOP-specific SecurityReplaceable::Vault
implementation is now available.
- Initial SSLIOP-specific
Credentials
implementation
is complete.
Current Status:
-
Began implementation of the interfaces in the
SecurityReplaceable IDL module. They provide the
ability to replace key security components in the ORB with
another implementation with ease. Thus, the security
components in the ORB become highly extensible.
-
Development of core SecurityLevel2 interfaces such as
Credentials, SecurityManager,
and PrincipalAuthenticator has been halted in favor
of Adiron's SecurityLevel3 interfaces
-
Advanced CSIv2 features, such as identity assertion, are
currently under testing.
Schedule:
Point of contact: Balachandran Natarajan
Current Status:
TAO supports the ORB level requirements to achieve Fault Tolerance for
CORBA Objects. The details of the ORB level support is described in the
FT chapter of the
CORBA 3.0 specification. Specifically TAO implements the sections
23.2.2, 23.2.3, 23.2.6 thru 23.2.8 of the document.
Future Work:
- Implement 23.2.9 of the document.
Point of contact: Ossama Othman
Current Status:
TAO's
Load Balancer currently implements the latest revision of the OMG
Load Balancing and Monitoring specification.
It provides many features and advantages over the previous non-standards
based prototype. Those features and advantages include:
- Multiple object group support
- Extensible load balancing strategies through IDL interfaces
- Extensible load monitoring
- Both "push" and "pull" style monitoring are supported
- Support for infrastructure and application controlled object group
membership
- Improved server-side transparency
The current Load Balancing and Monitoring specification defines
three built-in load balancing strategies. They are:
RoundRobin
(non-adaptive)
Random
(non-adaptive)
LeastLoaded
(adaptive)
TAO implements all of these and the following load balancing strategies.
-
LoadAverage (adaptive)
-
LoadMinimum (adaptive)
Known Issues:
-
CPU load monitoring is not working in Windows.
Recent Work
- Implemented LoadAverage load balancing strategy.
- Implemented LoadMinimum load balancing strategy.
- Implemented a CPU load utilization monitor in Linux.
Future Work:
-
Implement cooperative (distributed) load balancing support
-
Integrate multicast support
-
Implement a middleware load balancing performance measurement toolkit
-
Implement self adaptive load balancing strategies
Point of contact: Pradeep Gore
The COS compliant Event Service implements the Event Service Specification.
This implementation is based on the Real Time Event service.
Features in this release:
- There is a new implementation of the COS Event Service available.
This new implementation supports both the Push and Pull styles for event
communication, and it does not require the Real-time Event Service to work.
- A new testsuite for the COS Event Service has been started, they are
available at: $TAO_ROOT/orbsvcs/tests/CosEvent/
- A new example for the COS Event Service is provided in
$TAO_ROOT/orbsvcs/examples/CosEC/Simple/
- Both "push" and "pull" style monitoring are supported
- SA new binary to run the native COS Event Service was added, it is
compiled in: $TAO_ROOT/orbsvcs/CosEvent_Service/CosEvent_Service_Native
- A simple test ($TAO_ROOT/orbsvcs/tests/CosEC_Basic) demonstrates how
to create and use the event channel.
- Event Service ($TAO_ROOT/orbsvcs/CosEvent_Service)The Event Service
creates a COS compliant event channel and registers it with the naming
service with the default name "CosEventChannel". Please read the associated
README for more details.
- CosEC_Multiple: ($TAO_ROOT/orbsvcs/tests/CosEC_Multiple): This test
demonstrates how multiple CosEC's connect to one RtEC and how multiple
consumers and producers exchange events in this configuration.
Known bugs:
- CosEC_Multiple: ($TAO_ROOT/orbsvcs/tests/CosEC_Multiple): 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.
Multicast InterORB Protocol (MIOP)
Point of contact: Frank Hunleth
Current Status:
The final MIOP
specification has recently been adopted by the OMG. TAO's MIOP support
(located in $TAO_ROOT/orbsvcs/orbsvcs/PortableGroup) enables servants
to receive requests sent to multicast addresses. This is performed by
creating a GroupId that identifies the multicast group and associating
it with one or more servants. Additionally, the Unreliable IP Multicast
(UIPMC) pluggable protocol is used to send and receive multicast requests.
Multicast endpoints can be created dynamically at runtime.
Known Issues:
- MIOP packet reassembly is not performed yet, so the maximum request
size is limited to about 5-6kb depending on the platform.
Recent Work:
- Initial check in of MIOP implementation.
Future Work:
- Allow group references to be disassociated when no longer needed.
- Implement MIOP packet reassembly.
- Implement a Multicast Group Manager (MGM).
- Implement a Multicast Gateway (MG).
Point of contact: Nagarajan Surendran
Current Status:
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.
The various tests in the tests/POA test the different features of the
Portable Object Adapter interface like Explicit Activation, On Demand
Activation, etc.
MT_Cubit Current status:
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:
- Server. 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.
- Client. 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.
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.
Future work:
- Study the impacts of scheduling & concurrency strategies on performance.
- Evolve into a testbed for discovering sources of performance non-determinism
& priority inversion.
Pluggable Current status:
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.
Future work:
- Add options to redirect the output to a file.
- Script or otherwise automate the piping of the output to a spreadsheet.
Points of contact: Nanbor Wang
and Irfan Pyrarli
Recently Completed Work:
- Added special declaration to OS.h for
inet_ntoa
and
other functions because VxWorks doesn't provide full argument prototypes
for these library functions.
- 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
connect()
fails with EWOULDBLOCK
,
morph the error to -1 and clean up the request.
- 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.
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.
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.
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.
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.
Also added ~ACE_Cached_Connect_Strategy that will cleanup up the
connection cache.
Future work:
- None currently scheduled.
Points of contact: Michael Kircher
and Chris Gill.
This discussion focuses on the following goals:
- Have a DOVE Browser running using Java Beans as vizualization components.
- Have the Event Channel as DOVE Agent running with an Event Consumer
in the DOVE Browser.
- 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.
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.
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.
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.
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.
Object Diagrams
are available about this new concept.
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:
- Enhancing MIB functionality
- Monitoring the AV Streaming Service
For more information on the DOVE demo, please refer to:
$TAO_ROOT/orbsvcs/tests/Simulator/README.
Point of contact: Irfan Pyarali,
Michael Kircher.
For more information see Location forwarding
Point of contact: Irfan Pyarali,
Michael Kircher.
For more information see Leader-follower
model
Point of contact: Irfan Pyarali,
Michael Kircher.
For more information see Locate request
Points of contact: Alexander Arulanthu,
Michael Kircher and
Carlos O'Ryan
Status:
We've implemented the callback model of the
CORBA
Messaging specification. To activate the AMI for TAO and the TAO IDL
compiler define TAO_HAS_CORBA_MESSAGING
, TAO_HAS_AMI_CALLBACK
in your config.h file. The TAO IDL compiler can generate the AMI "callback"
stubs, ReplyHandler und reply stubs using the -GC
switch.
For an example see $TAO_ROOT/tests/AMI
and $TAO_ROOT/examples/AMI
.
Finished work:
- 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.
- Support for exceptions
- Support for attributes
- Support for buffering and batching AMI calls.
- Support for deferred synchronous invocations.
Jeff
Parsons
- Support for timeouts in combination with AMI calls, response handler
gets CORBA::TIMEOUT exception on timeout
-
The AMI support in TAO 1.4.7 is as described in the 2.6 spec, from 1.4.8 we support
by default the 3.0.3 described mapping.
Future Work:
- Implementation of the poller model.
Point of contact: Ossama Othman.
For more information see Portable Interceptors
Point of contact: Nanbor Wang.
Local interfaces are first defined in the CORBA Component Model
specification.
For more information on using the local interfaces, please refers to Section
11.1.1 to 11.1.4 of the spec
and our short guideline on implementing
local objects.
Future Work (aka. known problems):
- Supposedly, any constructed types that contains local types become
local automatically. TAO_IDL currently doesn't handle the array type
very well if one is defined outside the scope of a local interface.
- Need to test local object support more systematically and comprehensively.
(Does TAO throw a MARSHAL exception when trying to marshal a local type?)