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Common Object Request Broker Architecture — Open Issues

  • Acronym: CORBA
  • Issues Count: 8
  • Description: Issues not resolved
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Issues Descriptions

MAIN_THREAD_MODEL questions

  • Legacy Issue Number: 4155
  • Status: open  
  • Source: Borland Software Corporation ( Andy Cutright)
  • Summary:

    i have a few questions about the POA ThreadPolicy type
    MAIN_THREAD_MODEL.

    first, the 2.4.1 spec (00-11-03), sec 4.2.3.2 , 'perform_work' states,
    "If called by the main thread, this operation performs an
    implementation-defined unit of work; otherwise it does nothing."

    how is a distinguished main thread supposed to be reliably determined?
    i'm not sure we really need to define this. i'd think what we're trying
    to say is that the thread that calls perform_work() is the thread that
    will be used to do the work, and it is up to the application to make
    sure this happens. in section 4.2.3.3, the spec states,
    "For maximum portability an application should call either run or
    perform_work on its main thread."

    to me it seems the intent is to let the application determine what the
    'main thread' is.

    second, what happens if an application calls both run & perform_work?
    and what happens if the application calls run from multiple threads? it
    isn't really clear what the difference in request handling with regard
    to the thread used is between run() & perform_work().

    right now the spec seems to imply through the use of the message loop
    example in section 4.2.3.2 that perform_work is really intended to be
    used to handle situations where a single thread must be used for all
    application activity. now add to that the note on pg 11-12 about using
    the main thread model:
    "Note - Not all environments have such a special requirement. If
    not, while requests will be processessed sequentially, they may not all
    be processed on the same thread."

    my interpretation is that ORB::run would be used in cases where you
    simply want the POAs to be accessed sequentially, but the application
    doesn't care about which thread the implementation uses, but you would
    need to call perform_work to specifically hand the application defined
    main thread to process requests.

    my suggestion (finally ;^) is that we should state perform_work should
    be called, on whichever thread the application likes, if it wants to
    hand a specific thread to the ORB to do work. otherwise, calling
    ORB::run from any thread simply means the implementation is free to
    handle requests for servants associated with main thread model POAs on
    whatever thread the implementation may choose (including a new one), in
    keeping
    with the requirement that the requests be processed on each POA's
    servants sequentially..

    one more question: does it make sense to state that a callback type of
    architecture won't work when using this threading model?

  • Reported: CORBA 2.4.1 — Wed, 17 Jan 2001 05:00 GMT
  • Updated: Mon, 18 Feb 2019 00:03 GMT

BiDir GIOP Policy Clarification

  • Legacy Issue Number: 4115
  • Status: open  
  • Source: Network Associates ( Brian Niebuhr)
  • Summary:

    I am a little confused as to the scope of the BiDirPolicy in the 2.4.1
    specification. Is the BiDirPolicy a POA policy, an ORB policy, or both? In
    section 15.8 paragraph 5 on page 15-55, the specification states:

    "If the client ORB policy permits bi-directional use
    of a connection, a Request message should contain an IOP::ServiceContext
    structure in its Request header, which indicates that this GIOP connection
    is bi-directional."

    but then in section 15.9 paragraph 4 on page 15-59, the specification
    states:

    "In the absence of a BidirectionalPolicy being passed in the
    PortableServer::POA::create_POA operation, a POA will assume a policy value
    of
    NORMAL."

    but then again in the next sentence the specification states:

    "A client and a server ORB must each have a BidirectionalPolicy with a value
    of
    BOTH for bi-directional communication to take place."

    Could someone clarify for me what the intent for the scope of the policy was
    here, and what the rationale behind that decision was? We are currently
    reviewing how to use/fix BiDirIIOP in our submission to the firewall RFP,
    and I would like to understand the issues regarding the scope of the BiDir
    policy.

  • Reported: CORBA 2.4.1 — Tue, 19 Dec 2000 05:00 GMT
  • Updated: Mon, 18 Feb 2019 00:03 GMT

CosExternaliazation Service (bug?)

  • Legacy Issue Number: 4188
  • Status: open  
  • Source: Anonymous
  • Summary:

    Page 2-7 of the CosExternalization Service Specification (April 2000)
    defines the following interfaces:
    CosStream::Node
    CosStream::Role
    CosStream::Relationship

    A CosStream::Node inherits from the CosStream::Streamable interface and
    therefore is a streamable object – it has an external_form_id attribute
    that enables a FactoryFinder to recreate the object using the
    create_uninitialized operation.

    Unfortunately, the CosStream::Role and CosStream::Relationship interfaces do
    not support the CosStream::Streamable interface and therefore are not
    "streamable;" in particular, there is no standard method to obtain a KEY for
    them when it is time to internalize them.

    Perhaps, I am missing something (it wouldn't be the first time , but
    having them support the Streamable interface would certainly make
    implementation much easier. Might I suggest the following:

    interface Role: CosGraphs::Role, CosStream::Streamable

    { ... }
    interface Relationship: CosGraphs::Relationship, CosStream::Streamable { ... }

    at a minimum this would permit the CosStream::Node internalize_node()
    operation and the CosStream::StreamIO read_graph() operation to use a KEY
    value in the FactoryFinder to instantiate the object, before it is
    internalized.

  • Reported: CORBA 2.4.2 — Mon, 5 Feb 2001 05:00 GMT
  • Updated: Mon, 18 Feb 2019 00:03 GMT

Inconsisten IDL in the Minimum CORBA chapter

  • Legacy Issue Number: 4216
  • Status: open  
  • Source: University of California, Irvine ( Carlos O'Ryan)
  • Summary:

    Section 23.14 of the CORBA/IIOP 2.4.1 specification lists the
    complete IDL for a minimumCORBA implementation. However, the text in
    the chapter and the IDL are inconsistent, for example, section 23.4.2
    reads:

    ------------------------------------------------------------------------
    ---------------
    The is_a operation is omitted so as not to introduce a requirement
    either for holding

    detailed type information in the object reference or for getting type
    information over

    the wire. Instead, minimumCORBA relies on design time resolution of type
    checking

    issues.

    The non_existent operation is omitted, because of the design philosophy
    of making

    more decisions statically at design time.

    The create_request operation is omitted, as the Dynamic Invocation
    Interface is

    omitted.

  • Reported: CORBA 2.4.2 — Sat, 3 Mar 2001 05:00 GMT
  • Updated: Mon, 18 Feb 2019 00:03 GMT

Fixed Types in COM

  • Legacy Issue Number: 4507
  • Status: open  
  • Source: Anonymous
  • Summary:

    There is currently no specification for fixed-point types in the COM/CORBA mapping. I'm interested in getting this changed: how can we proceed? better still, is this work already under way??

  • Reported: CORBA 2.4.2 — Fri, 17 Aug 2001 04:00 GMT
  • Updated: Mon, 18 Feb 2019 00:03 GMT

Implications of any/valuetype marshalling

  • Legacy Issue Number: 4137
  • Status: open  
  • Source: Iconixx ( Thomas Hawker)
  • Summary:

    RE: CCM chapters document [orbrev] 99-10-04, section 61.6.2, page 61-45.
    The document citation indicates that the integrity of the valuetype –
    that is, the received marshalled state – is to be preserved in an
    ORB-mediated operation, even if that valuetype cannot be unmarshalled,
    either partially (truncated) or at all. If this value is then passed to
    another operation, the original marshalled state is to be transmitted.
    This preserves the transmitted object in its entirety, regardless of
    local implementation concerns. This is obviously necessary for bridges
    or event processing, such as through the notification service.

    So the question arises, what happens if you have a partial (truncated)
    unmarshall and the recipient application changes the local state of the
    valuetype through its attributes or local operations? How can/will you
    even know the state was changed? Do you ignore the changes and send the
    originally received marshalled stream, send only the new valuetype even
    though it is a truncation of the original, or "merge" the new values for
    the unmarshalled part followed by the original appended data for the
    truncated part? Should this third option be possible through an
    explicit ORB call – that is, the application is responsible to identify
    the change in state to the ORB? I assume that the semantics of
    "truncatable" must come to include the understanding that data in the
    truncatable portions may not be contextually dependent on the inherited
    parent of the valuetype.

    As a further question, is there a reason why this semantic
    interpretation should not be extended to be a general requirement rather
    than only with respect to transmission of anys? My experience has found
    that passing anys tends to be expensive and is avoided where it can be.
    A more general interpretation permits transmission of a comprehensive
    data structure among intermediate agents that only use (unmarshall) the
    information they need.

  • Reported: CORBA 2.4.1 — Fri, 5 Jan 2001 05:00 GMT
  • Updated: Mon, 18 Feb 2019 00:00 GMT

How does an ORB implement Object::get_policy for PI defined policies?

  • Legacy Issue Number: 4065
  • Status: open  
  • Source: Floorboard Software ( Jonathan Biggar)
  • Summary:

    The description for Object::get_policy (in the Core, section 4.3.7.1)
    states:

    "The get_policy operation returns the policy object of the specified
    type (see Policy Object on page 4-32), which applies to this object. It
    returns the effective Policy for the object reference. The effective
    Policy is the one that would be used if a request were made."

    For a policy defined by PI, I don't see anyway for the ORB to implement
    this operation correctly, since there isn't any way for it to know how
    to properly resolve any client override policies with the policy
    information stored in the IOR.

    When a invocation is actually in process, the ClientRequestInterceptor
    can use the information available in the ClientRequestInfo interface to
    get the client override and the IOR policy data and do the correct
    resolution before continuing with the request. However,
    Object::get_policy() needs to do the same type of thing, but it has no
    invocation context to do it in.

    I think the same problem also applies to the implementation of
    ClientRequestInfo::get_request_policy().

    I think we need a new interception point to do this work. Something
    like:

    local interface PolicyInterceptor

    { any determine_effective_policy(in PolicyInfo pi); }

    ;

    local interface PolicyInfo

    { readonly attribute Object target; readonly attribute Object effective_target; readonly attribute IOP::TaggedProfile effective_profile; IOR::TaggedComponent get_effective_component (in IOP::ComponentId id); IOP_N::TaggedComponentSeq get_effective_components (in IOP::ComponentId id); }

    ;

    If this turns out to be an acceptable solution, then we should also
    change ClientRequestInfo to:

    local interface ClientRequestInfo : RequestInfo, PolicyInfo

    { ... }

    ;

    and remove the redundant operations.

  • Reported: CORBA 2.4.1 — Sat, 18 Nov 2000 05:00 GMT
  • Updated: Mon, 18 Feb 2019 00:00 GMT

Avoiding RSC/TSC copy on server side

  • Legacy Issue Number: 4169
  • Status: open  
  • Source: Oracle ( Harold Carr)
  • Summary:

    During the interceptor FTF we changed the server-side threading
    requirements such that all server-side points run in the same thread
    as the ServantManager and servant except receive_request_service_contexts.

    We attempted to update 21.4.4.4 "Request Scope vs Thread Scope"
    accordingly but knew we screwed the picture and wording up. So we
    punted to the RTF.

    The main problem with the current wording is that is forces a copy of
    of TSC/RSC before the servant manager and then receive_request are
    called. This is necessary because 21.4.4.5 item 5 says: "The
    receive_request points may modify the RSC, but this no longer affects
    the TSC."

    The only way to make RSC identical to TSC in receive_request with
    respect to reading but also have them be independent with respect to
    writing is to make a copy (which could be optimized to copy-on-write,
    but why?).

    I suggest we just state they are equivalent after
    receive_request_service_contexts.

    Here is a proposed revision to ptc/00-08-06 along these lines.

    Comments?
    Harold

    21.4.4.4 Request Scope vs Thread Scope

    ... On the server-side, the request scope PICurrent is attached to
    the ServerRequestInfo and follows the request processing. It is
    logically equivalent to the thread scope PICurrent after the list of
    receive_request_service_contexts interception points are processed.

    21.4.4.5 Flow of PICurrent between Scopes

    5. The ORB logically makes the RSC equivalent to the server-side TSC
    after the receive_request_service_contexts points are processed and
    before the servant manager is called. This TSC is within the context
    for both the receive_request points, the invocation of the servant
    manager, and the invocation of the target operation.

    The receive_request points are called. These points have access to the
    RSC. Modifying the RSC at this point makes corresponding
    modifications on the TSC. Since these points execute in the same
    thread as the target operation invocation, these points may modify the
    server-side TSC which makes corresponding modifications on the RSC.

    6. After the receive_request points are called, control transfers to
    the server threads which may also read and write this server-side TSC.
    Any modifications to the TSC makes corresponding modifications on the
    RSC.

    7. <No change>

    8. <DELETE THIS ITEM>

    9. The send interception points have access to the RSC (and the
    equivalent TSC) from which they may populate the reply service context
    list. After the invocation result is sent back to the client, the
    server-side RSC is logically destroyed.

    ...

    The picture would also need updating, but let's agree on wording first.

  • Reported: CORBA 2.4.1 — Tue, 23 Jan 2001 05:00 GMT
  • Updated: Mon, 18 Feb 2019 00:00 GMT