[Orclib-users] subscriptions/callback for Oracle AQ

[Petr V. <pe...@ya...>]

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hi Vincent and gang,

I'd like to introduce you an idea about an addon to DCN or CQN
notifications/callback ocilib framework - notifications and callback
API for Advanced Queueing (AQ).

You can see it in this temporary git repository:

https://github.com/pvanek/ocilib

this is based on the latest ocilib 3.10.0 with these changes:


- - an initial support for AQ callback:
https://github.com/pvanek/ocilib/commit/0b44a5247829ef52c61694cfc2187396f88ef62f

Note: this is not a final code, I'd like to know your opinion first.
There is no doc etc.

  * backward compatibility stays as is - there are no changes in
existing public API
  * new function OCI_SubscriptionRegisterAQ, similar to
OCI_SubscriptionRegister but it uses AQ's OCI_SUBSCR_NAMESPACE_AQ
subscription context (instead of OCI_SUBSCR_NAMESPACE_DBCHANGE)
  * new functions OCI_EventGetAQQueueName and
OCI_EventGetAQConsumerName to get AQ related attributes from OCI_Event
  OCI_Event structure has been expanded to hold AQ attributes.

Here I'm not sure if it's a good idea to expanc existing OCI_Event or
create new AQ-only similar struct and related functions. I'm open to
suggestions here.

a small example:

#include "ocilib.h"

#ifdef _WINDOWS
  #define sleep(x) Sleep(x*1000)
#else
#include <unistd.h>
#endif

#define wait_for_events() sleep(15)

void event_handler(OCI_Event *event);
void error_handler(OCI_Error *err);

int main(void)
{
    OCI_Connection   *con;
    OCI_Subscription *sub;
    OCI_Statement    *st;

    printf("=> Initializing OCILIB in event mode...\n\n");

    if (!OCI_Initialize(error_handler, NULL, OCI_ENV_EVENTS))
        return EXIT_FAILURE;

    con = OCI_ConnectionCreate("stimpy", "omquser", "omquser",
OCI_SESSION_DEFAULT);

    sub = OCI_SubscriptionRegisterAQ(con, "omquser.testaq",
event_handler, 5468, 0);

    wait_for_events();

    OCI_ConnectionFree(con);
    OCI_SubscriptionUnregister(sub);
    OCI_Cleanup();
    return EXIT_SUCCESS;
}

void error_handler(OCI_Error *err)
{
    int         err_type = OCI_ErrorGetType(err);
    const char *err_msg  = OCI_ErrorGetString(err);

    printf("** %s - %s\n", err_type == OCI_ERR_WARNING ? "Warning" :
"Error", err_msg);
}

void event_handler(OCI_Event *event)
{
    unsigned int type     = OCI_EventGetType(event);
    unsigned int op       = OCI_EventGetOperation(event);
    OCI_Subscription *sub = OCI_EventGetSubscription(event);

    printf("** Notification      : %s\n\n", OCI_SubscriptionGetName(sub));
    printf("...  Queue Name      : %s\n",
OCI_EventGetAQQueueName(event));
    printf(". Consumer Name      : %s\n",
OCI_EventGetAQConsumerName(event));

    printf("\n");
}





- - pkg-config feature added (ocilib.pc):
https://github.com/pvanek/ocilib/commit/6ba08629bb3be6229b19bae577af241fade2202c
This feature is ready to be merged. It allows easy use of ocilib in
cmake, autotools, and similar build tools

cmake example:
find_package(PkgConfig)
pkg_check_modules(OCILIB REQUIRED ocilib>=3.10)
message(STATUS "includes: ${OCILIB_INCLUDE_DIRS}")
message(STATUS "    libs: ${OCILIB_LIBRARIES}")
message(STATUS "lib dirs: ${OCILIB_LIBRARY_DIRS}")



looking forward your comments,
petr
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