Re: [Sqlrelay-discussion] Blocking call when DB is offline

[Z S. <sha...@ho...>]

Some further information by analysis on this issue:

Using debug, I find out that the" sqlrcur_endQuery" calls sqlrcursor::sendQueryInternal() from it's inside:

"
bool sqlrcursor::sendQueryInternal(const char *query) {

    // if the first 8 characters of the query are "-- debug" followed
    // by a return, then set debugging on
    if (!charstring::compare(query,"-- debug\n",9)) {
        sqlrc->debugOn();
    }

    if (!endofresultset) {
        abortResultSet();
    }
    clearResultSet();

    if (!sqlrc->openSession()) {
        return false;
    }

    cached=false;
    endofresultset=false;

    if (sqlrc->debug) {
        sqlrc->debugPreStart();
        sqlrc->debugPrint("Sending Query:");
        sqlrc->debugPrint("\n");
        sqlrc->debugPrint(query);
    ...
}
"

Strange thing is, when I use "Step over", openSession() as whole always returns true. However, when I use "Step into", the openSession() returns false on the following Line:

bool sqlrconnection::openSession() {
   .... 
    if (!authenticateWithListener()) {
        closeConnection();
        return false;
    }
}

If openSession() fails, sqlrcur_endQuery will also return but with following debug messages for error:

Connecting to listener...
Inet socket: 10.10.10.120:9000
Authenticating with listener : bto_spp:bto_spp
Waiting for auth success/failure...
Setting Error
Failed to authenticate.
 A network error may have ocurred.

My question would be, why the return value of authenticateWithListener() could be different during run and debug (with "step-into" mode)? My expectation would be that  authenticateWithListener()  always return false (=>openSession() return false=>sqlrcur_sendQuery() can get returned) when DB get offline so that the system would not be blocked.


Shan

From: sha...@ho...
To: sql...@li...
Subject: Blocking call when DB is offline
Date: Thu, 10 May 2012 10:29:48 +0000





Hi,
My application needs to talk with Oracle DB. To improve performance, I use SQLRelay as intermediate layer.

Recently, I have met with following problem :


1 Both SQLRelay and Oracle DB are started

2 Send query from my App (use 'sqlrcur_sendQuery') => OK

3 Shutdown Oracle DB

4 Send query again from my App, the call on 
"sqlrcur_sendQuery"  is blocked (no return). 

5 Turn on Oracle DB again

6 The old call to  sqlrcur_sendQuery is returned. Further queries can all be processed.


I activated log flag of SqlRelay (SQLRDEBUG=ON), and see following output:

"
Connecting to listener...
Inet socket: 10.10.10.120:9000
Authenticating with listener : bto_spp:bto_spp
Waiting for auth success/failure...
No authentication error.
Must Reconnect.
Reconnecting to 
    server: 10.10.10.120
    inet port: 33681
Connected.
Authenticating with connection : bto_spp:bto_spp
Waiting for auth success/failure...
No authentication error.
Sending Query:
SELECT * FROM HSPGW_CONFIG_VIEW WHERE ZONE_ID = 1682 AND IS_ENABLED = 1 AND TARIFF_ID = 16
Length: 90
Requesting a new cursor.
Sending 0 Input Bind Variables:
Sending Output Bind Variables:
Send Column Info: yes
Skipping and Fetching
Skipping 0 rows
Fetching 0 rows
"

Is there any way to let 'sqlrcur_sendQuery' return after certain time when the connection to DB is failed  (like setting a timeout)? Otherwise the whole APP will hang as far as the DB is offline.

Any help will be appreciated.

Shan