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Posted by ImOk on 12/17/43 11:52
> Syntax errors are fatal errors which can't be caught with a user
> function (normally, anyways).
True, the compiler in theory should catch them up front. But this is
PHP. Anything can happen.
>Is INSERT ... ON DUPLICATE KEY standard SQL?
Usefull if you want to update a record if it exists. Not usefull if you
mean to insert a new record with a unique key. Also is this standard
SQL?
Richard Levasseur wrote:
> ImOk wrote:
> > This looks like a very good idea. I will have to study it.
> >
> > But you only need retries for cases where there is a chance of
> > recovery. E.g. Syntax errors or missing includes will never recover.
> > Neither will divide by zero.
> >
>
>
> Syntax errors are fatal errors which can't be caught with a user
> function (normally, anyways).
>
> > The main purpose of retries as far as Im concerned has to do with file
> > and resource connections and locks.
> >
> > Also using an error handler for unique key checking is better.You dont
> > have to perform a select first to see if the key already exists. Just
> > Insert and see if you get an error and retry with a different key.
> >
> >
>
> This could also be done using INSERT ... ON DUPLICATE KEY...
>
> > Tim Hunt wrote:
> > > ImOk wrote:
> > > > I just have a question about trapping and retrying errors especially
> > > > file locking or database locks or duplicate key errors.
> > > >
> > > > Is there a way after you trap an error to retry the same line that
> > > > cause the error?
> > > >
> > > > In many other languages you have the option of rertying certain errors.
> > > > In effect, its like a return to the exact same line. You can then retry
> > > > certain # of times and then produce an error if it keeps failing.
> > >
> > > If you use set_error_handler to collect the errors and debug_backtrace
> > > to see what caused the error it is possible to retry *some* errors.
> > >
> > > I could only get it working if the error occured inside a function. If
> > > you check the error message given to the event handler then you maybe
> > > able to handle other errors, not sure if it can be done though.
> > >
> > > Anyhoo the code below will try 3 times when a error occurs in any and
> > > all functions.
> > >
> > > <?php
> > >
> > > error_reporting(0);
> > >
> > > function retryErrorHandler($errNo, $errMsg ) {
> > >
> > > static $attempts = 1;
> > > $maxAttempts = 3;
> > >
> > > $backTrace = debug_backtrace();
> > >
> > > print "<br><br>Attempt $attempts<br>$errMsg<br>";
> > >
> > >
> > > if ( $attempts >= $maxAttempts ) {
> > > $attempts = 1;
> > > } else if ( isset($backTrace[1]) &&
> > > isset($backTrace[1]['function']) && isset($backTrace[1]['args']) ) {
> > >
> > > // $backTrace[0] is info about the call to retryErrorHandler
> > > // we need info about the previous function that triggered the
> > > error
> > > // so $backTrace[1] is used if a function + its arguments are
> > > available
> > >
> > > $attempts+=1;
> > > $func = $backTrace[1]['function'];
> > > $args = $backTrace[1]['args'];
> > >
> > > print "Retry function $func <br>";
> > >
> > > //Hmm..The error handler is only called the second time round if
> > > the handler is reset
> > > set_error_handler('retryErrorHandler');
> > > call_user_func_array( $func, $args );
> > >
> > > } else {
> > > print "Can't retry error: $errMsg<br>";
> > > $attempts = 1;
> > > }
> > >
> > > }
> > >
> > > $old_error_handler = set_error_handler('retryErrorHandler');
> > >
> > >
> > > // trigger a few errors...
> > >
> > > // will not retry, not enough info returned by debug_backtrace to try
> > > again
> > > $i = UNDEFINED_THING;
> > >
> > > // not enough info to try include() errors again - the dodgy filename
> > > isn't in the backtrace details
> > > // assume its because include is a language construct not a function
> > > call
> > > include('is not a file.php');
> > >
> > > // will retry three times
> > > fopen( 'no file', 'r' );
> > >
> > > // will retry three times
> > > mysql_connect( 'mysql wont connect' );
> > >
> > > // will retry user functions as well as internal ones
> > > testFunc();
> > >
> > > function testFunc() {
> > > $x = 3 / 0;
> > > }
> > >
> > > ?>
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