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Posted by Richard Levasseur on 12/17/84 11:52
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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