Re: Long running db queries and the "STOP" button

Thomas.Seiler@swisscom.com wrote:

Hi Jochem, Thanks for replying

I just had the idea (never tried it myself) that you could possibly fork the request process and let the child process perform the query

It makes perfectly sense to us, but it seems it is only possible to fork (pcntl_fork) with php running as CGI :(

oops missed that bit in the manual... still ... if you are using apache then virtual() might offer a solution? (just guessing) otherwise you might look into writing a little deamon (i.e. a webservice that only your pages anbd/or scripts can access) which handles running the queries can be polled as to the status of a query and its result (if finished) .. such a deamon would be CLI based and could use process forking to handle multiple requests to run long queries.... rather than use the <img src="monitorscript.php"> trick you might want to look into 'AJAX' on the client side (to do the polling, start the query, etc) in order to have more control/information on that end.

From php.net: <snip> arnold at helderhosting dot nl 13-Feb-2005 10:12 It is not possible to use the function 'pcntl_fork' when PHP is used as Apache module. You can only use pcntl_fork in CGI mode or from command-line. Using this function will result in: 'Fatal error: Call to undefined function: pcntl_fork()' <snip> This somehow makes sense, because one would fork the entire apache process, Including all the signal handlers, open file handles for log-files and so on... Furthermore fork is only supported on linux/*nix but not in the windows world, and it has to be enabled at configure time. We have so far tried to use javascript to detect when a windows is closed and send a second HTTP request to kill the database thread. This however does not work reliably, because javascript has no event for the "Stop" button of the browser :(

a daily annoyance. just like its impossible to trap when the window is actually closed (as opposed to the document merely unloading)

The next idea is to include a <img src="monitorscript.php"> in output generated by the query script. This should open a second HTTP connection to the monitor script on most recent browsers. In this script we can check connection_aborted() and sleep(1) in a while loop without sending any output. If the connection was aborted, we can kill the corresponding db thread. The remaining problem with that solution is that we also have to detect when the db query script has terminated and then exit the monitor script. Otherwise the browser keeps loading that monitorscript and never finishes. This solution has two drawbacks, it work over a http proxy (these tend to finish queries in order to cache the content) and it works only when the browser is doing several queries in parallel. Cheers, Thomas