Friday, November 30, 2007

IWDatacapture.callServer call fails / caveat


when i build teamsite DCTs i always find a new and wonderful way to break something.

Today i was building a DCT that used IWDatacapture.callServer to call a cgi script that would get some stuff from the database and then out put it into a hidden frame and do a javascript callback to the parent window.

everything was going well until i made the mistake of making 2 calls to different IWDatacapture.callServer cgi scripts one right after the other. one of them would always fail.


The problem stems from the fact that CGI scripts that output html make use of a single blank.html file to write out their contents. If you call 2 of them "almost at the same time" one of them will overwrite the other's blank.html file and cause it to fail. The only reasonable solution is to combine both CGIs into one file and let it write to one blank.html file, you can also try to make sure that CGIs dont get called at the same time, but that would be difficult to control.

So it seems that its probably a reasonable requirement to only allow ONE IWDatacapture.callServer call per DCR, otherwise things might break. How sad.

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