[pca] Problem install patch which the proxy has already started to download

[Martin Paul]

Richard Skelton wrote:
> There is a problem with PCA when trying to install a patch from a proxy 
> when the patch is already being downloaded by the proxy:-
> 120185 21 < 22 RS-   6 StarOffice 8 (Solaris): Update 17

There have been some timing issues with large patches in the past, and the 
StarOffice patches are likely to trigger those - e.g. 120185-22, which is around 
290MB.

> Looking for 120185-22 (25/212)
> Trying http://pcaproxy/cgi-bin/pca-proxy.cgi?
> Failed (Error 500: Another instance of pca is downloading 120185-22 to 
> /var/apache2/htdocs/pca right now)

When PCA is asked to download a patch, it checks for a lock file created by 
another instance of PCA which might download the same patch to the same 
directory. If a lock exists, it will wait up to 300 seconds until the lock is 
removed. Usually, the other instance of PCA completely downloads the patch in 
that time, and then the already downloaded copy will be used by the second 
instance of PCA.

Here it seems as if the download doesn't complete fast enough, due to the size 
and a slow Internet connection. If you re-run pca on the client, it usually will 
work, as the first instance then had at least 2x300 seconds for the download.

A general solution for this is difficult. Raising the time waiting for the lock 
will cause PCA to stuck on other hung PCA processes for a looong time. The other 
problem is that the HTTP server might kill the first instance of PCA because the 
CGI is taking so long that it believes it's hung (seen that before, too).

Suggestions are welcome :)

Martin.