mod_cache: will a Thundering Herd be caused by reading cached files?

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Hi guys,

I just read about mod_cache and Thundering Herd at http://httpd.apache.org/docs/2.2/mod/mod_cache.html

It describes a case of Thundering Herd which may happen when a cached file is being updated. I was wondering why it does not mention another possible Thundering Herd caused by reading a cached file. In latter case, when Apache is serving a request by reading a cached file, it may last for a big amount of time. Because the client that requests the cached file may be very slow, or the file may be very large in size.

While serving such a request, other requests may arrived and found that the cached file is stale and needs to be updated. But at the same time, the Apache has to wait until the read operation to finish. Because on some OSes e.g. Windows you can not delete/replace a file when it is open.

If you know details how Apache handles the situation, could you please share it with me? Thank you.

Regards,
Rex


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