Trouble understanding why Varnish retries on backend timeouts

[.]

I recently got bit by this functionality, and I was hoping that someone
could shed some light on why this is the default behavior for varnish.

For context, I have an internal POST call, that only recently became long
running, and would timeout (although the actually call would complete), and
as a result, varnish apparently retries the POST, which resulted in the
action being performed several times. From everything I have read online,
the retry should only occur once, but I could have sworn I saw it happen
multiple times.

I found some forum posts online indicating the retry logic exists:
https://www.varnish-cache.org/lists/pipermail/varnish-misc/2010-December/019538.html

and even a patch (which doesn't seem to have been applied):
https://www.varnish-cache.org/lists/pipermail/varnish-dev/2011-August/006857.html

Granted, I should move the long running process to a background job (which
I am doing now), but I was hoping to get some understanding as to why this
logic exists.

Thanks.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://www.varnish-cache.org/lists/pipermail/varnish-dev/attachments/20121108/7e086c33/attachment.html>