Varnish Dirty Caching
stonorn at giraffen.dk
Thu Jul 5 08:44:34 CEST 2007
Poul-Henning Kamp wrote:
> The critical question is how we define "backend is down" and how
> fast and efficient we can detect it.
> Ideas for how to express it in VCL are very welcome.
# First, we setup decide how to "sniff" that a backend is down
# options_ping: Send a HTTP OPTIONS (Perlbal does that)
# timeout: If the backend does not answer within x seconds, it is
# probably down
# icp: Abuse the protocol. (Squid + Zope does that)
backend.down_protocol = options_ping | timeout | icp
# What is the timeout limit?
backend.timeout = 30
# How long time should the backend be marked as "down" before we try
backend.retry_after = 300
# And then just use it
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