Presently we only record th state of the last 64 tries to poll the
backend in a shift register, which can be show with the interrim
CLI command "debug.health":

Health stats for backend b0
Oldest __________________________________________________ Newest
4444444444444444444444444444444444444444444444444444444444444444 Good IPv4
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX Good Xmit
SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS Good Shut
RR-RR-R-RRRR---RR-RR-R-R-R-R-R-RRRR-RR-----RR--RRRR--RRR-R-----R Good Recv

More to follow.


git-svn-id: http://www.varnish-cache.org/svn/trunk@3084 d4fa192b-c00b-0410-8231-f00ffab90ce4