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From Rainer Jung <rainer.j...@kippdata.de>
Subject Balancer Persist testing
Date Fri, 14 Dec 2012 12:10:53 GMT
I played around with the current backport proposal for balancer
persistence, ie. persisting config changes applied to proxy balancer via
the Balancer Manager GUI interface to disk and reloading them during
startup.

I made some observations. My setup uses a globally defined balancer with
two members and another two globally defined ones with each one member.
All members are different. Platform is Solaris 10 Sparc.

I also use two vhosts, but those are only the targets of the members.

Further local setting:

ProxyStatus Full
BalancerPersist On
ProxyPassInherit Off (also in the vhosts)

Findings:

- The "Used" count in balancer manager drops to "0" after restart/reboot
with persist on. It seems the slot management is not completely right.
Not yet further investigated.

- A warning might be needed about mixing changes via balancer manager
and via config:

  - If changing the path for a balancer in config while persist is on
    and then restarting, the balancer manager shows the old path
    from the persisted shm, but it seems the new one from the
    config is in effect.

  - E.g. setting a member state to stopped in config and again doing
    a persist restart, the old state from shm wins and the change in
    config is ignored.

So it seems before applying changes to the config one should always
backport all changes applied via the manager (not trivial, because you'd
have to check all displayed values against the configured ones), then
stop, then remove the *.persist files, apply config changes and start again.

- Switching persistence from on to off in config and then doing a
restart keeps the old .persist files around. They are ignored during the
startup as expected, but next time you'll switch back to persist on, the
outdated .persist file will again be loaded.

- "Elected" display in balancer manager survives restart, whereas
  "To" and "From" (byte counts) do not.

Findings for proxy unrelated to persistance:

- sometimes the busy display in balancer manager shows a "1" instead of
"0" after an ab test run. Often it goes down again to "0" after the next
test run.

- when using a high concurrency in ab the global server (reverse proxy)
which forwards to two vhosts reports

AH01102: error reading status line from remote server apache:9092

and I couldn't yet track it down to either keep alive, process recycles
or dynamic listener deactivation.

Regards,

Rainer


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