Thanks Peter and Robert for all the input. Very useful information.
Just to be clear for me. Is it correct to say that there is no difference in
the "parent mark down" behavior between Consistent Hash and any of the other
parent selection options (e.g. Round Robin)?
Cheers,
Nick
On 8/17/21, 1:09 PM, "CHOU, PETER" <pc6...@att.com> wrote:
Hi,
There is no background thread checking on the original parent. Once the
original parent is marked down, the parent selection process will ignore
it until it becomes retryable after a time-out period.
This is configurable using the "proxy.config.http.parent_proxy.retry_time"
setting.
Thanks,
Peter
From: Nick Dunkin <nick.dun...@vecima.com.INVALID>
Sent: Tuesday, August 17, 2021 8:40 AM
To: dev@trafficserver.apache.org
Subject: Question about Consistent Hash and parent retry
Hi,
I have a question about Consistent Hash behavior when a parent is “down”.
This is ATS 7.1
The documentation states the following: “If a parent is down, the traffic
that would go to the down parent is rehashed amongst the remaining parents. The
other traffic is unaffected. Once the downed parent becomes available, the
traffic distribution returns to the pre-down state.”
That second section implies that maybe:
* A background thread is periodically retying the original hashed
parent, in order to mark it back up
* The original hashed parent is being retried on every access until it
is available again
Please can someone clarify the exact behavior around Consistent Hash and
unavailable parents? The context here is that we believe we are seeing the
retries on the originally hashed parent occur more often than we would expect.
Many thanks,
Nick
Nick Dunkin
Director, Software Engineering
Manager – Architecture and New Product Introduction
o: +1 678.258.4071
e: nick.dun...@vecima.com<mailto:nick.dun...@vecima.com>
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