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Radosław pointed another bug
https://bugs.launchpad.net/keystonemiddleware/+bug/1883659
referring to the same fix
https://review.opendev.org/#/c/742193/

Regarding to the fix, The comment says "This flag is off by
default for backwards compatibility.". But I see this flag is
on by default in current code. That's how it causes issues.
This fix changes the default value from on to off. It does break
backwards compatibility. To keep Keystone working as the old way,
along with this fix, this flag has to be explicitly set to true
in keystone.conf. For neutron-server and nova-api, it's good to
leave this flag off by default. Am I correct?


Thanks!
Tony
> -----Original Message-----
> From: Herve Beraud <hberaud at redhat.com>
> Sent: Monday, September 14, 2020 8:27 AM
> To: Tony Liu <tonyliu0592 at hotmail.com>
> Cc: openstack-discuss <openstack-discuss at lists.openstack.org>
> Subject: Re: memchached connections
> 
> Hello,
> 
> python-memcached badly handles connections during a flush on reconnect
> and so connections can grow up exponentially [1].
> 
> 
> I don't know if it is the same issue that you faced but it could be a
> track to follow.
> 
> On oslo.cache a fix has been submitted but it is not yet merged [2].
> 
> 
> [1] https://bugs.launchpad.net/oslo.cache/+bug/1888394
> [2] https://review.opendev.org/#/c/742193/
> 
> Le ven. 11 sept. 2020 à 23:29, Tony Liu <tonyliu0592 at hotmail.com
> <mailto:tonyliu0592 at hotmail.com> > a écrit :
> 
> 
> 	Hi,
> 
> 	Is there any guidance or experiences to estimate the number
> 	of memcached connections?
> 
> 	Here is memcached connection on one of the 3 controllers.
> 	Connection number is the total established connections to
> 	all 3 memcached nodes.
> 
> 	Node 1:
> 	10 Keystone workers have 62 connections.
> 	11 Nova API workers have 37 connections.
> 	6 Neutron server works have 4304 connections.
> 	1 memcached has 4973 connections.
> 
> 	Node 2:
> 	10 Keystone workers have 62 connections.
> 	11 Nova API workers have 30 connections.
> 	6 Neutron server works have 3703 connections.
> 	1 memcached has 4973 connections.
> 
> 	Node 3:
> 	10 Keystone workers have 54 connections.
> 	11 Nova API workers have 15 connections.
> 	6 Neutron server works have 6541 connections.
> 	1 memcached has 4973 connections.
> 
> 	Before I increase the connection limit for memcached, I'd
> 	like to understand if all the above is expected?
> 
> 	How Neutron server and memcached take so many connections?
> 
> 	Any elaboration is appreciated.
> 
> 	BTW, the problem leading me here is memcached connection timeout,
> 	which results all services depending on memcached stop working
> 	properly.
> 
> 
> 	Thanks!
> 	Tony
> 
> 
> 
> 
> 
> 
> --
> 
> Hervé Beraud
> Senior Software Engineer
> 
> Red Hat - Openstack Oslo
> irc: hberaud
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