[Pulp-list] redis on a passive backup server

Bin Li (BLOOMBERG/ 120 PARK) bli111 at bloomberg.net
Thu Sep 23 20:56:33 UTC 2021


Thanks Brain and Matthias. It's really helpful to understand how this works.
I'd like to know the answer of the same question under two different scenarios.
In both scenarios, we will have 2 content servers behind a load balancer and share the same external db. Api server is only run on one of the hosts.
1) Both content servers have the same artifacts in its own filesystems (rsyned)
2) Both content servers shared the S3.

We currently use filesystem as the storage and would like to move to S3. Can redis be independent in above two cases?

From: mdellweg at redhat.com At: 09/21/21 16:50:53 UTC-4:00To:  bmbouter at redhat.com
Cc:  Bin Li (BLOOMBERG/ 120 PARK ) ,  pulp-list at redhat.com
Subject: Re: [Pulp-list] redis on a passive backup server

Right i did not read that correctly. It's a failover scenario. It
would even be safe to flush redis on failover.
I was thinking about multiple independent content app installations
each with their own redis server. But that is another challenge.

On Tue, Sep 21, 2021 at 7:32 PM Brian Bouterse <bmbouter at redhat.com> wrote:
>
>
>
> On Mon, Sep 20, 2021 at 5:40 PM Matthias Dellweg <mdellweg at redhat.com> wrote:
>>
>> I am not sure if the cache invalidations will be pushed to all redis
>> instances if deployed that way. Maybe there is a little bit of extra
>> work needed.
>
> I imagined the backup Pulp would have its Redis empty because that Pulp 
wasn't in use. If that were the case cache invalidations not reaching it would 
be fine because the cache would be empty at failover time. As always though, 
there could be more needed to handle some specific use cases.
>
>>
>> On Mon, Sep 20, 2021 at 10:31 PM Brian Bouterse <bmbouter at redhat.com> wrote:
>> >
>> > I believe with 3.14+ and new style workers, you can have an independant 
redis on the backup server.
>> >
>> > With the new-style tasking system (the default in 3.14) you no longer need 
Redis for tasking. It's only purpose then is to help speedup the content app 
which caches info about requests to make answering subsequent content-app 
requests easier. If those caches miss, e.g. if you had a failover event, Pulp 
will continue to work fine, just building the Redis cache data as it goes.
>> >
>> > On Mon, Sep 20, 2021 at 4:22 PM Bin Li (BLOOMBERG/ 120 PARK) 
<bli111 at bloomberg.net> wrote:
>> >>
>> >> We configured a redis slave on a passive backup server which shares the 
same external database with the primary pulp server. I noticed the task queues 
are now being tracked in the database. Is it still necessary to configure redis 
as a slave or we can have an independent instance of redis on the backup server?
>> >>
>> >> Thanks
>> >> _______________________________________________
>> >> Pulp-list mailing list
>> >> Pulp-list at redhat.com
>> >> https://listman.redhat.com/mailman/listinfo/pulp-list
>> >
>> > _______________________________________________
>> > Pulp-list mailing list
>> > Pulp-list at redhat.com
>> > https://listman.redhat.com/mailman/listinfo/pulp-list
>>


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