Re: Nodetool command to pre-load the chunk cache

[Chris Lohfink]

Something additional to consider (outside C* fix) is using a tool like
happycache  to have
consistent pagecache between them. Might be sufficient if the data is in
memory already.

Chris

On Tue, Mar 21, 2023 at 2:48 PM Jeff Jirsa  wrote:

> We serialize the other caches to disk to avoid cold-start problems, I
> don't see why we couldn't also serialize the chunk cache? Seems worth a
> JIRA to me.
>
> Until then, you can probably use the dynamic snitch (badness + severity)
> to route around newly started hosts.
>
> I'm actually pretty surprised the chunk cache is that effective, sort of
> nice to know.
>
>
>
> On Tue, Mar 21, 2023 at 10:17 AM Carlos Diaz  wrote:
>
>> Hi Team,
>>
>> We are heavy users of Cassandra at a pretty big bank.  Security measures
>> require us to constantly refresh our C* nodes every x number of days.  We
>> normally do this in a rolling fashion, taking one node down at a time and
>> then refreshing it with a new instance.  This process has been working for
>> us great for the past few years.
>>
>> However, we recently started having issues when a newly refreshed
>> instance comes back online, our automation waits a few minutes for the node
>> to become "ready (UN)" and then moves on to the next node.  The problem
>> that we are facing is that when the node is ready, the chunk cache is still
>> empty so when the node starts accepting new connections, queries that go to
>> take much longer to respond and this causes errors for our apps.
>>
>> I was thinking that it would be great if we had a nodetool command that
>> would allow us to prefetch a certain table or a set of tables to preload
>> the chunk cache.  Then we could simply add another check (nodetool info?),
>> to ensure that the chunk cache has been preloaded enough to handle queries
>> to this particular node.
>>
>> Would love to hear others' feedback on the feasibility of this idea.
>>
>> Thanks!
>>
>>
>>
>>

Apache TAC: assistance for travel to Berlin Buzzwords

[Josh McKenzie]

Cassandra Community!

The Travel Assistance Committee with the Apache Foundation is supporting travel 
to Berlin Buzzwords 2023 (https://2023.berlinbuzzwords.de, 18-20 June 2023) for 
up to 6 people. This conference has lined up pretty well with our project in 
the past and would probably be a great opportunity for folks from our community 
to attend: *"Germany’s most exciting conference on storing, processing, 
streaming and searching large amounts of digital data, with a focus on open 
source software projects"*.

Please see the below message from Gavin McDonald w/the TAC:



Hi All,

The ASF Travel Assistance Committee is supporting taking up to six (6)
people to attend Berlin Buzzwords In June this year.

This includes Conference passes, and travel & accommodation as needed.

Please see our website at https://tac.apache.org for more information and
how to apply.

Applications close on 15th April.

Good luck to those that apply.

Gavin McDonald (VP TAC)



~Josh