I appreciate the update to my understanding of the read path! Thanks, Jeff.
Sean Durity
From: Jeff Jirsa
Sent: Wednesday, November 11, 2020 10:33 AM
To: cassandra
Subject: [EXTERNAL] Re: local read from coordinator
What you describe is true for writes but not reads.
The read only gets sent t
Jeff, I was talking about driver -> coordinator communication, not from
where data will be read
On Wed, Nov 11, 2020 at 3:24 PM Jeff Jirsa wrote:
>
> This isn’t necessarily true and cassandra has no coordinator-only
> consistency level to force this behavior
>
> (The snitch is going to pick the
What you describe is true for writes but not reads.
The read only gets sent to enough nodes to meet the consistency level,
unless/until one of two things happen:
- You trigger probabilistic read repair, in which case it's sent to all
nodes (or all nodes in a DC), or
- One of the chosen replicas is
Doesn’t the read get sent to all nodes that own the data in parallel (from the
coordinator)? And the first one that is able to respond wins (for LOCAL_ONE).
That was my understanding.
Sean Durity
From: Jeff Jirsa
Sent: Wednesday, November 11, 2020 9:24 AM
To: user@cassandra.apache.org
Subject:
This isn’t necessarily true and cassandra has no coordinator-only consistency
level to force this behavior
(The snitch is going to pick the best option for local_one reads and any
compactions or latency deviations from load will make it likely that another
replica is chosen in practice)
> On
if you force routing key, then the replica that owns the data will be
selected as coordinator
On Wed, Nov 11, 2020 at 12:35 PM onmstester onmstester
wrote:
> Thanx,
>
> But i'm OK with coordinator part, actually i was looking for kind of read
> CL to force to read from the coordinator only with
Thanx,
But i'm OK with coordinator part, actually i was looking for kind of read CL to
force to read from the coordinator only with no other connections to other
nodes!
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