Skip to content

Clarify when changing number of cores is supported #850

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
kbatuigas merged 7 commits into from
Nov 18, 2024
Merged

Clarify when changing number of cores is supported #850

Show file tree
Hide file tree
Changes from 3 commits
Commits
Show all changes
7 commits
Select commit Hold shift + click to select a range
864544a
Add admomition regarding core number change
kbatuigas Nov 12, 2024
72809b5
Point users to upgrade RP version
kbatuigas Nov 13, 2024
864391d
Decrease core count is also mentioned in other pages
kbatuigas Nov 13, 2024
c91ff9c
Add link to upgrade to 24.3
kbatuigas Nov 15, 2024
a9d6c88
Remove explicit mention of version number
kbatuigas Nov 15, 2024
dda647a
Better to discuss RP behavior prior to this version in release notes …
kbatuigas Nov 18, 2024
85e7c6a
Update modules/manage/pages/cluster-maintenance/cluster-balancing.adoc
kbatuigas Nov 18, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
4 changes: 4 additions & 0 deletions modules/manage/pages/cluster-maintenance/cluster-balancing.adoc
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -125,6 +125,8 @@ This is a beta feature for v24.2 and is not recommended for use for production c
```bash
curl -X PUT -d '{"state": "active"}' http://127.0.0.1:9644/v1/features/node_local_core_assignment
```

xref:upgrade:index.adoc[Upgrade to 24.3 or later] to use this feature for production clusters.
====

In Redpanda, every partition replica is assigned to a CPU core on a broker. While Redpanda's default <<partition-replica-balancing,partition balancing>> monitors cluster-level events, such as the addition of new brokers or broker failure to balance partition assignments, it does not account for the distribution of partitions _within_ an individual broker.
Expand All @@ -133,6 +135,8 @@ Prior to Redpanda version 24.2, this meant that some cores on a broker could ina

Starting in v24.2, topic-aware intra-broker partition balancing allows for dynamically reassigning partitions within a broker. Redpanda prioritizes an even distribution of a topic's partition replicas across all cores in a broker. If a broker's core count changes, when the broker starts back up, Redpanda can check partition assignments across the broker's cores and reassign partitions, so that a balanced assignment is maintained across all cores. Redpanda can also check partition assignments when partitions are added to or removed from a broker, and rebalance the remaining partitions between cores.

NOTE: Decreasing the number of CPU cores in a running cluster is supported from v24.2 only, and requires that you enable `node_local_core_assignment` as described in the previous note.

To determine when to use intra-broker partition balancing, use the public metrics for CPU usage described in the xref:manage:monitoring.adoc#cpu-usage[Monitoring] guide.

Configure the following properties to trigger intra-broker partition balancing:
Expand Down
6 changes: 5 additions & 1 deletion modules/manage/pages/kubernetes/k-manage-resources.adoc
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,11 @@ kubectl describe nodes

== Limitations

Redpanda does not support decreasing the CPU cores for brokers in an existing cluster.
Redpanda supports decreasing the CPU cores for brokers in an existing cluster as of version 24.2.

In v24.2, you must enable the `node_local_core_assignment` flag to be able to decrease the core count.
Copy link
Contributor

@daisukebe daisukebe Nov 15, 2024

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Can you add a note that decreasing CPU core count is not supported for production clusters?


In v24.3 or later, decreasing CPU cores is enabled by default.
Copy link
Contributor

@daisukebe daisukebe Nov 15, 2024

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more. 

In v24.3 or later, the `node_local_core_assignment` flag is enabled and decreasing CPU cores is supported for production clusters.

Copy link
Contributor

@JakeSCahill JakeSCahill Nov 15, 2024 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I think we need a separate PR for the beta version of 24.3 docs that removes the limitations section.
We don't expect users to switch off feature flags.

In this PR, all we need is something like this (with links to intra-broker partition balancing and v24.3 docs):

Decreasing the number of CPU cores in a production cluster is not supported in this version of Redpanda. However, you can enable intra-broker partition balancing to reduce CPU cores in a development cluster.

Starting from version 24.3, decreasing the number of CPU cores in a production cluster is supported. Upgrade to version 24.3 or later to access this feature.


[[memory]]
== Configure memory resources
Expand Down