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split: replace seeded random source #94752

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kvoli opened this issue Jan 5, 2023 · 0 comments · Fixed by #94754
Closed

split: replace seeded random source #94752

kvoli opened this issue Jan 5, 2023 · 0 comments · Fixed by #94754
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A-kv-distribution Relating to rebalancing and leasing. C-enhancement Solution expected to add code/behavior + preserve backward-compat (pg compat issues are exception) T-kv KV Team

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kvoli commented Jan 5, 2023 •
edited by cockroach-jira-scripts
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In #93838 we started using a seeded rand for use in the load based +
splitter's reservoir sampling algorithm.

rand.Soure heap allocates on init approximately 4kb. When intialized
per-replica, this is problematic as nodes scale to large replica counts.

The splitter should instead be initialized with the global rand, to reduce
memory overhead per-replica.

xref #94737

Jira issue: CRDB-23121
@kvoli kvoli added C-enhancement Solution expected to add code/behavior + preserve backward-compat (pg compat issues are exception) A-kv-distribution Relating to rebalancing and leasing. labels Jan 5, 2023
@kvoli kvoli self-assigned this Jan 5, 2023
@blathers-crl blathers-crl bot added the T-kv KV Team label Jan 5, 2023
@kvoli kvoli mentioned this issue Jan 5, 2023
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craig bot pushed a commit that referenced this issue Jan 5, 2023
@arulajmani @kvoli
Merge #94644 #94754
e7713f1 
94644: tenantcapabilities: introduce TenantCapabilities proto r=ecwall a=arulajmani

This commit adds the skeletal structure for a `TenantCapabilities` proto,
which is intended to encapsulate capabilities for a specific tenant.
Capabilities are intended to be stored in the `system.tenants` table,
in its Info column. To that end, we modify `TenantInfo` to contain
capabilities. However, actually populating this field through SQL is
left to a future commit.

Future commits will also add the infrastructure required to check a
tenant's requests against its capabilities for "privileged" operations.
For now, I've only accounted for the `CanAdminSplit` capability -- this
will likely expand to a fuller set as we introduce other capabilities
in the system.

References #94643

Epic: CRDB-18503
Release note: None

94754: split: init replica lb splitter with global rand r=erikgrinaker a=kvoli

In #93838 we started initializing a new seeded rand for use in the load
based splitter's reservoir sampling algorithm. Previously, the splitter
was initialized using the global rand.

`rand.Source` heap allocates on init approximately 4kb. When initialized
per-replica, this is problematic as nodes scale to large replica counts.

This patch replaces initializing a new random source per-replica with
using the global rand instead.

This removes the heap allocation. This is shown below running 
`kv/splits/nodes=3/quiesce=true` (not at identical replica counts in the test,
 the proportions are the important part).

before:

![image](https://user-images.githubusercontent.com/39606633/210825416-a940904f-47c9-4271-9692-11b40be927f4.png)

after:

![image](https://user-images.githubusercontent.com/39606633/210825742-fc62ea6c-2125-44fe-ac07-984c22986089.png)

resolves: #94752
resolves: #94737

Release note: None

Co-authored-by: Arul Ajmani <[email protected]>
Co-authored-by: Austen McClernon <[email protected]>
@craig craig bot closed this as completed in 891e7a0 Jan 5, 2023
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split: init replica lb splitter with global rand kvoli/cockroach
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