[scd] Add hash lock option #1520
Open
the-glu wants to merge 1 commit into
Open
Conversation
the-glu
commented
Jun 10, 2026
| if err != nil { | ||
| return stacktrace.Propagate(err, "Failed to upsert OperationalIntent in repo") | ||
| } | ||
|
|
Member
Author
There was a problem hiding this comment.
This has been ordered as it has no impact and slightly reduce transaction restarts
Contributor
There was a problem hiding this comment.
This should be in a dedicated PR, please split it out.
This was referenced Jun 10, 2026
Member
|
I think we should check performance under conditions at least somewhat similar to real operations, which I think means at least multiple nodes, probably multiple instances, and latency between nodes. I first measured v0.22.0 with: With 10 users, I got: 
I then measured with this branch: 
Just to make sure my retag worked: I see some latency improvement versus v0.22.0 and a tiny throughput improvement, so looks reasonable to me. I will leave final approval to @barroco with his greater practical experience with database operations than me. |
the-glu
force-pushed
the
spread_lock
branch
6 times, most recently
from
86539e0 to
6a5d9fe
Compare
barroco
reviewed
Jun 17, 2026
barroco
left a comment
barroco
left a comment
Contributor
There was a problem hiding this comment.
Still reviewing the results.
| if err != nil { | ||
| return stacktrace.Propagate(err, "Failed to upsert OperationalIntent in repo") | ||
| } | ||
|
|
Contributor
There was a problem hiding this comment.
This should be in a dedicated PR, please split it out.
| !!! danger | ||
| All DSS instances in a DSS pool must use the same value for this option. Mixing will result in dramatically lower performance. | ||
|
|
||
| You can use the `/aux/v1/configuration/scd_lock_mode` endpoint to retrive the current values of locks for a specifc DSS instance. |
Contributor
There was a problem hiding this comment.
Suggested change
| You can use the `/aux/v1/configuration/scd_lock_mode` endpoint to retrive the current values of locks for a specifc DSS instance. | |
| You can use the `/aux/v1/configuration/scd_lock_mode` endpoint to retrieve the current values of locks for a specifc DSS instance. |
| !!! danger | ||
| This option requires migration 3.4.1 for CockroachDB and 1.1.1 for Yugabyte to be effective | ||
|
|
||
| Similar to the previous option, but use lock based on hashed cells (with 65k locks). |
Contributor
There was a problem hiding this comment.
Suggested change
| Similar to the previous option, but use lock based on hashed cells (with 65k locks). | |
| Similar to the SCD global lock option, but use lock based on hashed cells (with 65k locks). |
| for _, cell := range cells { | ||
| // Fibonacci hash: level-13 cell ids only differ in their high bits, | ||
| // so a plain modulo would map them all to the same stripe. | ||
| k := int64((uint64(cell) * 0x9e3779b97f4a7c15) >> 48 % lockStripes) |
Contributor
There was a problem hiding this comment.
nit: Move the value into a constant.
|
|
||
| Similar to the previous option, but use lock based on hashed cells (with 65k locks). | ||
|
|
||
| This should be better than global lock, as long as cells used don't colide and limit number of entries in the database. |
Contributor
There was a problem hiding this comment.
Suggested change
| This should be better than global lock, as long as cells used don't colide and limit number of entries in the database. | |
| This should be better than global lock, as long as cells used don't collide and limit number of entries in the database. |
| zap.Bool("global_lock", false), | ||
| zap.Duration("duration", duration), | ||
| zap.Int("cell_count", len(cells)), | ||
| zap.Int("explicit_subscription_id_count", len(subscriptionIds)), |
Contributor
There was a problem hiding this comment.
Please, add the number of locks acquired.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
This PR follow #1518 as it increase performance of that PR.
Add a new option to lock cells using an hash, as an intermediate between the global lock option and the subscriptions lock.
Using
FlightsInSubstest, with 8 clusters, on a single-local CRDB node we can see an improvement others lock methods.(Don't include option in terraform/helm/tanka yet)