fix(cluster): Remove per-call srand in valkey-cli (8.0 backport)#3671
Open
ranshid wants to merge 1 commit into
Open
fix(cluster): Remove per-call srand in valkey-cli (8.0 backport)#3671ranshid wants to merge 1 commit into
ranshid wants to merge 1 commit into
Conversation
Backport of valkey-io#3586 to 8.0 branch. clusterManagerNodePrimaryRandom() called srand(time(NULL)) on every invocation, then immediately rand() % primary_count. When called in a tight loop for uncovered slots, all calls within the same wall-clock second produce the identical seed, causing every uncovered slot to be assigned to the same primary node. Remove all per-call srand() invocations and consolidate into a single srand(time(NULL) ^ getpid()) at the start of main(). This allows rand() to advance its state across calls, distributing uncovered slots randomly across available primaries. (cherry picked from commit 7e2a2f7) Signed-off-by: Ran Shidlansik <ranshid@amazon.com>
enjoy-binbin
approved these changes
May 12, 2026
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
2 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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
Backport of #3586 to the 8.0 branch.
Problem
clusterManagerNodePrimaryRandom()calledsrand(time(NULL))on every invocation, then immediatelyrand() % primary_count. When called in a tight loop for uncovered slots, all calls within the same wall-clock second produce the identical seed, causing every uncovered slot to be assigned to the same primary node.The same issue existed in
clusterManagerOptimizeAntiAffinity,pipeMode, andLRUTestMode.Solution
Remove all per-call
srand()invocations and consolidate into a singlesrand(time(NULL) ^ getpid())at the start ofmain(). This allowsrand()to advance its state across calls, distributing uncovered slots randomly across available primaries.(cherry picked from commit 7e2a2f7)