fix(cluster): Remove per-call srand in clusterManagerNodePrimaryRandom#3586
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ranshid merged 3 commits intoApr 30, 2026
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This is only called in LRUTestMode, right? https://github.com/valkey-io/valkey/blob/unstable/src/valkey-cli.c#L9832-L9838 Overall, it would make sense to just srand once |
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## unstable #3586 +/- ##
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Thanks for the feedback @murphyjacob4 . Addressed the issue and made a single srand call now. this should not have the DCO issue either. |
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April 28, 2026 22:24
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 the srand() call since the PRNG is already seeded at startup (srand(time(NULL) ^ getpid()) at line 9838). This allows rand() to advance its state across calls, distributing uncovered slots randomly across available primaries. Signed-off-by: Abhishek Mathur <matshek@amazon.com>
Move the PRNG seeding to a single srand(time(NULL) ^ getpid()) call in main(), removing redundant per-function srand() calls from clusterManagerOptimizeAntiAffinity(), pipeMode(), and LRUTestMode(). This ensures consistent entropy (pid mixing) across all code paths and prevents any future tight-loop reseeding bugs like the one fixed in clusterManagerNodePrimaryRandom(). Signed-off-by: Abhishek Mathur <matshek@amazon.com>
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rainsupreme
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LGTM! Good find on the bug :)
roshkhatri
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LGTM,
Nit. can you please update the top comment and PRNG is already seeded at startup (srand(time(NULL) ^ getpid()) at line 9838), we can change it to this approach consolidated all srand calls into main()
ranshid
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valkey-io#3586) 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 the srand() call since the PRNG is already seeded at startup (srand(time(NULL) ^ getpid()) at line 9838). This allows rand() to advance its state across calls, distributing uncovered slots randomly across available primaries. --------- Signed-off-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Ran Shidlansik <ranshid@amazon.com>
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valkey-io#3586) 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 the srand() call since the PRNG is already seeded at startup (srand(time(NULL) ^ getpid()) at line 9838). This allows rand() to advance its state across calls, distributing uncovered slots randomly across available primaries. --------- Signed-off-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Ran Shidlansik <ranshid@amazon.com>
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valkey-io#3586) 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 the srand() call since the PRNG is already seeded at startup (srand(time(NULL) ^ getpid()) at line 9838). This allows rand() to advance its state across calls, distributing uncovered slots randomly across available primaries. --------- Signed-off-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Ran Shidlansik <ranshid@amazon.com>
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valkey-io#3586) 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 the srand() call since the PRNG is already seeded at startup (srand(time(NULL) ^ getpid()) at line 9838). This allows rand() to advance its state across calls, distributing uncovered slots randomly across available primaries. --------- Signed-off-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Ran Shidlansik <ranshid@amazon.com>
This was referenced May 12, 2026
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Backport of #3586 to the 9.1 branch. ## Problem `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. The same issue existed in `clusterManagerOptimizeAntiAffinity`, `pipeMode`, and `LRUTestMode`. ## Solution 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>
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#3586) 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 the srand() call since the PRNG is already seeded at startup (srand(time(NULL) ^ getpid()) at line 9838). This allows rand() to advance its state across calls, distributing uncovered slots randomly across available primaries. --------- Signed-off-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Ran Shidlansik <ranshid@amazon.com>
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#3586) 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 the srand() call since the PRNG is already seeded at startup (srand(time(NULL) ^ getpid()) at line 9838). This allows rand() to advance its state across calls, distributing uncovered slots randomly across available primaries. --------- Signed-off-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Ran Shidlansik <ranshid@amazon.com>
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#3586) 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 the srand() call since the PRNG is already seeded at startup (srand(time(NULL) ^ getpid()) at line 9838). This allows rand() to advance its state across calls, distributing uncovered slots randomly across available primaries. --------- Signed-off-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Ran Shidlansik <ranshid@amazon.com>
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#3586) 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 the srand() call since the PRNG is already seeded at startup (srand(time(NULL) ^ getpid()) at line 9838). This allows rand() to advance its state across calls, distributing uncovered slots randomly across available primaries. --------- Signed-off-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Ran Shidlansik <ranshid@amazon.com>
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#3586) 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 the srand() call since the PRNG is already seeded at startup (srand(time(NULL) ^ getpid()) at line 9838). This allows rand() to advance its state across calls, distributing uncovered slots randomly across available primaries. --------- Signed-off-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Ran Shidlansik <ranshid@amazon.com>
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#3586) 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 the srand() call since the PRNG is already seeded at startup (srand(time(NULL) ^ getpid()) at line 9838). This allows rand() to advance its state across calls, distributing uncovered slots randomly across available primaries. --------- Signed-off-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Ran Shidlansik <ranshid@amazon.com>
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#3586) 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 the srand() call since the PRNG is already seeded at startup (srand(time(NULL) ^ getpid()) at line 9838). This allows rand() to advance its state across calls, distributing uncovered slots randomly across available primaries. --------- Signed-off-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Ran Shidlansik <ranshid@amazon.com>
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#3586) 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 the srand() call since the PRNG is already seeded at startup (srand(time(NULL) ^ getpid()) at line 9838). This allows rand() to advance its state across calls, distributing uncovered slots randomly across available primaries. --------- Signed-off-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Ran Shidlansik <ranshid@amazon.com>
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#3586) 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 the srand() call since the PRNG is already seeded at startup (srand(time(NULL) ^ getpid()) at line 9838). This allows rand() to advance its state across calls, distributing uncovered slots randomly across available primaries. --------- Signed-off-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Ran Shidlansik <ranshid@amazon.com>
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#3586) 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 the srand() call since the PRNG is already seeded at startup (srand(time(NULL) ^ getpid()) at line 9838). This allows rand() to advance its state across calls, distributing uncovered slots randomly across available primaries. --------- Signed-off-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Ran Shidlansik <ranshid@amazon.com>
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#3586) 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 the srand() call since the PRNG is already seeded at startup (srand(time(NULL) ^ getpid()) at line 9838). This allows rand() to advance its state across calls, distributing uncovered slots randomly across available primaries. --------- Signed-off-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Abhishek Mathur <matshek@amazon.com> Co-authored-by: Ran Shidlansik <ranshid@amazon.com>
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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 the srand() call since the PRNG is already seeded at startup (srand(time(NULL) ^ getpid()) at line 9838). This allows rand() to advance its state across calls, distributing uncovered slots randomly across available primaries.