fix: prevent infinite drain loop in forked BGSave child process#894
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eliastam wants to merge 2 commits intovalkey-io:mainfrom
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fix: prevent infinite drain loop in forked BGSave child process#894eliastam wants to merge 2 commits intovalkey-io:mainfrom
eliastam wants to merge 2 commits intovalkey-io:mainfrom
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DrainMutationQueue spins forever in the BGSave forked child process because the mutation queue is a frozen snapshot that will never be drained by writer threads. Check VALKEYMODULE_CTX_FLAGS_IS_CHILD and return an error instead of attempting to drain. Also adds a configurable timeout (drain-mutation-queue-timeout-ms, default 5s) to DrainMutationQueue as a safety net, and an integration test covering the BGSAVE with non-empty mutation queue scenario. Signed-off-by: Elias Tamraz <tamrazelias@gmail.com>
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otherscase
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Mar 12, 2026
src/index_schema.cc
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| static const auto max_sleep = std::chrono::milliseconds(100); | ||
| auto sleep_duration = std::chrono::milliseconds(1); | ||
| auto timeout = std::chrono::milliseconds( | ||
| options::GetDrainMutationQueueTimeoutMs().GetValue()); |
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GetDrainMutationQueueOnSaveTimeoutMs?
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src/index_schema.cc
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| if (options::GetDrainMutationQueueOnSave().GetValue()) { | ||
| int flags = ValkeyModule_GetContextFlags(nullptr); | ||
| bool is_bgsave = (flags & VALKEYMODULE_CTX_FLAGS_IS_CHILD) != 0; | ||
| if (is_bgsave) { |
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We should still continue if the queue is empty at this point.
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| auto status = DrainMutationQueue(ctx); | ||
| if (!status.ok()) { | ||
| VMSDK_LOG(WARNING, ctx) | ||
| << "Failed to drain mutation queue on load for index " | ||
| << vmsdk::config::RedactIfNeeded(name_) << ": " << status; | ||
| } |
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Timeout should only apply for save. We should keep the load behaviour unchanged.
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reverted this change
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- Rename config to drain-mutation-queue-on-save-timeout-ms - Only error in forked child if mutation queue is non-empty - Keep load behavior unchanged, timeout only applies to save Signed-off-by: Elias Tamraz <tamrazelias@gmail.com>
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DrainMutationQueue spins forever in the BGSave forked child process because the mutation queue is a frozen snapshot that will never be drained by writer threads. Check VALKEYMODULE_CTX_FLAGS_IS_CHILD and return an error instead of attempting to drain.
Also adds a configurable timeout (drain-mutation-queue-timeout-ms, default 5s) to DrainMutationQueue as a safety net, and an integration test covering the BGSAVE with non-empty mutation queue scenario.