Prevent active defrag from triggering during replicaof db flush #14274
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New Issues (8)Checkmarx found the following issues in this Pull Request
Fixed Issues (4)Great job! The following issues were fixed in this Pull Request
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tezc
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Aug 13, 2025
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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Pull Request Overview
This PR fixes a critical bug where active defragmentation could be triggered during replica database flush operations, causing crashes due to concurrent database modifications. The fix temporarily disables active defrag before emptying the database and restores the setting afterward.
- Prevents active defrag from running during
replicationEmptyDbCallback()execution - Adds comprehensive test coverage to verify the fix works correctly
- Resolves crashes caused by defrag modifying the database while it's being emptied
Reviewed Changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| src/replication.c | Adds temporary disabling of active defrag around database flush operation |
| tests/unit/memefficiency.tcl | Adds test case to reproduce and verify the fix for issue #14267 |
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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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i see #13495 is part of 8.2, so do we really need to backport that to 8.0? |
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odd. the PR is part of the 8.2 project.. |
YaacovHazan
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Aug 18, 2025
…s#14274) Fix redis#14267 This bug was introduced by redis#13495 ### Summary When a replica clears a large database, it periodically calls processEventsWhileBlocked() in the replicationEmptyDbCallback() callback during the key deletion process. If defragmentation is enabled, this means that active defrag can be triggered while the database is being deleted. The defragmentation process may also modify the database at this time, which could lead to crashes when the database is accessed after defragmentation. Code Path: ``` replicationEmptyDbCallback() -> processEventsWhileBlocked() -> whileBlockedCron() -> defragWhileBlocked() ``` ### Solution This PR temporarily disables active defrag before emptying the database, then restores the active defrag setting after the empty is complete. --------- Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Merged
YaacovHazan
pushed a commit
that referenced
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Aug 18, 2025
Fix #14267 This bug was introduced by #13495 ### Summary When a replica clears a large database, it periodically calls processEventsWhileBlocked() in the replicationEmptyDbCallback() callback during the key deletion process. If defragmentation is enabled, this means that active defrag can be triggered while the database is being deleted. The defragmentation process may also modify the database at this time, which could lead to crashes when the database is accessed after defragmentation. Code Path: ``` replicationEmptyDbCallback() -> processEventsWhileBlocked() -> whileBlockedCron() -> defragWhileBlocked() ``` ### Solution This PR temporarily disables active defrag before emptying the database, then restores the active defrag setting after the empty is complete. --------- Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
sundb
added a commit
that referenced
this pull request
Sep 2, 2025
This PR fixes two crashes due to the defragmentation of the Lua script, which were by #13108 1. During long-running Lua script execution, active defragmentation may be triggered, causing the luaScript structure to be reallocated to a new memory location, then we access `l->node`(may be reallocatedd) after script execution to update the Lua LRU list. In this PR, we don't defrag during blocked scripts, so we don't mess up the LRU update when the script ends. Note that defrag is now only permitted during loading. This PR also reverts the changes made by #14274. 2. Forgot to update the Lua LUR list node's value. Since `lua_scripts_lru_list` node stores a pointer to the `lua_script`'s key, we also need to update `node->value` when the key is reallocated. In this PR, after performing defragmentation on a Lua script, if the script is in the LRU list, its reference in the LRU list will be unconditionally updated.
YaacovHazan
pushed a commit
to YaacovHazan/redis
that referenced
this pull request
Sep 28, 2025
This PR fixes two crashes due to the defragmentation of the Lua script, which were by redis#13108 1. During long-running Lua script execution, active defragmentation may be triggered, causing the luaScript structure to be reallocated to a new memory location, then we access `l->node`(may be reallocatedd) after script execution to update the Lua LRU list. In this PR, we don't defrag during blocked scripts, so we don't mess up the LRU update when the script ends. Note that defrag is now only permitted during loading. This PR also reverts the changes made by redis#14274. 2. Forgot to update the Lua LUR list node's value. Since `lua_scripts_lru_list` node stores a pointer to the `lua_script`'s key, we also need to update `node->value` when the key is reallocated. In this PR, after performing defragmentation on a Lua script, if the script is in the LRU list, its reference in the LRU list will be unconditionally updated.
YaacovHazan
pushed a commit
to YaacovHazan/redis
that referenced
this pull request
Sep 29, 2025
This PR fixes two crashes due to the defragmentation of the Lua script, which were by redis#13108 1. During long-running Lua script execution, active defragmentation may be triggered, causing the luaScript structure to be reallocated to a new memory location, then we access `l->node`(may be reallocatedd) after script execution to update the Lua LRU list. In this PR, we don't defrag during blocked scripts, so we don't mess up the LRU update when the script ends. Note that defrag is now only permitted during loading. This PR also reverts the changes made by redis#14274. 2. Forgot to update the Lua LUR list node's value. Since `lua_scripts_lru_list` node stores a pointer to the `lua_script`'s key, we also need to update `node->value` when the key is reallocated. In this PR, after performing defragmentation on a Lua script, if the script is in the LRU list, its reference in the LRU list will be unconditionally updated.
sundb
added a commit
to YaacovHazan/redis
that referenced
this pull request
Sep 30, 2025
This PR fixes two crashes due to the defragmentation of the Lua script, which were by redis#13108 1. During long-running Lua script execution, active defragmentation may be triggered, causing the luaScript structure to be reallocated to a new memory location, then we access `l->node`(may be reallocatedd) after script execution to update the Lua LRU list. In this PR, we don't defrag during blocked scripts, so we don't mess up the LRU update when the script ends. Note that defrag is now only permitted during loading. This PR also reverts the changes made by redis#14274. 2. Forgot to update the Lua LUR list node's value. Since `lua_scripts_lru_list` node stores a pointer to the `lua_script`'s key, we also need to update `node->value` when the key is reallocated. In this PR, after performing defragmentation on a Lua script, if the script is in the LRU list, its reference in the LRU list will be unconditionally updated.
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Fix #14267
This bug was introduced by #13495
Summary
When a replica clears a large database, it periodically calls processEventsWhileBlocked() in the replicationEmptyDbCallback() callback during the key deletion process.
If defragmentation is enabled, this means that active defrag can be triggered while the database is being deleted.
The defragmentation process may also modify the database at this time, which could lead to crashes when the database is accessed after defragmentation.
Code Path:
Solution
This PR temporarily disables active defrag before emptying the database, then restores the active defrag setting after the empty is complete.
Crash Report