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| -rw-r--r-- | modules/detect_time_jump/README.rst | 20 |
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diff --git a/modules/detect_time_jump/README.rst b/modules/detect_time_jump/README.rst new file mode 100644 index 0000000..240907f --- /dev/null +++ b/modules/detect_time_jump/README.rst @@ -0,0 +1,20 @@ +.. _mod-detect_time_jump: + +Detect discontinuous jumps in the system time +--------------------------------------------- + +This module detect discontinuous jumps in the system time when resolver +is running. It clears cache when a significant backward time jumps occurs. + +Time jumps are usually created by NTP time change or by admin intervention. +These change can affect cache records as they store timestamp and TTL in real +time. + +If you want to preserve cache during time travel you should disable +this module by ``modules.unload('detect_time_jump')``. + +Due to the way monotonic system time works on typical systems, +suspend-resume cycles will be perceived as forward time jumps, +but this direction of shift does not have the risk of using records +beyond their intended TTL, so forward jumps do not cause erasing the cache. + |