Jason Brown created CASSANDRA-11547:
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Summary: Add background thread to check for clock drift
Key: CASSANDRA-11547
URL: https://issues.apache.org/jira/browse/CASSANDRA-11547
Project: Cassandra
Issue Type: Improvement
Components: Core
Reporter: Jason Brown
Assignee: Jason Brown
Priority: Minor
The system clock has the potential to drift while a system is running. As a
simple way to check if this occurs, we can run a background thread that wakes
up every n seconds, reads the system clock, and checks to see if, indeed, n
seconds have passed.
* If the clock's current time is less than the last recorded time (captured n
seconds in the past), we know the clock has jumped backward.
* If n seconds have not elapsed, we know the system clock is running slow or
has moved backward (by a value less than n)
* If (n + a small offset) seconds have elapsed, we can assume we are within an
acceptable window of clock movement. Reasons for including an offset are the
clock checking thread might not have been scheduled on time, or garbage
collection, and so on.
* If the clock is greater than (n + a small offset) seconds, we can assume the
clock jumped forward.
In the unhappy cases, we can write a message to the log and increment some
metric that the user's monitoring systems can trigger/alert on.
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