Database Reference
In-Depth Information
Tip
Although we have mentioned that the timestamp for the column is provided by the client,
it is not true for CQL. CQL uses the server-side timestamp unless specified by the USING
TIMESTAMP clause.
Even if you do not use CQL, the importance of synchronization on the server-side expir-
ing columns is retained, and tombstone removal does require time to be correctly set. In
general, it is advisable to have your production servers (of any application) to be time syn-
chronized.
Note
With Amazon Web Services or any other cloud service, it is a general perception that de-
pending on a hardware clock is a safe bet. This is not correct. There may be situations
when time on these virtual instances gets drifted. In AWS EC2 instances, to be able to set
up NTP, you need to disable sync with the clock on the physical machine. You can do that
by using the following command:
$ echo 1 > /proc/sys/xen/independent_wallclock
This is transient, but to make it permanent, you can edit /etc/sysctl.conf by
adding the following line of code:
xen.independent_wallclock=1
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