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List:       cassandra-user
Subject:    Cassandra nightly process
From:       "Loïc CHANEL via user" <user () cassandra ! apache ! org>
Date:       2023-01-16 14:06:41
Message-ID: CAEg_P-K7dRa4fkUkMo0rWe-LiO7S5sLYp8GMdTKOhyFrca84Uw () mail ! gmail ! com
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Hi team,

I am currently running a 2-nodes Cassandra database. Although that's not
the best setup, the cluster is doing pretty fine.
Still, I noticed that for (at least) 5 days now, one of my two nodes is
writing hints during the night, and then it recovers the data-sync with the
other node in the morning. What's interesting here is that we can see that
the hints writing stuff happens at 0:00 every day, then it starts to
recover for a few minutes before 2:00, then the node starts writing hints
again at 2:00, then it (sometimes) starts to recover a few minutes before
4:00 and then it start writing hints again at 4:00 (and sometimes same
thing happens once more around 6:00).
See the following graph that shows the number of hints files in hints
directory :

[image: image.png]

I am not aware of any nightly sync or any such process in Cassandra
database, but I checked cron logs on the servers and nothing seems to
happen at these times, and there is no particular activity at that time on
the virtualization platform (the daily snapshot is taken at 1:30). So my
question here is : am I missing a Cassandra internal process that is
triggered on a daily basis at 0:00 and 2:00 ?
Thanks,


Lo=C3=AFc CHANEL
System Big Data engineer
SoftAtHome (Lyon, France)

[Attachment #5 (text/html)]

<div dir="ltr">Hi team,<div><br></div><div>I am currently running a 2-nodes Cassandra \
database. Although that&#39;s not the best setup, the cluster is doing pretty \
fine.</div><div>Still, I noticed that for (at least) 5 days now, one of my two nodes \
is writing hints during the night, and then it recovers the data-sync with the other \
node in the morning. What&#39;s interesting here is that we can see that the hints \
writing stuff happens at 0:00 every day, then it starts to recover for a few minutes \
before 2:00, then the node starts writing hints again at 2:00, then it (sometimes) \
starts to recover a few minutes before 4:00 and then it start writing hints again at \
4:00 (and sometimes same thing happens once more around 6:00).</div><div>See the \
following graph that shows the number of hints files in hints directory \
:</div><div><br></div><div><img src="cid:ii_lcyvhlrs0" alt="image.png" width="1480" \
height="261" style="margin-right: 0px;"><br></div><div><br></div><div>I am not aware \
of any nightly sync or any such process in Cassandra database, but I checked cron \
logs on the servers and nothing seems to happen at these times, and there is no \
particular activity at that time on the virtualization platform (the daily snapshot \
is taken at 1:30). So my question here is : am I missing a Cassandra internal process \
that is triggered on a daily  basis at 0:00 and 2:00 \
?</div><div>Thanks,</div><div><br></div><div><br clear="all"><div><div dir="ltr" \
class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div \
dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div \
dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div>Loïc CHANEL<br>System Big \
Data engineer<br>SoftAtHome (Lyon, \
France)<br></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div>


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