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From "Durity, Sean R" <SEAN_R_DUR...@homedepot.com>
Subject RE: [EXTERNAL] Issue while updating a record in 3 node cassandra cluster deployed using kubernetes
Date Tue, 09 Apr 2019 13:28:00 GMT
My first suspicion would be to look at the server times in the cluster. It looks like other
cases where a write occurs (with no errors) but the data is not retrieved as expected. If
the write occurs with an earlier timestamp than the existing data, this is the behavior you
would see. The write would occur, but it would not be the latest data to be retrieved. The
write looks like it fails silently, but it actually does exactly what it is designed to do.

Sean Durity

From: Mahesh Daksha <dakshme@gmail.com>
Sent: Tuesday, April 09, 2019 9:10 AM
To: user@cassandra.apache.org
Subject: [EXTERNAL] Issue while updating a record in 3 node cassandra cluster deployed using
kubernetes


Hello All,

I have a 3 node cassandra cluster with Replication factor as 2 and read-write consistency
set to QUORUM. We are using Spring data cassandra. All infrastructure is deployed using kubernetes.

Now in normal use case many records gets inserted to cassandra table. Then we try to modify/update
one of the record using save method of repo, like below:

ChunkMeta tmpRec = chunkMetaRepository.save(chunkMeta);

After execution of above statement we never see any exception or error. But still this update
state goes silent/fail intermittently. That is at times the record in the db gets updated
successfully where as other time it fails. Also in the above query when we print tmpRec it
contains the updated and correct value every time. Still in the db these updated values doesn't
get reflected.

We check the the cassandra transport TRACE logs on all nodes and found the our queries are
getting logged there and are being executed also with out any error or exception.

Now another weird observation is this all thing works erfectly fine if I am using single cassandra
node (in kubernetes) or if we deploy above infra using ansible (even works for 3 nodes for
Ansible).

It looks some issue is specifically with the kubernetes 3 node deployment of cassandra. Primarily
looks like replication among nodes causing this.

Please suggest.



I have a 3 node cassandra cluster with Replication factor as 2 and read-write consistency
set to QUORUM. We are using Spring data cassandra. All infrastructure is deployed using kubernetes.

Now in normal use case many records gets inserted to cassandra table. Then we try to modify/update
one of the record using save method of repo, like below:

ChunkMeta tmpRec = chunkMetaRepository.save(chunkMeta);

After execution of above statement we never see any exception or error. But still this update
fail intermittently. That is when we check the record in the db sometime it gets updated successfully
where as other time it fails. Also in the above query when we print tmpRec it contains the
updated and correct value. Still in the db these updated values doesnt get reflected.

We check the the cassandra transport TRACE logs on all nodes and found the our queries are
getting logged there and are being executed also.

Now another weird observation is this all thing works if I am using single cassandra node
(in kubernetes) or if we deploy above infra using ansible (even works for 3 nodes for Ansible).

It looks some issue is specifically with the kubernetes 3 node deployment of cassandra. Primarily
looks like replication among nodes causing this.

Please suggest.

Below are the contents of  my cassandra Docker file:

FROM ubuntu:16.04



RUN apt-get update && apt-get install -y python sudo lsof vim dnsutils net-tools &&
apt-get clean && \

    addgroup testuser && useradd -g testuser testuser && usermod --password
testuser testuser;



RUN mkdir -p /opt/test && \

    mkdir -p /opt/test/data;



ADD jre8.tar.gz /opt/test/

ADD apache-cassandra-3.11.0-bin.tar.gz /opt/test/



RUN chmod 755 -R /opt/test/jre && \

    ln -s /opt/test/jre/bin/java /usr/bin/java && \

    mv /opt/test/apache-cassandra* /opt/test/cassandra;



RUN mkdir -p /opt/test/cassandra/logs;



ENV JAVA_HOME /opt/test/jre

RUN export JAVA_HOME



COPY version.txt /opt/test/cassandra/version.txt



WORKDIR /opt/test/cassandra/bin/



RUN mkdir -p /opt/test/data/saved_caches && \

    mkdir -p /opt/test/data/commitlog && \

    mkdir -p /opt/test/data/hints && \

    chown -R testuser:testuser /opt/test/data && \

    chown -R testuser:testuser /opt/test;



USER testuser



CMD cp /etc/cassandra/cassandra.yml ../conf/conf.yml && perl -p -e 's/\$\{([^}]+)\}/defined
$ENV{$1} ? $ENV{$1} : $&/eg; s/\$\{([^}]+)\}//eg' ../conf/conf.yml > ../conf/cassandra.yaml
&& rm ../conf/conf.yml && ./cassandra -f

Please note conf.yml is basically cassandra.yml file having properties related to cassandra.



Thanks,

Mahesh Daksha

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