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 fails 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 don't get reflected.

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

Now another weird observation is all of this works if I am using a 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.

Contents of 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} : 
amp;/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.