Cassandra Error (Visualized)

Swapnil B. Bhisey — Thu, 08 Sep 2022 05:22:52 +0000

Success or Failure of Request in Cassandra depends on success or failure of request on more than one machine as per consistency type and driver setting. It's important to understand where request failed to troubleshoot further.
I am visual person so tried drawing diagram to make it easy to understand.

Refer following for more information

https://www.datastax.com/blog/2014/10/cassandra-error-handling-done-right https://docs.datastax.com/en/developer/java-driver/3.6/manual/retries/

Collecting Java Flight Recording (JFR) on openjdk

Swapnil B. Bhisey — Mon, 07 Jun 2021 23:26:17 +0000

From OpenJDK 8u262 has JFR support as its backported with - JDK-8223147: JFR Backport.

Following is just in case if you want to use JFR on openjdk (possible through azul). We just azul opnjdk and it works on my lab instance for collecting JFR. In case in future if anyone wants to use all steps.

With openjdk JFR compress=true don’t work but settings=profile does work.

Java Mission Control from oracle was not able to read the file but you can use zulu zmc .

To download azul OSS jdk

https://www.azul.com/downloads/zulu-community/?architecture=x86-64-bit&package=jdk

As my default JMC did not work with .jfr generated by zing jdk I used following.

https://www.azul.com/products/zulu-mission-control/

Unlock commercial features.

sudo -u <user> jcmd <pid>  VM.unlock_commercial_features

Start JFR collection with settings=profile

sudo -u <user> jcmd <PID> JFR.start name=<jfr_name> settings=profile

Dump JFR

sudo -u <user> jcmd <PID> JFR.dump name=<jfr_name> filename=/tmp/`hostname -i`.jfr

Make sure JFR file is generated.

ls -lrt /tmp/`hostname -i`.jfr

Stop JFR process

sudo -u <user> /usr/lib/jvm/java-1.8.0-openjdk/bin/jcmd  <PID> JFR.stop name=<jfr_name>

Check if any additional JFR process are runing and stop if its not in use

sudo -u <user> jcmd <PID> JFR.check

DEV Community: Swapnil B. Bhisey

Cassandra Error (Visualized)

Collecting Java Flight Recording (JFR) on openjdk