Author: TK

MySQL gap lock, next key lock by example

MySQL's gap lock or next key lock is a specific mechanism to guarantee it's isolation level. Gap lock is set on before or after values of the accessed record. Next key lock is the accessed row lock + gap lock. Therefore they have similar features. Gap lock is activated in the following conditions. Isolation level … Continue reading MySQL gap lock, next key lock by example →

The difference of Isolation level – Read Committed vs Repeatable Read

MySQL's default isolation level is "Repeatable Read". But Oracle's default isolation level is "Read Committed". In this post, I will show you the difference by example. Test environment : MySQL 5.7 Test table Test scenario 1 - Read Committed Seq Session 1 Session 2 1 set session transaction isolation level read committed; start transaction; set … Continue reading The difference of Isolation level – Read Committed vs Repeatable Read →

Spring Batch – Read once, Write multi example

Sometimes, we need to read once, write multi ETL with Spring Batch. Spring Batch supports it with CompositeItemWriter (org.springframework.batch.item.support.CompositeItemWriter). Sample table schema Declaration of CompositeItemWriter Make sure that CompositeItemWriter has 2 delegates (TestWriter1, TestWriter2). You can use any Writer as it's delegate. Full Job declaration Make sure that Job task is using new CompositeItemWriter instead … Continue reading Spring Batch – Read once, Write multi example →

More on Spring Batch Writer

Spring Batch Writer is the implementation of org.springframework.batch.item.ItemWriter. You can write a custom writer, but Spring Batch already has some useful implementations, such as org.springframework.batch.item.amqp.AmqpItemWriter for AMQP brokers such as RabbitMQ org.springframework.batch.item.file.FlatFileItemWriter for a file org.springframework.batch.item.database.JpaItemWriter for database using JPA org.springframework.batch.item.database.JdbcBatchItemWriter for writing to database with plain SQL This post shows detailed information on using … Continue reading More on Spring Batch Writer →

More on Spring Batch Reader

Spring Batch Job is composed of Reader, Processor and Writer. This post shows some more details on Reader. Reader is the implementation of org.springframework.batch.item.Reader. I recommend to use the following implementations. AmqpItemReader (org.springframework.batch.item.amqp.AmqpItemReader) : to interact with queue such as RabbitMQ FlatFileItemReader (org.springframework.batch.item.file.FlatFileItemReader) : to interact with a file JdbcCursorItemReader (org.springframework.batch.item.database.JdbcCursorItemReader) : to interact with … Continue reading More on Spring Batch Reader →

A tip on using user transaction on Mybatis

When using transation on Mybatis, there are 3 ways. Container managed transaction - JEE engine manages transaction User managed transaction - transaction is controlled by user source code Spring managed transaction - transaction is controlled by Spring Transaction policy I usually use Spring managed or container managed transaction. But sometimes, I need to control transaction … Continue reading A tip on using user transaction on Mybatis →

Some useful commands to manage Kafka

This post shows some useful commands to manage Kafka. (based on version 2.12) Detailed information is on Kafka official documentation Notice that some commands use zookeeper ip/port and others use kafka ip/port Topic management commands List all topics ${KAFKA_HOME}/bin/kafka-topics.sh --list --zookeeper zookeeper_ip:port Create a topic ${KAFKA_HOME}/bin/kafka-topics.sh --create --zookeeper zookeeper_ip:port --replication-factor num --partitions num --topic topic_name … Continue reading Some useful commands to manage Kafka →