Problem: When a
spring batch has multiple jobs implemented, it is expected to run in parallel
within the JVM instance. I noticed that the jobs are executed sequentially, not
in parallel. In my case, we had 8 jobs with the project, irrespective of the
cron schedule, the jobs are executed in sequential mode.
Root Cause: I was
using JobLauncher instance (@Autowired instance-Singleton) every time while
initiating jobs using @Scheduled annotation. It makes the execution of jobs in
a sequential fashion.
Singleton JobLauncher makes the execution of multiple jobs
sequential.
Solution: I’ve
modified the code to create SimpleJobLauncher instance to initiate the job
everytime, so that the execution of jobs were made parallel.
Also,
Use ThreadPoolTaskExecutor, while building a Step for a Job.
For example, refer the below snapshot of code. During execution, 2 threads will
be created for processing the Reader data. Based on the chunk size, the reader
data will be processed by 2 threads in parallel.
1,2,3 will be processed by Thread 1
4,5,6 will be processed by Thread 2
7,8 will be processed by Thread 1
If you want to initiate specific job instance as standalone,
refer the below code snippet. Read the beanName from Program Argument and
invoke the method with cronPattern. If there are multiple jobs, then you can
specify the beanName and start jvm instance. So that you will have control over
the job execution.
