How to choose chunk model or tasklet model

Here, how to choose chunk model and tasklet model is explained by organizing each feature. Refer to the following chapters which are explained in detail appropriately.

Understand the following contents as examples of concepts without any constraints or recommendations. Refer to it while creating a job depending on the characteristics of the users and systems.

The main differences between the chunk model and the tasklet model are given below.

Comparison of chunk model and tasklet model.
Item	Chunk	Tasklet
Components	It consists of 3 components mainly `ItemReader`, `ItemProcessor` and `ItemWriter`.	It is consolidated in one `Tasklet`.
Transaction	A certain number of records are processed by issuing intermediate commit. Batch commit cannot be done. It can be processed by specific machine resources regardless of the data count. If an error occurs in the midway, then unprocessed data and processed data will get mixed.	The data is entirely processed by batch commit. There is a need for the user to implement intermediate commit. If the data to be processed is large, machine resources may get exhausted. If an error occurs in the midway, only the unprocessed data is rolled back.
Restart	It can be restarted based on the record count.	It cannot be restarted based on the record count.

Based on this, we will introduce some examples of using each one as follows.

To make recovery as simple as possible: When the job having error, is to be recovered by only re-running the target job, tasklet model can be chooseed to make recovery simple.
In chunk model, it should be dealt by returning the processed data to the state before executing the job and by creating a job to process only the unprocessed data.
To consolidate the process contents: When you want to prioritize the outlook of job such as 1 job in 1 class, tasklet can be chooseed.
To process large data stably: When performing batch process of 10 million records, consider to use chunk model in case the record count that influences the resources is the target. It means stabilizing the process by intermediate commit. Even in tasklet model, intermediate commit can be used, but it is simpler to implement in chunk model.
To restart based on the record count for the recovery after error: When batch window is difficult and you want to resume from error data onwards, chunk model should be chooseed to use restart based on the record count provided by Spring Batch. This eliminates the need to create that mechanism for each job.

Chunk model and tasklet model are basically used in combination.
It is not necessary to implement only one model in all jobs in the batch system.
Use one model based on the characteristics of jobs of the entire system and use the other model in accordance with the situation.

For example, in most cases it is to choose a tasklet model if there is a margin in the number of processesing records and processing time. In a very small number of cases, choosing a chunk model for jobs that process large numbers of records.