Spring Batch Learning (iii) jobrepository

The spring batch job has a lot of metadata at run time, which is typically stored in memory or in the database, because spring batch is configured to use HSQLDB in the default configuration, which means that all of the metadata is stored in memory during job operation. The end of the job will automatically disappear as the process ends, where we recommend configuring Jobrepository to use MySQL.

In this case, Spring batch uses the database to maintain state in a single execution or from one execution to another, and the job execution information includes the job instance, the parameters passed in, the results of the execution, and the results of each step execution are stored in the database The database uses 6 tables to store related information:

batch_job_instance

As we all know, a job instance is created when the job is run, the job instance contains the job instance itself and the job parameters, and all the job instance itself information will be saved in the Batch_job_instance table:

Field	Describe
job_instance_id	Primary key of the table
VERSION	Version of the record
Job_name	Job name to be executed
Job_key	The hash value of the job name and job parameter, which is used to uniquely indicate a job instance

Batch_job_params

This table contains all the parameters that are passed to the job, as mentioned above, and the parameters are used by spring batch as part of the job label. This table contains the following fields:

Field	Describe
job_instance_id	A foreign key that represents batch_job_instance
Type_cd	The type that represents the stored value (string, date, long, double)
Key_name	The key for the job parameter (the job parameter is passed as a key-value pair)
String_val	When this parameter is a string type, the value
Date_val	Date type parameter values
Long_val	Long Integer parameter values
Double_val	Double or single-precision parameter values

batch_job_executionand thebatch_step_execution

When a job is created and executed, the running state of the job is saved in the Batch_job_execution table, which includes: Start time, end time, the result of the most recent execution;

The Batch_step_execution table is similar to Batch_job_execution, which contains the parameters of the start time, the end time, the number of commits and the step status of each step in the execution process.

batch_job_execution field information for the table:

Field	Describe
job_execution_id	Primary key of the table
VERSION	Version of the record
job_instance_id	Foreign keys to the Batch_job_instance table
Create_time	The time that the job instance was created
Start_time	Time the job started executing
End_time	The time at which the job execution ended, whether successful or not
STATUS	Status of the job being executed
Exit_code	Exit code on Job return
Exit_message	Launch message on Job return
last_updated	The time the current record was last updated

batch_step_execution field information for the table:

step_execution_id	Primary key of the table
VERSION	Version of the record
Step_name	The name of step that is configured in the job XML
job_execution_id	Foreign keys connected to the Batch_job_execution table
Start_time	Time of Step start
End_time	Step completion time, whether successful or not
STATUS	Current status of step
Commit_count	Number of times the current step was commit
Read_count	Number of times the current step reads the database
Filter_count	The number of item currently read by step
Write_count	The number of item currently written by step
Read_skip_count	Number skipped when reading item
Write_skip_count	Number of skipped when writing item
Process_skip_count	Number of item not itemprocessor processed after Itemreader read
Rollback_count	The total number of rollback during step execution
Exit_code	Exit code returned when step is completed
Exit_message	Exit message returned when step completes
last_updated	The time the record was last updated

Batch_job_execution_contextand theBatch_step_execution_context

This is a two context-related table that is used to store the persisted version of the job or step-related executioncontext, and the ExecutionContext in Spring batch is similar to a servlet in a Web application The context or session, which provides a global space for storing information, is essentially a key-value pair of scopes in a job or step; the job or step's executioncontext is used to pass information in a specific scope, if the job , it is used to pass information between step and step, which, if it is step, is used to pass information during the processing of multiple records.

table Batch_job_execution_context and Batch_step_execution_context are serialized versions of these key-value pairs, which are almost identical except for a foreign key;  

TD style= "border:1px solid silver; Border-collapse:collapse; Padding:3px ">  a serialized ExecutionContext to use when retrying in the future.

Fields	description
	reference from table batch_job_execution or batch_step_execution foreign key
short_context
serialized_context

Spring Batch Learning (iii) Jobrepository