为什么Spring Batch为每个线程使用1个数据库连接？

为什么Spring Batch为每个线程使用1个数据库连接？

堆：

• Java 8

• Spring Boot 1.5

• Spring Batch 3.0.7

• HikariCP 2.7.6

DataSource配置：

• batcdb（postgres）

• readdb（oracle）

• writedb（postgres）

每个数据源都使用HikariCP，每个数据源默认10个连接 .

Spring Batch配置：ThreadExecutor-1：

core-pool-size: 10
max-pool-size: 10
throttle-limit: 10

Job-1 Config / ThreadPoolTaskExecutor :(通过application.yml设置的池大小和限制）

@Bean
public Step job1Step() {
    return stepBuilderFactory.get("job1Step")
            .<ReadModel, WriteModel>chunk(chunkSize)
            .reader(itemReader())
            .processor(compositeProcessor())
            .writer(itemWriter())
            .faultTolerant()
            .taskExecutor(job1TaskExecutor())
            .throttleLimit(throttleLimit)
            .build();
}

@Bean
public ThreadPoolTaskExecutor job1TaskExecutor() {
     ThreadPoolTaskExecutor pool = new ThreadPoolTaskExecutor();
     pool.setCorePoolSize(poolSize);
     pool.setMaxPoolSize(maxPoolSize);
     pool.setWaitForTasksToCompleteOnShutdown(false);
     return pool;
 }

@Bean
@StepScope
public Job1ItemReader job1ItemReader() {
    return new Job1ItemReader(readdb, pageSize);
}

Job1-ItemReader的缩写代码

public class Job1ItemReader extends JdbcPagingItemReader<ReadModel> {
...
}

ThreadExecutor-2：

core-pool-size: 5
max-pool-size: 5
throttle-limit: 5

Job-2 Config / ThreadPoolTaskExecutor：

@Bean
public Step job2Step() throws Exception {
    return stepBuilderFactory.get("job2Step")
            .<ReadModel2, WriteModel2>chunk(chunkSize)
            .reader(job2ItemReader())
            .processor(job2CompositeProcessor())
            .writer(job2ItemWriter())
            .faultTolerant()
            .taskExecutor(job2TaskExecutor())
            .throttleLimit(throttleLimit)
            .build();
}

@Bean
public ThreadPoolTaskExecutor job2TaskExecutor() {
    ThreadPoolTaskExecutor pool = new ThreadPoolTaskExecutor();
    pool.setCorePoolSize(corePoolSize);
    pool.setMaxPoolSize(maxPoolSize);
    pool.setQueueCapacity(queueCapacity);
    pool.setWaitForTasksToCompleteOnShutdown(false);
    return pool;
}

@Bean
@StepScope
public Job2ItemReader job2ItemReader() {
    return new Job2ItemReader(readdb, pageSize);    
}

Job2-ItemReader的缩写代码

public class Job2ItemReader extends JdbcPagingItemReader<ReadModel2> {
...
}

• 有2个职位

• Job-1长时间运行（多天）

• Job-2通常在一小时或两小时内完成，并且每天按计划运行

• 作业在同一个JVM上运行'application'

• 每个Job都有自己定义的ThreadPoolTaskExecutor

当Job-1正在运行，并且Job-2启动时，Job-2无法连接到 readdb . Job-2的批处理读取器抛出以下错误 .

Caused by: org.springframework.jdbc.support.MetaDataAccessException: Could not get Connection for extracting meta data; nested exception is org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLTransientConnectionException: HikariPool-3 - Connection is not available, request timed out after 30000ms.
at org.springframework.jdbc.support.JdbcUtils.extractDatabaseMetaData(JdbcUtils.java:339)
at org.springframework.jdbc.support.JdbcUtils.extractDatabaseMetaData(JdbcUtils.java:366)
at org.springframework.batch.support.DatabaseType.fromMetaData(DatabaseType.java:97)
at org.springframework.batch.item.database.support.SqlPagingQueryProviderFactoryBean.getObject(SqlPagingQueryProviderFactoryBean.java:158)
... 30 common frames omitted
Caused by: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLTransientConnectionException: HikariPool-3 - Connection is not available, request timed out after 30000ms.
at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:80)
at org.springframework.jdbc.support.JdbcUtils.extractDatabaseMetaData(JdbcUtils.java:326)
... 33 common frames omitted
Caused by: java.sql.SQLTransientConnectionException: HikariPool-3 - Connection is not available, request timed out after 30000ms.
at com.zaxxer.hikari.pool.HikariPool.createTimeoutException(HikariPool.java:666)
at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:182)
at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:147)
at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:123)
at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:111)
at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:77)

（编辑以保护无辜者）

参考：

• multi-threaded step

• 类似question/issue，除了我的交易应该在 writedb 上，在这种情况下 HikariPool-3 是 readdb .