Spring事务路由
首先,我们将创建一个DataSourceType
Java枚举,定义我们的事务路由选项:
public enum DataSourceType {
READ_WRITE,
READ_ONLY
}
为了将读写事务路由到主 node ,将只读事务路由到副本 node ,我们可以定义连接到主 node 的ReadWriteDataSource
和连接到副本 node 的ReadOnlyDataSource
.
读写和只读事务路由由Spring AbstractRoutingDataSource
抽象完成,由TransactionRoutingDatasource
实现,如下图所示:
TransactionRoutingDataSource
很容易实现,如下所示:
public class TransactionRoutingDataSource
extends AbstractRoutingDataSource {
@Nullable
@Override
protected Object determineCurrentLookupKey() {
return TransactionSynchronizationManager
.isCurrentTransactionReadOnly() ?
DataSourceType.READ_ONLY :
DataSourceType.READ_WRITE;
}
}
基本上,我们判断存储当前事务上下文的Spring TransactionSynchronizationManager
类,以判断当前运行的Spring事务是否为只读.
determineCurrentLookupKey
方法返回用于 Select 读写或只读JDBC DataSource
的鉴别器值.
Spring读写和只读JDBC数据源配置
DataSource
配置如下所示:
@Configuration
@ComponentScan(
basePackages = "com.vladmihalcea.book.hpjp.util.spring.routing"
)
@PropertySource(
"/META-INF/jdbc-postgresql-replication.properties"
)
public class TransactionRoutingConfiguration
extends AbstractJPAConfiguration {
@Value("${jdbc.url.primary}")
private String primaryUrl;
@Value("${jdbc.url.replica}")
private String replicaUrl;
@Value("${jdbc.username}")
private String username;
@Value("${jdbc.password}")
private String password;
@Bean
public DataSource readWriteDataSource() {
PGSimpleDataSource dataSource = new PGSimpleDataSource();
dataSource.setURL(primaryUrl);
dataSource.setUser(username);
dataSource.setPassword(password);
return connectionPoolDataSource(dataSource);
}
@Bean
public DataSource readOnlyDataSource() {
PGSimpleDataSource dataSource = new PGSimpleDataSource();
dataSource.setURL(replicaUrl);
dataSource.setUser(username);
dataSource.setPassword(password);
return connectionPoolDataSource(dataSource);
}
@Bean
public TransactionRoutingDataSource actualDataSource() {
TransactionRoutingDataSource routingDataSource =
new TransactionRoutingDataSource();
Map<Object, Object> dataSourceMap = new HashMap<>();
dataSourceMap.put(
DataSourceType.READ_WRITE,
readWriteDataSource()
);
dataSourceMap.put(
DataSourceType.READ_ONLY,
readOnlyDataSource()
);
routingDataSource.setTargetDataSources(dataSourceMap);
return routingDataSource;
}
@Override
protected Properties additionalProperties() {
Properties properties = super.additionalProperties();
properties.setProperty(
"hibernate.connection.provider_disables_autocommit",
Boolean.TRUE.toString()
);
return properties;
}
@Override
protected String[] packagesToScan() {
return new String[]{
"com.vladmihalcea.book.hpjp.hibernate.transaction.forum"
};
}
@Override
protected String databaseType() {
return Database.POSTGRESQL.name().toLowerCase();
}
protected HikariConfig hikariConfig(
DataSource dataSource) {
HikariConfig hikariConfig = new HikariConfig();
int cpuCores = Runtime.getRuntime().availableProcessors();
hikariConfig.setMaximumPoolSize(cpuCores * 4);
hikariConfig.setDataSource(dataSource);
hikariConfig.setAutoCommit(false);
return hikariConfig;
}
protected HikariDataSource connectionPoolDataSource(
DataSource dataSource) {
return new HikariDataSource(hikariConfig(dataSource));
}
}
/META-INF/jdbc-postgresql-replication.properties
资源文件提供了读写和只读JDBC DataSource
组件的配置:
hibernate.dialect=org.hibernate.dialect.PostgreSQL10Dialect
jdbc.url.primary=jdbc:postgresql://localhost:5432/high_performance_java_persistence
jdbc.url.replica=jdbc:postgresql://localhost:5432/high_performance_java_persistence_replica
jdbc.username=postgres
jdbc.password=admin
jdbc.url.primary
属性定义主 node 的URL,而jdbc.url.replica
属性定义副本 node 的URL.
readWriteDataSource
Spring组件定义读写JDBCDataSource
,而readOnlyDataSource
组件定义只读JDBCDataSource
.
请注意,读写和只读数据源都使用HikariCP进行连接池.
actualDataSource
充当读写和只读数据源的门面,并使用TransactionRoutingDataSource
实用程序实现.
readWriteDataSource
使用DataSourceType.READ_WRITE
键注册,readOnlyDataSource
使用DataSourceType.READ_ONLY
键注册.
因此,当执行读写@Transactional
方法时,将使用readWriteDataSource
,而当执行@Transactional(readOnly = true)
方法时,将使用readOnlyDataSource
.
请注意,additionalProperties
方法定义了hibernate.connection.provider_disables_autocommit
Hibernate属性,我将其添加到Hibernate中,以推迟资源本地JPA事务的数据库获取.
不仅hibernate.connection.provider_disables_autocommit
允许您更好地利用数据库连接,而且这是我们让这个示例工作的唯一方法,因为在没有这种配置的情况下,连接是在调用determineCurrentLookupKey
方法TransactionRoutingDataSource
之前获得的.
构建JPA EntityManagerFactory
所需的其余Spring组件由AbstractJPAConfiguration
基类定义.
基本上,actualDataSource
由数据源代理进一步包装,并提供给JPA EntityManagerFactory
.您可以查看source code on GitHub以了解更多详细信息.
测试时间
为了判断事务路由是否有效,我们将通过在postgresql.conf
配置文件中设置以下属性来启用PostgreSQL查询日志(log):
log_min_duration_statement = 0
log_line_prefix = '[%d] '
log_min_duration_statement
属性设置用于记录所有PostgreSQL语句,而第二个属性将数据库名称添加到SQL日志(log)中.
所以,当调用newPost
和findAllPostsByTitle
方法时,如下所示:
Post post = forumService.newPost(
"High-Performance Java Persistence",
"JDBC", "JPA", "Hibernate"
);
List<Post> posts = forumService.findAllPostsByTitle(
"High-Performance Java Persistence"
);
我们可以看到PostgreSQL记录了以下消息:
[high_performance_java_persistence] LOG: execute <unnamed>:
BEGIN
[high_performance_java_persistence] DETAIL:
parameters: $1 = 'JDBC', $2 = 'JPA', $3 = 'Hibernate'
[high_performance_java_persistence] LOG: execute <unnamed>:
select tag0_.id as id1_4_, tag0_.name as name2_4_
from tag tag0_ where tag0_.name in ($1 , $2 , $3)
[high_performance_java_persistence] LOG: execute <unnamed>:
select nextval ('hibernate_sequence')
[high_performance_java_persistence] DETAIL:
parameters: $1 = 'High-Performance Java Persistence', $2 = '4'
[high_performance_java_persistence] LOG: execute <unnamed>:
insert into post (title, id) values ($1, $2)
[high_performance_java_persistence] DETAIL:
parameters: $1 = '4', $2 = '1'
[high_performance_java_persistence] LOG: execute <unnamed>:
insert into post_tag (post_id, tag_id) values ($1, $2)
[high_performance_java_persistence] DETAIL:
parameters: $1 = '4', $2 = '2'
[high_performance_java_persistence] LOG: execute <unnamed>:
insert into post_tag (post_id, tag_id) values ($1, $2)
[high_performance_java_persistence] DETAIL:
parameters: $1 = '4', $2 = '3'
[high_performance_java_persistence] LOG: execute <unnamed>:
insert into post_tag (post_id, tag_id) values ($1, $2)
[high_performance_java_persistence] LOG: execute S_3:
COMMIT
[high_performance_java_persistence_replica] LOG: execute <unnamed>:
BEGIN
[high_performance_java_persistence_replica] DETAIL:
parameters: $1 = 'High-Performance Java Persistence'
[high_performance_java_persistence_replica] LOG: execute <unnamed>:
select post0_.id as id1_0_, post0_.title as title2_0_
from post post0_ where post0_.title=$1
[high_performance_java_persistence_replica] LOG: execute S_1:
COMMIT
使用high_performance_java_persistence
前缀的日志(log)语句在主 node 上执行,而使用high_performance_java_persistence_replica
前缀的日志(log)语句在副本 node 上执行.
所以,一切都像一个魅力!
所有的源代码都可以在我的High-Performance Java Persistence GitHub存储库中找到,所以你也可以try 一下.
结论
您需要确保为连接池设置了正确的大小,因为这会产生巨大的差异.为此,我建议使用Flexy Pool.
您需要非常勤奋,并确保相应地标记所有只读事务.不寻常的是,只有10%的事务是只读的.是因为您有这样一个写操作最多的应用程序,还是因为您使用的是只发出查询语句的写事务?
对于批处理,您肯定需要读写事务,因此请确保启用JDBC批处理,如下所示:
<property name="hibernate.order_updates" value="true"/>
<property name="hibernate.order_inserts" value="true"/>
<property name="hibernate.jdbc.batch_size" value="25"/>
对于批处理,您还可以使用单独的DataSource
,该DataSource
使用连接到主 node 的不同连接池.
只需确保所有连接池的总连接大小小于PostgreSQL配置的连接数.
每个批处理作业(job)必须使用专用事务,因此请确保使用合理的批处理大小.
此外,您希望持有锁并尽快完成事务.如果批处理程序正在使用并发处理工作进程,请确保关联的连接池大小等于工作进程的数量,这样他们就不会等待其他人释放连接.