Esper企业版介绍(四)Esper JDBC

客官°小女子只卖身不卖艺 2022-08-18 05:44 114阅读 0赞

**Server+Client构造模块**

Server端JDBC实现：Esper JDBC(server行为)

Client端JDBC实现：Esper JDBC driver(单一jar包，~100kb)

Esper JDBC driver为 type 4 (full java)

**Java Database Connectivity(JDBC)**

定义的行业标准和接口(JAVA规范)

允许java和外部系统的互操作像数据库一样，也像CEP服务一样

**客户端没有专门的锁定代码**

Drivers以名字加载.

接口完全标准化.

Esper JDBC为JDBC3.0/JSR-54/SQL-92 compliant.

**将Esper变成JDBC兼容的服务**

通过Esper获得一个不断计算的随需而定的数据视图.

远程和本地的.

**与现有的工具保持共通性：  
![Center][]**

![Center 1][]

**Esper server必须在Esper JDBC server endpoint上启动**

IP,Port(默认为8450)，session idle timeout,threads.

JDBCEndpointConfiguration config = new JDBCEndpointConfiguration();
    config.setListenPort(8450);
    config.setSessionIdleTimeout(60); // 60-second idle timeout
    JDBCEndpoint endpoint = new JDBCEndpoint(config);
    endpoint.start();

**Esper JDBC driver**

JDBC Driver and URL or DataSource

Class.forName("com.espertech.esper.jdbc.remote.EPLRemoteJdbcDriver");
    String url = "jdbc:esper:remote:127.0.01:8450"; // hostname:port
    Connection connection = DriverManager.getConnection(url);
    // or using Esper JDBC Data Source
    EPLRemoteDataSource remoteDataSource = new EPLRemoteDataSource();
    remoteDataSource.setServer("myhostname");
    remoteDataSource.setPortNumber(8450);
    Connection connection = remoteDataSource.getConnection();

**Esper Named Window**

一个持续流.

Esper JDBC 允许SQL-92查询 :select ... from \[Named window\] where ...

// Esper EPL (server side)
    create window TickSummary.win:time(60 sec)
    as select symbol, price from Tick
    // JDBC (client side)
    // import java.sql*;
    String query = "select * from TickSummary where symbol = ‘GOOG’";
    PreparedStatement stmt = connection.prepareStatement(query);
    ResultSet rs = stmt.executeQuery();
    //... code to interrogate the result set
    … rs.next();
    … rs.getDouble(“price”);

**Esper EPL Statement**

在实时流内的持续查询.

Esper JDBC允许SQL-92存储过程call:  call \[EPL Statement name\]

// Esper EPL (server side)
    select symbol, avg(price) as avp from Tick group by symbol
    // assume statement name is avgPriceBySymbol
    // JDBC (client side)
    // import java.sql*;
    String epl = "avgPriceBySymbol";
    PreparedStatement stmt = connection.prepareStatement(epl);
    ResultSet rs = stmt.executeQuery();
    //... code to interrogate the result set
    … rs.next();
    … rs.getDouble(“avp”);

![Center 2][]

**Example Named Windows**

create window SearchRequests.win:time(1 min) as select * from SearchRequest

Example EPL Statements

select serviceName, count(*)
    from SubmittedWorkEvent.win:time(60 sec) group by serviceName
    output every 1 seconds
    select serviceName, instanceId, avg(msecClockTime), count(*)
    from CompletionEvent.win:time(60 sec) group by serviceName, instanceId
    output every 1 seconds
    select serviceName, avg(msecClockTime), count(*)
    from CompletionEvent.win:time(60 sec) group by serviceName
    output every 1 seconds
    select queueName, avg(depth)
    from QueueReportEvent.win:time(60 sec) group by queueName
    output every 1 seconds

[Center]: /images/20220731/fd78ad8a456b44d99f5d2248819999a0.png
[Center 1]: /images/20220731/941d0641f5df438eb847468d7b6307b4.png
[Center 2]: /images/20220731/1aa2bf5671fb42c992b53c09fecf4c8c.png