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SPRING REACTOR 之Flux和Mono

paulwong — Tue, 23 Nov 2021 06:30:00 GMT

SPRING REACTOR 之Flux和Mono�Q�有点象SPRING INTEGRATION的IntegrationFlow�Q�有如下特点

定义了针�Ҏ��U�类型数据的处理��程
可以�q�行�c�d��转换
长期�q�行�Q�除非被要求中止
��程中的每种操作可以在新的线�E�中执行
可以正常中止�Q�如果中途有异常�Q�则该流�E�也会中�?/li>
要subscribe�Q�流�E�才开始被启动
可以分割成各个子��程
可以聚合子流�E?/li>
Mono发送一个数据，��发送中止信�?/li>
Flux发送�Q意数据，��q��序决定何时发送中止信�?/li>

�~�程则比较简单，先根据不同的数据�c�d��定义不同的Flux或Mono�Q�业务操作用Function包装后，攑֜�map/flatmap中，再调用subscribe启动��程�?/div>

paulwong 2021-11-23 14:30 发表评论

EVEN DRIVEN - SPRING CLOUD STREAM - @PollableBean for Reactive Suppliers

paulwong — Tue, 23 Nov 2021 02:03:00 GMT

Supplier beans, or functions that only publish messages in Spring Cloud Stream, are a bit special in that they aren't triggered by the receiving of events like Function or Consumer beans. This means that you often need a way to trigger them to be executed periodically.

For imperative functions the framework by default "polls" a Supplier function every 1 second, but that duration is configurable using the spring.cloud.stream.poller.fixed-delay property.

However, for reactive functions supplying a Flux it is only triggered once by default. This is because a Flux itself is potentially an infinite stream of events so in many cases it will only need to be triggered once. But don't worry, if you want to periodically trigger a reactive Supplier because you are producing a finite stream of events you can still do so using @PollableBean. This annotation then allows you to configure how often the function is triggered using the same spring.cloud.stream.poller.fixed-delay property!

One example use case here could be periodically querying a data store and publishing each entry/row as an event. The number of rows in your data store is a finite number at any given time.

Example code:

@PollableBean
public Supplier> stringSupplier() { return () -> Flux.just("foo","bar","baz"); }

Reference:
https://solace.community/discussion/360/pollablebean-for-reactive-suppliers-in-spring-cloud-stream

paulwong 2021-11-23 10:03 发表评论

EVEN DRIVEN - SPRING CLOUD STREAM - 从非SCS�l��g发送消息到SCS�l��g

paulwong — Fri, 19 Nov 2021 03:47:00 GMT

在SPRING INTEGRATION中，如果要从非SPRING INTEGRATION代码发送MESSAGE到SPRING INTEGRATION�E�序�Q�通常用BUS GATEWAY�?br />
那么在SPRING CLOUD STREAM中，如果要从非SPRING CLOUD STREAM代码发送MESSAGE到SPRING CLOUD STREAM�E�序�Q�通常��p��先通知框架自动生成一个SOURCE�?br />
application.property

spring.cloud.stream.source=supplier
spring.cloud.stream.bindings.supplier-out-0.destination=notification-events

java

streamBridge.send("supplier-out-0", userDto);

Reference:
https://blog.devgenius.io/event-driven-microservices-with-spring-cloud-stream-e034eee3f394

paulwong 2021-11-19 11:47 发表评论

EVEN DRIVEN - SPRING CLOUD STREAM - Error Handling

paulwong — Wed, 17 Nov 2021 02:50:00 GMT

如果Function中抛出异常，�pȝ��没有配置捕获异常�Q�则异常消息会被丢弃。通常会进行配�|��?br />

@ServiceActivator(inputChannel = "my-destination.my-group.errors")
    public void handleError(ErrorMessage message) {
        Throwable throwable = message.getPayload();
        log.error("截获异常", throwable);

        Message originalMessage = message.getOriginalMessage();
        assert originalMessage != null;

        log.info("原始消息�?nbsp;= {}", new String((byte[]) originalMessage.getPayload()));
    }

详情参考：
https://www.itmuch.com/spring-cloud/spring-cloud-stream-error-handling/

paulwong 2021-11-17 10:50 发表评论

EVEN DRIVEN - SPRING CLOUD STREAM - Function Component

paulwong — Mon, 15 Nov 2021 09:40:00 GMT

如果要在SPRING CLOUD STREAM中和其他中间件打交道�Q�如FILE、FTP、HTTP�{�，则要用到SPRING CLOUD FUNCTION�?br />
�l��g地址�Q?br />https://github.com/spring-cloud/stream-applications/tree/main/functions

�Ҏ��l��g�Q�将FUNCTION变成HTTP ENDPOINTS�Q?br />https://github.com/spring-cloud/spring-cloud-function/tree/main/spring-cloud-starter-function-web
https://github.com/spring-cloud/spring-cloud-function/tree/main/spring-cloud-starter-function-webflux

paulwong 2021-11-15 17:40 发表评论

EVEN DRIVEN - SPRING CLOUD STREAM 3.x - Functional Programming Model

paulwong — Wed, 10 Nov 2021 07:10:00 GMT

SPRING CLOUD STREAM 3.x 版本�Ӟ��之前的一些编�E�模式，如@Enablebindding�Q�@StreamListenner�{�注释被废弃了，�q�是�׃��一些框架的代码必需��q��L��写，如配�|�框架用的Input MessageChannel�Q�Output MessageChannel�Q�连接MessageHandler与MessageChannel�{�，被视��Z��必要的动作。�ؓ了简化用户代码，于是推出Functional Programming Model�?br />
引入了新名词�Q�Supplier、Function与Consumer。实际上�q�几个类可视为Adapter�Q�如果之前已�l�有存在的Service�c�，且方法名为各�U�各��P��可以重新包装成Supplier、Function与Consumer�Q��ƈ在固定的�Ҏ��名：apply/get/accept中调用Service的方法�?br />

Supplier

当在配置文�g中注入此�c�d��的Bean�Q��ƈ在spring.cloud.stream.function.definition加入此Bean的名�U�ͼ�SPRING CLOUD STREAM��׃��帮你生成一个Output MessageChannel�Q��ƈ�q�接上此Bean�Q�后�l�只需要在BINDDING中加入对应的Destination Name�Q�即可向BROKER发消息了�?br />

Consumer

当在配置文�g中注入此�c�d��的Bean�Q��ƈ在spring.cloud.stream.function.definition加入此Bean的名�U�ͼ�SPRING CLOUD STREAM��׃��帮你生成一个Input MessageChannel�Q��ƈ�q�接上此Bean�Q�后�l�只需要在BINDDING中加入对应的Destination Name�Q�即可收到BROKER推送关于此Destination的消息了�?br />

Function

当在配置文�g中注入此�c�d��的Bean�Q��ƈ在spring.cloud.stream.function.definition加入此Bean的名�U�ͼ�SPRING CLOUD STREAM��׃��帮你生成一个Input和Output MessageChannel�Q��ƈ�q�接上此Bean�Q�后�l�只需要在BINDDING中分别对Input和Output MessageChannel加入对应的Destination Name1/Name2�Q�即可收到BROKER推送关于此Destination的消息，也可以向BROKER发消息了�?br />

与SPRING INTEGRATION的整�?/h2>如果要对消息�q�行复杂处理�Q�如拆分消息、聚合消息、IF ELSE消息�{�，��p��借助SPRING INTEGRATION了�?br />
@Bean
    public IntegrationFlow upperCaseFlow(LoanService loanService) {
        return IntegrationFlows
                    //turn this IntegrationFlow as a gateway, here is a Function interface
                    //with loadCheckerFunction as bean name
                    .from(LoadCheckerFunction.class, gateway -> gateway.beanName("loadCheckerFunction"))
                    .handle(loanService, "check")
                    .logAndReply(LoggingHandler.Level.WARN);
    }

    public interface LoadCheckerFunction extends Function{

    }

IntegrationFlows.from(Class serviceInterface)是可以将本IntegrationFlow包装成serviceInterface的实现类�Q�如果调用此接口�Q�最�l�会�q�回IntegrationFlow最后一个步骤的实体�Q�如果这个serviceInterface是Function的话�Q�刚好和SPRING CLOUD STREAM�Ҏ��上�?br />
后箋在spring.cloud.stream.function.definition加入此Bean的名�U�loadCheckerFunction�Q�SPRING CLOUD STREAM��׃��帮你生成一个Input和Output MessageChannel�Q��ƈ�q�接上此Bean�Q�再在BINDDING中分别对Input和Output MessageChannel加入对应的Destination Name1/Name2�Q�即可收到BROKER推送关于此Destination的消息，也可以向BROKER发消息�?br />
application.yaml
# This setting can increase or decrease the rate of message production (1000 = 1s)
# spring.cloud.stream.poller.fixed-delay=1000

# This setting can control which function method in our code will be triggered if there are multiple
# spring.cloud.function.definition=supplyLoan

# Give the autogenerated binding a friendlier name
spring:
   application:
      name: loan-check-rabbit
   banner:
      location: classpath:/banner-rabbit.txt
   cloud:
      stream:
         function.definition: loadCheckerFunction
         #BindingProperties
         bindings:
            loadCheckerFunction-in-0:
               destination: queue.pretty.log.messages
               binder: local_rabbit
            loadCheckerFunction-out-0:
               destination: queue.pretty.approved.messages
               binder: local_rabbit
         #BinderProperties
         binders:
            local_rabbit:
               type: rabbit
               environment:
                  spring:
                     rabbitmq:
                        host: 10.80.27.69
                        port: 5672
                        username: guest
                        password: guest
                        virtual-host: my-virtual-host

Reference

https://spring.io/blog/2019/10/25/spring-cloud-stream-and-spring-integration

paulwong 2021-11-10 15:10 发表评论

EVEN DRIVEN - SPRING CLOUD STREAM - SPRING CLOUD微服务的EVEN DRIVEN框架

paulwong — Fri, 05 Nov 2021 06:58:00 GMT

通常微服务应用之间的通信是通过HTTP调用�Q�吞吐性不建都高，高�ƈ发的场景��使用EVENT DRIVEN的框�Ӟ��即��用MESSAGE通信�?br />
即A微服务应用将数据发送到MESSAGE BROKER中的某个DESTINATION�Q�此DESTINATION是广播型�Q�非点对点型。B微服务应用订阅此DESTINATION�Q�当有新MESSAGE到达此DESTINATION�Ӟ��MESSAGE BROKER会将此MESSAGE推送给B应用。所有对此MESSAGE有需要的应用均可订阅�Q�从而收到此MESSAGE�?br />
SPRING CLOUD 中EVENT DRIVEN的框架就是SPRING CLOUD STREAM。其底层是��用SPRING INTEGRATION实现�?br />
SPRING CLOUD STREAM有以下新名词�Q?br />

BINDER�Q?/li>

是对MESSAGE BROKER操作�Ҏ��的抽象，卛_��用通过此BINDER操作MESSAGE BROKER。目前只实现了RABITMQ和KAFKA�?br />

CHANNEL

MESSAGE从SPRING CLOUD STREAM传给应用或相反是通过CHANNEL传递的�Q�这点和SPRING INTEGRATION是一��L��?br />

SOURCE

MESSAGE从应用传�l�SPRING CLOUD STREAM的CHANNEL�Q�叫@INPUT�Q�包含这�U�CHANNEL的接口叫SOURCE�?br />

SINK

MESSAGE从SPRING CLOUD STREAM传给应用的CHANNEL�Q�叫@OUPUT�Q�包含这�U�CHANNEL的接口叫SINK�?br />

BIDDING

�l�定哪个@INPUT或哪个@OUPUT与哪个DESTINATION发送或接收关系的MAPPING�?br />

EnableBinding

应用启动时就会徏立EnableBinding指定的接口中的CHANNEL

消费者群�l?/li>

默认下如果同一个应用部�|�了多个实例�Q�则每个实例都会收到MESSAGE�Q�这时如果设�|�了消费者群�l�名�U�ͼ�则同一个名�U�C��的多个实例，只有一个能收到MESSAGE�?br />

PARTITION

如果为MESSAGE指定规则�Q�如MESSAGE某个字段��g��A开头�ؓ一个规则，以B开头�ؓ一个规则，那么以A开头的MESSAGE会放到同一个分��Z��?br />
�q�样使用��很��单了�Q�只要取得OUTPUT CHANNEL�Q�就可以发送MESSAGE�Q�将代码兌��到INPUT CHANNEL�Q�就能在收到MESSAGE�Ӟ��相关代码��׃��被执行�?br />

paulwong 2021-11-05 14:58 发表评论