I am new to Spring integration;If i understand right, spring integration has 3 key players;
1 Publisher
2 Subscriber
3 Channel.
I can understand the Publisher, subscriber frameworks where DB/File system is used as queue. Where does spring integration queue resides? If publisher and subscriber are individual process by itself, how do they share channel? Is channel accessible to both Publisher process and subscriber process because they run in same JVM?
Does that mean that, if publisher runs in one machine and subscriber runs in another machine, can't we use Spring integration?
The Spring Integration is Framework for developing integration solutions. It is lightweight and doesn't provide a Broker solution.
If your producer and consumer are in separate JVMs, you really have to use third-party Messaging Broker like ActiveMQ, RabbitMQ, Apache Kafka, Hazelcast etc.
Spring Integration just only provides building blocks, everything rest is up to use. The main feature of the channel that you always can switch it into different implementations without impacting producer and consumer. Right, if both producer and consumer are in the same JVM, there is no reason in the external network communication. In most cases you even don't need to use QueueChannel - the DirectChannel is enough to perform consuming in the producer's thread.
See Message Channels for more info.
Related
Learning Spring Integration. I am trying to understand the IntegrationFlow DSL and the use of its to(IntegrationFlow) method.
It seems that this allows us to daisy-chain the end of Flow 1 with the beginning of Flow 2.
Is this the DSL's implementation of the Message Bridge pattern, where channels are connected to each other? If not, how is this different than a Message Bridge? Is it similar to the direct: and seda: endpoints in Apache Camel parlance, that is, a way of snapping routes together?
Yes, we can treat it that way, but technically it is just composition of more high-level messaging abstractions together. There is no EIP Message Bridge pattern implementation as a single top-level component.
Let's see it objective:
How can multiple messaging systems be connected so that messages available on one are also available on the others?
Use a Messaging Bridge, a connection between messaging systems, to replicate messages between systems.
So, let's say we need to transfer data from Apache Kafka topic into some IBM MQ queue. For Kafka we use an KafkaMessageDrivenChannelAdapter and for IBM MQ - JmsSendingMessageHandler. We connect them via DirectChannel the rest is done with internal (de)serializers to remap Kafka records into JMS messages. Does this approach implement the mentioned pattern? I think yes. And with different channel adapters we can implement many use-cases transferring data from one source to another.
And that Message Bridge confirms our assumption:
The Messaging Bridge is a set of Channel Adapters.
Now about to(IntegrationFlow) operator. This is just a convenient API to decompose your configuration between different logical, reusable pieces. At runtime we don't have any IntegrationFlows interacting: only endpoints are exchanging messages via channels between them.
Yes, you can treat Camel's direct: and seda: as a MessageChannel abstraction in terms of Spring Integration. Yes, we can say that this separation via channel is a bridge we have talked before. But in terms of Spring Integration sometimes there is no reason to separate the logic and people just do this:
IntegrationFlow.from(Kafka.messageDrivenChannelAdapter())
.handle(Jms.outboundAdapter())
.get();
Is this a bridge we saw before? I guess yes. Even if we don't have an explicit channel definition it is still there for us auto-created by the framework.
I'm working on Java JMS application connecting to Azure ServiceBus. Once I found out JMS is supported I did not expect any problems. However, when I started creating the connections and added Spring JmsTransactionManager I got an error which said my Azure subscription is "Base" tier and thus transactions are not supported. What I did was upgrading to "Standard" tier and the error was resolved. This is covered here.
However during testing I was not sure it is working as expected and I'm testing the behavior and in the meantime I got confused by another MS documentation saying "transacted sessions" are not supported in this JMS over AMQP protocol.
Question:
Can I rely the queue in Service bus will be transacted meaning the message won't be removed from queue until my transaction manager explicitly calls COMMIT?
How can anyone claim JMS compliance but at the same time say I don't support transacted sessions.
Thank you for any response because I'm confused.
Update:
The Azure Service Bus starter for Spring Boot has Qpid as dependency so that is what I'm using under the hood - I was not aware of this first:
<!--Qpid-->
<dependency>
<groupId>org.apache.qpid</groupId>
<artifactId>qpid-jms-client</artifactId>
</dependency>
There is not currently a specification for distributed (XA) transactions over AMQP and as such the Qpid JMS client does not offer an XA ConnectionFactory implementation so if you are using that then for sure you would not get any support for distributed transactions.
The Qpid JMS client itself does implement local transactions so in that sense you could use a standard locally transaction JMS session but it is possible that MS has disabled that through the spring boot bits to dissuade folks from using it as the benefit of local transactions is quite small especially for folks using spring how might think that they are participating in a larger distributed transaction when they are in fact not.
Perhaps a silly question, but keep reading about SIs "lightweight messaging within Spring-based applications". I want to know how (if) SI uses messaging internally. When I run an SI (Boot) application (one that doesn't require AMPQ ... aka 'messaging' support), I don't have to run a Rabbit server. But, from what I gather, SI uses messaging internally. How is this accomplished? I can't seem to find any reference explaining this & what infrastructure is required to make this possible. Thanks!
The messages are simply Java objects (o.s.messaging.Message) passed between components. No external broker is needed, unless you need persistence.
I suggest you read Mark Fisher's book (Spring Integration in Action) and/or the reference manual.
The messaging inside spring integration are in-memory java objects passed from one service to another via channels/queue. It provides a mechanism to define the flow and order of processing, also allowing each service step to work in isolation. The spring integration queue is eventually an implementation of java.util.Queue interface.
It is different from commercial Messaging tools like IBM MQ or Active MQ as it doesnt offer persistence. Which means if you kill the jvm or the app process is stopped, all the messages in flight on the Spring queue/channel are lost. A lot if times this is acceptable if the process in idempotent, i.e When the application comes up, I can restart the process from beginning.
I have too many emails. I should write scheduler in order to send messages to them. Messages are different. I use spring framework 4.x.
I can write simple class, which connects to SMTP server. But in this case I should write my thread library too in order to send emails parallel.
Do spring have already written library which give me more flexible way to do this tasks? I do not want to use threads. It will be nice if spring already have this functionality.
Do I need Spring integration for this?
Best regards,
Yes, you definitely can do that with Spring Integration, because there is an ExecutorChannel implementation with can be supplied with an TaskExecutor from the Spring Core:
<channel id="sendEmailChannel">
<dispatcher task-executor="threadPoolTaskExecutor"/>
</channel>
<int-mail:outbound-channel-adapter channel="sendEmailChannel" mail-sender="mailSender"/>
But anyway you should keep in mind that all Spring Integration components are based on the Java and that ExecutorService is used on the background.
From other side if you need only the mail sending stuff from the Spring Integration, it would be an overhead and can simply use Core Spring Framework legacy like JavaMailSender as a bean and #Async for the sendMail method to achieve your parallel requirement.
UPDATE
could you tell me whether I need JMS for this situation?
I don't see any JMS-related stuff here. You don't have (or at least don't show) any real integration points in your solution. The same I can say even about Spring Integration just for email sending. However with the Spring Boot your SI config will be enough short. From other side if you'll study Spring Integration better eventually you'll get more gain to rely on the Integration components for your systems, as internally, as well as externally with other systems through JMS, AMQP, Kafka etc.
To be honest: a lot of years ago my first acquaintance with Spring Integration was due the requirement to get files from the FTP and have ability to pick up new files automatically. I found the solution only in the Spring Integration 1.0.0.M1. After that short XML config for the <int-ftp:inbound-channel-adapter> I loved Spring Integration and since that time it became as a part of my life. :-)
So, it's up to you to go ahead with Spring Integration in your simple app, or just follow with more formal solution with JavaMailSender direct usage.
You should use java executors framework. For example you can write something like the code below:
ExecutorService executor = Executors.newWorkStealingPool();
executor.execute(() -> mailSender.send(mail));
Spring integration is used to make the communication between two systems easier.
So does that mean the if two systems are talking using JMS queus, then we can remove queues and integrate two systems using Spring Integration Framework?
Looks like you should study more on the matter. I mean EIP-book, Spring Integration in Action or, at least the Reference Manual from Spring IO site.
The main Spring Integration goal is integration and JMS is only one way to do that.
If your two system can get deal with JMS, there is no stops to integrate them using Spring Integration: just provide JMS adapters for boht of them.
As per my understanding,
Spring Integration solution a framework level solutions to Design Patterns listed in http://eaipatterns.com/
I might be an alternate to ESB which is like one big tunnel & everything passes through that.
Spring Integration provides end to end message between different de-coupled, disparate connecting points.
On the other hand JMS is an API in the Java EE spec which can be used in conjunction with Spring-Integration.
You might as well want to read about AMQP which is a messaging protocol.