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.
Related
The documentation of Service Fabric recommends service remoting, ICommunicationClient or WcfCommunicationClient to realize the communication between the micro services.
The ServiceBus, which I always used for inter-service communication, is not even mentioned. Why?
I think you misinterpreted the docs. It does not recommend any protocol or service (the word is not even present on the page). What it does do is list the built-in communication options and appropriate situations of when to use them.
There is nothing that prevent you from using service bus for inter service communications. In fact, if you google around you will find some projects like this one
The ability to plug in any desired service or protocol is one of the great things about SF, but they leave the implementation to you.
There are many approaches to do service to service communication, if they had to document all of then, they would spend more time writing the possible approaches than doing the actual communication.
They probably decided for the one with closest relation to the platform, but they could write about any possible, it is just a matter o preference.
I could name a few from many just to have an idea:
Http
Remoting
WCF
Service Bus
Event Hub
AMQP
MQTT
gRPC + protobuf
TCP
UDP
Pipes
And many more, Imagine if they had to document all of then.
The communication is flexible enough to let you implement using any communication mechanism.
Regarding the ones you mentioned,
I always opt for HTTP for being platform agnostic and widely implemented on most platforms, does not matter if is .Net, Java, NodeJs, Windows or Linux, they all talk the same language, the others are very tight to the .Net and Windows platform and force every other solution to be also tighten or adapted to then. And also there is the fact of some being synchronous and other asynchronous like Service bus.
Then, when performance is an issue, I evaluate the other options.
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'm trying to build MQTT support into my Spring application. For this I'm looking at the references provided by Spring, which can be found here here.
They provide sample code for inbound and outbound channel adapters, but this concept of adapters is unclear to me. I couldn't find a lot of information about it on the web.
What exactly are these adapters and why are they needed?
Where do I need to define these adapters and how do I access them?
I'm using eclipse as my IDE and maven as my buildtool.
The adapters are a concept from Spring Integration which is yet another Spring project that provides an implementation of the Enterprise Integration Patterns and provides an abstraction layer that standardizes the way you integrate with external system, whether they are based on JMS, FTP or as in your case MQTT.
As with so many other Spring projects, the driver behind it is a loose coupling and standardization that will enable you to swap your channel provider (e.g. if its a JMS provider swap RabbitMQ with ActiveMQ or vice-versa) with a minimal impact to the rest of you code.
Its comparable to Apache Camel, in case your more familiar with it, and this comparison is quite an interesting read
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.
i am using the node.js as client to jms topic.There are two protocols available to make the connection on Topic.
Theses are Stomp and AMQP. I am read brief about them at http://en.wikipedia.org/wiki/Advanced_Message_Queuing_Protocol
and http://en.wikipedia.org/wiki/Streaming_Text_Oriented_Messaging_Protocol. Both seems to be wire level protocol i.e
data that is sent across the network as a stream of octets.I do not find any
concrete reason which one should be preferred. If someone can shed light on it, it would be helpful.
Another point is both the protocol takes pride in stating them as interoprable. Does the interoperable term means that if someone
want to take off specific message broker implementation say apache active MQ and instead want to plugin Websphere MQ , transition
will be smooth(provided both support AMQP/STOMP or any other wire levl protocol)?
You may see a difference in performance (refer to this benchmark based upon many factors including message size and persistence requirements for the queue entries.
As is often the case, there are other factors to consider as well, especially if your message size/count/etc. doesn't mean there's a clear winner in terms of performance and no one protocol meets your functional requirements in a way the other does not.
This article in particular hints there may be more fragmentation in the different STOMP broker implementations. Quoting from that article
STOMP...uses a SEND semantic with a “destination” string. The broker must map onto something that it understands internally such as a topic, queue, or exchange. Consumers then SUBSCRIBE to those destinations. Since those destinations are not mandated in the specification, different brokers may support different flavours of destination. So, it’s not always straightforward to port code between brokers.
At least with AMQP (which touts interoperability as one of its most important advantages) the only issues you should have with switching providers/languages are those inherent in setting up said new providers. For example, I've read ZeroMQ is likely to take more configuration work on your part than RabbitMQ, but that's not really due to any attributes specific to AMQP.