I have this question that keeps popping up and looking through my notes and slides I cannot seem to find the answer.
The question that's been asked is:
"In OSGi, how does a bundle make its interfaces known to the gateway. How is
this information used by the gateway"
I understand the principles of OSGi framework but I'm not sure how the interface becomes known.
Any help would be really appreciated :)
Thanks :)
It's called the Service Registry. Providers register their services, and consumers get their services from this facility.
It is an implementation of something called a Whiteboard Pattern, the gist of which is that providers and consumers don't directly interact or depend on each other. They have their offerings and requirements satisfied by a mutual 3rd party via published contracts (i.e. the interfaces).
Related
I am a newbie in Microservices, having theoretical knowledge. I want to make a small application in Microservices. Can anyone please help me with the idea of how to implement microservices?
Thanks in Advance!!
You can create something like a currency conversion app with three microservices like these:
Limit service;
Exchange service;
Currency conversion service.
Limit service and currency conversion service can communicate with the database for retrieving the values of the limits and currencies conversion.
For more info check github.com/in28minutes and look after a microservice repository.
No matter how perfect the code of your microservice is, you may face issues with support and development if the microservice architecture doesn’t work according to certain
rules.
The following rules can help you with microservices a lot:
You have to do everything by yourself because you do not have any Rails and architecture out of the box that can be started by one command. Your microservice should load libraries, establish client connections, and be able to release resources if it stops working for any reason.
It means that being in the microservice folder and having made the 'ruby server.rb' command (a file for starting a microservice) we should make the microservice do the following:
Load used gems, vendor libraries (if used), and our own libraries
Use the configuration (depend on the environment) for adapters or classes of client connections
Establish client connections (permanent connections are meant here). As your microservice should be ready for any shutdowns, you should take care of closing these client connections at such moments. EventMachine and its callback mechanism helps a lot with this.
After that your microservice should be loaded and ready for work.
Incapsulate your communication with the services into abstractly named adapters. We name these adapters based on their role (PubSub, SMSMessenger, Mailer, etc.). This way, we can always change the inner implementation of these adapters by replacing the service if the names of our classes are service agnostic.
For example, we almost always use Redis in our application from the very beginning, thus it is also possible to use it as a message bus, so that we don’t have to integrate any other services. However, with the application growth we should think about solutions like RabbitMQ which are more appropriate for cases like ours.
If your code is designed in such a way that your classes are coupled with each other, do it according to the dependency inversion principle. This will help your code to avoid issues with lib booting.
Learn more here
You can try splitting an existing Monolithic application to gain perspective on microservice architecture.
I wrote this article, which talks about splitting a Django App into microservices. Hope it helps.
hello again, WSO2 community.
My last question about your architecture for my research is not a technical question, but a future-oriented one instead.
I was thinking about the OSGi approach the Suite has, that is one of the most interesting abstract things about SOA in general and WSO2 in particular I have found. An OSGi is sure a puzzling puzzle.
Thinking about pieces connected together reminded me about Service Component Architecture: a mean to see all the pieces as a whole easier.
Well, my question, son of my thoughts, is: "Why not to enable SCA for WSO2, when all the pieces have Carbon as a common denominator?" Carbon seems to be a nice candidate to be SCA.
The architecture could have only one instance of Carbon underneath, and WSO2 components above. The user should be able to interact with Carbon through only one interface and see all the pieces and their installed feature.
Is it possible? If it's not, why?
I hope I've been of some use through all the way here, and I thank you for having accompanied me to the end of my journey!
I hope there will occasions to collaborate or simply sharing ideas again!
It is conceptually similar to what it does with OSGi and Endpoint References in Carbon App model. Possibly can look at SCA Assembly as an alternative wiring model.
I'm in the middle of a project where we will migrate a major software system based on a larger set of custom made technologies to be based on OSGi services. For this we will likely need a some sort of message bus that plays nice with OSGi services.
Sync and ASync delivery
Point-to-point only
Guaranteed delivery - preferable with persistence via files
Strict message ordered from the same client (Async mode), but necessarily from different clients
Support for process-to-process and node-to-node nice but not strictly required
Open source solutions will be preferred, but not required.
I have looked at eventbus (as recommended in https://stackoverflow.com/a/1953453/796559), but that does not seem to work well.
So the question is, which technologies match the above?
Tonny,
Having just come from a very similar, and successful project, please let me share my experience with you to save you some time and your company some money. First and foremost, ESB's were a really good idea 8 years ago when they were proposed. And, they solved an important problem: how do you define a business problem in a way that those pesky coders will understand? The goal was to develop a system that would allow a business person to create a software solution with little or no pesky developer interaction needed that would suck up money better spent on management bonuses.
To answer this the good folks at many organizations came up with JBI, BPMN and a host of other solutions that let business folks model the business processes they wanted to "digitize". But really, they were all flawed at a very critical level: they addressed business issues, but not integration issues. As such, many of these implementations were unsuccessful unless done by some high-priced consultant, and even then your prospects were sketchy.
At the same time, some really smart folks in the very late 90's published a book called "Enterprise Integration Patterns" which identified over 60 design patterns used to solve common integration problems. Many of the folks performing ESB stuff realized that their problem wasn't one of business modelling. Rather the problem was how to integrate thier existing applications. To help solve this Michael Strachan and some really smart guys started the Apache Software Foundation Project "Camel". Camel is a strict implementation of Enterprise Integration Patterns in addition to a huge number of components designed to allow folks like you and I to hook stuff together.
So, if you think of your business process as simply a need to send data from one application to another to another, with the appropriate data transformations between, then Camel is your answer. Now, what if you want to base the "route" (a specified series of application endpoints you want to send data thorugh) off of a set of configurable rules in a database? Well, Camel can do that too! There's an endpoint for that! Anyhow, dont' do the traditional ESB, its old and busted. And Absolutely do the camel thing.
Please let me know if this helps.
The OSGi specification defines a component "Event Admin" which is a lightweight pub-sub event subsystem.
From the RFC0157:
Event Admin specifies a means for an event source to send events to
event listeners. Event sources can create events with a topic and
properties and request Event Admin to deliver the events to event
listeners which have declared interest in specific event topics and/or
property values. The event source can request synchronous (and
unordered) delivery or asynchronous (and ordered) delivery.
Compared to your requirements, it would score as follows:
Sync and ASync delivery: Check
Point-to-point only: No. Pub-Sub
Guaranteed delivery - preferable with persistence via files: NO
Strict message ordered from the same client (Async mode): YES
Support for process-to-process: if (process == OSGi service) -> Yes
Support for node-to-node: Not yet. The guys of
Distributed OSGi have been working on this, but I've not seen
anything concrete.
I like the concept of Camel, but recently decided to go for the (lighter) Event Admin as my requirements are limited. +1 to Mike on the Camel motivation. I'd look into it and then compare options before deciding.
Aren't you looking for an ESB? ServiceMix is a:
flexible, open-source integration container that unifies the features and functionality of Apache ActiveMQ, Camel, CXF, ODE, Karaf into a powerful runtime platform you can use to build your own integrations solutions. It provides a complete, enterprise ready ESB exclusively powered by OSGi.
iPOJO Event Admin Handlers are a nicer-to-use way to access the Event Admin service mentioned by #maasg.
looks like you are talking about an ESB here. If its the case, then you might have look at wso2 ESB. It is powered by apache synapse. it uses OSGi as the modular framework, so that you can add/remove features according to your requirement. There is a whole product stack from wso2 like message brokers, Business process servers (ODE), etc based on the same OSGi core platform.
disclaimer : I work for wso2.
As per title. I don't know if this is the right place or way to ask this, admins feel free to edit/move/close the question if appropriate.
I'd like to get pointers to recent material clarifying the market trends, as well as real life examples. Even pseudo-pundit, Gartner-like stuff is OK. Thanks.
I am curious about the second part of the question. What is the basis of your statement that 'the ESB thing' appears to be fading? I don't believe it is.
The problem with ESBs however is that some vendors call their product an ESB, but it actually is much much more than that. In some companies this happened with their integration product just because Gartner or some other analysts company says that ESB is hot. Marketing strategy is changed: The product is called ESB and maybe somethings are added that are expected in an ESB.
Paul Fremantle of WSO2 wrote a very good article about what an ESB really is [1].
As for OSGi: The first company I saw using it in their middleware was WSO2. I have heard, that TIBCO, another middleware vendor, is also moving or has moved towards using it in their Active Matrix platform.
OSGi may help in various ways. The most important is that it decreases the effort of the installation of the platform. Install a minimum on each system used to deploy the application, and during deployment the components required to run the application will be added. You do not have to worry about having installed the right plug-ins, add-ons and what not. This is what both WSO2 and TIBCO are doing.
With some vendors, you see that you need to install an awful amount of software, of which you in the end may be using just a small part (e.g. IBM WebSphere). Because of this, you may have to use over-dimensioned systems, which adds extra costs.
OSGi may prevent this.
Have a look at the presentation of WSO2 about the WSO2 Carbon platform [2].
The statement at the end of the presentation says it all:
Adapt the middleware to your architecture, not the architecture to the middleware
So yes, I think OSGi has a future in enterprise apps.
[1] http://wso2.org/library/2913
[2] http://www.slideshare.net/wso2.org/the-carbon-story-presentation-855666
Disclaimer:
I am in no way affiliated with WSO2, TIBCO or IBM. I am a certified TIBCO BusinessWorks Developer and have been developing applications for the IBM WebSphere Process Server platform. Above all, I am a WSO2 Enthusiast.
I would say yes..WSO2 has proof for that..Check the following links
http://osgi.dzone.com/articles/carbon-osgi-and-soa
http://www.infoworld.com/d/developer-world/wso2-upgrades-osgi-middleware-695
I am looking for a library which I can plug into a distributed application which implements any gossip-based membership protocol.
Such a library would allow me to send/receive membership lists, merge received membership lists, etc... Even better would be if the library implemented a protocol with performance O(logn) performance guarantees.
Does anyone know of any open source library like this? It doesn't need to meet all of the aforementioned requirements; even something partially implemented would be helpful.
Take a look at this on google code:
http://code.google.com/p/gossip-protocol-java/
I happen to stumble upon it yesterday whilst looking for java based gossip implementation. It's more a reference implementation for someone to build upon, but it gives the general idea, and after reading through the code you'll definitely be able to build your own or branch what's there to add any features you need.
HTH
Have you looked at Apache Zookeeper? I'm not sure if it's what you're looking for.
ZooKeeper is a high-performance
coordination service for distributed
applications. It exposes common
services - such as naming,
configuration management,
synchronization, and group services -
in a simple interface so you don't
have to write them from scratch. You
can use it off-the-shelf to implement
consensus, group management, leader
election, and presence protocols.
C# bindings are also available.