Maybe this question seems odd ?
I am working on OSGi-fication of our software based on Agents collecting some informations on servers.
Concerning Bundles update, it's natively supported by OSGi frameworks (OBR, Apache ACE, ...)
But, concerning the OSGI Container itself (Felix, Karaf, ...), is there a mechanism or a framework/tool having capacity to upgrade the container "automatically"?
Any idea? Any feedback?
Not in the OSGi specification. It assumes the framework is available on the classpath and can be launched. Any ability to update the framework implementation would be specific to a framework implementation as a value add.
Related
I have quite a sophisticated OSGi application which uses Declarative Services and was designed to be deployed in Equinox. Now the task is to make this application be deployable in WAS 8.
The first try was quite pragmatic: I have deployed an EAR which has started basically the same Equinox and after some WAS class loading policy tweaks it has worked.
Now I want to go further: get rid of the Equinox runtime and deploy my bundles "natively" in WAS 8. So I have composed an EBA, consisting out of my business bundles, their dependencies and Equinox DS runtime. The EBA is deployed as an asset and integrated into a BLA. The application has even started and runs but the components are not initialized.
The point is that one has to start equinox.ds in front of the own business bundles (UPDATE: not a must, s. discussion below) in order to make DS do its job. But how do I tell the bundles which is to be started first within the deployed EBA? I need some analog of Equinox' config.ini file.
I know I can rewire my components with natively supported Blueprint, but frankly this is the last thing I'd like to do. It should be possible to make Equinox DS work, shouldn't it?
Another question is: how to get the OSGi console for one's own application deployed under WAS 8? I want to control my bundles but seems that there is no way to do it from the Management Console.
UPDATE
Thanks to BJ and Neil (s. discussion below), the question takes down to "How do I start a specific bundle in my own OSGi application deployed in WAS 8.0?"
To answer the OSGi console part of your question, a normal OSGi console won't work because the OSGi applications are managed in nested frameworks. WebSphere provides its own console which can navigate the nested applications: http://pic.dhe.ibm.com/infocenter/wasinfo/v8r0/index.jsp?topic=%2Fcom.ibm.websphere.osgi.nd.multiplatform.doc%2Ftopics%2Fta_admin_runtime_console.html
We run Restlet 2.1 in an OSGi environment (Equinox) as bundle (ie. not as library within a bundle). The problem is that the Restlet Engine does not detect helpers (like converters) that are provided by Restlet extensions. Specifically, the EngineClassLoader#getResources() call does not return any result. The extensions are also deployed as OSGi bundles in the target platform.
Is automatic converter registration actually supposed to work within OSGi environments?
In fact, Restlet supports such feature thanks to a dedicated activator (see the Activator class in the package org.restlet.engine.internal).
This activator introspects bundles to find out the following things:
servers corresponding to registered servers
servers corresponding to registered clients
authenticators corresponding to registered clients
converters
Be aware that to use this feature, we must use the OSGi edition of Restlet since it's the only that has the MANIFEST file of the org.restlet bundle with the activator class specified. Otherwise you don't have to care about the bundle loading order...
Hope it helps you.
Thierry
Unless the Restlet-bundle explicitly imports the packages that contain the extensions (and I doubt it does, and it shouldn't), it wouldn't be able to load them, because bundles have isolated class-spaces.
A possible solution would be to provide the extensions as fragments attached to the Restlet-bundle. Thus, if you make it use the bundle-classloader (the documentation says this can be done by setting the Engines classloader), it would be able to load classes from the fragments.
Indeed it doesn't quite work for OSGi, as it depends on the ability to see the entire class space.
The way to do this in OSGi would be to use the service registry for the extensions, but that only works for OSGi aware libraries.
There is some help on the way: In the recently released OSGi 5 (Service Loader Mediator) there will be support to 'bridge' META-INF/services (I don't know if Restlet uses those, though) onto OSGi services, so 'legacy' libraries should work well within OSGi.
There is an implementation in Apache Aries called Spi-Fly. I looked at it briefly a while back. It might do the trick for you, it might not.
We're working on an OSGi-based infrastructure for processing stream-based data flows. Specific processing tasks are executed by individual OSGi components. We now need the possibility to distribute those components over different machines, which means, we need some kind of communication mechanism between OSGi components/containers.
During my research I came across different potential solutions: R-OSGi, Apache CXF for Distributed OSGi, Eclipse Communication Framework.
ECF seems particularly interesting as it supports different transports formats and provides support for stuff like service discovery.
My central questions:
Are there any detailed tutorials/walk-throughs for setting up an ECF infrastructure within Felix? (from my research, I found, that Felix support has been added recently)
Are there any solutions besides the three listed above which I might have missed?
Is there a reason for taking Apache CXF instead of ECF?
The first question -- whether there is a detailed walk-through for setting up ECF with Felix -- I don't know the answer to, though one might use a search engine to find out combinations of those terms.
The problem is ECF uses the Equinox infrastructure, and has at times inadvertently relied on packages that are non-public through transitive dependencies (particularly the Runtime API which uses Equinox for non-public debugging). This, in turn, means that ECF relies on a whole host of other components to be available and it's this set which typically isn't well defined on a Felix runtime.
You have missed out Paremus' Service Fabric, which is a commercial OSGi cloud solution. I'm not sure if you were specifically focussing on open-source or not; but if you are including commercial licenses then they have a very robust architecture for remote services.
Finally, the Apache CXF over ECF question -- if you're using Felix, I'd argue that going with Apache CXF is probably easier than going with ECF. This is mainly due to the dependency set and getting it working, combined with the fact that ECF may not be tested on Felix and so may assume particular aspects of the Equinox runtime (which includes, for example, the runtime's parent classloader delegation to pick up things on the boot classpath). This isn't really the fault of ECF per se, but rather an artefact of how the Eclipse ecosystem works.
If you want to communicate with non-OSGi runtimes, there's an advantage in the Apache CXF in that they can generate WDSL for interaction with other languages. I believe that you can do the same thing in ECF with a bit more work. The CXF solution is likely to be more verbose than a corresponding ECF one (WSDL always is) but if you're not using high volumes of requests this isn't likely to make a significant difference.
Is anyone using Karaf instead of Servicemix? If so, how did you come to this decision? I'm aware that Servicemix adds a layer of functionality around Karaf, just curious if Karaf is being used on its own and why...
We're using Karaf for a number of our applications. We were already using Camel (JMS and Esper) for integration between several different platforms (a JBoss 4.2 instance, a Tomcat and several Felix instances) and as this was working well there was little justification in migrating this too (which would have been cause to consider ServiceMix).
The only reason we have some Felix nodes, is that they're limited in use (on client desktops), rarely need/get updated and I wanted the smallest footprint for these nodes. For anything OSGi on the serverside we're using Karaf.
Karaf provides all of the features you'd expect and need for a production environment (see the apache-karaf tag's info). We do our development and testing against standard minimal framework (using pax-exam) but deploy to Karaf.
If you don't need an ESB, JCA, BPEL, etc but want a solid, tunable OSGi container, then Karaf on it's own is more than adequate. (And if you found yourself needing a limited subset of ServiceMix's functionality you can always install these in a Karaf instance).
You can also customise the Karaf distribution as part of a maven build - personally I like have the container as part of the application's build, as I can checkout, build and run the entire setup from the command line in minimal time.
Recently there's a clustering subproject of Karaf called Cellar using HazelCast, I not sure if this applies to ServiceMix too.
Karaf's life started as the ServiceMix core. Currently, ServiceMix is really a set of bundles that are deployed into a Karaf container. ServiceMix has a number of very handy bundles which do a lot of cool stuff that karaf doesn't. That said, the two primary reason for using ServiceMix is if you want:
1) an ESB,
2) NMR (a feature that allows you to community between bundles AND instances of Karaf).
This all said, the ServiceMix group is currently planning version 5, which will remove the ESB and NMR features and will be focused on being a management container for Camel. In ESB's a great deal of effort when into creating components that could be described using BPL (Business Process Language). However, the folks that wrote ServiceMix began to focus on the implementation of EIP's (Enterprise Integration Patterns) which largely does the same stuff as BPL, but does it in a more standardized and accepted manner. This work was done under the Camel project.
So, in short. If you are using ServiceMix 4+, you're also using Karaf. If you want a more robust integration environment, the environment of choice today (in the Apache/Felix world at least) is Karaf, Camel, and a few bundles from Servicemix.
Here's a little comparative illustration I made. Going from the simplest case (JVM with OSGi functions provided by Apache Felix at the bottom), to more complete/manageable OSGi functions (Apache Karaf in the middle), to enough functions to implement complete ESB instances (Apache ServiceMix at the top) (note that "an ESB" is not a product but a set of endpoints, routers, databases, ETL functions and whatnot configured together in a particular task-specific way).
Karaf does NOT come with CXF.
Its pure extracted kernel of ServiceMix. However, you can install CXF on Karaf as below.
karaf:root()> feature:repo:add cxf
Once the feature URL is added we can see the "provided" features by using the following command.
karaf:root()> feature:repo:feature:list | grep cxf
To install cxf fire the command below
karaf:root()> feature:install cxf
I have been trying to understand a bit more about the wider picture of OSGi without reading thru the entire specification. As with so many things, the introduction to what OSGi actually is was probably written by someone who had been working on it for a decade and perhaps wasn't best placed to put themselves in the mindset of someone who knows nothing about it :-)
Looking at Felix's example DictionaryService, I don't really understand what is going on. Is OSGi a distinct instance of a JVM into which you load bundles which can then find each other?
Obviously it is not just this because other answers on StackOverflow are explicit that OSGi can solve the dependency problem of a distributed system containing modules deployed within distinct JVMs (plus the FAQ keeps talking about networks).
In this latter case, how does a component running in one JVM interact with another component in a separate JVM? Can the two components "use" each other as if they were running within the same JVM (i.e. via local method calls), and how does OSGi manage the marshalling of data across a network (do you have to use Serializable for example)?
Or does the component author have to use some other distinct mechanism (either provided by OSGi or written themselves) for communication between remote components?
Any help much appreciated!
Yes, OSGi only deals with bundles and services running on the same VM. However, one should note that it is a distinct feature of OSGi that it facilitates running multiple applications (in a controlled way and sharing common modules) on the same JVM at all.
When it comes to accessing services outside the clients JVM, there is currently no standardized solution. Paremus Infiniflow and the derived open-source project Newton use an SCA approach. The upcoming 4.2 release of the OSGi specs will address one side of the problem, namely how to use generic distribution software in such a way that it can bring remote services into the client's JVM.
As somebody mentioned R-OSGi, this approach also deals with the other side of the problem, being how to manage dependencies between distributed OSGi frameworks. Since R-OSGi is not generic distribution software but explicitly deals with the lifecycle issues and dependency management of OSGi bundles.
As far as I know, OSGi does not solve this problem out of the box. There are OSGi-bundles, for example Remote OSGi, which allow the programmer to distribute services across a network.
Not yet, i think it's being worked on for the next release.
But some companies have already implemented distributed osgi. One i'm aware of is Paremus' Infiniflow (http://www.paremus.com/products/products.html). At linkedin they are also working on this. More info here: Building Linkedin next gen architecture with osgi and here: Matt raible: building linkedin next gen architecture
Here's a summary of the changes for OSGI 4.2: Some thoughts on the OSGi R4.2 draft, There's a section on RFC-119 dealing with distributed OSGi.
AFAIK, bundles are running in the same JVM, but are not loaded using the same class loader (that why you can use two different versions of the same bundle at the same time).
To interact with components in another JVM, you must use a network protocol such as rmi.
The OSGi alliance is working on a standard for distributed OSGi:
http://www.osgi.org/download/osgi-4.2-early-draft2.pdf
There even is an early Apache implementation of this new standard:
http://cxf.apache.org/distributed-osgi.html
#Patriarch24
The accepted answer to this question would seem to indicate otherwise (unless I'm misreading it). Also, taken from the FAQ:
The OSGi Service Platform provides the functions to change the composition dynamically on the device of a variety of networks, without requiring a restart
(Emphasis my own). Although in the same FAQ it describes OSGi as in-VM.
Why am I so confused about this? Why is such a basic question about a decade-old technology not clear?
The original problem of OSGI was more related to distribution of code (and then configuration of bundle) than to distribution of execution.
People looking at distributed components are rather looking towards SCA
The "introduction" link is not really an intro, it is a FAQ entry. For more information, see http://www.osgi.org/About/WhatIsOSGi Not hard to find I would think.
Anyway, OSGi is an in-VM SOA. That is, the OSGi Framework is about what happens inside the VM, it provides a framework for structuring your application inside the VM so you can built it too a large extent from components. So the core has nothing to do with distribution, it is completely oblivious of who implements the services, it just provides a mechanism for modules to meet each other in a loosely coupled way.
That said, the µService model reifies the joints between the modules and it turns out that you can build support on top of the framework that provides distribution to the other components. In the last releases we specified some mechanisms that make this standardized in the core and provide a special service Remote Service Admin that can manage a distributed topology.
If you are looking for a distributed OSGi centric Cloud runtime - then the Paremus Service Fabric ( https://docs.paremus.com/display/SF16/Introduction ) provides these capabilities.
One or more Systems each consisting of a number of OSGi assemblies (Blueprint or Declarative Services) can be dynamically deployed and maintained across a population of OSGi runtime Frameworks (Knopflerfish, Felix or Equinox).
A light weight RSA remote framework is provided which provides Service discovery by default using DDS (a seriously good middleware messaging technology) - (thought ZooKeeper and other approach can be used). Currently supported re-moting protocols include RMI and Avro.
Regards
Richard