in Sling, configuration can be deployed either via a sling:osgiConfig node and via a nt:file node having the configuration values.
When i make some changes in Felix Console in some configuration deployed via sling:osgiConfig node, it gets converted to nt:file format.
Why there are these two different formats for configurations in Sling. is there any significant difference between the two?
I'd say this is mostly for historical reasons, in some cases it's more convenient to provide configurations as hierarchical resources (sling:OsgiConfig) and if the config is coming from a filesystem for example, files are more convenient.
#Shashi sling:osgiConfig changing to nt:file when you make changes in felix console is expected behaviour. This will not cause any issue when you try to read the config value from java class. You will just not be able to edit the run mode config via crxde when it has changed to nt:file as it stores data as binary content.
However there is a way to disable this behaviour, you will have to uncheck "Enable Write Back" at /system/console/configMgr/org.apache.sling.installer.provider.jcr.impl.JcrInstaller as mentioned in this thread.
OSGi config best practices
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When we update any configuration for a component in the Configurations tab in the Apache Felix Web OSGi Console, where are these configuration settings saved? This is with respect to AEM 6.0 or above.
The manually saved configuration settings are stored in the the crx-quickstart/launchpad/config directory (in your AEM installation folder in the local file system) and, on top of that, as .config files in the Content Respository at /apps/system/config.
For example, if you're looking for the configuration of com.example.MyComponent, you can find it as a text file in crx-quickstart/launchpad/config/com/example/MyComponent.config (in the local file system) and at /apps/system/config/com.example.MyComponent.config inside your Content Repository.
The files at these two locations are updated when you change the settings manually in the OSGi console.
In AEM you can also store configuration in JCR nodes of the type sling:OsgiConfig. These will not be created or updated when you manually save the config but they offer a neat way of managing configuration as content.
When AEM looks for the configuration, the following order of resolution is used:
nodes under /apps/*/config, be it property files or JCR nodes with the node jcr:primaryType of sling:OsgiConfig
nodes with type sling:OsgiConfig under /libs/*/config, these are OOTB definitions for components that come with AEM
.config files from <aem-installation-directory>/crx-quickstart/launchpad/config/ on the local file system.
Depending on the OSGi configuration of Apache Sling JCR Installer, the sling:OsgiConfig nodes can be written back to when you manually change the config. There's also a number of settings affecting the lookup of said configurations so it's a good idea to familiarise oneself with this config.
Please check out the official documentation for more comprehensive information.
If you're trying to get a config stored in a sling:OsgiConfig node to work as expected and you're unsure if another config for the same service has been cached somewhere, here's a sequence of steps that has worked for me consistently in AEM 6.4:
Delete the sling:OsgiConfig node you just created
Go to the Felix console's configMgr, find the relevant service and Delete the configuration.
Recreate the sling:OsgiConfig node (I usually keep those in a CRX package that I can simply reinstall)
The configurations are stored by the felix configadmin bundle inside the felix bundle cache. Not sure where this cache is located in AEM. In Apache Karaf the configs in my case are in:
data/cache/bundle7/date/config
Where bundle id 7 is the id of the configadmin bundle.
Rather than manually making configuration changes to OSGi components in Felix, it's good practice to create sling:OsgiConfig nodes in the JCR to make sure that the settings are version controlled, applied the same across environments, etc.
Similarly, I want to disable an out-of-the-box component on each environment. Is there any way to achieve this via configuration? Rather than going to system/console/components and disabling it there?
Anything I've read about this has mentioned making changes internally within the bundle, but since it's one that I don't own, I'd need some external configuration to do this.
You can do this with the ScrService, which is published by the SCR runtime bundle. API documentation is here.
Note that ScrService is not "standard", i.e. it doesn't come from the OSGi specification. However it is supported by Felix and Equinox and Knopflerfish, so it's pretty much a de facto standard. In fact this service is used by the Web Console when you go to system/console/components.
Try to use attribute policy=ConfigurationPolicy.REQUIRE on #Component.
Then you could prepare a set of packages with configurations for each environment as part of the build. This is also a good practice for having different OSGI configurations for each environment.
So for some of enironments you could just simply not provide a configuration for a particular component. Such component would not run - it would have unsatisfied status.
I believe I've seen this approach in AEM itself.
You can also create a filter to remove current configurations but it still would require to disable the Component at least once. And this solution will work only if this component has mentioned policy.
The other way around is to prepare a Service that would be responsible for disabling other components - it could be configurable. But it doesn't sound like a good solution to me.
I'd like to create a Configuration object in OSGi, but one that won't be persisted, so it won't be there when the framework is restarted. Similar to START_TRANSIENT for bundles.
Some background: I've got an OSGi (Felix) based client side application, deployed over OBR. The configuration object I'm talking about effectively boots the application. That works fine, but sometimes the content has changed while the context was stopped. In that case, it boots the application as OSGi revives all bundles and adds all configuration options. Then I inject the correct configuration, the application stops and then restarts again.
So it does actually work, but the app starts twice, and I can't get access to the framework before it reconstructs its old state.
Any ideas?
As BJ said there is no standard support for this in the Configuration Admin spec.
However the Felix implementation supports two features which may help you. First, you can set the felix.cm.dir property which configures where the configadmin saves its internal state (which by default will be somewhere under the Framework storage directory). You could set this to a location that you control and then simply wipe it every time you start OSGi (you could also wipe out the entire OSGi Framework storage directory on every start... some people do this but it has wider consequences that what you asked for).
Second, if you need a bit more control, Felix ConfigAdmin supports customising its persistence with a PersistenceManager service. You could probably implement this and return empty/doesn't-exist for the particular pids that you want to control.
The OSGi Config Admin spec does not support this. I also do not know of a non-standard means either for any of the CM impls I am familiar with.
Ok, what I did in the end was the following:
I created a special really small 'boot' bundle, which I do not provision from OBR, instead, I install it from the classpath.
That bundle controls the configuration, and I use START_TRANSIENT the moment I really want to load that configuration.
Not exactly pretty, it gets the job done. I do think transient configuration would make sense to have in OSGi.
I have a dynamic application that uses OSGi to load modular functionality at runtime. OSGi bundles contain the modular functionality and the application loads the bundles when they are needed. This approach works okay, but I would like a more granular solution. The bundles contain components controlled through Declarative Services. I'd like to be able to load a bundle, and only enable the components that are needed within the bundle. I've done research in this area, but cannot find a solution that I'm satisfied with. One approach was to create a "gatekeeper" component that is always enabled in the bundle and through the ComponentContext let it call enable and disable component. It's a viable solution, but I could not figure out a way for the "gatekeeper" to "know about" the other components in the bundle without hard coding the component names as properties in the "gatekeepers" SCR xml descriptor.
What I prefer is a way to load bundles and "know about" all components within the loaded bundles. Be able to determine what bundle the components are located in and what state they are currently in (similar to the equinox console command 'ls' that lists out all components). I would like to enable and disable the components when needed.
How does the console do this and how could I do this in an application?
Update:
#Neil Bartlett: Sorry for the delay. I had to move on to something else. Now I'm back on this issue. Really would appreciate any further assistance. My application is role based. I need to enable components based on the functionality they provide. The goal is for all role based components to initially be disabled. Upon role change, a role manager polls each component for its provided functionality and determines whether to load it. Each component will broadcast what functionality it provides (through a common service interface). ScrService will not allow me to enable an initially disabled service component. Having the components initially enabled and let ScrService disable them as soon as possible during application startup does not fit my needs.
Have a look at ScrService. Bothe equinox and felix has it.
However, components can be made to load lazily, i.e. only when needed by other components/bundles; but that is perhaps not what you want.
In your service description, mark the components as enabled, but requiring configuration information provided by the Configuration Management service. you then can write a CM plugin service (can't remember the exact term) that can publish and modify the configuration of your components. Services by default are identified by their name, which by default is their implementation class name. Configuration data is passed as a map, and it can be empty. DS will make the service available as soon as the CM provides a configuration.
I have a similar issue, but for a different purpose:
- I have apache file install and configuration admin service to configure my components externally with property files.
- I needed to make sure that some components get the config from the outer file and the only way I've found so far is that I mark my components with ConfigurationPolicy.REQUIRED.
- But that way my plugin projects doesn't run in eclipse (where there are no config files).
- The component.xml also contains a default development configuration so I'm okay with that, just my component doesn't start until there is a config data avalilable with configadmin. My components ar unsatisfied this way, until someone creates a configadmin entry.
- I figured out that if I create a osgi command line extender that sends empty configurations to service pid's they would start up with default values in component.xml files.
- I just came here to find a way to list all bundles
But I think this solution I use can also work with your setup and that's why I write this.
Just mark all your components with the configurtationpolicy.require and you can selectively start and stop them with adding and removing configurations with configadmin. This could be hard if you already use the configadmin for other purposes too, but it may be managable as a last resort.
I'm using Spring 2.5.6. I have a bean whose properties are being assign from a property file via a PropertyPlaceholderConfigurer. I'm wondering whether its possible to have the property of the bean updated when the property file is modified. There would be for example some periodic process which checks the last modified date of the property file, and if it has changed, reload the bean.
I'm wondering if there is already something that satisfies my requirements. If not, what would be the best approach to solving this problem?
Thanks for your help.
Might also look into useing Spring's PropertyOverrideConfigurer. Could re-read the properties and re-apply it in some polling/schedular bean.
It does depend on how the actual configured beans use these properties. They might, for example, indirectly cache them somewhere themself.
If you want dynamic properties at runtime, perhaps another way to do it is JMX.
One way to do this is to embed a groovy console in your application. Here's some instructions. They were very simple to do, btw - took me very little time even though I'm not that familiar with groovy.
Once you do that you can simply go into the console and change values inside the live application on the fly.
You might try to use a custom scope for the bean that recreates beans on changes of the properties file. See my more extensive answer here.
Spring Cloud Config has facilities to change configuration properties at runtime via the Spring Cloud Bus and using a Cloud Config Server. The configuration or .properties or .yml files are "externalized" from the Spring app and instead retrieved from a Spring Cloud Config Server that the app connects to on startup. That Cloud Config Server retrieves the appropriate configuration .properties or .yml files from a GIT repo (there are other storage solutions, but GIT is the most common). You can then change configuration at runtime by changing the contents of the GIT repo's configuration files--The Cloud Config Server broadcasts the changes to any Client Spring applications via the Spring Cloud Bus, and those applications' configuration is updated without needing a restart of the app. You can find a working simple example here: https://github.com/ldojo/spring-cloud-config-examples