Revision as of 12:01, 22 March 2010

What is ZooDiscovery?

ZooDiscovery is a discovery mechanism that runs as an OSGi service. It leverage Apache ZooKeeper robustness and implements Eclipse ECF Discovery API.(Hence the name!). ZooDiscovery is flexible and easy to configure.

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The concept in some words

ZooDiscovery implements both ECF discovery interfaces: IDiscoveryAdvertiser and IDiscoveryLocator. That is, ZooDiscovery can publish our services and gets us noticed about discovered services. Perfect! But how? A ZooDiscovery instance running at your machine does its job by exchanging data with other ZooDiscovery instance(s) running elsewhere. So each running ZooDiscovety service must know where that other "elsewhere" exactly is. This is why we should first make our ZooDiscovery happy, giving it an IP address to play with.
To keep it smooth, let's take it step by step following these cases:

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How to get ZooDiscovery service?

IContainer container = null;
try {
//"ecf.discovery.zookeeper" is the container name we want to initiate.
container = ContainerFactory.getDefault().createContainer("ecf.discovery.zookeeper");
} catch(ContainerCreateException e1){ // TODO 
} 
/*
 Build a target id to connect to. Please replace with usable IP address(es). A comma separated list of one or more IP address is also valid. 
 Something like: "discovery.flavor.standalone=192.1.32.10,192.1.32.11" means our ZooDiscovery instance will connect to both address 192.1.32.10 and 192.1.32.11
 where other ZooDiscovery services are running.
*/
ID serverId = container.getConnectNamespace().createInstance(  
new String[] { "discovery.flavor.standalone=192.1.32.10" });
try {
//we then connect to other instance of 
container.connect(serverId, null);
} catch (ContainerConnectException e1) { // TODO  
}
// Our provider is ready.

// To advertise services we need adapting our container this way:
IDiscoveryAdvertiser discoveryAdvertiser = (IDiscoveryAdvertiser) container.getAdapter(IDiscoveryAdvertiser.class);
//then we enjoy calling IDiscoveryAdvertiser contract methods

// To localize/discover services we need adapting it this way:
IDiscoveryLocator discoveryLocator = (IDiscoveryLocator) container.getAdapter(IDiscoveryLocator.class);
//then we enjoy calling IDiscoveryLocator  contract methods

How to publish/advertise my services

I want ZooDiscovery publishing my OSGi services without me interfering

OSGi services registered with property "osgi.remote.interface=*" are candidate for auto-publication. By default this option is disabled. To make ZooDiscovery autopublish all services having the above property once connected, you basically use the same way as above with the added propety:

//.. same as above but "discovery.publish.auto=true" is added
ID serverId = container.getConnectNamespace().createInstance(  
new String[] { "discovery.flavor.standalone=192.1.32.10" ,"discovery.publish.auto=true"});
//...same as above
// Once connected ZooDiscovery will publish all OSGi services registered with "osgi.remote.interface=*". You can still adapt and use as above, though.

I want to get notified about discovered services

Advanced configuration

ZooDiscovery Flavors

Standalone mode: discovery.flavor.standalone

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Centralized mode: discovery.flavor.centralized

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Replicated mode: discovery.flavor.replicated

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Fine tuning the underlying ZooKeeper

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Recipes

Automate proxying discovered services using R-OSGi and ZooDiscovery

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