[jira] [Commented] (CURATOR-457) Configuring service discovery paths

["Jordan Zimmerman (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CURATOR-457?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16382073#comment-16382073 ] 

Jordan Zimmerman commented on CURATOR-457:
------------------------------------------

What's the use-case for this? Why should the paths matter?

> Configuring service discovery paths
> -----------------------------------
>
>                 Key: CURATOR-457
>                 URL: https://issues.apache.org/jira/browse/CURATOR-457
>             Project: Apache Curator
>          Issue Type: Improvement
>            Reporter: Aleksander Melnichnikov
>            Assignee: Jordan Zimmerman
>            Priority: Minor
>
> Right now paths for services in service discovery hardcoded to pattern: */\{basePath} /\{serviceName}/\{instanceId}.* And that's impossible to configure paths this way:  */\{basePathPart1} /\{serviceName}/\{basePathPart2}/\{instanceId}*
> For example:
>  If basePath = */base1/base2/base3*, serviceName = *serviceName*, instanceId - *serviceId*
>  then path will be */**base1**/**base2**/**base3**/**serviceName**/**serviceId*, that can't be configured like this: */**base1**/**base2/serviceName**/**base3**/**serviceId.*
> Because of strong encapsulation in ServiceDiscoveryImpl class (package private method modifiers)
> {code:java}
> @VisibleForTesting
> String pathForName(String name) 
> { 
>     return ZKPaths.makePath(basePath, name); 
> }
> @VisibleForTesting 
> String pathForInstance(String name, String id)
> { 
>    return ZKPaths.makePath(pathForName(name), id);
> }
> {code}
> So, can we rethink visibility modifiers or add some extendable entity which would be responsible for constructing paths? 
> For example:
> Create interface
> {code:java}
> /**
>  * A constructor which constructs path to services for service discovering
>  */
> public interface DiscoveryPathConstructor
> {
>     /**
>      * Return the path where all service names registered
>      * @return basePath
>      */
>     String getBasePath();
>     /**
>      * Return the path where all instances of service registered
>      * @param name service name
>      * @return path to service instances
>      */
>     String getPathForInstances(String name);
>     /**
>      * Return the path where concrete instance registered
>      * @param name service name
>      * @param id concrete instance id
>      * @return path to concrete instance
>      */
>     String getPathForInstance(String name, String id);
> }
> {code}
> Also make a constructor and field in ServiceDiscoveryImpl:
> {code:java}
>     private final DiscoveryPathConstructor pathConstructor;
>   /**
>      * @param client the client
>      * @param pathConstructor constructor for instances path
>      * @param serializer serializer for instances (e.g. {@link JsonInstanceSerializer})
>      * @param thisInstance instance that represents the service that is running. The instance will get auto-registered
>      * @param watchInstances if true, watches for changes to locally registered instances
>      */
>     public ServiceDiscoveryImpl(CuratorFramework client, DiscoveryPathConstructor pathConstructor, InstanceSerializer<T> serializer,
>                                 ServiceInstance<T> thisInstance, boolean watchInstances)
>     {
>         this.watchInstances = watchInstances;
>         this.client = Preconditions.checkNotNull(client, "client cannot be null");
>         this.serializer = Preconditions.checkNotNull(serializer, "serializer cannot be null");
>         this.pathConstructor = Preconditions.checkNotNull(pathConstructor, "pathConstructor cannot be null");
>         if ( thisInstance != null )
>         {
>             Entry<T> entry = new Entry<T>(thisInstance);
>             entry.cache = makeNodeCache(thisInstance);
>             services.put(thisInstance.getId(), entry);
>         }
>     }
> {code}
> You can view commit in my fork of framework, if that's ok - I can make a pull request. 
> https://github.com/Me1kaa/curator/commit/6e6a34db7d71a84e3a53d284fc94e1fe2e3c10d8



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