Versions Compared

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.

...

Developers would be required to implement only the ConnectRestExtension interface to provide an extension.  ConnectRestExtension provides an implementation of ConnectRestExtensionContext whose configurable() provides an implementation of javax.ws.rs.core.Configurable. Using this developers can register new JAX-RS resources like filter, new end points, etc

 

Code Block
package org.apache.kafka.connect.runtime.rest.extension;
public interface ConnectRestExtension extends Configurable, Versionable, Closeable {
    /**
     * voidConnectRestExtension implementations register(ConnectRestExtensionContext restPluginContext);
}

As mentioned above, even though the developers are required to only implement the ConnectRestExtension, they will be using several new public interfaces that are implemented by the framework.

ConnectRestExtensionContext

This is a request Context interface that composes and provides access to 

  • Configurable - register JAX-RS resources
  • workerConfig - access user provided worker configs
  • clusterState - A new interface that helps provide some cluster state information
    Code Block
    interface ConnectRestExtensionContext{ custom JAX-RS resources via the {@link
         * #register(ConnectRestExtensionContext)} method. Framework will invoke this method after
        Configurable configurable();
    * registering the default WorkerConfig workerConfig();
        ConnectClusterState clusterState();
    }

    ConnectClusterState

    This interface provides methods for the extension to get the connector states and list of running connectors.

     

    ...

    Connect resources. If the implementations attempt to re-register any
        

    ...

     *

    ...

     of the Connect Resources, it 

    ...

    will 

    ...

    be 

    ...

    be 

    ...

    ignored 

    ...

    and 

    ...

    will 

    ...

    be 

    ...

    logged.
     

    ...

     

    ...

     

    ...

     

    ...

     

    ...

    *
     

    ...

     

    ...

     

    ...

     

    ...

     

    ...

    * 

    ...

    @param 

    ...

    restPluginContext 

    ...

    The 

    ...

    context provides access to JAX-RS 

    ...

    {@link javax.ws.rs.core.Configurable}
         *

    ...

        

    ...

     

    ...

     

    ...

        

    ...

         

    ...

     

    ...

     

    ...

     

    ...

     

    ...

     

    ...

     

    ...

     

    ...

        and 

    ...

    {@link ConnectClusterState}.The custom JAX-RS resources can be
         *                          registered via the {@link ConnectRestExtensionContext#configurable()}
         */
        

    ...

    void 

    ...

    register(

    ...

    ConnectRestExtensionContext 

    ...

    restPluginContext);
    

    ...

    }

    As mentioned above, even though the developers are required to only implement the ConnectRestExtension, they will be using several new public interfaces that are implemented by the framework.

    Versionable

    A new Versionable interface that will be used by all the plugins/components that support version. The Connector interface would be modified to extend this new interface instead of exposing the version() method itself.

    Code Block
    package org.apache.kafka.connect.components;
    public interface Versionable {
        /**
         * Get the version of this component.
         *
         * @return the version, formatted as a String
         */
        String version();
    }

     

    ConnectRestExtensionContext

    This is a request Context interface that composes and provides access to 

    • Configurable - register JAX-RS resources
    • clusterState - A new interface that helps provide some cluster state information

    Code Block
    package org.apache.kafka.connect.rest.extension;
    interface ConnectRestExtensionContext{
        /**
         *
         * @return return a  implementation of {@link javax.ws.rs.core.Configurable} that be used ot
         * register JAX-RS resources
         */
        Configurable<? extends Configurable> configurable();
        /**
         * Provides meta data about connector's and its health
         * @return instance of {@link ConnectClusterState}
         */
        ConnectClusterState clusterState();
    }

    ConnectClusterState

    This interface provides methods for the extension to get the connector states and list of running connectors.

     

    Code Block
    package org.apache.kafka.connect.rest.extension;
    interface ConnectClusterState{
        /**
         * Get a list of connectors currently running in this cluster. This is a full list of connectors in the cluster gathered

    ...

    Proposed Changes

    Plugin Interface

    Users will be able to create a plugin by implementing the ConnectRestExtension interface, which has a single method that takes a ConnectRestExtensionContext instance as the only parameter. This allows us to change the interface easily in future to add new parameters. Connect runtime would also provide a default implementation for the interface ConnectRestExtensionContext.  One or more of the implementation can be configured via the configuration rest.extension.classes as a comma separated list of class names.

     

    Implementations would use the javax.ws.rs.core.Configurable to register one or more JAX-RS resources. They can use the WorkerConfig to get any plugin specific configuration.
    Code Block
    interface ConnectRestExtension extends Closeable{
        void register(ConnectRestExtensionContext restPluginContext);
    }
     
    interface ConnectRestExtensionContext{
        javax.ws.rs.core.Configurable configurable();
        WorkerConfig workerConfig();
        ConnectClusterState clusterState();
    }
     
    class ConnectRestExtensionContextImpl implements ConnectRestExtensionContext{
        private final Configurable configurable;
        private final WorkerConfig workerConfig;
        private final ConnectClusterState clusterState;
     
        ConnectRestExtensionContext(Configurable configurable, WorkerConfig workerConfig, ConnectClusterState clusterState){
            this.configurable = configurable;
            this.workerConfig = workerConfig;
            this.clusterState = clusterState;
        }
     
        public Configurable configurable(){
            return this.configurable;
        }
     
        public WorkerConfig workerConfig(){
            return this.workerConfig;
        }
     
        public ConnectClusterState clusterState(){
            return this.clusterState;
        }
    }

     

    We will be introducing another new public API ConnectClusterState which will at present provide some of the read only methods from the Herder.  The change would also include a default implementation ConnectClusterStateImpl in the connect runtime that will delegate to the underlying Herder. This will be useful when you want to add new resources like healthcheck, monitoring, etc.

    ...

    
         * 

    ...

    from 

    ...

    the 

    ...

    current 

    ...

    configuration.
     

    ...

     

    ...

     

    ...

     

    ...

     *

    ...

    /
        Collection<String> connectors();
     
        /**
         * Lookup the current status of a connector.
         * @param connName name of the connector
         */
        

    ...

    ConnectorHealth connectorHealth(String connName);
     
    }
     
    package org.apache.kafka.connect.rest.extension.entities;
    public class ConnectorHealth {
    
        private final String name;
        private final ConnectorState connector;
        private final Map<Integer, TaskState> tasks;
        private final ConnectorType type;
    
    
        public ConnectorHealth(String name,
                               ConnectorState connector,
                               Map<Integer, TaskState> tasks,
                               ConnectorType type) {
            this.name = name;
            this.connector = connector;
            this.tasks = tasks;
            this.type = type;
        }
    
    
        public String name() {
            return name;
        }
    
    
        public ConnectorState connectorState() {
            return connector;
        }
    
    
        public Map<Integer, TaskState> tasksState() {
            return tasks;
        }
    
    
        public ConnectorType type() {
            return type;
        }
    
        public abstract static class AbstractState {
    
            private final String state;
            private final String trace;
            private final String workerId;
    
            public AbstractState(String state, String workerId, String trace) {
                this.state = state;
                this.workerId = workerId;
                this.trace = trace;
            }
    
            public String state() {
                return state;
            }
    
    
            public String workerId() {
                return workerId;
            }
    
            public String trace() {
                return trace;
            }
        }
    
        public static class ConnectorState extends AbstractState {
    
            public ConnectorState(String state, String worker, String msg) {
                super(state, worker, msg);
            }
        }
    
        public static class TaskState extends AbstractState implements Comparable<TaskState> {
    
            private final int id;
    
            public TaskState(int id, String state, String worker, String msg) {
                super(state, worker, msg);
                this.id = id;
            }
    
            public int id() {
                return id;
            }
    
            @Override
            public int compareTo(TaskState that) {
                return Integer.compare(this.id, that.id);
            }
    
            @Override
            public boolean equals(Object o) {
                if (o == this) {
                    return true;
                }
                if (!(o instanceof TaskState)) {
                    return false;
                }
                TaskState other = (TaskState) o;
                return compareTo(other) == 0;
            }
    
            @Override
            public int hashCode() {
                return Objects.hash(id);
            }
        }
    
    }
    
    



    This also introduces a new configuration that  rest.extension.classes that allows to configure a comma separated list of Rest extension implementations.

    Proposed Changes

    Plugin Interface

    Users will be able to create a plugin by implementing the ConnectRestExtension interface, which has a single method that takes a ConnectRestExtensionContext instance as the only parameter. This allows us to change the interface easily in future to add new parameters. Connect runtime would also provide a default implementation for the interface ConnectRestExtensionContext.  One or more of the ConnectRestExtension  implementation can be configured via the configuration rest.extension.classes as a comma separated list of class names.

     

    Implementations would use the javax.ws.rs.core.Configurable to register one or more JAX-RS resources and get access to the Worker's Configs through the configure(Map<String, ?> configs) method in the ConnectRestExtension implementation( through org.apache.kafka.common.Configurable)
     

    Code Block
    package org.apache.kafka.connect.runtime.rest.extension;
    class ConnectRestExtensionContextImpl implements ConnectRestExtensionContext{
        private final Configurable configurable;
        private final ConnectClusterState clusterState;
     
        ConnectRestExtensionContext(Configurable configurable, ConnectClusterState clusterState){
            this.configurable = configurable;
            this.clusterState = clusterState;
        }
     
        public Configurable configurable(){
            return this.configurable;
        }
     
        public ConnectClusterState clusterState(){
            return this.clusterState;
        }
    }

     

    We will be introducing another new public API ConnectClusterState which will at present provide some of the read only methods from the Herder.  The change would also include a default implementation ConnectClusterStateImpl in the connect runtime that will delegate to the underlying Herder. This will be useful when you want to add new resources like healthcheck, monitoring, etc.

    Code Block
    package org.apache.kafka.connect.runtime.rest.extension;
    connectorStatus(String connName);
     
    }
     
    class ConnectClusterStateImpl implements ConnectClusterState{
        private final Herder herder;
     
        public ConnectClusterStateImpl(Herder herder){
            this.herder = herder;
        }
     
        @Override
        Collection<String> connectors(){
            //delegate to herder
        }
     
        @Override
        ConnectorStateInfoConnectorHealth connectorStatusconnectorHealth(String connName);{
            //delegate to herder
        }
    }
    Rest Extension Integration with Connect

    The plugin's would be registered in the RestServer.start(Herder herder) method after registering the default Connect resources. Connect Ru time would provide an implementation of Configurable interface that would do the following.

    • Constructed with the ResourceConfig available in the RestServer
    • Will check if resource is already registered. If not, it would delegate to ResourceConfig. If already registered would log a warning message.
    • For non-register methods would just delegate to the ResourceConfig instance

    The above approach helps alleviate any issues that could arise if Extension accidentally reregister the 

    Code Block
    class ConnectRestConfigurable implements Configurable{
    	ResourceConfig resourceConfig;
     
    	public ConnectRestConfigurable(ResourceConfig resourceConfig) {
    		this.resourceConfig = resourceConfig;
    	}
     
    	//implement methods and delegate to resourceConfig
    }

     

    The close for the plugins would be invoked as part of the stop() in the same class. 

    The new extension class and its dependencies would need to be as part of the plugin path. Hence ConnectRestExtension would be defined as a new plugin to be loaded by the PluginClassLoader.The plugin would be looked up based on Java's Service Provider API instead of the Reflections scan that is used for other plugins. This will help in terms of not adding class loader cost that is associated in scanning the classes today for other plugins. Hence the implementation must provide a `META-INF/services/org.apache.kafka.connect.rest.ConnectRestExtension` as part of the jar file containing the fully qualified implementation class .

    Example

    Consider the following example that defines a single plugin to add an authenticating filter and a health check resource.

    Code Block
    class  ExampleConnectRestExtension implements ConnectRestExtension{
     
    	private Map<String, ?> configs;
     
    	@Override
        public void register(ConnectRestExtensionContext restPluginContext){ register(ConnectRestExtensionContext restPluginContext){
            restPluginContext.configurable().register(new AuthenticationFilter(configs));
            restPluginContext.configurable().register(new AuthenticationFilterHealthCheckResource(restPluginContext.workerConfig()));configs, restPluginContext.clusterState()));
        }
     
        @Override
        public void close() throws IOException {
        }
    
        @Override
         restPluginContext.configurable().register(new HealthCheckResource(restPluginContext.workerConfig(), restPluginContext.clusterState()));
        }
     public void configure(Map<String, ?> configs) {
    		this.configs = configs;
        }
    
        @Override
        public voidString closeversion() {
            //close any resourcesreturn AppInfoParser.getVersion();
        }
    }
     
    class AuthenticationFilter implements ContainerRequestFilter {
     
      public AuthenticationFilter(WorkerConfig workerConfigMap<String, ?> configs){
        //set up filter
      }
         
      @Override
      public void filter(ContainerRequestContext requestContext) {
            //authentication logic
      }
     
    }
     
    @Path("/connect")
    class HealthCheckResource {
     
        public HealthCheckResource(WorkerConfig workerConfigMap<String, ?> configs, ConnectClusterState clusterState){
            //initialize resource
        }
     
        @path("/health")
        public void healthcheck(){
            //check herder health
        }
    }

    The above illustrated plugin can then be configured in the worker's configuration as below

     

    Code Block
    titleconnect-worker.properties
     // configure plugin
    rest.pluginsextension.classes=com.example.ExampleConnectPlugin


    For the RestExtension implementation to be found, the JAR should include the classes required by the implementation (excluding any Connect API or JAX-RS JARs) and should include

    a META-INF/services/org.apache.kafka.connect.rest.ConnectRestExtension

     file

    file that contains the fully-qualified names of the extension implementation class(es) found within the JAR. This is the standard Java Service Loader API mechanism.

     


    Code Block
    titleMETA-INF/services/org.apache.kafka.connect.rest.ConnectRestException
    com.example.ExampleConnectRestExtension

     

    ...

    The KIP proposes to include a reference implementation that allows users to authenticate incoming Basic Auth headers against a properties file containing list of username & passwordsthe configured JAASLoginModule.

    Compatibility, Deprecation, and Migration Plan

    ...