content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.beam.runners.fnexecution.state;
  
  import org.apache.beam.model.fnexecution.v1.BeamFnApi.StateRequest;
  
  /**
   * The {@link StateDelegator} is able to delegate {@link StateRequest}s to a set of registered
   * handlers. Any request for an unregistered process bundle instruction id is automatically failed.
   */
  public interface StateDelegator {
    /**
     * Registers the supplied handler for the given process bundle instruction id for all {@link
     * StateRequest}s with a matching id. A handle is returned which allows one to deregister from
     * this {@link StateDelegator}.
     */
    Registration registerForProcessBundleInstructionId(
        String processBundleInstructionId, StateRequestHandler handler);
  
    /** Allows callers to deregister from receiving further state requests. */
    interface Registration {
      /**
       * De-registers the handler for all future requests for state for the registered process bundle
       * instruction id.
       */
      void deregister();
  
      /**
       * De-registers the handler for all future requests for state for the registered process bundle
       * instruction id. Aborts all in-flight state requests.
       */
      void abort();
    }
  }
  