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.sdk.transformservice;
  
  import java.io.IOException;
  import java.net.Socket;
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.concurrent.TimeoutException;
  import org.apache.beam.model.expansion.v1.ExpansionApi;
  import org.apache.beam.model.expansion.v1.ExpansionApi.ExpansionResponse;
  import org.apache.beam.model.expansion.v1.ExpansionServiceGrpc;
  import org.apache.beam.model.pipeline.v1.Endpoints;
  import org.apache.beam.sdk.util.construction.DefaultExpansionServiceClientFactory;
  import org.apache.beam.sdk.util.construction.ExpansionServiceClientFactory;
  import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.ManagedChannelBuilder;
  import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.stub.StreamObserver;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.annotations.VisibleForTesting;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Throwables;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  public class ExpansionService extends ExpansionServiceGrpc.ExpansionServiceImplBase
      implements AutoCloseable {
  
    private static final ExpansionServiceClientFactory DEFAULT_EXPANSION_SERVICE_CLIENT_FACTORY =
        DefaultExpansionServiceClientFactory.create(
            endPoint -> ManagedChannelBuilder.forTarget(endPoint.getUrl()).usePlaintext().build());
  
    private final ExpansionServiceClientFactory expansionServiceClientFactory;
  
    final List<Endpoints.ApiServiceDescriptor> endpoints;
  
    private boolean checkedAllServices = false;
  
    private static final long SERVICE_CHECK_TIMEOUT_MILLIS = 60000;
  
    private boolean disableServiceCheck = false;
  
    ExpansionService(
        List<Endpoints.ApiServiceDescriptor> endpoints,
        @Nullable ExpansionServiceClientFactory clientFactory) {
      this.endpoints = endpoints;
      this.expansionServiceClientFactory =
          clientFactory != null ? clientFactory : DEFAULT_EXPANSION_SERVICE_CLIENT_FACTORY;
    }
  
    // Waits till all expansion services are ready.
    private void waitForAllServicesToBeReady() throws TimeoutException {
      if (disableServiceCheck) {
        // Service check disabled. Just returning.
        return;
      }
  
      outer:
      for (Endpoints.ApiServiceDescriptor endpoint : endpoints) {
        long start = System.currentTimeMillis();
        long duration = 10;
        while (System.currentTimeMillis() - start < SERVICE_CHECK_TIMEOUT_MILLIS) {
          try {
            String url = endpoint.getUrl();
            int portIndex = url.lastIndexOf(":");
            if (portIndex <= 0) {
              throw new RuntimeException(
                  "Expected the endpoint to be of the form <host>:<port> but received " + url);
            }
            int port = Integer.parseInt(url.substring(portIndex + 1));
            String host = url.substring(0, portIndex);
            new Socket(host, port).close();
            // Current service is up. Checking the next one.
            continue outer;
          } catch (IOException exn) {
            try {
              Thread.sleep(duration);
            } catch (InterruptedException e) {
              // Ignore
            }
            duration = (long) (duration * 1.2);
          }
        }
        throw new TimeoutException(
            "Timeout waiting for the service "
                + endpoint.getUrl()
                + " to startup after "
                + (System.currentTimeMillis() - start)
                + " milliseconds.");
      }
    }
  
    @VisibleForTesting
    void disableServiceCheck() {
      disableServiceCheck = true;
    }
  
    @Override
    public void expand(
        ExpansionApi.ExpansionRequest request,
        StreamObserver<ExpansionApi.ExpansionResponse> responseObserver) {
      if (!checkedAllServices) {
        try {
          waitForAllServicesToBeReady();
        } catch (TimeoutException e) {
          throw new RuntimeException(e);
        }
        checkedAllServices = true;
      }
      try {
        responseObserver.onNext(processExpand(request));
        responseObserver.onCompleted();
      } catch (RuntimeException exn) {
        responseObserver.onNext(
            ExpansionApi.ExpansionResponse.newBuilder()
                .setError(Throwables.getStackTraceAsString(exn))
                .build());
        responseObserver.onCompleted();
      }
    }
  
    @Override
    public void discoverSchemaTransform(
        ExpansionApi.DiscoverSchemaTransformRequest request,
        StreamObserver<ExpansionApi.DiscoverSchemaTransformResponse> responseObserver) {
      if (!checkedAllServices) {
        try {
          waitForAllServicesToBeReady();
        } catch (TimeoutException e) {
          throw new RuntimeException(e);
        }
        checkedAllServices = true;
      }
      try {
        responseObserver.onNext(processDiscover(request));
        responseObserver.onCompleted();
      } catch (RuntimeException exn) {
        responseObserver.onNext(
            ExpansionApi.DiscoverSchemaTransformResponse.newBuilder()
                .setError(Throwables.getStackTraceAsString(exn))
                .build());
        responseObserver.onCompleted();
      }
    }
  
    private ExpansionApi.ExpansionResponse getAggregatedErrorResponse(
        Map<String, ExpansionApi.ExpansionResponse> errorResponses) {
      StringBuilder errorMessageBuilder = new StringBuilder();
  
      errorMessageBuilder.append(
          "Aggregated errors from " + errorResponses.size() + " expansion services." + "\n");
      for (Map.Entry<String, ExpansionApi.ExpansionResponse> entry : errorResponses.entrySet()) {
        errorMessageBuilder.append(
            "Error from expansion service "
                + entry.getKey()
                + ": "
                + entry.getValue().getError()
                + "\n");
      }
  
      return errorResponses
          .values()
          .iterator()
          .next()
          .toBuilder()
          .setError(errorMessageBuilder.toString())
          .build();
    }
  
    ExpansionApi.ExpansionResponse processExpand(ExpansionApi.ExpansionRequest request) {
      // Trying out expansion services in order till one succeeds.
      // If all services fail, re-raises the last error.
      Map<String, ExpansionResponse> errorResponses = new HashMap<>();
      RuntimeException lastException = null;
      for (Endpoints.ApiServiceDescriptor endpoint : endpoints) {
        try {
          ExpansionApi.ExpansionResponse response =
              expansionServiceClientFactory.getExpansionServiceClient(endpoint).expand(request);
          if (!response.getError().isEmpty()) {
            errorResponses.put(endpoint.getUrl(), response);
            continue;
          }
          return response;
        } catch (RuntimeException e) {
          lastException = e;
        }
      }
      if (lastException != null) {
        throw new RuntimeException("Expansion request to transform service failed.", lastException);
      }
      if (!errorResponses.isEmpty()) {
        return getAggregatedErrorResponse(errorResponses);
      } else if (lastException != null) {
        throw new RuntimeException("Expansion request to transform service failed.", lastException);
      } else {
        throw new RuntimeException("Could not process the expansion request: " + request);
      }
    }
  
    ExpansionApi.DiscoverSchemaTransformResponse processDiscover(
        ExpansionApi.DiscoverSchemaTransformRequest request) {
      // Trying out expansion services and aggregating all successful results.
      // If all services fail, return the last successful response any.
      // If there are no successful responses, re-raises the last error.
      List<ExpansionApi.DiscoverSchemaTransformResponse> successfulResponses = new ArrayList<>();
      ExpansionApi.DiscoverSchemaTransformResponse lastErrorResponse = null;
      for (Endpoints.ApiServiceDescriptor endpoint : endpoints) {
        try {
          ExpansionApi.DiscoverSchemaTransformResponse response =
              expansionServiceClientFactory.getExpansionServiceClient(endpoint).discover(request);
          if (response.getError().isEmpty()) {
            successfulResponses.add(response);
          } else {
            lastErrorResponse = response;
          }
        } catch (RuntimeException e) {
          // We just ignore this error and continue to try the next expansion service.
        }
      }
      if (successfulResponses.isEmpty()) {
        if (lastErrorResponse != null) {
          return lastErrorResponse;
        } else {
          // Returning a discovery response with an error message since none of the expansion services
          // supported discovery.
          return ExpansionApi.DiscoverSchemaTransformResponse.newBuilder()
              .setError("Did not find any expansion service that support the discovery API")
              .build();
        }
      } else {
        return aggregateDiscoveryRespones(successfulResponses);
      }
    }
  
    private ExpansionApi.DiscoverSchemaTransformResponse aggregateDiscoveryRespones(
        List<ExpansionApi.DiscoverSchemaTransformResponse> responses) {
      ExpansionApi.DiscoverSchemaTransformResponse.Builder responseBuilder =
          ExpansionApi.DiscoverSchemaTransformResponse.newBuilder();
      for (ExpansionApi.DiscoverSchemaTransformResponse response : responses) {
        responseBuilder.putAllSchemaTransformConfigs(response.getSchemaTransformConfigsMap());
      }
  
      return responseBuilder.build();
    }
  
    @Override
    public void close() throws Exception {}
  }
  