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.kafka.raft;
  
  import org.apache.kafka.common.utils.Utils;
  import org.apache.kafka.raft.generated.QuorumStateData;
  import org.apache.kafka.raft.generated.QuorumStateDataJsonConverter;
  import org.apache.kafka.server.common.KRaftVersion;
  
  import com.fasterxml.jackson.databind.JsonNode;
  import com.fasterxml.jackson.databind.ObjectMapper;
  import com.fasterxml.jackson.databind.node.ObjectNode;
  import com.fasterxml.jackson.databind.node.ShortNode;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.BufferedReader;
  import java.io.BufferedWriter;
  import java.io.EOFException;
  import java.io.File;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.OutputStreamWriter;
  import java.io.UncheckedIOException;
  import java.nio.charset.StandardCharsets;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.util.Optional;
  
  /**
   * Local file based quorum state store. It takes the JSON format of {@link QuorumStateData}
   * with an extra data version number field (data_version) as part of the data.
   *
   * Example version 0 format:
   * <pre>
   * {
   *   "clusterId": "",
   *   "leaderId": 1,
   *   "leaderEpoch": 2,
   *   "votedId": -1,
   *   "appliedOffset": 0,
   *   "currentVoters": [],
   *   "data_version": 0
   * }
   * </pre>
   *
   * Example version 1 format:
   * <pre>
   * {
   *   "leaderId": -1,
   *   "leaderEpoch": 2,
   *   "votedId": 1,
   *   "votedDirectoryId": "J8aAPcfLQt2bqs1JT_rMgQ",
   *   "data_version": 1
   * }
   * </pre>
   * */
  public class FileQuorumStateStore implements QuorumStateStore {
      private static final Logger log = LoggerFactory.getLogger(FileQuorumStateStore.class);
      private static final String DATA_VERSION = "data_version";
  
      static final short LOWEST_SUPPORTED_VERSION = 0;
      static final short HIGHEST_SUPPORTED_VERSION = 1;
  
      public static final String DEFAULT_FILE_NAME = "quorum-state";
  
      private final File stateFile;
  
      public FileQuorumStateStore(final File stateFile) {
          this.stateFile = stateFile;
      }
  
      private QuorumStateData readStateFromFile(File file) {
          try (final BufferedReader reader = Files.newBufferedReader(file.toPath(), StandardCharsets.UTF_8)) {
              final String line = reader.readLine();
              if (line == null) {
                  throw new EOFException("File ended prematurely.");
              }
  
              final ObjectMapper objectMapper = new ObjectMapper();
              JsonNode readNode = objectMapper.readTree(line);
  
              if (!(readNode instanceof ObjectNode dataObject)) {
                  throw new IOException("Deserialized node " + readNode +
                      " is not an object node");
              }
  
              JsonNode dataVersionNode = dataObject.get(DATA_VERSION);
              if (dataVersionNode == null) {
                  throw new IOException("Deserialized node " + readNode +
                      " does not have " + DATA_VERSION + " field");
              }
  
              final short dataVersion = dataVersionNode.shortValue();
              if (dataVersion < LOWEST_SUPPORTED_VERSION || dataVersion > HIGHEST_SUPPORTED_VERSION) {
                  throw new IllegalStateException(
                      String.format(
                          "data_version (%d) is not within the min (%d) and max (%d) supported version",
                          dataVersion,
                          LOWEST_SUPPORTED_VERSION,
                          HIGHEST_SUPPORTED_VERSION
                      )
                  );
              }
  
              return QuorumStateDataJsonConverter.read(dataObject, dataVersion);
          } catch (IOException e) {
              throw new UncheckedIOException(
                  String.format("Error while reading the Quorum status from the file %s", file), e);
          }
      }
  
      /**
       * Reads the election state from local file.
       */
      @Override
      public Optional<ElectionState> readElectionState() {
          if (!stateFile.exists()) {
              return Optional.empty();
          }
  
          return Optional.of(ElectionState.fromQuorumStateData(readStateFromFile(stateFile)));
      }
  
      @Override
      public void writeElectionState(ElectionState latest, KRaftVersion kraftVersion) {
          short quorumStateVersion = kraftVersion.quorumStateVersion();
  
          writeElectionStateToFile(
              stateFile,
              latest.toQuorumStateData(quorumStateVersion),
              quorumStateVersion
          );
      }
  
      @Override
      public Path path() {
          return stateFile.toPath();
      }
  
      private void writeElectionStateToFile(final File stateFile, QuorumStateData state, short version) {
          if (version > HIGHEST_SUPPORTED_VERSION) {
              throw new IllegalArgumentException(
                  String.format(
                      "Quorum state data version (%d) is greater than the supported version (%d)",
                      version,
                      HIGHEST_SUPPORTED_VERSION
                  )
              );
          }
          final File temp = new File(stateFile.getAbsolutePath() + ".tmp");
          deleteFileIfExists(temp);
  
          log.trace("Writing tmp quorum state {}", temp.getAbsolutePath());
  
          try {
              try (final FileOutputStream fileOutputStream = new FileOutputStream(temp);
                   final BufferedWriter writer = new BufferedWriter(
                       new OutputStreamWriter(fileOutputStream, StandardCharsets.UTF_8)
                   )
              ) {
                  ObjectNode jsonState = (ObjectNode) QuorumStateDataJsonConverter.write(state, version);
                  jsonState.set(DATA_VERSION, new ShortNode(version));
                  writer.write(jsonState.toString());
                  writer.flush();
                  fileOutputStream.getFD().sync();
              }
              Utils.atomicMoveWithFallback(temp.toPath(), stateFile.toPath());
          } catch (IOException e) {
              throw new UncheckedIOException(
                  String.format(
                      "Error while writing the Quorum status from the file %s",
                      stateFile.getAbsolutePath()
                  ),
                  e
              );
          } finally {
              // cleanup the temp file when the write finishes (either success or fail).
              deleteFileIfExists(temp);
          }
      }
  
      /**
       * Clear state store by deleting the local quorum state file
       */
      @Override
      public void clear() {
          deleteFileIfExists(stateFile);
          deleteFileIfExists(new File(stateFile.getAbsolutePath() + ".tmp"));
      }
  
      @Override
      public String toString() {
          return "Quorum state filepath: " + stateFile.getAbsolutePath();
      }
  
      private void deleteFileIfExists(File file) {
          try {
              Files.deleteIfExists(file.toPath());
          } catch (IOException e) {
              throw new UncheckedIOException(
                  String.format("Error while deleting file %s", file.getAbsoluteFile()), e);
          }
      }
  }
  