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.camel.component.file;
  
  import org.apache.camel.Exchange;
  import org.apache.camel.LoggingLevel;
  
  /**
   * Strategy for acquiring exclusive read locks for files to be consumed. After granting the read lock it is released, we
   * just want to make sure that when we start consuming the file its not currently in progress of being written by third
   * party.
   * <p/>
   * Camel supports out of the box the following strategies:
   * <ul>
   * <li>FileRenameExclusiveReadLockStrategy waiting until its possible to rename the file.</li>
   * <li>FileLockExclusiveReadLockStrategy acquiring a RW file lock for the duration of the processing.</li>
   * <li>MarkerFileExclusiveReadLockStrategy using a marker file for acquiring read lock.</li>
   * <li>FileChangedExclusiveReadLockStrategy using a file changed detection for acquiring read lock.</li>
   * <li>FileIdempotentRepositoryReadLockStrategy using a {@link org.apache.camel.spi.IdempotentRepository} to hold the
   * read locks which allows to support clustering.</li>
   * </ul>
   */
  public interface GenericFileExclusiveReadLockStrategy<T> {
  
      /**
       * Allows custom logic to be run on startup preparing the strategy, such as removing old lock files etc.
       *
       * @param  operations generic file operations
       * @param  endpoint   the endpoint
       * @throws Exception  can be thrown in case of errors
       */
      void prepareOnStartup(GenericFileOperations<T> operations, GenericFileEndpoint<T> endpoint) throws Exception;
  
      /**
       * Acquires exclusive read lock to the file.
       *
       * @param  operations generic file operations
       * @param  file       the file
       * @param  exchange   the exchange
       * @return            <tt>true</tt> if read lock was acquired. If <tt>false</tt> Camel will skip the file and try it
       *                    on the next poll
       * @throws Exception  can be thrown in case of errors
       */
      boolean acquireExclusiveReadLock(GenericFileOperations<T> operations, GenericFile<T> file, Exchange exchange)
              throws Exception;
  
      /**
       * Releases the exclusive read lock granted by the <tt>acquireExclusiveReadLock</tt> method due an abort operation
       * (acquireExclusiveReadLock returned false).
       *
       * @param  operations generic file operations
       * @param  file       the file
       * @param  exchange   the exchange
       * @throws Exception  can be thrown in case of errors
       */
      void releaseExclusiveReadLockOnAbort(GenericFileOperations<T> operations, GenericFile<T> file, Exchange exchange)
              throws Exception;
  
      /**
       * Releases the exclusive read lock granted by the <tt>acquireExclusiveReadLock</tt> method due a rollback operation
       * (Exchange processing failed)
       *
       * @param  operations generic file operations
       * @param  file       the file
       * @param  exchange   the exchange
       * @throws Exception  can be thrown in case of errors
       */
      void releaseExclusiveReadLockOnRollback(GenericFileOperations<T> operations, GenericFile<T> file, Exchange exchange)
              throws Exception;
  
      /**
       * Releases the exclusive read lock granted by the <tt>acquireExclusiveReadLock</tt> method due a commit operation
       * (Exchange processing succeeded)
       *
       * @param  operations generic file operations
       * @param  file       the file
       * @param  exchange   the exchange
       * @throws Exception  can be thrown in case of errors
       */
      void releaseExclusiveReadLockOnCommit(GenericFileOperations<T> operations, GenericFile<T> file, Exchange exchange)
              throws Exception;
  
      /**
       * Sets an optional timeout period.
       * <p/>
       * If the readlock could not be granted within the time period then the wait is stopped and the
       * <tt>acquireExclusiveReadLock</tt> method returns <tt>false</tt>.
       *
       * @param timeout period in millis
       */
      void setTimeout(long timeout);
  
      /**
       * Sets the check interval period.
       * <p/>
       * The check interval is used for sleeping between attempts to acquire read lock. Setting a high value allows to
       * cater for <i>slow writes</i> in case the producer of the file is slow.
       * <p/>
       * The default period is 1000 millis.
       *
       * @param checkInterval interval in millis
       */
      void setCheckInterval(long checkInterval);
  
      /**
       * Sets logging level used when a read lock could not be acquired.
       * <p/>
       * Logging level used when a read lock could not be acquired.
       * <p/>
       * The default logging level is WARN
       *
       * @param readLockLoggingLevel LoggingLevel
       */
      void setReadLockLoggingLevel(LoggingLevel readLockLoggingLevel);
  
      /**
       * Sets whether marker file should be used or not.
       *
       * @param markerFile <tt>true</tt> to use marker files.
       */
      void setMarkerFiler(boolean markerFile);
  
      /**
       * Sets whether orphan marker files should be deleted upon startup
       *
       * @param deleteOrphanLockFiles <tt>true</tt> to delete files, <tt>false</tt> to skip this check
       */
      void setDeleteOrphanLockFiles(boolean deleteOrphanLockFiles);
  
  }
  