How to use

skipTo

method

in

org.apache.hadoop.hdfs.server.common.GenerationStamp

/**
 * Upgrades the generation stamp for the filesystem
 * by reserving a sufficient range for all existing blocks.
 * Should be invoked only during the first upgrade to
 * sequential block IDs.
 */
public long upgradeLegacyGenerationStamp() {
 Preconditions.checkState(generationStamp.getCurrentValue() ==
  GenerationStamp.LAST_RESERVED_STAMP);
 generationStamp.skipTo(legacyGenerationStamp.getCurrentValue() +
  HdfsServerConstants.RESERVED_LEGACY_GENERATION_STAMPS);
 legacyGenerationStampLimit = generationStamp.getCurrentValue();
 return generationStamp.getCurrentValue();
}

/**
 * Upgrades the generation stamp for the filesystem
 * by reserving a sufficient range for all existing blocks.
 * Should be invoked only during the first upgrade to
 * sequential block IDs.
 */
public long upgradeGenerationStampToV2() {
 Preconditions.checkState(generationStampV2.getCurrentValue() ==
  GenerationStamp.LAST_RESERVED_STAMP);
 generationStampV2.skipTo(generationStampV1.getCurrentValue() +
  HdfsConstants.RESERVED_GENERATION_STAMPS_V1);
 generationStampV1Limit = generationStampV2.getCurrentValue();
 return generationStampV2.getCurrentValue();
}

/**
 * Upgrades the generation stamp for the filesystem
 * by reserving a sufficient range for all existing blocks.
 * Should be invoked only during the first upgrade to
 * sequential block IDs.
 */
public long upgradeGenerationStampToV2() {
 Preconditions.checkState(generationStampV2.getCurrentValue() ==
  GenerationStamp.LAST_RESERVED_STAMP);
 generationStampV2.skipTo(generationStampV1.getCurrentValue() +
  HdfsConstants.RESERVED_GENERATION_STAMPS_V1);
 generationStampV1Limit = generationStampV2.getCurrentValue();
 return generationStampV2.getCurrentValue();
}