import org.apache.hadoop.hdfs.protocol.LayoutVersion.FeatureInfo; //导入依赖的package包/类
/**
 * Given feature {@code f}, ensures the layout version of that feature
 * supports all the features supported by it's ancestor.
 */
private void validateFeatureList(LayoutFeature f) {
  final FeatureInfo info = f.getInfo();
  int lv = info.getLayoutVersion();
  int ancestorLV = info.getAncestorLayoutVersion();
  SortedSet<LayoutFeature> ancestorSet = NameNodeLayoutVersion.getFeatures(ancestorLV);
  assertNotNull(ancestorSet);
  for (LayoutFeature  feature : ancestorSet) {
    assertTrue("LV " + lv + " does nto support " + feature
        + " supported by the ancestor LV " + info.getAncestorLayoutVersion(),
        NameNodeLayoutVersion.supports(feature, lv));
  }
}
 

import org.apache.hadoop.hdfs.protocol.LayoutVersion.FeatureInfo; //导入依赖的package包/类
/**
 * Tests that attempting to add a new NameNode feature out of order with
 * respect to minimum compatible layout version will fail fast.
 */
@Test(expected=AssertionError.class)
public void testNameNodeFeatureMinimumCompatibleLayoutVersionOutOfOrder() {
  FeatureInfo ancestorF = LayoutVersion.Feature.RESERVED_REL2_4_0.getInfo();
  LayoutFeature f = mock(LayoutFeature.class);
  when(f.getInfo()).thenReturn(new FeatureInfo(
      ancestorF.getLayoutVersion() - 1, ancestorF.getLayoutVersion(),
      ancestorF.getMinimumCompatibleLayoutVersion() + 1, "Invalid feature.",
      false));
  Map<Integer, SortedSet<LayoutFeature>> features = new HashMap<>();
  LayoutVersion.updateMap(features, LayoutVersion.Feature.values());
  LayoutVersion.updateMap(features, new LayoutFeature[] { f });
}
 

import org.apache.hadoop.hdfs.protocol.LayoutVersion.FeatureInfo; //导入依赖的package包/类
@Override
public FeatureInfo getInfo() {
  return info;
}
 

import org.apache.hadoop.hdfs.protocol.LayoutVersion.FeatureInfo; //导入依赖的package包/类
/**
 * NameNode feature that is added at layout version {@code ancestoryLV}.
 * @param lv new layout version with the addition of this feature
 * @param ancestorLV layout version from which the new lv is derived from.
 * @param description description of the feature
 * @param reserved true when this is a layout version reserved for previous
 *        versions
 * @param features set of features that are to be enabled for this version
 */
Feature(final int lv, final int ancestorLV, final String description,
    boolean reserved, Feature... features) {
  info = new FeatureInfo(lv, ancestorLV, description, reserved, features);
}
 

import org.apache.hadoop.hdfs.protocol.LayoutVersion.FeatureInfo; //导入依赖的package包/类
/**
 * DataNode feature that is added at layout version {@code ancestoryLV}.
 * @param lv new layout version with the addition of this feature
 * @param ancestorLV layout version from which the new lv is derived from.
 * @param description description of the feature
 * @param reserved true when this is a layout version reserved for previous
 *        version
 * @param features set of features that are to be enabled for this version
 */
Feature(final int lv, final int ancestorLV, final String description,
    boolean reserved, Feature... features) {
  info = new FeatureInfo(lv, ancestorLV, description, reserved, features);
}
 

import org.apache.hadoop.hdfs.protocol.LayoutVersion.FeatureInfo; //导入依赖的package包/类
/**
 * NameNode feature that is added at layout version {@code ancestoryLV}.
 * @param lv new layout version with the addition of this feature
 * @param ancestorLV layout version from which the new lv is derived from.
 * @param minCompatLV minimum compatible layout version
 * @param description description of the feature
 * @param reserved true when this is a layout version reserved for previous
 *        versions
 * @param features set of features that are to be enabled for this version
 */
Feature(final int lv, final int ancestorLV, int minCompatLV,
    final String description, boolean reserved, Feature... features) {
  info = new FeatureInfo(lv, ancestorLV, minCompatLV, description, reserved,
      features);
}