boolean canRollback = false;
FSImage prevState = new FSImage(conf);
try {
prevState.getStorage().layoutVersion = HdfsConstants.LAYOUT_VERSION;
for (Iterator<StorageDirectory> it = storage.dirIterator(); it.hasNext();) {
StorageDirectory sd = it.next();
File prevDir = sd.getPreviousDir();
if (!prevDir.exists()) { // use current directory then
LOG.info("Storage directory " + sd.getRoot()
+ " does not contain previous fs state.");
// read and verify consistency with other directories
storage.readProperties(sd);
continue;
}
// read and verify consistency of the prev dir
prevState.getStorage().readPreviousVersionProperties(sd);
if (prevState.getLayoutVersion() != HdfsConstants.LAYOUT_VERSION) {
throw new IOException(
"Cannot rollback to storage version " +
prevState.getLayoutVersion() +
" using this version of the NameNode, which uses storage version " +
HdfsConstants.LAYOUT_VERSION + ". " +
"Please use the previous version of HDFS to perform the rollback.");
}
canRollback = true;
}
if (!canRollback)
throw new IOException("Cannot rollback. None of the storage "
+ "directories contain previous fs state.");
// Now that we know all directories are going to be consistent
// Do rollback for each directory containing previous state
for (Iterator<StorageDirectory> it = storage.dirIterator(); it.hasNext();) {
StorageDirectory sd = it.next();
File prevDir = sd.getPreviousDir();
if (!prevDir.exists())
continue;
LOG.info("Rolling back storage directory " + sd.getRoot()
+ ".\n new LV = " + prevState.getStorage().getLayoutVersion()
+ "; new CTime = " + prevState.getStorage().getCTime());
File tmpDir = sd.getRemovedTmp();
assert !tmpDir.exists() : "removed.tmp directory must not exist.";
// rename current to tmp
File curDir = sd.getCurrentDir();
assert curDir.exists() : "Current directory must exist.";
NNStorage.rename(curDir, tmpDir);
// rename previous to current
NNStorage.rename(prevDir, curDir);
// delete tmp dir
NNStorage.deleteDir(tmpDir);
LOG.info("Rollback of " + sd.getRoot()+ " is complete.");
}
isUpgradeFinalized = true;
} finally {
prevState.close();
}