/*
* Roll back to old snapshot at the block pool level
* If previous directory exists:
* <ol>
* <li>Rename <SD>/current/<bpid>/current to removed.tmp</li>
* <li>Rename * <SD>/current/<bpid>/previous to current</li>
* <li>Remove removed.tmp</li>
* </ol>
*
* Do nothing if previous directory does not exist.
* @param bpSd Block pool storage directory at <SD>/current/<bpid>
*/
void doRollback(StorageDirectory bpSd, NamespaceInfo nsInfo) throws IOException {
File prevDir = bpSd.getPreviousDir();
// regular startup if previous dir does not exist
if (!prevDir.exists()) return;
// read attributes out of the VERSION file of previous directory
BlockPoolSliceStorage prevInfo = new BlockPoolSliceStorage();
prevInfo.readPreviousVersionProperties(bpSd);
// We allow rollback to a state, which is either consistent with
// the namespace state or can be further upgraded to it.
// In another word, we can only roll back when ( storedLV >= software LV)
// && ( DN.previousCTime <= NN.ctime)
if (!(prevInfo.getLayoutVersion() >= HdfsConstants.DATANODE_LAYOUT_VERSION
&& prevInfo.getCTime() <= nsInfo.getCTime())) { // cannot rollback
throw new InconsistentFSStateException(
bpSd.getRoot(),
"Cannot rollback to a newer state.\nDatanode previous state: LV = "
+ prevInfo.getLayoutVersion()
+ " CTime = "
+ prevInfo.getCTime()
+ " is newer than the namespace state: LV = "
+ HdfsConstants.DATANODE_LAYOUT_VERSION
+ " CTime = "
+ nsInfo.getCTime());
}
LOG.info(
"Rolling back storage directory "
+ bpSd.getRoot()
+ ".\n target LV = "
+ nsInfo.getLayoutVersion()
+ "; target CTime = "
+ nsInfo.getCTime());
File tmpDir = bpSd.getRemovedTmp();
assert !tmpDir.exists() : "removed.tmp directory must not exist.";
// 1. rename current to tmp
File curDir = bpSd.getCurrentDir();
assert curDir.exists() : "Current directory must exist.";
rename(curDir, tmpDir);
// 2. rename previous to current
rename(prevDir, curDir);
// 3. delete removed.tmp dir
deleteDir(tmpDir);
LOG.info("Rollback of " + bpSd.getRoot() + " is complete");
}
