code in blog.sheimi.me: 2012-05-17-source-code-02 (3) injector

injector.java

public static void install(JobConf job, Path crawlDb) throws IOException {
  Path newCrawlDb = FileOutputFormat.getOutputPath(job);
  FileSystem fs = new JobClient(job).getFs();
  Path old = new Path(crawlDb, "old");
  Path current = new Path(crawlDb, CURRENT_NAME);
  if (fs.exists(current)) {
    if (fs.exists(old)) fs.delete(old, true);
    fs.rename(current, old);
  }
  fs.mkdirs(crawlDb);
  fs.rename(newCrawlDb, current);
  if (fs.exists(old)) fs.delete(old, true);
  Path lock = new Path(crawlDb, LOCK_NAME);
  LockUtil.removeLockFile(fs, lock);
}