Now Env has unify all environment operation, such as file operation.
However some of our old functions don't leverage it. This change unify
FileUtils::scan_dir to use Env's function.
Sometime the broker writer failed to close, but we do not handle this failure.
This may create an empty file on remote storage but be treated as normal.
Also enhance some usabilities:
1. getting latest 2000 transactions instead of getting the earliest.
2. Show backend which download and upload tasks are being executed.
NOTE: This patch would modify all Backend's data.
And this will cause a very long time to restart be.
So if you want to interferer your product environment,
you should upgrade backend one by one.
1. Refactoring be is to clarify the structure the codes.
2. Use unique id to indicate a rowset.
Nameing rowset with tablet_id and version will lead to
many conflicts among compaction, clone, restore.
3. Extract an rowset interface to encapsulate rowsets
with different format.
1. Print broker address for debug.
2. Do not letting backup job cancelled if it already in state UPLOAD_INFO.
3. Cancel task on Backends when job is cancelled.
4. Show detail progress of backup and restore job.
5. Make 'show snapshot' result more readable.
6. Change upload and download thread num of backup and restore in Backend to 1.
1. Apache HDFS broker support HDFS HA and Hadoop kerberos authentication.
2. New Backup and Restore function. Use Fs Broker to backup your data to HDFS or restore them from HDFS.
3. Table-Level Privileges. Grant fine-grained privileges on table-level to specified user.
4. A lot of bugs fixed.
5. Performance improvement.
