This feature is propsoed in [DSIP-1](https://cwiki.apache.org/confluence/display/DORIS/DSIP-001%3A+Java+UDF).
This PR support fixed-length input and output Java UDF. Phase I in DIP-1 is done after this PR.
To support Java UDF effeciently, I use no data copy in JNI call and all compute operations are off-heap in Java.
To achieve that, I use a UdfExecutor instead.
For users, a UDF class must have a public evaluate method.
This is a minor issue when we had FE start after a fresh installation,
but it will occur an error about the log directory is missing due to log directory is not existed
before some environment check message outputing to the log file.
the log directory creation code in bin/start_fe.sh is in the wrong place,
only need to put the log directory creation code in the beginning.
1. Fix error class in start_fe.sh and start_broker.sh.
2. Add log4j2.xml in fe/src/test/resources/ to run fe ut without log4j warnings.
3. Reduce the test file size in be ut.
2. add 2 new proc '/current_queries' and '/current_backend_instances' to monitor the current running queries.
3. add a manual compaction api on Backend to trigger cumulative or base compaction manually.
4. add Frontend config 'max_bytes_per_broker_scanner' to limit to bytes per one broker scanner. This is to limit the memory cost of a single broker load job
5. add Frontend config 'max_unfinished_load_job' to limit load job number: if number of running load jobs exceed the limit, no more load job is allowed to be submmitted.
6. a log of bug fixed
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.
1. fixed a bug when cast float to string
2. delay result's cancelled time
3. update type check in CastTo
4. remove unused mysql channel log
5. update stop_be.sh, use kill -0 instead of flock -nx
6. update jprotobuf-rpc to 3.5.15 in Frontend, the previous version will cause too many threads in JVM
Add new features:
1. plugins of Ambari and k8s deploy
2. specified config 'priority_network' to solve some ip problems
Fix bugs:
fix bugs that rebalance does not work in some case.
fix count(*) from union stmt bug
fix some union stmt bugs
fix bugs when try to schema change a clone replica
