[IMPALA-8923] Don't need synchronized in HBaseTable.getEstimatedRowStats

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Impala 2.7.0, Impala 2.8.0, Impala 2.7.1, Impala 2.9.0, Impala 2.10.0, Impala 2.11.0, Impala 3.0, Impala 2.12.0, Impala 3.1.0, Impala 3.2.0, Impala 3.3.0
• Fix Version/s: Impala 3.4.0
• Component/s: Frontend
• Epic Color: ghx-label-7
• Assignee: Quanlong Huang
• Reporter: Quanlong Huang
• Created: 06/Sep/19 13:39
• Updated: 08/Sep/19 06:48
• Resolved: 08/Sep/19 06:48

Description

HBaseTable.getEstimatedRowStats() estimates #rows and row size by sampling on hbase table in target key range. It requires HBase RPCs so could be slow.

Currently, HBaseTable.getEstimatedRowStats() is marked as synchronized. The purpose is to protect the HTable (old HBase API) object in legacy codes (before commit cf9d248). However, after commit cf9d248, we create org.apache.hadoop.hbase.client.Table object for each task (See comments and usages of FeHBaseTable.Util.getHBaseTable()). So we don't need the "synchronized" marker anymore in HBaseTable.getEstimatedRowStats().

Keeping the "synchronized" marker is further harmful. In high qps workload, queries on the same table will wait for entering this method and cost a lot of time in waiting (if this method is comparable slow).

This can be revealed by manually adding a latency (e.g. 100ms) in FeHBaseTable.Util.getEstimatedRowStats() and run concurrent queries on the same hbase table. In my experiment, removing "synchronized" gains 40% boost in 95% percentil query time. 

Issue Links

• links to: Code Review