Use BackendStatus to show BE's infomation in show backends; (#3713)

The infomation is displayed in JSON format.For example: {"lastTabletReportTime":"2020-05-28 15:29:01"}
2020-06-05 22:37:48 -05:00
parent 3b6a781862
commit a7bf006b51
5 changed files with 37 additions and 6 deletions
--- a/docs/en/sql-reference/sql-statements/Administration/SHOW
+++ b/docs/en/sql-reference/sql-statements/Administration/SHOW
@ -42,6 +42,7 @@ Explain:
 9. Total Capacity represents total disk space. Total Capacity = AvailCapacity + DataUsedCapacity + other non-user data files take up space.
 10. UsedPct represents the percentage of disk usage.
 11. ErrMsg is used to display error messages when a heartbeat fails.
+12. Status is used to display some Status information about BE in JSON format, including the last time that BE reported it's tablet.

 ## keyword
 SHOW, BACKENDS