Description:
During a large remote clone, if you query this:
select * from performance_schema.clone_progress;
select * from performance_schema.clone_status ;
from multiple connections, the outputs have duplicate and/or NULL values occasionally..
e.g. this is bad output:
mysql> select * from performance_schema.clone_progress ;select * from performance_schema.clone_status ;
+------+-----------+-------------+----------------------------+----------------------------+---------+--------------+-------------+-------------+------------+---------------+
| ID | STAGE | STATE | BEGIN_TIME | END_TIME | THREADS | ESTIMATE | DATA | NETWORK | DATA_SPEED | NETWORK_SPEED |
+------+-----------+-------------+----------------------------+----------------------------+---------+--------------+-------------+-------------+------------+---------------+
| 1 | FILE COPY | In Progress | 2021-10-11 06:18:54.064422 | NULL | 0 | 0 | 0 | 0 | 0 | 0 |
| 1 | DROP DATA | Not Started | NULL | NULL | 0 | 0 | 0 | 0 | 0 | 0 |
| 1 | RESTART | Not Started | NULL | NULL | 0 | 0 | 0 | 0 | 0 | 0 |
| 1 | DROP DATA | Completed | 2021-10-11 06:18:53.941984 | 2021-10-11 06:18:54.064338 | 1 | 0 | 0 | 0 | 0 | 0 |
| 1 | FILE COPY | In Progress | 2021-10-11 06:18:54.064422 | NULL | 2 | 129465894491 | 37635802715 | 37637820865 | 60334730 | 60337952 |
| 1 | PAGE COPY | Not Started | NULL | NULL | 0 | 0 | 0 | 0 | 0 | 0 |
| 1 | REDO COPY | Not Started | NULL | NULL | 0 | 0 | 0 | 0 | 0 | 0 |
| 1 | FILE SYNC | Not Started | NULL | NULL | 0 | 0 | 0 | 0 | 0 | 0 |
| 1 | RESTART | Not Started | NULL | NULL | 0 | 0 | 0 | 0 | 0 | 0 |
| 1 | RECOVERY | Not Started | NULL | NULL | 0 | 0 | 0 | 0 | 0 | 0 |
+------+-----------+-------------+----------------------------+----------------------------+---------+--------------+-------------+-------------+------------+---------------+
10 rows in set (0.00 sec)
+------+------+-------------+-------------------------+----------+----------------+----------------+----------+---------------+-------------+-----------------+---------------+
| ID | PID | STATE | BEGIN_TIME | END_TIME | SOURCE | DESTINATION | ERROR_NO | ERROR_MESSAGE | BINLOG_FILE | BINLOG_POSITION | GTID_EXECUTED |
+------+------+-------------+-------------------------+----------+----------------+----------------+----------+---------------+-------------+-----------------+---------------+
| NULL | NULL | In Progress | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL |
| 1 | 8 | In Progress | 2021-10-11 06:18:53.716 | NULL | 127.0.0.1:3306 | LOCAL INSTANCE | 0 | | | 0 | |
+------+------+-------------+-------------------------+----------+----------------+----------------+----------+---------------+-------------+-----------------+---------------+
2 rows in set (0.00 sec)
here is the output when queried only by a single connection:
mysql> select * from performance_schema.clone_progress ;select * from performance_schema.clone_status ;
+------+-----------+-------------+----------------------------+----------------------------+---------+--------------+-------------+-------------+------------+---------------+
| ID | STAGE | STATE | BEGIN_TIME | END_TIME | THREADS | ESTIMATE | DATA | NETWORK | DATA_SPEED | NETWORK_SPEED |
+------+-----------+-------------+----------------------------+----------------------------+---------+--------------+-------------+-------------+------------+---------------+
| 1 | DROP DATA | Completed | 2021-10-11 06:18:53.941984 | 2021-10-11 06:18:54.064338 | 1 | 0 | 0 | 0 | 0 | 0 |
| 1 | FILE COPY | In Progress | 2021-10-11 06:18:54.064422 | NULL | 2 | 129465894491 | 44463081051 | 44465463817 | 37308883 | 37310824 |
| 1 | PAGE COPY | Not Started | NULL | NULL | 0 | 0 | 0 | 0 | 0 | 0 |
| 1 | REDO COPY | Not Started | NULL | NULL | 0 | 0 | 0 | 0 | 0 | 0 |
| 1 | FILE SYNC | Not Started | NULL | NULL | 0 | 0 | 0 | 0 | 0 | 0 |
| 1 | RESTART | Not Started | NULL | NULL | 0 | 0 | 0 | 0 | 0 | 0 |
| 1 | RECOVERY | Not Started | NULL | NULL | 0 | 0 | 0 | 0 | 0 | 0 |
+------+-----------+-------------+----------------------------+----------------------------+---------+--------------+-------------+-------------+------------+---------------+
7 rows in set (0.00 sec)
+------+------+-------------+-------------------------+----------+----------------+----------------+----------+---------------+-------------+-----------------+---------------+
| ID | PID | STATE | BEGIN_TIME | END_TIME | SOURCE | DESTINATION | ERROR_NO | ERROR_MESSAGE | BINLOG_FILE | BINLOG_POSITION | GTID_EXECUTED |
+------+------+-------------+-------------------------+----------+----------------+----------------+----------+---------------+-------------+-----------------+---------------+
| 1 | 8 | In Progress | 2021-10-11 06:18:53.716 | NULL | 127.0.0.1:3306 | LOCAL INSTANCE | 0 | | | 0 | |
+------+------+-------------+-------------------------+----------+----------------+----------------+----------+---------------+-------------+-----------------+---------------+
1 row in set (0.00 sec)
How to repeat:
create a large database (many gigabytes).
start a new clone e.g.
clone instance from 'root'@'127.0.0.1':3306 identified by '';
in a few threads execute this continuously:
select * from performance_schema.clone_progress;
select * from performance_schema.clone_status ;
and examine the outputs.. I'll attach some outputs.
