Details
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Bug
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Status: On Hold
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Low
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Resolution: Unresolved
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8.0.13-4, 5.7.25-28, Not 5.6.x
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None
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None
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See pt-summary and pt-mysql-summary in the following ticket.
Description
Per the documentation found here...
The variable rocksdb_rate_limiter_bytes_per_sec should be able to be set dynamically, however in testing I've found that this does not work when changing it from/to a 0 value. A warning stating that the variable cannot be changed dynamically in this case. You may want to update the documentation for this.
mysql> show global variables like '%rocksdb_rate_limiter_bytes_per_sec%'; +------------------------------------+-------+ | Variable_name | Value | +------------------------------------+-------+ | rocksdb_rate_limiter_bytes_per_sec | 0 | +------------------------------------+-------+ 1 row in set (0.11 sec)mysql> set global rocksdb_rate_limiter_bytes_per_sec = 10485760; Query OK, 0 rows affected, 1 warning (0.00 sec)mysql> show warnings; +---------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------+ | Warning | 1210 | RocksDB: rocksdb_rate_limiter_bytes_per_sec cannot be dynamically changed to or from 0. Do a clean shutdown if you want to change it from or to 0. | +---------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec)mysql> show global variables like '%rocksdb_rate_limiter_bytes_per_sec%'; +------------------------------------+-------+ | Variable_name | Value | +------------------------------------+-------+ | rocksdb_rate_limiter_bytes_per_sec | 0 | +------------------------------------+-------+ 1 row in set (0.00 sec)
Below I confirmed that I can change the value dynamically so long as it's not to/from a 0 value.
[[email protected] ~]# systemctl restart mysqld [[email protected] ~]# mysql -u root -p Enter password: Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 2 Server version: 5.7.24-27 Percona Server (GPL), Release 27, Revision bd42700Copyright (c) 2009-2018 Percona LLC and/or its affiliates Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners.Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.mysql> show global variables like 'rocksdb_rate_limiter_bytes_per_sec'; +------------------------------------+----------+ | Variable_name | Value | +------------------------------------+----------+ | rocksdb_rate_limiter_bytes_per_sec | 10485760 | +------------------------------------+----------+ 1 row in set (0.01 sec)mysql> set global rocksdb_rate_limiter_bytes_per_sec = 10240; Query OK, 0 rows affected (0.00 sec)mysql> show global variables like 'rocksdb_rate_limiter_bytes_per_sec'; +------------------------------------+-------+ | Variable_name | Value | +------------------------------------+-------+ | rocksdb_rate_limiter_bytes_per_sec | 10240 | +------------------------------------+-------+ 1 row in set (0.00 sec)