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Use SELECT @@global.read_only for Monitor #1621

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renecannao opened this issue Jul 26, 2018 · 1 comment
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Use SELECT @@global.read_only for Monitor #1621

renecannao opened this issue Jul 26, 2018 · 1 comment
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v1.4.10

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On a large system with around 1000 ProxySQL instances it was detected that SHOW GLOBAL VARIABLES LIKE 'read_only' could cause serious contention/locking issues.
The average execution time to run SHOW GLOBAL VARIABLES LIKE 'read_only' is 2ms, but could spike to 300ms at high concurrency.
On the other hand, the average execution time for SELECT @@global.read_only is around 0.05ms (40 times faster than SHOW GLOBAL.
@renecannao renecannao added this to the v1.4.10 milestone Jul 26, 2018
@renecannao renecannao self-assigned this Jul 26, 2018
@renecannao renecannao mentioned this issue Jul 26, 2018
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renecannao added a commit that referenced this issue Jul 30, 2018
@renecannao
Use SELECT @@global.read_only #1621
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renecannao added a commit that referenced this issue Aug 2, 2018
@renecannao
Use SELECT @@global.read_only #1621
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Applied in 1.4.10 and 2.0.0
Closing

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