Fix thread safety of prevent_writes #36868
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As demonstrated in the test added and in rails#36830 the code that prevents writes wasn't thread safe. If one thread does a read, then another does a write, and then another does a read the second read will cause the first write to be unwriteable. This change removes the instance variable and instead uses a getter/setter on Thread.current[:prevent_writes] for the connection handler to set whether writes are allowed. Fixes rails#36830
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activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
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…safe Fix thread safety of prevent_writes
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Backported to 6-0-stable |
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As demonstrated in the test added and in #36830 the code that prevents
writes wasn't thread safe. If one thread does a read, then another does
a write, and then another does a read the second read will cause the
first write to be unwriteable.
This change removes the instance variable and instead uses a
getter/setter on Thread.current[:prevent_writes] for the connection
handler to set whether writes are allowed.
Fixes #36830
Thanks to @matthewd for helping me with writing this test.
cc/ @matthewd @tenderlove @jhawthorn
Thanks to @kiyot for the original report