Make middleware thread-safe #105
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Rack middleware must not use instance variables for state, as it is not thread safe. This patch changes the middleware to pass all request state as method arguments.
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it'd be nice if this could get merged. |
jubishop
approved these changes
May 2, 2021
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I've published my own version of |
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Rack middleware must not use instance variables for state, as the same instance can be called by multiple threads. This patch changes the middleware to pass all request state as method arguments.
As a result of the lack of thread safety in the current version, it is possible for the middleware to handle a request incorrectly, using the
@requestinstance variable from another request. This can present itself as random redirects to other URLs for a small subset of requests, when using a threaded Rack server like Puma.I have reproduced and verified this issue using a test application with many requests in a specific pattern that we observed in production to trigger this issue. After this patch, the issue no longer occurs.