From the doc [1] there's a few instances you can use. `MonadResource` sounds like the most obvious choice, with its `allocate` [2], but that'll require you to refactor your application a bit. It's what I'd recommend though. If that's unfeasable, there's always the new `bracket_` on `MonadUnliftIO` [3]

[1] https://www.stackage.org/haddock/lts-11.6/yesod-core-1.6.3/Yesod-Core-Handle... [2] https://www.stackage.org/haddock/lts-11.6/resourcet-1.2.1/Control-Monad-Tran... [3] https://www.stackage.org/haddock/lts-11.6/unliftio-0.2.6.0/UnliftIO-Exceptio... 2018-04-25 13:26 GMT+02:00 waldmann :

Dear Cafe,

I wonder what's the recommended way to catch an exception, clean up resources, etc., in a yesod Handler. I was using Control.Monad.Catch.bracket_ in legacy code but now I get "No instance for (Control.Monad.Catch.MonadMask (HandlerFor App))"

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