798d9e8967
Uses the fix mentioned by @arianvp in https://github.com/haskell-servant/servant/pull/425. See also https://github.com/haskell-servant/servant/issues/51#issuecomment-250737727 The cause of the issue very is similar to the issue described in this blog post: https://www.fpcomplete.com/blog/2016/06/async-exceptions-stm-deadlocks The main thread creates a waiter, creates an asynchronous callback which is called when the `readyState` of the request changes. When the readyState changes to 4, which means 'request finished', the waiter MVar is put. The main thread takes the MVar and continues to do stuff with the response. The problem is that the `readyState` can change to 4 more than once, for some reason. The second time this happens, the waiter MVar can be put again, since the main thread took it. The main thread, however, won't take it again. After all, it only needed to take the MVar once to know that the request was finished. The third time `readyState` is set to 4, the putMVar would block, causing the following exception to be thrown: ``` thread blocked indefinitely in an MVar operation ``` Since state 4 should really mean that the response is ready, it seems appropriate to decide that all changes of the state to 4 after the initial one can be safely ignored. |
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| .. | ||
| include | ||
| src/Servant | ||
| test | ||
| CHANGELOG.md | ||
| docs.sh | ||
| LICENSE | ||
| README.md | ||
| servant-client.cabal | ||
| Setup.hs | ||
| tinc.yaml | ||
servant-client
This library lets you automatically derive Haskell functions that let you query each endpoint of a servant webservice.
Example
type MyApi = "books" :> Get '[JSON] [Book] -- GET /books
:<|> "books" :> ReqBody Book :> Post '[JSON] Book -- POST /books
myApi :: Proxy MyApi
myApi = Proxy
getAllBooks :: Manager -> BaseUrl -> ExceptT String IO [Book]
postNewBook :: Book -> Manager -> BaseUrl -> ExceptT String IO Book
-- 'client' allows you to produce operations to query an API from a client.
(getAllBooks :<|> postNewBook) = client myApi