[Haskell-cafe] Help with async library and killing child processes

[Branimir Maksimovic]

I use my nonblocking library:

eg for IRC bot:

    let myCallbacks = defaultCallbacks {
                                 done_connected = binded,
                                 done_reading = response_get tm ref 
stdgen gsref,
                                 done_writing = response_written,
                                 done_closed = \pl s -> do
                                     putStrLn "peer closed, reconnecting"
                                     s <- socket myCallbacks
                                     connect pl s "83.140.172.212:6667"
                                     return 1,
                                 handle_error = \pl s buf len-> do
                                     str <- peekCStringLen 
(buf,fromIntegral len)
                                     putStrLn $ "error "++str++", 
reconnecting"
                                     s <- socket myCallbacks
                                     connect pl s "83.140.172.212:6667"
                                     return 1,
                                 tick = binded_tick tm
                               }
     s <- socket myCallbacks

     pl <- epoll 1000
     connect pl s "83.140.172.212:6667"
     run_loop pl (-1)

On 3/19/20 3:40 PM, Michael Hull wrote:
> Hi Niklas and Patrick,
>
> Thankyou both for the comments -- this is what I am looking for.
>
> I have a follow-on question, if I have code like
>
> getPages :: IO()
> getPages = do (page1, page2, page3)
>      <- runConcurrently $ (,,)
>      <$> Concurrently (getURL "url1")
>      <*> Concurrently (getURL "url2")
>      <*> Concurrently (getURL "url3")
>
> main :: IO()
> main = do
>     f <- async getPages
>     cancel f
>
> Am I guaranteed the the getURL() calls will definitely have either 
> finished, or cancel? (I looked through the source 
> (https://hackage.haskell.org/package/async-2.2.2/docs/src/Control.Concurrent.Async.html#Concurrently), 
> and I think so, because runConcurrently is implemented in terms of 
> race, which is implemented using withAsync, but I'm not confident with 
> interpreting Haskell!)
>
>
> Many thanks,
>
> Mike
>
>
>
> On Wed, 18 Mar 2020 at 03:15, Niklas Hambüchen <mail at nh2.me 
> <mailto:mail at nh2.me>> wrote:
>
>     I've you're new to async, also check out my recent rework of the
>     docs that talk about this topic specifically:
>
>     https://github.com/simonmar/async/pull/105/files
>
>     (To be available in the next release of async.)
>
>
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