How? Task.forget_about(t1) → like this?
kaa.python
kaa.python
I’ve said: in general. Forget about HttpPoison. Say, I’ve implemented my own http library or found one without timeout and I’m using it instead of HttpPoison.
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kaa.python
NobbZ
I’ve said: in general. Forget about HttpPoison. Say, I’ve implemented my own http library without timeout.
Thats a completely different question and does totally depend on how you have implemented your library and how much you have implemented yourself.
HTTPoison and -Potion are both just wrappers around well tested erlang libraries. And in fact both of them do handle the actual timeout, neither -Potion nor -Poison do it on their own.
Well, you have done it were? HTTPotion das have a default timeout of 8 seconds, Tasks of 5. HTTPotions timeout needs to be shorter than the tasks one to make it actually work inside a task.
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kaa.python
NobbZ
Also. Since you wanted a generic answer how to handle timeout in a Task…
Short: A Task on itself does not time out, it will do it work until its very end.
Some kind of timeout will only happen if you use Task.await/1 or Task.yield/1. The former will exit the waiting process, the task itself will continue to work until it has finished its payload. A yield will return nil on timeout and your waiting process will continue to run, as well as the Task. The Task will eventually send a simple message of the form {ref, response} to its owner. This message needs to get handled.
If you start a linked task, await/1 will kill that task as well, since no linked task can exist without its parent. This though will risk that used resources by the Task won’t be freed accordingly without doing some extra lifting.
Also since network connections are potentially a strictly limited ressource you have to share not only within your application but throughout the entire system, you should try to use some kind of pool and not try to create a potentially infinite number of connections.
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NobbZ
The libraries you found, do provide mechanisms to time out correctly, you DO NOT NEED to implement it on your own
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kaa.python
Do you forget something you’re just read in a second?
One more time:
I’ve said: in general. Forget about HttpPoison. Say, I’ve implemented my own http library or found one without timeout and I’m using it instead of HttpPoison.
How can I know that :exit has come from one of Task.await because of timeout? How can I flush all messages that’ll arive to the mailbox of GenServer after timeout from Task.await that have timed out?
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NobbZ
I overread this, since when I find a library which does not provide the functionality I need, I continue my search.
Even if I do not find something that fuillfils my needs, but I have to use my first find because it does have everything except the missed timeouts, I can’t tell how I’d put it in, since I can’t answer that question in general. It totally depends on how that library works, if it uses pooled or shared ressources which needs to be freed or if it doesn’t.
As a starting point, though, there are some functions available which send messages after a delay which you can specify, also you can specify a timeout in a receive. Those can be used as primitives to build your own timeout. Still you have to consider freeing up ressources.
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alexandrubagu
Why you don’t use :httpc library from erlang ?
iex(1)> :inets.start
:ok
iex(2)> :httpc.request(:get, {'http://localhost/index', []}, [timeout: :timer.seconds(1)], [])
{:error, :timeout}
http://localhost/index has a sleep for 6 seconds
Also :http has options for async requests and to notify the caller:
iex(1)> :inets.start
:ok
iex(2)> pid = self()
#PID<0.84.0>
iex(3)> :httpc.request(:get, {'http://localhost/index', []}, [], [sync: false, receiver: pid])
{:ok, #Reference<0.2595546524.2142502913.38782>}
iex(4)> flush()
:ok
iex(5)> flush() #after 6 seconds
{:http,
{#Reference<0.2595546524.2142502913.38782>,
{{'HTTP/1.1', 200, 'OK'},
[{'connection', 'Keep-Alive'}, {'date', 'Wed, 14 Jun 2017 10:48:44 GMT'},
{'server', 'Apache/2.4.25 (Ubuntu)'}, {'content-length', '9'},
{'content-type', 'text/html; charset=UTF-8'},
{'keep-alive', 'timeout=5, max=100'}], "index.php"}}}
:ok
make an async request and store reference in state, http will notify the gen_server by calling handle_call({:http, {:ref, result}, state) when request is finished, after some time you can call gen_server to give the response … so the problem with http timeouts is resolved.
If you want to know how to manage exists from Task.Supervisor.async_nolink for example you can take a look over this topic
Hope will help 
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