How to read from stdin in new process? I can put line and print it only in main process. Should I pass to get_line console device or sth similar or it's not possible?
My code:
-module(inputTest).
-compile([export_all]).
run() ->
Message = io:get_line("[New process] Put sth: "),
io:format("[New process] data: ~p~n", [Message]).
main() ->
Message = io:get_line("[Main] Put sth: "),
io:format("[Main] data: ~p~n", [Message]),
spawn(?MODULE, run, []).
The problem is that your main/0 process spawns run/0 and then immediately exits. You should make main/0 wait until run/0 is finished. Here's how you can do that:
-module(inputTest).
-compile([export_all]).
run(Parent) ->
Message = io:get_line("[New process] Put sth: "),
io:format("[New process] data: ~p~n", [Message]),
Parent ! {self(), ok}.
main() ->
Message = io:get_line("[Main] Put sth: "),
io:format("[Main] data: ~p~n", [Message]),
Pid = spawn(?MODULE, run, [self()]),
receive
{Pid, _} ->
ok
end.
After spawning run/1 — and note that we changed it to pass our process ID to it — we wait to receive a message from it. In run/1 once we print to the output, we send the parent a message to let it know we're done. Running this in an erl shell produces the following:
1> inputTest:main().
[Main] Put sth: main
[Main] data: "main\n"
[New process] Put sth: run/1
[New process] data: "run/1\n"
ok
Related
I'm toying around with Elm processes in order to learn more about how they work. In parts of this, I'm trying to implement a timer.
I bumped into an obstacle, however: I can't find a way to access the result of a process' task in the rest of the code.
For a second, I hoped that if I make the task resolve with a Cmd, the Elm runtime would be kind enough to perform that effect for me, but that was a naive idea:
type Msg
= Spawned Process.Id
| TimeIsUp
init _ =
( Nothing
, Task.perform Spawned (Process.spawn backgroundTask)
)
backgroundTask : Task.Task y (Platform.Cmd.Cmd Msg)
backgroundTask =
Process.sleep 1000
-- pathetic attempt to send a Msg starts here
|> Task.map ( always
<| Task.perform (always TimeIsUp)
<| Task.succeed ()
)
-- and ends here
|> Task.map (Debug.log "Timer finished") -- logs "Timer finished: <internals>"
update msg state =
case msg of
Spawned id ->
(Just id, Cmd.none)
TimeIsUp ->
(Nothing, Cmd.none)
view state =
case state of
Just id ->
text "Running"
Nothing ->
text "Time is up"
The docs say
there is no public API for processes to communicate with each other.
I'm not sure if that implies that a process can't cummunicate with the rest of the app.
Is there any way to have update function receive a TimeIsUp once the process exits?
There is one way but it requires a port of hell:
make a fake HTTP request from the process,
then intercept it via JavaScript
and pass it back to Elm.
port ofHell : (() -> msg) -> Sub msg
subscriptions _ =
ofHell (always TimeIsUp)
backgroundTask : Task.Task y (Http.Response String)
backgroundTask =
Process.sleep 1000
-- nasty hack starts here
|> Task.andThen ( always
<| Http.task { method = "EVIL"
, headers = []
, url = ""
, body = Http.emptyBody
, resolver = Http.stringResolver (always Ok "")
, timeout = Nothing
}
)
Under the hood, Http.task invokes new XMLHttpRequest(), so we can intercept it by redefining that constructor.
<script src="elm-app.js"></script>
<div id=hack></div>
<script>
var app = Elm.Hack.init({
node: document.getElementById('hack')
})
var orig = window.XMLHttpRequest
window.XMLHttpRequest = function () {
var req = new orig()
var orig = req.open
req.open = function (method) {
if (method == 'EVIL') {
app.ports.ofHell.send(null)
}
return orig.open.apply(this, arguments)
}
return req
}
</script>
The solution is not production ready, but it does let you continue playing around with Elm processes.
Elm Processes aren't a fully fledged API at the moment. It's not possible to do what you want with the Process library on its own.
See the notes in the docs for Process.spawn:
Note: This creates a relatively restricted kind of Process because it cannot receive any messages. More flexibility for user-defined processes will come in a later release!
and the whole Future Plans section, eg.:
Right now, this library is pretty sparse. For example, there is no public API for processes to communicate with each other.
There is a program of three modules. The Print module receives a number from the keyboard, passes it to another module, receives the response, and displays it on the screen. The Proc1 and Proc2 modules receive a number, perform calculations, and send the result back.
defmodule Launch do
#moduledoc """
Documentation for `Launch`.
"""
#doc """
"""
def start() do
children = [
%{
id: Print,
start: {Print, :print, []}
},
%{
id: Proc1,
start: {Proc1, :proc1, []}
},
%{
id: Proc2,
start: {Proc2, :proc2, []}
}
]
Supervisor.start_link(children, strategy: :one_for_one)
end
end
defmodule Print do
def print() do
num =
IO.gets("Input number: ")
|> String.trim()
|> String.to_integer()
if num >= 0 do
send(Proc1, {self(), num})
else
send(Proc2, {self(), num})
end
receive do
num -> IO.puts(num)
after
500 ->
print()
end
print()
end
end
defmodule Proc1 do
def proc1() do
receive do
{pid, num} ->
send(pid, 100/num)
proc1()
_e ->
IO.puts("Error")
end
end
end
defmodule Proc2 do
def proc2() do
receive do
{pid, num} ->
send(pid, 1000/num)
proc2()
_e ->
IO.puts("Error")
end
end
end
I am trying to run all processes under the supervision of a single Supervisor. But there is a problem-only the first "child" is started, the other "children" are not started. In the example above, the Print process will start, but Proc1 and Proc2 will not start. How do I run all processes under one Supervisor? Important note: the Print process must get the addresses of the Proc1 and Proc2 processes for communication.
There are many issues with the code you’ve posted.
Registered processes
To be able to use process name as Process.dest() in a call to Kernel.send/2, one should start the named process.
Supervisor.start_link/2
Supervisor.start_link/2 expects a list of tuples, with modules and functions that immediately return, having the process started as a side effect. These functions are called, and there would not be any magic: if this is an infinitely recursive function, the execution flow would be deadlocked inside, waiting for the message in receive/1.
Supervisor performs some magic by automatically monitoring and restarting children for you, but it does nothing to spawn the separate processes. GenServer encapsulates this functionality and provides a handy way to not bother about spawning processes.
Solution
What you might do, is to spawn all three processes, manually monitor them, and react on {:DOWN, ref, :process, pid, reason} message respawning the died process. This is exactly what Supervisor effectively does under the hood for children.
Launch
defmodule Launch do
def start() do
proc1 = spawn(&Proc1.proc1/0)
proc2 = spawn(&Proc2.proc2/0)
print = spawn(fn -> Print.print(proc1, proc2) end)
Process.monitor(proc1)
Process.monitor(proc2)
Process.monitor(print)
receive do
msg -> IO.inspect(msg)
end
end
end
Print
defmodule Print do
def print(pid1, pid2) do
num =
IO.gets("Input number: ")
|> String.trim()
|> String.to_integer()
if num >= 0 do
send(pid1, {self(), num})
else
send(pid2, {self(), num})
end
receive do
num -> IO.puts(num)
end
print(pid1, pid2)
end
end
The other two modules are fine.
Here is how it will look like in iex
iex|1 ▶ c "/tmp/test.ex"
#⇒ [Launch, Print, Proc1, Proc2]
iex|2 ▶ Launch.start
Input number: 10
10.0
Input number: 1000
0.1
Input number: a
#⇒ {:DOWN, #Reference<0.3632020665.3980394506.95298>,
# :process, #PID<0.137.0>,
# {:badarg,
# [
# {:erlang, :binary_to_integer, ["a"], []},
# {Print, :print, 2, [file: '/tmp/test.ex', line: 22]}
# ]}}
Now instead of printing this out, respawn the failed process, and you will get a bare implementation of the supervised intercommunicating processes. For all_for_one strategy that could be achieved with:
receive do
{:DOWN, _, _, _, _} ->
Process.exit(print, :normal)
Process.exit(proc1, :normal)
Process.exit(proc2, :normal)
start()
end
I am trying to have a process that is launched only if a combination of conditions is met, but when checking if a channel has a path to a file, it always returns it as empty. Probably I am doing something wrong, in that case please correct my code. I tried to follow some of the suggestions in this issue but no success.
Consider the following minimal example:
process one {
output:
file("test.txt") into _chProcessTwo
script:
"""
echo "Hello world" > "test.txt"
"""
}
// making a copy so I check first if something in the channel or not
// avoids raising exception of MultipleInputChannel
_chProcessTwo.into{
_chProcessTwoView;
_chProcessTwoCheck;
_chProcessTwoUse
}
//print contents of channel
println "Channel contents: " + _chProcessTwoView.toList().view()
process two {
input:
file(myInput) from _chProcessTwoUse
when:
(!_chProcessTwoCheck.toList().isEmpty())
script:
def test = _chProcessTwoUse.toList().isEmpty() ? "I'm empty" : "I'm NOT empty"
println "The outcome is: " + test
}
I want to have process two run if and only if there is a file in the _chProcessTwo channel.
If I run the above code I obtain:
marius#dev:~/pipeline$ ./bin/nextflow run test.nf
N E X T F L O W ~ version 19.09.0-edge
Launching `test.nf` [infallible_gutenberg] - revision: 9f57464dc1
[c8/bf38f5] process > one [100%] 1 of 1 ✔
[- ] process > two -
[/home/marius/pipeline/work/c8/bf38f595d759686a497bb4a49e9778/test.txt]
where the last line are actually the contents of _chProcessTwoView
If I remove the when directive from the second process I get:
marius#mg-dev:~/pipeline$ ./bin/nextflow run test.nf
N E X T F L O W ~ version 19.09.0-edge
Launching `test.nf` [modest_descartes] - revision: 5b2bbfea6a
[57/1b7b97] process > one [100%] 1 of 1 ✔
[a9/e4b82d] process > two [100%] 1 of 1 ✔
[/home/marius/pipeline/work/57/1b7b979933ca9e936a3c0bb640c37e/test.txt]
with the contents of the second worker .command.log file being: The outcome is: I'm empty
I tried also without toList()
What am I doing wrong? Thank you in advance
Update: a workaround would be to check _chProcessTwoUse.view() != "" but that is pretty dirty
Update 2 as required by #Steve, I've updated the code to reflect a bit more the actual conditions i have in my own pipeline:
def runProcessOne = true
process one {
when:
runProcessOne
output:
file("inputProcessTwo.txt") into _chProcessTwo optional true
file("inputProcessThree.txt") into _chProcessThree optional true
script:
// this would replace the probability that output is not created
def outputSomething = false
"""
if ${outputSomething}; then
echo "Hello world" > "inputProcessTwo.txt"
echo "Goodbye world" > "inputProcessThree.txt"
else
echo "Sorry. Process one did not write to file."
fi
"""
}
// making a copy so I check first if something in the channel or not
// avoids raising exception of MultipleInputChannel
_chProcessTwo.into{
_chProcessTwoView;
_chProcessTwoCheck;
_chProcessTwoUse
}
//print contents of channel
println "Channel contents: " + _chProcessTwoView.view()
println _chProcessTwoView.view() ? "Me empty" : "NOT empty"
process two {
input:
file(myInput) from _chProcessTwoUse
when:
(runProcessOne)
script:
"""
echo "The outcome is: ${myInput}"
"""
}
process three {
input:
file(defaultInput) from _chUpstreamProcesses
file(inputFromProcessTwo) from _chProcessThree
script:
def extra_parameters = _chProcessThree.isEmpty() ? "" : "--extra-input " + inputFromProcessTwo
"""
echo "Hooray! We got: ${extra_parameters}"
"""
}
As #Steve mentioned, I should not even check if a channel is empty, NextFlow should know better to not initiate the process. But I think in this construct I will have to.
Marius
I think part of the problem here is that process 'one' creates only optional outputs. This makes dealing with the optional inputs in process 'three' a bit tricky. I would try to reconcile this if possible. If this can't be reconciled, then you'll need to deal with the optional inputs in process 'three'. To do this, you'll basically need to create a dummy file, pass it into the channel using the ifEmpty operator, then use the name of the dummy file to check whether or not to prepend the argument's prefix. It's a bit of a hack, but it works pretty well.
The first step is to actually create the dummy file. I like shareable pipelines, so I would just create this in your baseDir, perhaps under a folder called 'assets':
mkdir assets
touch assets/NO_FILE
Then pass in your dummy file if your '_chProcessThree' channel is empty:
params.dummy_file = "${baseDir}/assets/NO_FILE"
dummy_file = file(params.dummy_file)
process three {
input:
file(defaultInput) from _chUpstreamProcesses
file(optfile) from _chProcessThree.ifEmpty(dummy_file)
script:
def extra_parameters = optfile.name != 'NO_FILE' ? "--extra-input ${optfile}" : ''
"""
echo "Hooray! We got: ${extra_parameters}"
"""
}
Also, these lines are problematic:
//print contents of channel
println "Channel contents: " + _chProcessTwoView.view()
println _chProcessTwoView.view() ? "Me empty" : "NOT empty"
Calling view() will emit all values from the channel to stdout. You can ignore whatever value it returns. Unless you enable DSL2, the channel will then be empty. I think what you're looking for here is a closure:
_chProcessTwoView.view { "Found: $it" }
Be sure to append -ansi-log false to your nextflow run command so the output doesn't get clobbered. HTH.
For the sake of learning, I'm trying to load content only when I click on a button. So far I've managed to :
Reload the content when I click the button.
And Filter the Signal when I click (if the String I send is not "GETPERF")
But my problem is that the Ajax call is still triggered once the page loads.
Here's the code:
-- SIGNALS & MAILBOX
inbox : Signal.Mailbox String
inbox =
Signal.mailbox "SOME TEXT"
result : Signal.Mailbox String
result =
Signal.mailbox ""
-- VIEW
view : String -> Html
view msg =
div [] [
h1 [] [text "Mailbox3"],
p [] [text msg],
button
[onClick inbox.address "GETPERF"]
[text "click perf"],
]
main : Signal Html
main =
Signal.map view result.signal
-- TASK & EFFECTS
port fetchReadme : Signal (Task Http.Error ())
port fetchReadme =
inbox.signal
|> Signal.filter (\sig -> sig == "GETPERF" ) "boo"
|> Signal.map (\_ -> Http.getString "http://localhost:3000/dates" `andThen` report)
report : String -> Task x ()
report html =
Signal.send result.address html
Is there any way to prevent the first Ajax call on page load ? (Or some more idiomatic way of doing all this ?)
The reason you're getting an initial ajax request is that Signal.filter is still keeping that initial value of "boo" (See the Signal.filter documentation here). That value is ignored in the next Signal.map statement by your use of the underscore parameter, but the Http Task is still getting returned and that's why you see an initial ajax request on page load.
Instead of using Signal.filter, you could write a conditional that only sends the ajax request in the correct circumstances, when sig is "GETPERF". And if sig is not "GETPERF" (as in page load), you can, in essence, do nothing by returning Task.succeed (). Here is a refactored fetchReadme function with these changes:
port fetchReadme : Signal (Task Http.Error ())
port fetchReadme =
let
fetchAndReport sig =
if sig == "GETPERF" then
Http.getString "http://localhost:3000/dates"
`andThen` report
else
Task.succeed ()
in
Signal.map fetchAndReport inbox.signal
I'm currently testing a bit my push notification module.
When the Device Token is invalid, it disconnects...
According to Apple push notification developer documentation I should get an error-response packet just before the apple push server disconnect...
The thing is I get disconnected, but I do not get anything on the Socket just before that, and I need to know if the push failed because of a malformed push (so I can fix the bug), or an invalid device token (so I can remove it from the database).
Here's my code :
-module(pushiphone).
-behaviour(gen_server).
-export([start/1, init/1, handle_call/3, handle_cast/2, code_change/3, handle_info/2, terminate/2]).
-import(ssl, [connect/4]).
-record(push, {socket, state, cert, key}).
start(Provisioning) ->
gen_server:start_link(?MODULE, [Provisioning], []).
init([Provisioning]) ->
gen_server:cast(self(), {connect, Provisioning}),
{ok, #push{}}.
send(Socket, DT, Payload) ->
PayloadLen = length(Payload),
DTLen = size(DT),
PayloadBin = list_to_binary(Payload),
Packet = <<0:8,
DTLen:16/big,
DT/binary,
PayloadLen:16/big,
PayloadBin/binary>>,
ssl:send(Socket, Packet).
handle_call(_, _, P) ->
{noreply, P}.
handle_cast({connect, Provisioning}, P) ->
case Provisioning of
dev -> Address = "gateway.sandbox.push.apple.com";
prod -> Address = "gateway.push.apple.com"
end,
Port = 2195,
Cert="/apns-" ++ atom_to_list(Provisioning) ++ "-cert.pem",
Key="/apns-" ++ atom_to_list(Provisioning) ++ "-key.pem",
Options = [{certfile, Cert}, {keyfile, Key}, {password, "********"}, {mode, binary}, {active, true}],
Timeout = 1000,
{ok, Socket} = ssl:connect(Address, Port, Options, Timeout),
{noreply, P#push{socket=Socket}};
handle_cast(_, P) ->
{noreply, P}.
handle_info({ssl, Socket, Data}, P) ->
<<Command, Status, SomeID:32/big>> = Data,
io:fwrite("[PUSH][ERROR]: ~p / ~p / ~p~n", [Command, Status, SomeID]),
ssl:close(Socket),
{noreply, P};
handle_info({push, message, DT, Badge, [Message]}, P) ->
Payload = "{\"aps\":{\"alert\":\"" ++ Message ++ "\",\"badge\":" ++ Badge ++ ",\"sound\":\"" ++ "msg.caf" ++ "\"}}",
send(P#push.socket, DT, Payload),
{noreply, P};
handle_info({ssl_closed, _SslSocket}, P) ->
io:fwrite("SSL CLOSED !!!!!!~n"),
{stop, normal, P};
handle_info(AnythingElse, P) ->
io:fwrite("[ERROR][PUSH][ANYTHING ELSE] : ~p~n", [AnythingElse]),
{noreply, P}.
code_change(_, P, _) ->
{ok, P}.
terminate(_, _) ->
ok.
It works great when the payload and the deviceToken are both right. if deviceToken is invalid, it only get's disconnected.
Does anyone can spot the issue ? because after 4 hours of searching, I have only found out that I clearly can't !
Here's the error-response table :
Status code Description
0 No errors encountered
1 Processing error
2 Missing device token
3 Missing topic
4 Missing payload
5 Invalid token size
6 Invalid topic size
7 Invalid payload size
8 Invalid token
255 None (unknown)
You seem to be using the simple notification format as defined by figure 5-1 in the apple documentation you've linked to (judging by your send() function). When this format is used, no error response is provided when the request is malformed - you just get the disconnect.
To get the error response you should be using the enhanced notification format detailed in figure 5-2.