The problem seems to that HttpServer can not run @async - it exits
immediately.
===
using HttpServer
http = HttpHandler() do req::Request, res::Response
Response( ismatch(r"^/hello/", req.resource) ? exit(2) : 404 )
end
server = Server( http )
run( server, 8001 ) # <--- this works but blocks
@async run( server, 8001 ) # <--- this exits immediately
===
It's not necessarily a problem that HttpServer blocks. But what drives me
nuts is: if I run
$ julia app.jl &
in the shell, it works perfectly. The process is placed in the background,
the server happily listens to the assigned port, etc.
Why can't I run the same command from within another julia process and get
the same effect?
vineri, 22 ianuarie 2016, 22:40:56 UTC+1, Stefan Karpinski a scris:
>
> @spawn runs a command on a (random) worker process. If you want to do
> "background" work in the current process, you can use @async:
>
> julia> t = @async (sleep(5); rand())
> Task (runnable) @0x0000000112d746a0
>
> julia> wait(t)
> 0.14543742643271207
>
>
> On Fri, Jan 22, 2016 at 4:33 PM, Adrian Salceanu <[email protected]
> <javascript:>> wrote:
>
>> Oh! The ruby analogy made me think about actually spawning the detached
>> command! Which produced the desired effect!
>>
>> julia> @spawn run(detach(`ping www.google.com`))
>>
>>
>>
>> vineri, 22 ianuarie 2016, 22:29:27 UTC+1, Adrian Salceanu a scris:
>>>
>>> I guess what I'm looking for is the equivalent of Ruby's Process#spawn
>>>
>>> In REPL:
>>>
>>> >> pid = Process.spawn("ping www.google.com", :out => '/dev/null')
>>> 83210
>>> >> <-- the process is running in the background
>>> and control has been returned to the REPL
>>>
>>>
>>> vineri, 22 ianuarie 2016, 22:06:01 UTC+1, Adrian Salceanu a scris:
>>>>
>>>> Hi,
>>>>
>>>> I'm hammering at a web app and I'm trying to setup functionality to
>>>> monitor the file system for changes and restart/reload the server
>>>> automatically so the changes are picked up (I'm using Mux which uses
>>>> HttpServer).
>>>>
>>>> The approach I have in mind is:
>>>>
>>>> 1. have a startup script which is run from the command line, something
>>>> like:
>>>> $ julia -L startup.jl
>>>>
>>>> 2. the startup script launches the web app, which starts the web
>>>> server. My intention was to run
>>>> $ julia -L app.jl
>>>> as a command inside startup.jl, detached, and have the startup.jl
>>>> script get back control, with app.jl running detached in the background.
>>>>
>>>> 3. once startup.jl gets back control, it begins monitoring the file
>>>> system and when changes are detected, kills the app and relaunches it.
>>>>
>>>> That was the theory. Now, I might be missing something but I can't find
>>>> a way to detach the command I'm running and get control back to the
>>>> startup
>>>> script. And I tried a lot of things!
>>>>
>>>> ===
>>>>
>>>> I'm providing simpler example using "ping", which also run
>>>> indefinitely, similar to the web server.
>>>>
>>>> julia> run(detach(`ping "www.google.com"`)) # the command is detached
>>>> and continues to run after the julia REPL is closed, but at this point the
>>>> REPL does not get control, there's no cursor available in the REPL
>>>> PING www.google.com (173.194.45.82): 56 data bytes
>>>> 64 bytes from 173.194.45.82: icmp_seq=0 ttl=54 time=30.138 ms
>>>> 64 bytes from 173.194.45.82: icmp_seq=1 ttl=54 time=30.417 ms
>>>> ... more output ...
>>>> 64 bytes from 173.194.45.82: icmp_seq=7 ttl=54 time=30.486 ms
>>>> 64 bytes from 173.194.45.82: icmp_seq=8 ttl=54 time=30.173 ms
>>>> ^CERROR: InterruptException:
>>>> <---- here I press Ctrl+C and only now the REPL gets
>>>> back the cursor, with the command still running in the background
>>>>
>>>> ===
>>>>
>>>> Also, related to this, passing "&" into the command to detach does not
>>>> work as expected, the "&" is interpreted as argument of the command. Not
>>>> sure if this would help anyway to return control to the startup.jl script?
>>>>
>>>> julia> run(detach(`ping "www.google.com" &`));
>>>> usage: ping [-AaDdfnoQqRrv] [-b boundif] [-c count] [-G sweepmaxsize]
>>>> [-g sweepminsize] [-h sweepincrsize] [-i wait] [−k
>>>> trafficclass]
>>>> [-l preload] [-M mask | time] [-m ttl] [-p pattern]
>>>> [-S src_addr] [-s packetsize] [-t timeout][-W waittime] [-z
>>>> tos]
>>>> host
>>>> ping [-AaDdfLnoQqRrv] [-b boundif] [-c count] [-I iface] [-i
>>>> wait]
>>>> [−k trafficclass] [-l preload] [-M mask | time] [-m ttl]
>>>> [-p pattern] [-S src_addr]
>>>> [-s packetsize] [-T ttl] [-t timeout] [-W waittime]
>>>> [-z tos] mcast-group
>>>> ERROR: failed process: Process(`ping www.google.com &`,
>>>> ProcessExited(64)) [64]
>>>> in run at /usr/local/Cellar/julia/0.4.2/lib/julia/sys.dylib
>>>>
>>>> ===
>>>>
>>>> Thanks
>>>>
>>>
>
