Send a large file with HTTP.jl - http

Question

I would like to implement a server with HTTP.jl and julia. After some computation the server would return a "large" file (about several 100 MB). I would like to avoid having to read all the file in memory and then send it to the client.
Some framework allow have a specific function for this (e.g. Flask http://flask.pocoo.org/docs/0.12/api/#flask.send_file) or allow to stream the content to the client (http://flask.pocoo.org/docs/0.12/patterns/streaming/).
Are one for these two options also available in HTTP.jl ? Or any other Julia web package?
Here is a test code which reads the file testfile.txt, but I want to avoid loading the complete file in memory.
import HTTP
f = open("testfile.txt","w")
write(f,"test")
close(f)
router = HTTP.Router()
function testfun(req::HTTP.Request)
f = open("testfile.txt")
data = read(f)
close(f)
return HTTP.Response(200,data)
end
HTTP.register!(router, "GET", "/testfun",HTTP.HandlerFunction(testfun))
server = HTTP.Servers.Server(router)
task = #async HTTP.serve(server, ip"127.0.0.1", 8000; verbose=false)
sleep(1.0)
req = HTTP.request("GET","http://127.0.0.1:8000/testfun/")
# end server
put!(server.in, HTTP.Servers.KILL)
#show String(req.body)

Answer 1

You can use memory mapped IO like this:
function testfun(req::HTTP.Request)
data = Mmap.mmap(open("testfile.txt"), Array{UInt8,1})
return HTTP.Response(200,data)
end
data now looks like a normal byte array to julia, but is actually liked to the file, which might be exactly what you want. The file will be closed upon garbage collection - if you have many requests and no garbage collection is triggered, you might end up with a lot of open files. If your request takes quite long anyway, you might consider calling gc() at the begin of the request.