Serve stdin with HTTP json

jsontail

from queue import Queue
from threading import Thread
import json
import sys
import tornado.ioloop
import tornado.web

MAX_NUM_LINES_IN_BUFFER=1000
MAX_NUM_LINES_PER_CHUNK=10


def reader(buffer):
    def reader_task(buffer):
        while True:
            if buffer.qsize() > MAX_NUM_LINES_IN_BUFFER:
                buffer.get(False)
            buffer.put(sys.stdin.readline())

    reader_worker = Thread(target=reader_task, args=(buffer,))
    reader_worker.setDaemon(True)
    reader_worker.start()


def writer(buffer, port):
    class MainHandler(tornado.web.RequestHandler):
        def get(self):
            self.add_header('Content-Type', 'application/json')
            tail = ''
            for line in range(MAX_NUM_LINES_PER_CHUNK):
                if not buffer.empty():
                    tail += buffer.get(False)
            self.write(json.dumps({'tail': tail}))

    application = tornado.web.Application([
        (r"/", MainHandler),
    ])
    application.listen(port)
    tornado.ioloop.IOLoop.current().start()


if __name__ == "__main__":
    try:
        port = int(sys.argv[1])
    except:
        port = 8000
    buffer = Queue()
    reader(buffer)
    writer(buffer, port)