core

fastdaemon protocol and client

Since this module defines the client, it’s important that it has minimal dependencies for us to actually benefit from faster startup. The protocol is largely based on fastcgi though much less feature-full.

import time
from io import BytesIO, BufferedReader
from pathlib import Path
from socketserver import UnixStreamServer,StreamRequestHandler

from fastcore.parallel import threaded

Protocol

---

send_record

 send_record (w, c)

Send a sequence of length-prefixed utf-8-encoded strings

ss = ['from fastcore.all import *', 'nbdev_clean --stdin']
f = BytesIO()
send_record(f.write, ss)
b = f.getvalue(); b

b'\x00\x00\x00\x1afrom fastcore.all import *\x00\x00\x00\x17nbdev_clean --stdin'

_recv_len(BufferedReader(BytesIO(b)).read)

26

---

recv_record

 recv_record (r)

Receive two variable-length utf-8-encoded strings

recv_record(BytesIO(b).read)

['from fastcore.all import *', 'nbdev_clean --stdin']

---

start_client

 start_client (port, host=None, dgram=False)

Create a socket client on port, with optional host, of type dgram

---

transfer

 transfer (data, port, host=None, dgram=False)

Send a request and receive a reply in one socket using the fastdaemon protocol

class EchoHandler(StreamRequestHandler):
    def handle(self): self.wfile.write(self.rfile.readline())

p = Path('fdaemon.sock')
if p.exists(): p.unlink()

@threaded
def _f():
    with UnixStreamServer(str(p), EchoHandler) as srv: srv.handle_request()
_f()
time.sleep(0.2) # wait for server to start

transfer(['Input via stdin', 'world\n'], str(p)) # trailing \n is required since TestHandler uses `readline`

['Input via stdin', 'world\n']

Client

---

fastdaemon_client

 fastdaemon_client (argv=None)

Forward sys.argv and sys.stdin to server and write response to sys.stdout and sys.stderr

!fastdaemon_client -h

usage: fastdaemon_client [-h] [--host HOST] [--dgram] port

Forward `sys.argv` and `sys.stdin` to server and write response to
`sys.stdout` and `sys.stderr`

positional arguments:
  port         Server port. Use int for TCP, and str for Unix socket

optional arguments:
  -h, --help   show this help message and exit
  --host HOST  Server host (default: `socket.gethostname()`)
  --dgram      Use `SOCK_DGRAM`?