Cannot send commands to Docker unix socket via Python

Question

I have a script that send signals to containers using nc (specifically the openbsd version that supports -U for Unix domain sockets):

echo -e "POST /containers/$HAPROXY_CONTAINER/kill?signal=HUP HTTP/1.0\r\n" | \
nc -U /var/run/docker.sock

I wanted to see if I could avoid the openbsd nc dependency or a socat dependency, so I tried to do the same thing in Python 3 with the following:

import socket

sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
sock.connect('/var/run/docker.sock')
sock.sendall(str.encode('POST /containers/{}/kill?signal=HUP HTTP/1.0\r\n'.format(environ['HAPROXY_CONTAINER'])))

I don't get any errors raised from the Python version, however my container doesn't receive the signal I'm attempting to send.

Answer 1

In the bash version, echo provides an additional new line. HTTP requires two new lines after the headers, so the Python sendall needed a second \\n like so:

sock.sendall(str.encode('POST /containers/{}/kill?signal=HUP HTTP/1.0\r\n\n'.format(environ['HAPROXY_CONTAINER'])))