#!/usr/bin/env python3
# stall.py: a client that gets its backend stuck in ClientWrite and stays alive.
# Used by repro-standby.sh (rows 1-5 and 9 of coverage-matrix.txt).
# usage: python3 stall.py PORT DBNAME "SQL"   (TCP to 127.0.0.1, trust auth)
# It sends one simple Query, never reads the result, and prints "SENT <backend pid> <local port>".
import os, socket, struct, sys, time

port, dbname, sql = int(sys.argv[1]), sys.argv[2], sys.argv[3]
user = os.environ.get("PGUSER") or os.environ.get("USER", "postgres")
s = socket.create_connection(("127.0.0.1", port))

def recv_exact(n):
    buf = b""
    while len(buf) < n:
        c = s.recv(n - len(buf))
        if not c:
            sys.exit("server closed the connection")
        buf += c
    return buf

params = b"user\0" + user.encode() + b"\0database\0" + dbname.encode() + b"\0\0"
s.sendall(struct.pack("!II", 8 + len(params), 196608) + params)
pid = 0
while True:
    t = recv_exact(1)
    (ln,) = struct.unpack("!I", recv_exact(4))
    body = recv_exact(ln - 4)
    if t == b"R" and struct.unpack("!I", body[:4])[0] != 0:
        sys.exit("only trust authentication is supported")
    if t == b"K":
        pid = struct.unpack("!I", body[:4])[0]
    if t == b"E":
        sys.exit("error during startup: %r" % body)
    if t == b"Z":
        break
q = sql.encode() + b"\0"
s.sendall(b"Q" + struct.pack("!I", 4 + len(q)) + q)
print("SENT", pid, s.getsockname()[1], flush=True)
while True:
    time.sleep(3600)