russell@unturf.com
bbb0c316c5
Synchronous TCP client for Erlang Port Mapper Daemon. One request type
(PORT_PLEASE2_REQ, tag 122), one response type (PORT2_RESP, tag 119).
Returns EpmdInfo dataclass or None if the node is not registered.
Tests run two layers:
- Unit tests against recorded byte streams captured from a real EPMD
answering for `erl -sname testnode` and for an unregistered name.
- Integration tests spawn `erl -sname erldistpy_itest` in a fixture
and verify lookup() returns the live port; skipped if erl or EPMD
are absent.
10 new tests, 68 total green, lint clean.
145 lines
4 KiB
Python
145 lines
4 KiB
Python
"""EPMD client tests.
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Unit tests run against recorded byte streams captured from a real EPMD
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talking to a real named Erlang node (``erl -sname testnode``). The
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integration test only runs if an EPMD is reachable on localhost and a
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node is registered under the name we ask for.
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"""
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from __future__ import annotations
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import shutil
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import socket
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import subprocess
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import time
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import pytest
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from erldistpy.epmd import (
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DEFAULT_PORT,
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EpmdError,
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EpmdInfo,
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build_port_please2_req,
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lookup,
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parse_port2_resp,
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)
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# Captured from a real EPMD answering for `erl -sname testnode`.
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# port = 36205, node_type = 77 (normal), proto = 0 (tcp/ipv4),
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# hi_ver = 6, lo_ver = 5, name = "testnode", extra = empty.
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PORT2_RESP_OK = bytes.fromhex("77008d6d4d00000600050008746573746e6f64650000")
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# Captured from EPMD when the asked-for node is not registered.
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PORT2_RESP_NOT_FOUND = bytes.fromhex("7701")
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def test_build_request_known_shape():
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req = build_port_please2_req("testnode")
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# 2-byte length prefix (BE) + tag 122 + name
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assert req[:2] == b"\x00\x09" # 9 bytes follow
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assert req[2] == 122 # PORT_PLEASE2_REQ
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assert req[3:] == b"testnode"
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def test_build_request_rejects_fully_qualified_name():
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with pytest.raises(ValueError):
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build_port_please2_req("testnode@somehost")
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def test_parse_port2_resp_ok():
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info = parse_port2_resp(PORT2_RESP_OK)
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assert info == EpmdInfo(
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name="testnode",
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port=36205,
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node_type=77,
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protocol=0,
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highest_version=6,
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lowest_version=5,
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extra=b"",
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)
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def test_parse_port2_resp_not_found_returns_none():
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assert parse_port2_resp(PORT2_RESP_NOT_FOUND) is None
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def test_parse_port2_resp_wrong_tag():
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with pytest.raises(EpmdError, match="unexpected response tag"):
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parse_port2_resp(b"\x00\x00")
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def test_parse_port2_resp_truncated():
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with pytest.raises(EpmdError, match="truncated|too short"):
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parse_port2_resp(b"\x77\x00\x00")
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def test_lookup_rejects_fully_qualified_name():
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with pytest.raises(ValueError):
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lookup("testnode@somehost")
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def test_lookup_unreachable_host():
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# Reserved port unlikely to be open
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with pytest.raises(EpmdError, match="unreachable"):
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lookup("any", host="127.0.0.1", port=1, timeout=0.5)
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# --------------------------------------------------------------------------
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# Integration — requires a live EPMD + a named Erlang node
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# --------------------------------------------------------------------------
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def _epmd_running() -> bool:
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try:
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with socket.create_connection(("localhost", DEFAULT_PORT), timeout=0.5):
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return True
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except OSError:
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return False
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@pytest.fixture(scope="module")
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def named_erlang_node():
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"""Spawn `erl -sname testnode`, register with EPMD, tear down after."""
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if not shutil.which("erl"):
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pytest.skip("erl not installed")
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if not _epmd_running():
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pytest.skip("EPMD not running on localhost")
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proc = subprocess.Popen(
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["erl", "-sname", "erldistpy_itest", "-noshell", "-eval", "timer:sleep(infinity)."],
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stdout=subprocess.DEVNULL,
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stderr=subprocess.DEVNULL,
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)
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# Wait for the node to register with EPMD
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for _ in range(40):
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time.sleep(0.1)
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info = lookup("erldistpy_itest", timeout=0.5)
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if info is not None:
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break
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else:
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proc.terminate()
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proc.wait(timeout=2)
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pytest.skip("erl node failed to register with EPMD")
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yield "erldistpy_itest"
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proc.terminate()
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try:
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proc.wait(timeout=2)
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except subprocess.TimeoutExpired:
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proc.kill()
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def test_live_lookup_returns_info(named_erlang_node):
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info = lookup(named_erlang_node)
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assert info is not None
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assert info.name == named_erlang_node
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assert info.port > 0
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assert info.node_type == 77
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assert info.protocol == 0
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# OTP 23+ speaks at least version 6
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assert info.highest_version >= 5
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def test_live_lookup_unknown_node_returns_none(named_erlang_node):
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assert lookup("definitely_not_a_real_node_qzxw") is None
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