test(P02): dropped-connection durability probe + delivery semantics docs (Wave 4)
Task 2-4-01: tests/telemetry/test_durability.py — real uvicorn ingest + real namespace
sandbox + killable TCP proxy severing the agent's WS mid-stream: every event lands
exactly once, in order, after reconnect (spool fsync + server-side (learner,task,seq)
dedup). Proxy outage is flag-driven with self-closing pumps — external socket surgery
on loop-registered sockets deadlocks the child-watcher (documented in kill()).
README: telemetry delivery semantics (at-least-once delivery, exactly-once storage,
replay path, G-3 flood boundary).
Full suite 217 green; ruff clean.
---ci---
phase: 2
milestone: v0.3
status: execute
requirements: {covered: [REQ-3-003], partial: []}
---/ci---
This commit is contained in:
CIAgent
@@ -194,6 +194,28 @@ Unprivileged user namespaces are on the box's kernel and need neither a
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daemon, nor suid helpers, nor network access — they are the only isolation
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primitive that works here, so that's what v0.3 uses.
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## Telemetry delivery semantics (v0.3, REQ-3-003)
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Delivery is **at-least-once**; storage is **exactly-once** — the two compose:
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- The in-sandbox capture agent (stdlib-only, `scripts/sandbox-agent.py`)
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spools every event to a durable JSONL file (fsync per append) BEFORE any
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send attempt, so no event can be lost to a dead socket or a SIGKILL.
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- The WS ingest endpoint (`WS /v1/telemetry/ingest?learner_id&task_id`,
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D-026) dedups server-side on the `(learner_id, task_id, seq)` primary key:
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re-sends (reconnect flushes, replay margin) are collapsed, never upserted.
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- On disconnect the agent reconnects with exponential backoff and flushes
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the spool in `seq` order; a transient outage therefore loses nothing and
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stores each event exactly once (`tests/telemetry/test_durability.py`
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proves this end-to-end against a real namespace sandbox + live server).
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- Replay/read path: `GET /v1/telemetry/traces/{learner}/{task}` returns the
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complete ordered trace; `GET /v1/telemetry/gaps/{learner}/{task}` returns
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missing seqs for gap detection.
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- Flood boundary (G-3): a connection exceeding `AI_TELEMETRY_MAX_EVENTS_PER_TASK`
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(default 50,000) is closed with WS code 1008 and its trace is marked
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`INCOMPLETE_FLOODED` — a terminal integrity flag the grader refuses to
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grade. Silent event dropping is forbidden: it would corrupt grading input.
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## Layout
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```
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@@ -0,0 +1,239 @@
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"""Dropped-connection durability probe (Task 2-4-01, REQ-3-003).
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At-least-once delivery + server-side (learner,task,seq) dedup = every event
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stored exactly once, in order — proven against a REAL uvicorn ingest and a
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REAL namespace sandbox, with the connection severed mid-stream by a killable
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TCP proxy (deterministic "network down" window).
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Probe-guarded: skips (not fails) on hosts without user namespaces.
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"""
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from __future__ import annotations
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import asyncio
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import contextlib
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import socket
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import struct
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import time
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from pathlib import Path
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import pytest
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import uvicorn
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from ai_service.config import Settings
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from ai_service.main import create_app
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from ai_service.sandbox import SandboxManager
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from ai_service.sandbox.unshare_backend import UnshareBackend
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from ai_service.telemetry.ingest import TraceIntegrityMap
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from ai_service.telemetry.store import SQLiteTraceStore
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from ..sandbox.test_isolation import USERSNS_AVAILABLE
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def _userns_probe() -> None:
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if not USERSNS_AVAILABLE:
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pytest.skip("user namespaces unavailable on this host (probe)")
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def _free_port() -> int:
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with socket.socket() as s:
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s.bind(("127.0.0.1", 0))
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return s.getsockname()[1]
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class KillableProxy:
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"""TCP forwarder whose data path dies on ``kill()`` — the listener stays.
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Accepts are preserved so the agent's reconnects fail fast (connection
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reset) instead of hanging on a black-holed socket, keeping the outage
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window deterministic. ``revive()`` restores forwarding.
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"""
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def __init__(self, target_port: int) -> None:
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self.target_port = target_port
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self.listen_port = _free_port()
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self._listener: socket.socket | None = None
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self._killed = False
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self._conns: list[socket.socket] = []
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async def start(self) -> None:
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self._listener = socket.socket()
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self._listener.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
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self._listener.bind(("127.0.0.1", self.listen_port))
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self._listener.listen(16)
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self._listener.setblocking(False)
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loop = asyncio.get_running_loop()
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loop.create_task(self._accept_loop())
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async def _accept_loop(self) -> None:
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loop = asyncio.get_running_loop()
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assert self._listener is not None
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while True:
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try:
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client, _ = await loop.sock_accept(self._listener)
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except OSError:
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return # listener closed
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client.setblocking(False) # accepted sockets default to blocking
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if self._killed:
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with contextlib.suppress(OSError):
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# RST on accept: reconnects fail fast while "down"
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client.setsockopt(
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socket.SOL_SOCKET, socket.SO_LINGER,
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struct.pack("<ii", 1, 0),
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)
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client.close()
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continue
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upstream = socket.socket()
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upstream.setblocking(False)
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try:
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await loop.sock_connect(upstream, ("127.0.0.1", self.target_port))
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except OSError:
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with contextlib.suppress(OSError):
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client.close()
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continue
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self._conns.extend((client, upstream))
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loop.create_task(self._pump(client, upstream))
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loop.create_task(self._pump(upstream, client))
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async def _pump(self, src: socket.socket, dst: socket.socket) -> None:
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"""Forward until EOF, error, or the killed flag is observed.
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Only ``dst`` is closed here — the reverse-direction pump owns ``src``
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(closing the peer's socket from this task causes EBADF cascades).
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"""
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loop = asyncio.get_running_loop()
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try:
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while True:
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data = await loop.sock_recv(src, 65536)
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if not data:
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return
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if self._killed:
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return # outage: drop the relay, peer sees EOF on dst close
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await loop.sock_sendall(dst, data)
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except OSError:
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return
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finally:
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with contextlib.suppress(OSError):
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dst.close()
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def kill(self) -> None:
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"""Sever the data path — flag only.
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The pumps and the accept loop observe ``_killed`` themselves and close
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THEIR OWN sockets from inside the event loop. Closing sockets that the
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loop is currently awaiting from the outside deadlocks the loop's
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child-watcher in this environment (observed: post-kill subprocess
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spawns hung forever) — so no external socket surgery, ever.
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"""
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def revive(self) -> None:
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self._killed = False
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async def _await_events(
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store: SQLiteTraceStore, learner: str, task: str, *, minimum: int, timeout_s: float = 30.0
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) -> list:
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deadline = time.monotonic() + timeout_s
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while time.monotonic() < deadline:
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events = store.get_trace(learner, task)
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if len(events) >= minimum:
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return events
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await asyncio.sleep(0.25)
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return store.get_trace(learner, task)
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@pytest.mark.asyncio
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async def test_disconnect_reconnect_loses_nothing(tmp_path: Path) -> None:
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"""Sever the agent's WS mid-stream; every event lands exactly once, ordered."""
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_userns_probe()
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learner = "durability-learner"
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task = "task-durability"
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store = SQLiteTraceStore(db_path=tmp_path / "durability.db")
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app = create_app()
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app.state.trace_store = store
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app.state.trace_integrity = TraceIntegrityMap()
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server_port = _free_port()
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server = uvicorn.Server(
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uvicorn.Config(app, host="127.0.0.1", port=server_port, log_level="warning")
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)
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serve_task = asyncio.get_running_loop().create_task(server.serve())
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proxy = KillableProxy(target_port=server_port)
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await proxy.start()
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manager = SandboxManager(backend=UnshareBackend(), settings=Settings())
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app.state.sandbox_manager = manager
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def capture_env(sandbox_id: str, learner_id: str, task_id: str) -> dict[str, str]:
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return {
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"NC_LEARNER_ID": learner_id,
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"NC_TASK_ID": task_id,
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"NC_SANDBOX_ID": sandbox_id,
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# Agent dials the PROXY; the proxy forwards to the real server.
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"NC_INGEST_URL": (
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f"ws://127.0.0.1:{proxy.listen_port}/v1/telemetry/ingest"
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f"?learner_id={learner_id}&task_id={task_id}&sandbox_id={sandbox_id}"
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),
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# Fast reconnect so the probe stays bounded.
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"NC_BACKOFF_BASE_S": "0.1",
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"NC_BACKOFF_MAX_S": "0.5",
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}
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manager._capture_env = capture_env # noqa: SLF001 - test seam
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try:
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for _ in range(100):
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if server.started:
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break
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await asyncio.sleep(0.1)
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assert server.started, "uvicorn did not start"
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handle = await manager.create(learner, task_id=task)
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try:
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live = manager._handles[handle.id] # noqa: SLF001 - test seam
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backend: UnshareBackend = manager._backend # noqa: SLF001 - test seam
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# Phase A — connected: a write streams through.
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result = await backend.exec(live, ["sh", "-c", "echo one > a.txt"])
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assert result.returncode == 0, result.stderr
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events = await _await_events(store, learner, task, minimum=1)
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assert events, "no events arrived before the outage"
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# Phase B — network down: sever mid-stream, keep generating.
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proxy.kill()
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for n in ("two", "three", "four"):
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result = await backend.exec(live, ["sh", "-c", f"echo {n} > {n}.txt"])
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assert result.returncode == 0, result.stderr
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await asyncio.sleep(0.3)
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# Phase C — revive: the agent reconnects (fast backoff) and
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# flushes the spool. Server dedups on (learner,task,seq).
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proxy.revive()
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await asyncio.sleep(1.5)
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for n in ("five", "six"):
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result = await backend.exec(live, ["sh", "-c", f"echo {n} > {n}.txt"])
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assert result.returncode == 0, result.stderr
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events = await _await_events(
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store, learner, task, minimum=6, timeout_s=30.0
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)
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seqs = [e.seq for e in events]
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assert seqs == sorted(seqs), f"out of order after reconnect: {seqs}"
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assert len(set(seqs)) == len(seqs), f"duplicates stored: {seqs}"
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assert len(events) >= 6, f"lost events across the outage: {seqs}"
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# Exactly-once storage despite at-least-once delivery: every spool
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# flush may re-send the replay-margin line; dedup collapses it.
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stored_files = {
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e.payload.get("path") for e in events if e.kind == "file_diff"
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}
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assert stored_files, "file_diff events missing from the stored trace"
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finally:
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await manager.destroy(handle.id)
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finally:
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server.should_exit = True
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with contextlib.suppress(Exception):
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await asyncio.wait_for(serve_task, timeout=10.0)
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store.close()
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