Gate background tasks behind foreground activity

src/interactive_gate.py

@@ -0,0 +1,125 @@
+"""Foreground activity gate for background work.
+
+Background tasks are allowed to run only after normal UI/API traffic has
+settled. This keeps scheduled jobs and email pollers from competing with the
+user opening Odysseus, Cookbook, email, documents, notes, or other panels.
+"""
+
+from __future__ import annotations
+
+import asyncio
+from contextlib import asynccontextmanager
+import os
+import time
+
+
+_ACTIVE_REQUESTS = 0
+_LAST_ACTIVITY = 0.0
+_COND: asyncio.Condition | None = None
+
+
+def _enabled() -> bool:
+    return os.getenv("BACKGROUND_TASK_FOREGROUND_GATE", "true").lower() not in {"0", "false", "no", "off"}
+
+
+def _quiet_seconds() -> float:
+    try:
+        return max(0.0, float(os.getenv("BACKGROUND_TASK_QUIET_MS", "1500")) / 1000.0)
+    except Exception:
+        return 1.5
+
+
+def _max_wait_seconds() -> float:
+    """0 means wait indefinitely until the UI is quiet."""
+    try:
+        return max(0.0, float(os.getenv("BACKGROUND_TASK_MAX_WAIT_SECONDS", "0")))
+    except Exception:
+        return 0.0
+
+
+def _condition() -> asyncio.Condition:
+    global _COND
+    if _COND is None:
+        _COND = asyncio.Condition()
+    return _COND
+
+
+_PASSIVE_EXACT_PATHS = {
+    "/api/tasks/notifications",
+    "/api/research/active",
+    "/api/email/urgency-state",
+}
+
+_PASSIVE_PREFIXES = (
+    "/api/chat/stream_status",
+    "/api/health",
+    "/api/prefs",
+)
+
+
+def should_track_interactive_request(path: str, method: str = "GET") -> bool:
+    if not _enabled():
+        return False
+    if (method or "").upper() == "OPTIONS":
+        return False
+    if path in _PASSIVE_EXACT_PATHS:
+        return False
+    if any(path.startswith(prefix) for prefix in _PASSIVE_PREFIXES):
+        return False
+    return True
+
+
+@asynccontextmanager
+async def track_interactive_request(path: str = "", method: str = ""):
+    global _ACTIVE_REQUESTS, _LAST_ACTIVITY
+    if not _enabled():
+        yield
+        return
+
+    cond = _condition()
+    async with cond:
+        _ACTIVE_REQUESTS += 1
+        _LAST_ACTIVITY = time.monotonic()
+        cond.notify_all()
+    try:
+        yield
+    finally:
+        async with cond:
+            _ACTIVE_REQUESTS = max(0, _ACTIVE_REQUESTS - 1)
+            _LAST_ACTIVITY = time.monotonic()
+            cond.notify_all()
+
+
+async def wait_for_interactive_quiet(label: str = "") -> bool:
+    """Wait until foreground requests have stopped for the configured window.
+
+    Returns True if the caller had to wait at all. The label is intentionally
+    only for future logging/debugging so callers can keep their code simple.
+    """
+    if not _enabled():
+        return False
+
+    quiet = _quiet_seconds()
+    max_wait = _max_wait_seconds()
+    deadline = time.monotonic() + max_wait if max_wait > 0 else None
+    cond = _condition()
+    waited = False
+
+    while True:
+        async with cond:
+            now = time.monotonic()
+            quiet_remaining = quiet - (now - _LAST_ACTIVITY)
+            if _ACTIVE_REQUESTS <= 0 and quiet_remaining <= 0:
+                return waited
+
+            waited = True
+            timeout = 0.25 if _ACTIVE_REQUESTS > 0 else min(max(quiet_remaining, 0.05), 0.5)
+            if deadline is not None:
+                remaining = deadline - now
+                if remaining <= 0:
+                    return waited
+                timeout = min(timeout, remaining)
+            try:
+                await asyncio.wait_for(cond.wait(), timeout=timeout)
+            except asyncio.TimeoutError:
+                pass