| """Small, thread-safe shared-recognition quota; stores timestamps, never keys.""" |
| from contextlib import contextmanager |
| from pathlib import Path |
| import sqlite3 |
| import threading |
| import time |
|
|
|
|
| class SharedLimit(Exception): |
| pass |
|
|
|
|
| class SharedUsage: |
| def __init__(self,path,daily=200,per_minute=20,concurrent=2): |
| self.path=Path(path);self.daily=daily;self.per_minute=per_minute |
| self.slots=threading.BoundedSemaphore(concurrent) |
| self.path.parent.mkdir(parents=True,exist_ok=True) |
| with sqlite3.connect(self.path) as db: |
| db.execute('CREATE TABLE IF NOT EXISTS recognition_usage (started REAL NOT NULL)') |
| db.execute('CREATE INDEX IF NOT EXISTS recognition_started ON recognition_usage(started)') |
|
|
| def summary(self,now=None): |
| now=time.time() if now is None else now |
| with sqlite3.connect(self.path) as db: |
| used=db.execute('SELECT COUNT(*) FROM recognition_usage WHERE started>?',(now-86400,)).fetchone()[0] |
| return {'per_24_hours':self.daily,'per_minute':self.per_minute,'used_24_hours':used,'remaining':max(0,self.daily-used)} |
|
|
| def reserve(self,now=None): |
| now=time.time() if now is None else now |
| with sqlite3.connect(self.path,timeout=10,isolation_level=None) as db: |
| db.execute('BEGIN IMMEDIATE') |
| try: |
| db.execute('DELETE FROM recognition_usage WHERE started<=?',(now-86400,)) |
| daily=db.execute('SELECT COUNT(*) FROM recognition_usage').fetchone()[0] |
| minute=db.execute('SELECT COUNT(*) FROM recognition_usage WHERE started>?',(now-60,)).fetchone()[0] |
| if daily>=self.daily:raise SharedLimit('The classroom’s shared recognition allowance has been used for now. Please try again later or ask the teacher.') |
| if minute>=self.per_minute:raise SharedLimit('The classroom is making lots of guesses. Please wait a minute and try again.') |
| db.execute('INSERT INTO recognition_usage(started) VALUES(?)',(now,));db.execute('COMMIT') |
| except Exception: |
| db.execute('ROLLBACK');raise |
|
|
| @contextmanager |
| def lease(self,now=None): |
| if not self.slots.acquire(blocking=False):raise SharedLimit('Other drawings are being recognized. Please try again in a moment.') |
| try: |
| self.reserve(now);yield |
| finally:self.slots.release() |
|
|
