"""Report SQLAlchemy pool saturation from inside the API container.

WHY: MySQL's max_connections is NOT the ceiling that binds first. The effective
limit is per-process: pool_size + max_overflow, multiplied by worker count.
With the defaults (5 + 10) and 4 workers that is 60, not 151. A peak of 52
therefore means 87 percent of the real ceiling, not 34 percent.

Prints the computed ceiling so a measured high-water mark can be compared
against the right number.

Usage (inside the api container, PYTHONPATH=/app):
    python pool_status.py
"""
import json
import os

from shopdb import create_app
from shopdb.api import db


def main():
    app = create_app(os.environ.get('FLASK_ENV', 'production'))
    with app.app_context():
        engine = db.engine
        pool = engine.pool
        size = pool.size()
        overflow = getattr(pool, '_max_overflow', 0)
        workers = int(os.environ.get('GUNICORN_WORKERS', '4'))
        print(json.dumps({
            'pool_class': type(pool).__name__,
            'pool_size': size,
            'max_overflow': overflow,
            'per_worker_ceiling': size + overflow,
            'workers': workers,
            'effective_ceiling': (size + overflow) * workers,
            'checkedout': pool.checkedout(),
            'status': pool.status(),
        }, indent=2))


if __name__ == '__main__':
    main()