session.py

from typing import Any
import os
from contextvars import ContextVar
from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session, sessionmaker
from sqlalchemy.exc import PendingRollbackError
import traceback

from . import daemon
from .business_objects import general
from .util import collect_engine_variables
from threading import Lock
import time

session_lock = Lock()

request_id_ctx_var = ContextVar("request_id", default=None)


def get_request_id():
    return request_id_ctx_var.get()


(
    pool_size,
    pool_max_overflow,
    pool_recycle,
    pool_use_lifo,
    pool_pre_ping,
) = collect_engine_variables()


engine = create_engine(
    os.getenv("POSTGRES"),
    pool_size=pool_size,
    max_overflow=pool_max_overflow,
    pool_recycle=pool_recycle,
    pool_use_lifo=pool_use_lifo,
    pool_pre_ping=pool_pre_ping,
)

session = scoped_session(
    sessionmaker(autocommit=False, autoflush=True, bind=engine),
    scopefunc=get_request_id,
)

## uncomment following lines to enable db logging
""" import logging
logging.basicConfig()
logging.getLogger('sqlalchemy.engine').setLevel(logging.INFO)

 """


def check_session_and_rollback():
    try:
        _ = session.connection()
    except PendingRollbackError:
        print("session issue detected, rollback initiated", flush=True)
        print(traceback.format_exc(), flush=True)
        while session.registry().in_transaction():
            session.rollback()


def get_engine_dialect() -> Any:
    if not engine:
        return None
    return engine.dialect


def start_session_cleanup_thread():
    """
    Start a thread that cleans up sessions older than 5 minutes.
    """
    daemon.run_without_db_token(__start_session_cleanup)


def __start_session_cleanup():
    while True:
        with session_lock:
            sessions = general.get_session_lookup(exclude_last_x_seconds=20 * 60)
            for session in sessions:
                try:
                    general.force_remove_and_refresh_session_by_id(
                        session["session_id"]
                    )
                    print("Session removed", session, flush=True)
                except Exception:
                    traceback.print_exc()
        time.sleep(10)