mirror of
https://github.com/ArchiveBox/ArchiveBox
synced 2024-11-25 13:40:20 +00:00
103 lines
3.4 KiB
Python
103 lines
3.4 KiB
Python
import uuid
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from functools import wraps
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from django.db import connection, transaction
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from django.utils import timezone
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from huey.exceptions import TaskLockedException
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from archivebox.config import CONSTANTS
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class SqliteSemaphore:
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def __init__(self, db_path, table_name, name, value=1, timeout=None):
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self.db_path = db_path
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self.table_name = table_name
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self.name = name
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self.value = value
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self.timeout = timeout or 86400 # Set a max age for lock holders
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# Ensure the table exists
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with connection.cursor() as cursor:
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cursor.execute(f"""
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CREATE TABLE IF NOT EXISTS {self.table_name} (
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id TEXT PRIMARY KEY,
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name TEXT,
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timestamp DATETIME
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)
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""")
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def acquire(self, name=None):
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name = name or str(uuid.uuid4())
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now = timezone.now()
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expiration = now - timezone.timedelta(seconds=self.timeout)
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with transaction.atomic():
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# Remove expired locks
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with connection.cursor() as cursor:
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cursor.execute(f"""
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DELETE FROM {self.table_name}
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WHERE name = %s AND timestamp < %s
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""", [self.name, expiration])
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# Try to acquire the lock
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with connection.cursor() as cursor:
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cursor.execute(f"""
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INSERT INTO {self.table_name} (id, name, timestamp)
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SELECT %s, %s, %s
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WHERE (
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SELECT COUNT(*) FROM {self.table_name}
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WHERE name = %s
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) < %s
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""", [name, self.name, now, self.name, self.value])
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if cursor.rowcount > 0:
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return name
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# If we couldn't acquire the lock, remove our attempted entry
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with connection.cursor() as cursor:
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cursor.execute(f"""
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DELETE FROM {self.table_name}
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WHERE id = %s AND name = %s
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""", [name, self.name])
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return None
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def release(self, name):
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with connection.cursor() as cursor:
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cursor.execute(f"""
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DELETE FROM {self.table_name}
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WHERE id = %s AND name = %s
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""", [name, self.name])
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return cursor.rowcount > 0
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LOCKS_DB_PATH = CONSTANTS.DATABASE_FILE.parent / 'locks.sqlite3'
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def lock_task_semaphore(db_path, table_name, lock_name, value=1, timeout=None):
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"""
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Lock which can be acquired multiple times (default = 1).
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NOTE: no provisions are made for blocking, waiting, or notifying. This is
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just a lock which can be acquired a configurable number of times.
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Example:
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# Allow up to 3 workers to run this task concurrently. If the task is
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# locked, retry up to 2 times with a delay of 60s.
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@huey.task(retries=2, retry_delay=60)
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@lock_task_semaphore('path/to/db.sqlite3', 'semaphore_locks', 'my-lock', 3)
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def my_task():
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...
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"""
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sem = SqliteSemaphore(db_path, table_name, lock_name, value, timeout)
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def decorator(fn):
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@wraps(fn)
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def inner(*args, **kwargs):
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tid = sem.acquire()
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if tid is None:
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raise TaskLockedException(f'unable to acquire lock {lock_name}')
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try:
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return fn(*args, **kwargs)
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finally:
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sem.release(tid)
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return inner
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return decorator
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