sqlalchemy_dlock.impl.mysql module¶

class sqlalchemy_dlock.impl.mysql.SessionLevelLock(connection_or_session: Union[sqlalchemy.engine.base.Connection, sqlalchemy.orm.session.Session, sqlalchemy.orm.scoping.scoped_session], key, *, convert: Optional[Callable[[Any], str]] = None, **_)¶

Bases: sqlalchemy_dlock.sessionlevellock.AbstractSessionLevelLock

MySQL named-lock

MySQL named lock requires the key given by string.

If key is not a str:

When int or float, the constructor will force convert it to str:
```
key = str(key)
```
When bytes, the constructor tries to decode it with default encoding:
```
key = key.decode()
```

Or you can specify a convert function to that argument. The function is like:

def convert(val: Any) -> str:
    # do something ...
    return string

acquire(block: bool = True, timeout: Optional[Union[float, int]] = None, **_) → bool¶

Acquire a lock, blocking or non-blocking.

With the block argument set to True (the default), the method call will block until the lock is in an unlocked state, then set it to locked and return True.
With the block argument set to False, the method call does not block. If the lock is currently in a locked state, return False; otherwise set the lock to a locked state and return True.
When invoked with a positive, floating-point value for timeout, block for at most the number of seconds specified by timeout as long as the lock can not be acquired. Invocations with a negative value for timeout are equivalent to a timeout of zero. Invocations with a timeout value of None (the default) set the timeout period to infinite. The timeout argument has no practical implications if the block argument is set to False and is thus ignored. Returns True if the lock has been acquired or False if the timeout period has elapsed.

release(**_)¶

Release a lock.

Since the class is thread-local, this cannot be called from other thread or process, and also can not be called from other connection (PostgreSQL’s shared advisory lock supports so, but we haven’t).

When the lock is locked, reset it to unlocked, and return. If any other threads are blocked waiting for the lock to become unlocked, allow exactly one of them to proceed.

When invoked on an unlocked lock, a ValueError is raised.

There is no return value.

sqlalchemy_dlock.impl.mysql.default_convert(key: Union[bytearray, bytes, int, float]) → str¶