key-value-ds

File based Key-Value datastore

Supports basic CRD (Create, Read, Delete)

Functionalities:

1. It can be initialized using an optional file path. If one is not provided, it will reliably create itself using uuid.
2. Key string capped at 32 characters and Value must be a JSON object capped at 16KB. (These values can be changed in config.py)
3. Every key supports setting a Time-To-Live property when it is created. This property is optional. If provided, it will be evaluated as an integer defining the number of seconds. Once the Time-To-Live for a key has expired, the key will no longer be available for Read or Delete operations.
4. Only one process can access the datastore (local file) at a time.
5. Thread safe.

Usage:

Creating an instance

import key_value_ds
ds_instance = key_value_ds.get_instance()

Note: If file_path is provided in the get_instance() call, it will obtain lock on that file using fcntl. If object is created for the same file path twice, BlockingIOError is thrown.

Creating an data

data_key = 'test_key'
data_value = {"value": 1}  # must be a JSON
time_to_live = 5*1000  # in milliseconds
ds_instance.create(data_key, data_value, ttl=time_to_live)

Retrieving data

retrieve_key = 'test_key'
ds_instance.get(retrieve_key)   # returns {"value": 1} if retrieved within 5 seconds else ValueError

Deleting data

key_to_delete = 'test_key'
ds_instance.delete(key_to_delete)  # key-value is removed from the datastore

Delete all data

ds_instance.delete_all()