redis-lock | locking primitive using redis | Learning library
kandi X-RAY | redis-lock Summary
kandi X-RAY | redis-lock Summary
Implements a locking primitive using redis in node.js. Fully non-blocking and asynchronous, and uses the algorithm described in the [redis docs] Useful for concurrency control. For example, when updating a database record you might want to ensure that no other part of your code is updating the same record at that time. Used heavily at [errorception] Starting Node 8, you can promisify the lock function.
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Top functions reviewed by kandi - BETA
- Acquires a lock .
- Acquires a lock on a lock .
- Retry the lock function
redis-lock Key Features
redis-lock Examples and Code Snippets
Community Discussions
Trending Discussions on redis-lock
QUESTION
I have an API that in order to insert a new item it needs to be validated. The validation basically is a type validator(string, number, Date, e.t.c) and queries the database that checks if the "user" has an "item" in the same date, which if it does the validation is unsuccessful.
Pseudocode goes like this:
...ANSWER
Answered 2019-Apr-11 at 10:04You should create a composite index or a composite primary key that includes the id_user and the start_date fields. This will ensure that no documents for the same user with the same date can be created, and the database will throw an error if you'll try to do it.
Composite index with mongoose
You could also use transactions. To do it, you should execute the find and the create methods inside a transaction, to ensure that no concurrent queries on the same document will be executed.
Mongoose transactions tutorial
I would go with an unique composite index, that in your specific case should be something like
QUESTION
Except that python-redis-lock module provides contextmanager for the lock object - what are the differences when compared to the lock object you get from redispy module? what is so special about python-redis-lock?
...ANSWER
Answered 2018-Sep-21 at 23:04I think the context manager is not the major difference here, because if you see code of redis-py Lock they have the __enter__ and __exit__ added in there.
Both the Lock's seem to use SETNX for acquiring the lock:
The major difference I saw in there was the way blocking the threads work.
- In case of python-redis-lock they have been using BLPOP mechanism to block the thread, which to me seems like using redis's own version of blocking mechanism. Github code
Something like:
timed_out = not self._client.blpop(self._signal, blpop_timeout) and timeout
- In case of redis-py they seem use time module and its sleep method to block the thread to check whether the blocking has timedout.
Something like:
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