mirror of
https://github.com/mCaptcha/cache.git
synced 2024-11-22 08:35:21 +03:00
41 lines
1.3 KiB
Markdown
41 lines
1.3 KiB
Markdown
# mCaptcha Redis Module Mechanism
|
|
|
|
## Data types
|
|
|
|
1. Bucket
|
|
2. Bucket safety
|
|
3. mCaptcha
|
|
4. mCaptcha safety
|
|
|
|
## Bucket
|
|
|
|
- Timer queue, used for scheduling decrements.
|
|
- Timer used for scheduling can't be persisted so requires a safety
|
|
|
|
## Bucket Safety
|
|
|
|
- Has expiry timer(Redis `EXIPRE`)
|
|
- Key name includes bucket name for which this safety was created for
|
|
- When Redis is started after crash, bucket safety expires and expire
|
|
event is fired, the corresponding bucket is fetched and executed.
|
|
|
|
## mCaptcha
|
|
|
|
- Contains mCaptcha defense details and current state
|
|
- When redis performs resharding, it's possible that mCaptcha gets
|
|
separated from its bucket.
|
|
- We can't pin mCaptcha by using hashtags because the client figures out
|
|
where a key should be placed/is available and will have no
|
|
knowledge about node IDs that we use for pinning.
|
|
|
|
- So this too requires a safety to make sure that when recovering from a
|
|
crash, it's counter doesn't have residues permanently.
|
|
|
|
## mCaptcha safety
|
|
|
|
- Has expire timer(Redis `EXIPRE`)
|
|
- Key name includes mCaptcha name for which this safety was created for
|
|
- when expiry event is fired for this type, a bucket for corresponding
|
|
mCaptcha is created to decrement it by `x`(where `x` is the count of mCaptcha
|
|
when this event is fired). It's not perfect but at least we get
|
|
eventual consistency.
|