Distributed cache feature using Redis

[a9raag]

Distributed Cache using Redis #496

Feature for distributed cache. This allows us to store keys in Redis key-value store.
Sorry, it took a while I spent too much time thinking about a design for this and how it will integrate into GPTCache's existing code base.

I have also attached a high-level design of how Distributed Cache works.

Notes

A couple of notes about how the eviction will work based on different scalar storage configurations:

Scenario 1:
Scalar Storage is MongoDB,
Eviction Base is Redis.
Then the keys will be stored in Redis, and cache call back will update the TTL.

Scenario 2:
Scalar Storage is Redis,
Eviction Base is also Redis,
Then storing keys separately becomes redundant since Redis eviction is based on Memory usage rather than the number of keys.
Also, we'll be fetching values multiple times both while getting scalar data and while hitting cache callback, and it will add network overhead.

To tackle this I created a NoOpEviction implementation (which skips cache operations) since,

1. Redis internally manage the eviction based on memory size and eviction policy for all keys.
2. We can configure RedisCacheStorage to update TTL upon creation and during access. This way values will be fetched from Redis only once.

[a9raag]

@SimFG
Can you help the test cases are failing because of

'(ReadTimeoutError("HTTPSConnectionPool(host='huggingface.co', port=443): Read timed out. (read timeout=10.0)"),
 '(Request ID: 3afc7015-e7b6-4b6a-abd6-acd698b9469f)')' thrown while requesting GET 
https://huggingface.co/GPTCache/paraphrase-albert-small-v2/resolve/main/tokenizer.json

[SimFG]

@a9raag ok, I have rerun it

[a9raag]

@SimFG it failed again

[codecov]

Codecov Report

Merging #518 (ce8db36) into dev (5aa7e1e) will decrease coverage by 0.16%.
Report is 1 commits behind head on dev.
The diff coverage is 93.33%.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #518      +/-   ##
==========================================
- Coverage   94.05%   93.89%   -0.16%     
==========================================
  Files          94       95       +1     
  Lines        3920     4014      +94     
==========================================
+ Hits         3687     3769      +82     
- Misses        233      245      +12     

Files Changed	Coverage Δ
gptcache/manager/eviction/memory_cache.py	90.90% <ø> (ø)
gptcache/manager/eviction/distributed_cache.py	89.65% <89.65%> (ø)
gptcache/manager/scalar_data/redis_storage.py	96.13% <93.18%> (-1.51%)	⬇️
gptcache/__init__.py	100.00% <100.00%> (ø)
gptcache/manager/data_manager.py	89.60% <100.00%> (+0.10%)	⬆️
gptcache/manager/eviction/manager.py	100.00% <100.00%> (ø)
gptcache/manager/factory.py	96.55% <100.00%> (+0.89%)	⬆️

... and 1 file with indirect coverage changes

[a9raag]

@SimFG apologies if I keep bugging you but the Unit Test workflow failed again 😭

Here's the error log

/home/runner/work/_temp/c7cf298b-8f2b-475f-995a-f3f5562139f1.sh: line 3:  3496 Illegal instruction    
 (core dumped) python3 -m pytest -k "not embedding and not processor" --cov=gptcache --cov-report xml:coverage.xml --cov-append ./tests/
Error: Process completed with exit code 132.

[a9raag]

Hi @SimFG and @xiaofan-luan
I've updated the PR.
The Unit Tests and CodeCov have now passed.
Could you please review it when you get a chance?
Thanks : )

[SimFG]

@a9raag great!!! i will check it today

[SimFG]

/lgtm
/approve

[sre-ci-robot]

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