Clear the KV cache

The clear interface is defined as the following:

clear(instance_id: str, tokens: Optional[List[int]], locations: Optional[List[str]]) -> success: bool

The function takes the instance_id and optionally tokens and locations as input. The return value is a boolean indicating whether the clear operation was successful or not. If tokens and locations are not provided, all the KV caches on the given instance will be cleared.

Example usage:

First, we need to start the lmcache controller at port 9000 and the monitor at port 9001:

python -m lmcache.controller --port 9000 --monitor_port 9001

Second, we need a yaml file example.yaml to properly configure the lmcache instance:

chunk_size: 256
local_cpu: True
max_local_cpu_size: 5

# cache controller configurations
enable_controller: True
lmcache_instance_id: "lmcache_default_instance"
controller_url: "localhost:9001"
lmcache_worker_url: "localhost:8001"

Third, we need to start the vllm/lmcache instance:

LMCACHE_USE_EXPERIMENTAL=True LMCACHE_CONFIG_FILE=example.yaml vllm serve meta-llama/Meta-Llama-3.1-8B-Instruct --max-model-len 4096  --gpu-memory-utilization 0.8 --port 8000 --kv-transfer-config '{"kv_connector":"LMCacheConnectorV1", "kv_role":"kv_both"}'

Then, we can send a request to vllm:

curl -X POST http://localhost:8000/v1/completions \
-H "Content-Type: application/json" \
-d '{
    "model": "meta-llama/Meta-Llama-3.1-8B-Instruct",
    "prompt": "Explain the significance of KV cache in language models.",
    "max_tokens": 10
}'

We send a clear request to the lmcache controller:

curl -X POST http://localhost:9000/clear \
-H "Content-Type: application/json" \
-d '{
    "instance_id": "lmcache_default_instance_id"
}'

We should be able to see the response like this:

{"success": True}

This indicates all the KV caches on the lmcache_default_instance have been cleared.

We can further verify this by sending a lookup request to the lmcache controller:

curl -X POST http://localhost:9000/lookup \
-H "Content-Type: application/json" \
-d '{
    "tokens": [128000, 849, 21435, 279, 26431, 315, 85748, 6636, 304, 4221, 4211, 13]
}'

We should be able to see an empty the response, indicating the KV cache for the given tokens has been cleared.