Lookup the KV cache

The lookup interface is defined as the following:

lookup(tokens: List[int]) -> event_id: str, layout_info: Dict[str, Tuple[str, int]]

The function takes a list of tokens as input and returns event_id and a dictionary containing the layout information for each token. The layout information is represented as a mapping between instance_id and a tuple of (location, matched_prefix_length).

Example usage:

First, 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"
distributed_url: "localhost:8002"
lmcache_worker_port: 8001

Second, we need to start the vllm/lmcache instance at port 8000:

PYTHONHASHSEED=123 CUDA_VISIBLE_DEVICES=0 LMCACHE_CONFIG_FILE=example.yaml vllm serve meta-llama/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"}'

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

PYTHONHASHSEED=123 lmcache_controller --host localhost --port 9000 --monitor-port 9001

Then we can send a request to vllm to see if it works properly:

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

Now we send a request to tokenize the prompt:

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

We should be able to see token ids in response:

{"count":12,"max_model_len":4096,"tokens":[128000,849,21435,279,26431,315,85748,6636,304,4221,4211,13],"token_strs":null}

Finally, we can send 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 the response like this:

{"event_id": "xxx", "lmcache_default_instance": ("LocalCPUBackend", 12)}

The field lmcache_default_instance shows the instance ID, followed by a tuple of (location, matched_prefix_length) indicating the cache location within that instance and matched prefix length. event_id is an identifier of the controller operation and can typically be ignored.