Disaggregate prefill for kv cache register style (#950)

### What this PR does / why we need it?
This PR adopt `LLMDataDist` for kv cache register and `pull_blocks`
style disaggregate prefill implementation. The interface implementation
mainly follows the design of NIXL PR
https://github.com/vllm-project/vllm/pull/17751/files#diff-7eaad0b7dee0626bf29d10081b0f0c5e3ea15a4af97e7b182a4e0d35f8346953
.

This PR can be test with the following step:
- Generate the rank table for all machine.
- execute`toy_proxy.py` to launch the disaggregate prefill proxy server,
specify the prefill ip, port and the decode ip, port
- Run the prefill server and decode server.
- send the request to the disaggregate prefill proxy

### Does this PR introduce _any_ user-facing change?

### How was this patch tested?


- vLLM version: v0.9.2
- vLLM main:
8d0a01a5f2

---------

Signed-off-by: ganyi <pleaplusone.gy@gmail.com>
Signed-off-by: machenglong <machenglong_yewu@cmss.chinamobile.com>
Signed-off-by: liziyu179 <3475441767@qq.com>
Signed-off-by: underfitc <hucong24@huawei.com>
Signed-off-by: zouyida2052 <zouyida@huawei.com>
Signed-off-by: liziyu <liziyu16@huawei.com>
Signed-off-by: underfituu <hzhucong@163.com>
Co-authored-by: machenglong <machenglong_yewu@cmss.chinamobile.com>
Co-authored-by: liziyu179 <3475441767@qq.com>
Co-authored-by: underfitc <hucong24@huawei.com>
Co-authored-by: zouyida2052 <zouyida@huawei.com>
Co-authored-by: liziyu <liziyu16@huawei.com>
Co-authored-by: underfituu <hzhucong@163.com>

vllm_ascend/envs.py

@@ -133,6 +133,28 @@ env_variables: Dict[str, Callable[[], Any]] = {
     "VLLM_ASCEND_ENABLE_TOPK_TOPP_OPTIMIZATION":
     lambda: bool(
         int(os.getenv("VLLM_ASCEND_ENABLE_TOPK_TOPP_OPTIMIZATION", '0'))),
+
+    # `LLMDataDistCMgrConnector` required variable. `DISAGGREGATED_PREFILL_RANK_TABLE_PATH` is
+    # used for llmdatadist to build the communication topology for kv cache transfer, it is
+    # a required variable if `LLMDataDistCMgrConnector` is used as kv connector for disaggregated
+    # pd. The rank table can be generated by adopting the script `gen_ranktable.sh`
+    # in vllm_ascend's example folder.
+    "DISAGGREGATED_PREFILL_RANK_TABLE_PATH":
+    lambda: os.getenv("DISAGGREGATED_PREFILL_RANK_TABLE_PATH", None),
+    # `LLMDataDistCMgrConnector` required variable. `VLLM_ASCEND_LLMDD_RPC_IP` is used as the
+    # rpc communication listening ip, which will be used to receive the agent metadata from the
+    # remote worker.
+    "VLLM_ASCEND_LLMDD_RPC_IP":
+    lambda: os.getenv("VLLM_ASCEND_LLMDD_RPC_IP", "0.0.0.0"),
+    # `LLMDataDistCMgrConnector` required variable. `VLLM_LLMDD_RPC_PORT` is used as the
+    # rpc communication listening port, which will be used to receive the agent metadata from the
+    # remote worker.
+    "VLLM_LLMDD_RPC_PORT":
+    lambda: int(os.getenv("VLLM_LLMDD_RPC_PORT", 5557)),
+    # Whether to enable mla_pa for deepseek mla decode, this flag will be removed after its available torch_npu is public accessible
+    # and the mla_pa will be the default path of deepseek decode path.
+    "VLLM_ASCEND_MLA_PA":
+    lambda: int(os.getenv("VLLM_ASCEND_MLA_PA", 0))
 }
 
 # end-env-vars-definition