[Hardware][TPU] Optionally import for TPU backend (#18269)

Signed-off-by: Siyuan Liu <lsiyuan@google.com>
Signed-off-by: Jade Zheng <zheng.shoujian@outlook.com>
Co-authored-by: Carol Zheng <cazheng@google.com>
Co-authored-by: Jade Zheng <zheng.shoujian@outlook.com>
Co-authored-by: Hongmin Fan <fanhongmin@google.com>

vllm/distributed/device_communicators/tpu_communicator.py

@@ -91,3 +91,12 @@ class TpuCommunicator(DeviceCommunicatorBase):
     def all_gather(self, input_: torch.Tensor, dim: int = -1) -> torch.Tensor:
         assert dim == -1, "TPUs only support dim=-1 for all-gather."
         return xm.all_gather(input_, dim=dim)
+
+
+try:
+    from tpu_commons.distributed.device_communicators import (
+        TpuCommunicator as TpuCommonsCommunicator)
+    TpuCommunicator = TpuCommonsCommunicator  # type: ignore
+except ImportError:
+    logger.info("tpu_commons not found, using vLLM's TpuCommunicator")
+    pass

vllm/platforms/tpu.py

@@ -194,3 +194,11 @@ class TpuPlatform(Platform):
             if params.sampling_type == SamplingType.RANDOM_SEED:
                 raise ValueError(
                     "Torch XLA does not support per-request seed.")
+
+
+try:
+    from tpu_commons.platforms import TpuPlatform as TpuCommonsPlatform
+    TpuPlatform = TpuCommonsPlatform  # type: ignore
+except ImportError:
+    logger.info("tpu_commons not found, using vLLM's TpuPlatform")
+    pass

vllm/v1/worker/tpu_worker.py

@@ -267,3 +267,11 @@ def init_tpu_worker_distributed_environment(
     ensure_model_parallel_initialized(parallel_config.tensor_parallel_size,
                                       parallel_config.pipeline_parallel_size,
                                       parallel_config.enable_expert_parallel)
+
+
+try:
+    from tpu_commons.worker import TPUWorker as TPUCommonsWorker
+    TPUWorker = TPUCommonsWorker  # type: ignore
+except ImportError:
+    logger.info("tpu_commons not found, using vLLM's TPUWorker.")
+    pass