[Core] Add a random suffix to frontend-provided request IDs (#27987)

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Nick Hill <nhill@redhat.com>
Co-authored-by: Nick Hill <nhill@redhat.com>

tests/v1/engine/test_process_multi_modal_uuids.py

@@ -6,6 +6,7 @@ import pytest
 from vllm.assets.image import ImageAsset
 from vllm.assets.video import VideoAsset
 from vllm.config import CacheConfig, DeviceConfig, ModelConfig, VllmConfig
+from vllm.multimodal import MultiModalUUIDDict
 from vllm.sampling_params import SamplingParams
 from vllm.v1.engine import input_processor as input_processor_mod
 from vllm.v1.engine.input_processor import InputProcessor
@@ -166,7 +167,7 @@ def test_multi_modal_uuids_ignored_when_caching_disabled(monkeypatch):
         monkeypatch, mm_cache_gb=0.0, enable_prefix_caching=False
     )
 
-    captured: dict[str, object] = {}
+    captured: dict[str, MultiModalUUIDDict] = {}
 
     def fake_preprocess(
         prompt, *, tokenization_kwargs=None, lora_request=None, mm_uuids=None
@@ -196,7 +197,16 @@ def test_multi_modal_uuids_ignored_when_caching_disabled(monkeypatch):
     )
 
     # Expect request-id-based overrides are passed through
-    assert captured["mm_uuids"] == {
-        "image": [f"{request_id}-image-0", f"{request_id}-image-1"],
-        "video": [f"{request_id}-video-0"],
-    }
+    mm_uuids = captured["mm_uuids"]
+    assert set(mm_uuids.keys()) == {"image", "video"}
+    assert len(mm_uuids["image"]) == 2
+    assert len(mm_uuids["video"]) == 1
+    assert mm_uuids["image"][0].startswith(f"{request_id}-image-") and mm_uuids[
+        "image"
+    ][0].endswith("-0")
+    assert mm_uuids["image"][1].startswith(f"{request_id}-image-") and mm_uuids[
+        "image"
+    ][1].endswith("-1")
+    assert mm_uuids["video"][0].startswith(f"{request_id}-video-") and mm_uuids[
+        "video"
+    ][0].endswith("-0")