[CI/Build] Pin OpenTelemetry versions and make availability errors clearer

.buildkite/test-pipeline.yaml

@@ -111,10 +111,10 @@ steps:
   commands:
   - pytest -v -s metrics 
   - "pip install \
-      opentelemetry-sdk \
-      opentelemetry-api \
-      opentelemetry-exporter-otlp \
-      opentelemetry-semantic-conventions-ai"
+      'opentelemetry-sdk>=1.26.0,<1.27.0' \
+      'opentelemetry-api>=1.26.0,<1.27.0' \
+      'opentelemetry-exporter-otlp>=1.26.0,<1.27.0' \
+      'opentelemetry-semantic-conventions-ai>=0.4.1,<0.5.0'"
   - pytest -v -s tracing
 
 ##### fast check tests  #####

examples/production_monitoring/Otel.md

@@ -3,10 +3,10 @@
 1. Install OpenTelemetry packages:
     ```
     pip install \
-        opentelemetry-sdk \
-        opentelemetry-api \
-        opentelemetry-exporter-otlp \
-        opentelemetry-semantic-conventions-ai
+      'opentelemetry-sdk>=1.26.0,<1.27.0' \
+      'opentelemetry-api>=1.26.0,<1.27.0' \
+      'opentelemetry-exporter-otlp>=1.26.0,<1.27.0' \
+      'opentelemetry-semantic-conventions-ai>=0.4.1,<0.5.0'
     ```
 
 1. Start Jaeger in a docker container:

vllm/config.py

@@ -12,7 +12,7 @@
 from vllm.model_executor.layers.quantization import QUANTIZATION_METHODS
 from vllm.model_executor.models import ModelRegistry
 from vllm.platforms import current_platform
-from vllm.tracing import is_otel_installed
+from vllm.tracing import is_otel_available, otel_import_error_traceback
 from vllm.transformers_utils.config import get_config, get_hf_text_config
 from vllm.utils import (STR_NOT_IMPL_ENC_DEC_CUDAGRAPH, GiB_bytes,
                         cuda_device_count_stateless, get_cpu_memory, is_cpu,
@@ -1721,9 +1721,11 @@ class ObservabilityConfig:
     collect_model_execute_time: bool = False
 
     def __post_init__(self):
-        if not is_otel_installed() and self.otlp_traces_endpoint is not None:
-            raise ValueError("OpenTelemetry packages must be installed before "
-                             "configuring 'otlp_traces_endpoint'")
+        if not is_otel_available() and self.otlp_traces_endpoint is not None:
+            raise ValueError(
+                "OpenTelemetry is not available. Unable to configure "
+                "'otlp_traces_endpoint'. Ensure OpenTelemetry packages are "
+                f"installed. Original error:\n{otel_import_error_traceback}")
 
         if ((self.collect_model_forward_time
              or self.collect_model_execute_time)

vllm/tracing.py

@@ -8,7 +8,8 @@
 
 logger = init_logger(__name__)
 
-_is_otel_installed = False
+_is_otel_imported = False
+otel_import_error_traceback: Optional[str] = None
 try:
     from opentelemetry.context.context import Context
     from opentelemetry.sdk.environment_variables import (
@@ -19,8 +20,14 @@
     from opentelemetry.trace import SpanKind, Tracer, set_tracer_provider
     from opentelemetry.trace.propagation.tracecontext import (
         TraceContextTextMapPropagator)
-    _is_otel_installed = True
+    _is_otel_imported = True
 except ImportError:
+    # Capture and format traceback to provide detailed context for the import
+    # error. Only the string representation of the error is retained to avoid
+    # memory leaks.
+    # See https://github.com/vllm-project/vllm/pull/7266#discussion_r1707395458
+    import traceback
+    otel_import_error_traceback = traceback.format_exc()
 
     class Context:  # type: ignore
         pass
@@ -35,14 +42,17 @@ class Tracer:  # type: ignore
         pass
 
 
-def is_otel_installed() -> bool:
-    return _is_otel_installed
+def is_otel_available() -> bool:
+    return _is_otel_imported
 
 
 def init_tracer(instrumenting_module_name: str,
                 otlp_traces_endpoint: str) -> Optional[Tracer]:
-    assert is_otel_installed(), ("OpenTelemetry packages must be installed "
-                                 "prior to initializing a tracer")
+    if not is_otel_available():
+        raise ValueError(
+            "OpenTelemetry is not available. Unable to initialize "
+            "a tracer. Ensure OpenTelemetry packages are installed. "
+            f"Original error:\n{otel_import_error_traceback}")
     trace_provider = TracerProvider()
 
     span_exporter = get_span_exporter(otlp_traces_endpoint)
@@ -70,7 +80,7 @@ def get_span_exporter(endpoint):
 
 def extract_trace_context(
         headers: Optional[Mapping[str, str]]) -> Optional[Context]:
-    if is_otel_installed():
+    if is_otel_available():
         headers = headers or {}
         return TraceContextTextMapPropagator().extract(headers)
     else: