Engineering Logs for Troubleshooting & Debugging
Problem – Intermittent CUDA OOM and Tensor Shape Mismatches During Batched Audio Inference In a Kubernetes cluster that runs containerized PyTorch inference services, pods processing variable‑length audio streams occasionally crash with: CUDA out of memory. Tried to allocate 2.34 GiB (GPU 0; 8.00 GiB total capacity; 6.12 GiB already allocated; 1.23 GiB free; 6.12 GiB … Read more
Problem Description – Inconsistent Citation Formatting in vLLM RAG Pipelines In a production Kubernetes deployment that serves high‑throughput GPU‑accelerated inference, the vLLM engine is used to generate responses augmented with retrieved documents (RAG). The downstream reference validator expects a strict JSON payload that contains a citations array, each citation delimited by the marker syntax defined … Read more
Problem Description The Hugging Face Trainer crashes during the initialization phase of a distributed training run on a Kubernetes cluster. The failure manifests as a FileNotFoundError or PermissionError when the trainer tries to read the shared dataset directory or create the checkpoint folder. Typical log excerpts from the failing pod (rank 2) are: 2026-07-31 10:12:45,123 … Read more
Problem – Intermittent 401 Unauthorized Errors During Long‑Running Training In a multi‑node GPU cluster orchestrated by Kubernetes, a distributed PyTorch/TensorFlow training job pushes metrics, parameters, and artifacts to a remote MLflow tracking server that is protected by an OIDC/OAuth2 provider. After several hours of execution the training process receives repeated 401 Unauthorized responses: HTTPError 401 – Unauthorized while … Read more
Problem Description – Empty Retrieval Results on A100/H100 GPU Cluster When executing a Retrieval‑Augmented Generation (RAG) pipeline on a multi‑node GPU cluster (A100/H100), the RAGRetriever consistently returns an empty document list despite: Valid natural‑language queries. A fully populated FAISS index built from the knowledge base. Successful generation of query embeddings on the GPU. Typical log … Read more
Problem: vLLM token refresh fails after cluster restoration from snapshot During disaster‑recovery drills and production failovers, a vLLM cluster restored from a persistent snapshot repeatedly logs errors such as: TokenRefreshError: token expired Invalid token in session state Failed to refresh token: authentication failed Session token mismatch after restore Token cache not found or corrupted All … Read more
Problem: MLflow tracking server not found in a local Docker development setup During local development an engineer runs an MLflow tracking server inside a Docker container (or via docker‑compose) and then starts a separate client container (or a host‑side script) that attempts to log runs. The client immediately fails with errors such as: mlflow.exceptions.RestException: Unable … Read more
Problem – RAG inference fails because the prompt template is malformed In a distributed micro‑services deployment the Retrieval‑Augmented Generation (RAG) service invokes an ONNX Runtime sidecar via gRPC. The sidecar builds a prompt by substituting variables (e.g., {{question}}, {{context}}) into a JSON‑encoded template before feeding the concatenated string to a transformer model. Symptoms observed in … Read more
Problem Description The Horizontal Pod Autoscaler (HPA) attached to a Deployment that serves Hugging Face Transformers inference never creates additional replicas, even when the pods report CPU utilization above the configured target (e.g., 80%). The symptom manifests as: CPU usage in kubectl top pod consistently >90%. Inference latency spikes and occasional request time‑outs. HPA status shows … Read more
Problem – TensorRT Batch Inference Times Out Under High Concurrency In a production GPU inference service the following symptoms appear when the request rate spikes: Requests that submit a batched input to IExecutionContext::enqueueV2 return false after ~10 s. Server logs contain messages such as: [ERROR] Failed to enqueue inference: Timeout while waiting for GPU [TensorRT] Execution … Read more