Engineering Logs for Troubleshooting & Debugging
Jordan Lee 
Intermittent 502/504 OAuth2 Token Errors Behind HAProxy in Kubernetes Problem Description In a production GKE data‑pipeline, several microservices acquire an OAuth2 access token from an internal /token endpoint. The endpoint is exposed through a HAProxy Ingress controller. Under normal load the token exchange succeeds, but during rolling updates, high‑load spikes, or after pod eviction the … Read more
PostgreSQL SSL Handshake Failure After Certificate Expiration in Docker Development Problem Description During a local AI model training run, the Python script that connects to the PostgreSQL service via psycopg2 started throwing: psycopg2.OperationalError: SSL SYSCALL error: certificate verify failed PostgreSQL container logs showed the corresponding server‑side error: 2026-09-12 10:45:23.456 UTC [1] LOG: SSL error: certificate … Read more
Problem – 401 Token Limit Exceeded During Canary Scrape During a staged rollout of a new microservice, Prometheus began reporting scrape failures with the following error: error scraping target “http://service-canary:9090/metrics”: unexpected status code 401 Unauthorized (token limit exceeded) Additional log entries from the Prometheus server process show the token acquisition step failing: 2024-08-12T14:23:07Z level=error msg=”failed to fetch bearer … Read more
Problem – Model Weight Synchronization Lag Behind Nginx Load Balancer In a staging environment we run three Docker‑based inference replicas behind an Nginx upstream. Model artifacts are stored on a shared NFS mount and are updated by a CI/CD pipeline that copies a new .pt file into /models. After each deployment the expectation is that … Read more
Problem Description Microservices that run on GKE, Cloud Run, or Cloud Functions invoke the Google Gemini API using SAML‑based workload identity federation. During inter‑service calls the Gemini client returns: SAML Assertion is invalid: Expired or SAML Assertion is invalid: Audience mismatch These errors prevent the services from authenticating to Gemini, causing request failures such as … Read more
Problem – GPU OOM on a Single A100 During DDP Mixed‑Precision Training When training a large transformer (e.g., 1.5 B‑parameter GPT‑like) on a 4 × NVIDIA A100 40 GB node with torch.nn.parallel.DistributedDataParallel (DDP) and mixed‑precision (AMP), one rank repeatedly crashes with an out‑of‑memory (OOM) error: torch.cuda.OutOfMemoryError: CUDA out of memory. Tried to allocate 5.23 GiB (GPU 2; 40.00 GiB total … Read more
Problem – Streaming queries never terminate after stop‑sequence trigger fails In a high‑throughput real‑time pipeline that ingests and queries vectors via Weaviate’s gRPC API, clients observed that streaming GraphQL queries kept the connection open indefinitely. The expected stop sequence (e.g., \n\n) never caused the server to close the stream, resulting in: Growing memory usage on … Read more
Problem Description – Claude API Authentication Failures After Secret Rotation in Staging CI/CD During nightly staging deployments the integration test suite intermittently receives 401 Unauthorized – “Invalid API key” or 403 Forbidden – “API key expired or revoked” responses from the Anthropic Claude endpoint. The failure correlates with the automated secret‑rotation step that fetches a … Read more
Problem: NGINX Ingress Controller PVC Stays Pending After Adding a Logging Volume The NGINX Ingress Controller is deployed via the official Helm chart. After extending the chart to mount a dedicated PersistentVolumeClaim (PVC) for request logging and cache files, the PVC nginx-logging never reaches the Bound phase. The controller pod remains in Pending and the … Read more
Problem Description The inference service deployed on an AWS EC2 instance (private subnet) cannot establish a TCP connection to the remote RAG vector store (Milvus, Pinecone, or Qdrant). Every request to retrieve relevant documents ends with a timeout, causing the entire inference pipeline to fail. Typical log excerpts: 2024-09-10T12:34:56.123Z ERROR langchain.vectorstores.milvus: connect ETIMEDOUT 172.31.45.23:443 2024-09-10T12:34:57.001Z … Read more