Engineering Logs for Troubleshooting & Debugging
Problem The LangChain service is deployed as a stateless Deployment behind an API gateway in a Kubernetes cluster. An HorizontalPodAutoscaler (HPA) is configured to scale the Deployment based on CPU utilization (target 70%) and a custom latency metric exported to Prometheus. Under load the request latency spikes and the CPU usage reported by the metrics-server … Read more
Problem During automated performance benchmarking of LangChain pipelines, the test suite spawns multiple parallel LLM calls. After a few seconds the benchmark aborts with HTTP 429 “Rate limit exceeded” errors. The failure appears only when the benchmark runs with concurrency greater than a single worker; serial runs complete successfully. Root Cause LangChain delegates LLM invocations to … Read more
Problem During the execution of integration tests on a Jenkins build agent, the CI job fails with a connection timeout when trying to reach the Haystack API server. In some runs the logs also show DNS resolution failures. The failure aborts the test suite and marks the build as unstable. [2026-10-13 02:14:37] INFO – Starting … Read more
Problem: Haystack pod rejected by admission controller after adding GPU request When deploying a Haystack inference service to a GPU‑enabled Kubernetes cluster (A100/H100 nodes), the pod creation fails with an admission controller error. The pod never reaches the Pending state; instead the API server returns a 400 Bad Request response indicating an invalid or missing … Read more
Problem When streaming user messages into a LangChain chain that generates live responses, the application intermittently throws a TokenLimitExceededError. The exception originates from the underlying LLM provider (e.g., OpenAI, Anthropic) and aborts the current generation, causing a visible pause or failure in the UI. Typical log excerpt: 2024-10-05 14:23:11,842 – app.chain – ERROR – TokenLimitExceededError: … Read more
Problem After a bulk indexing run of several hundred thousand documents, the Haystack SearchQuerySet latency spikes dramatically. The 95th‑percentile response time, which normally sits around 0.8 s, climbs to 5 s–12 s for simple term queries. The issue appears only after the indexing job finishes; during indexing the query latency remains low. Typical symptoms observed in production: API … Read more
Problem In a multi‑region replication deployment of Haystack, queries that should be served from any replica start failing with a 400 Bad Request error. The failure appears only after a recent configuration change that introduced a new sampling parameter in the haystack.yaml file. The symptom is observed across all regions, but the primary region shows … Read more
Problem During peak traffic periods the API gateway that fronts a Haystack‑based search service starts returning 504 Gateway Timeout, 502 Bad Gateway and occasional 429 Too Many Requests errors. The downstream Haystack document store logs show repeated failures when trying to fetch source documents from the cloud storage provider (e.g., AWS S3, GCP Cloud Storage, … Read more
Problem After upgrading the Kubernetes service mesh (Istio 1.18 → 1.20), LangChain‑based microservices that call external Large Language Model (LLM) APIs over HTTPS start failing with SSL/TLS handshake errors. The failures manifest as connection timeouts and requests.exceptions.SSLError exceptions in the Python runtime. Typical Symptoms Python traceback in LangChain worker pods: Traceback (most recent call last): File … Read more
Problem During load testing and in production traffic spikes, the RAG reranker component of LlamaIndex running inside a Docker container consistently throws timeout errors. The failure manifests as: 2024-09-28 12:34:56,789 ERROR reranker – RerankerTimeoutError: Reranking request timed out after 30.0 seconds Traceback (most recent call last): File “/app/llama_index/reranker.py”, line 212, in rank response = self.client.post(payload, … Read more