UNAVAILABLE communication network_error ai_generated true

grpc::UNAVAILABLE: No route to host on connection attempt to remote endpoint

ID: communication/grpc-unavailable-no-route-to-host

Also available as: JSON · Markdown · 中文
86%Fix Rate
88%Confidence
1Evidence
2024-01-10First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
gRPC 1.45.0 active — — —
gRPC 1.50.2 active — — —
gRPC 1.56.0 active — — —

Root Cause

gRPC client fails to establish TCP connection because the target IP address is unreachable due to network partition, firewall blocking, or incorrect DNS resolution.

generic

中文

gRPC 客户端无法建立 TCP 连接，因为目标 IP 地址由于网络分区、防火墙阻止或 DNS 解析错误而不可达。

Official Documentation

https://grpc.io/docs/guides/error-codes/

Workarounds

  1. 90% success Verify network connectivity using 'ping' and 'traceroute' to the target host: ensure the IP address is reachable and no intermediate hops are dropping packets. Then fix DNS if needed by updating /etc/hosts or DNS server records. 
    Verify network connectivity using 'ping' and 'traceroute' to the target host: ensure the IP address is reachable and no intermediate hops are dropping packets. Then fix DNS if needed by updating /etc/hosts or DNS server records.
  2. 85% success Check firewall rules on both client and server: ensure the gRPC port (default 50051) is open. Use 'iptables -L' or 'ufw status' to verify, and add allow rules if blocked. 
    Check firewall rules on both client and server: ensure the gRPC port (default 50051) is open. Use 'iptables -L' or 'ufw status' to verify, and add allow rules if blocked.
  3. 80% success If using Kubernetes, verify network policies and service endpoints: 'kubectl get endpoints <service-name>' to ensure pods are correctly targeted, and check for misconfigured network policies blocking cross-namespace traffic. 
    If using Kubernetes, verify network policies and service endpoints: 'kubectl get endpoints <service-name>' to ensure pods are correctly targeted, and check for misconfigured network policies blocking cross-namespace traffic.

中文步骤

  1. Verify network connectivity using 'ping' and 'traceroute' to the target host: ensure the IP address is reachable and no intermediate hops are dropping packets. Then fix DNS if needed by updating /etc/hosts or DNS server records.
  2. Check firewall rules on both client and server: ensure the gRPC port (default 50051) is open. Use 'iptables -L' or 'ufw status' to verify, and add allow rules if blocked.
  3. If using Kubernetes, verify network policies and service endpoints: 'kubectl get endpoints <service-name>' to ensure pods are correctly targeted, and check for misconfigured network policies blocking cross-namespace traffic.

Dead Ends

Common approaches that don't work:

  1. 80% fail

    Increasing gRPC client timeout (e.g., setting 'grpc.timeout' to 60s) only delays failure; the underlying network issue persists.

  2. 95% fail

    Disabling TLS verification ('GRPC_SSL_CIPHER_SUITES=ALL') does not resolve routing issues and introduces security vulnerabilities.

  3. 70% fail

    Retrying with exponential backoff (e.g., using gRPC retry policy) may mask the issue temporarily but doesn't fix the route, leading to eventual timeout.