nginx config_error ai_generated true

nginx: [emerg] the "server_names_hash_bucket_size" directive value is too small

ID: nginx/name-too-long-buffer-overflow

Also available as: JSON · Markdown · 中文
90%Fix Rate
85%Confidence
1Evidence
2024-02-15First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
nginx/1.18.0 active — — —
nginx/1.20.0 active — — —
nginx/1.24.0 active — — —
nginx/1.26.0 active — — —

Root Cause

The configured server_names_hash_bucket_size is insufficient for the length of server names defined, causing hash table bucket overflow.

generic

中文

配置的 server_names_hash_bucket_size 不足以容纳定义的服务器名称长度，导致哈希表桶溢出。

Official Documentation

https://nginx.org/en/docs/http/ngx_http_core_module.html#server_names_hash_bucket_size

Workarounds

  1. 90% success Increase server_names_hash_bucket_size to at least 128 in the http block: `http { server_names_hash_bucket_size 128; ... }` 
    Increase server_names_hash_bucket_size to at least 128 in the http block: `http { server_names_hash_bucket_size 128; ... }`
  2. 85% success If the error persists, double the value (e.g., 256) and reload: `http { server_names_hash_bucket_size 256; }` 
    If the error persists, double the value (e.g., 256) and reload: `http { server_names_hash_bucket_size 256; }`
  3. 75% success Shorten long server names or use wildcards (e.g., *.example.com instead of very-long-subdomain.example.com) to reduce name length. 
    Shorten long server names or use wildcards (e.g., *.example.com instead of very-long-subdomain.example.com) to reduce name length.

中文步骤

  1. 在 http 块中将 server_names_hash_bucket_size 增加到至少 128：`http { server_names_hash_bucket_size 128; ... }`
  2. 如果错误仍然存在，将值加倍（例如 256）并重新加载：`http { server_names_hash_bucket_size 256; }`
  3. 缩短长服务器名称或使用通配符（例如 *.example.com 替代 very-long-subdomain.example.com）以减少名称长度。

Dead Ends

Common approaches that don't work:

  1. 70% fail

    server_names_hash_max_size sets the total hash size, while bucket size controls per-bucket alignment; max_size without increasing bucket_size still causes overflow for long names.

  2. 50% fail

    The error is configuration-specific; removing names only avoids the symptom, not the root cause, and names must be re-added eventually.

  3. 60% fail

    The value must be a power of two (e.g., 32, 64, 128, 256) to align with CPU cache lines; non-power-of-two values are ignored or cause other errors.