api resource_error ai_generated true

503 Service Unavailable: Connection pool exhausted. Maximum connections to backend reached.

ID: api/rate-limit-connection-pool-exhausted

Also available as: JSON · Markdown · 中文
78%Fix Rate
85%Confidence
1Evidence
2023-09-05First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
Python requests 2.31.0 active — — —
Node.js http module 18.x active — — —
Go net/http 1.21 active — — —

Root Cause

Client-side HTTP connection pool (e.g., requests.Session or Node.js http.Agent) has no available connections due to slow responses or leaks.

generic

中文

客户端HTTP连接池（如requests.Session或Node.js http.Agent）因慢响应或泄漏而无可用连接。

Official Documentation

https://docs.python-requests.org/en/latest/user/advanced/#transport-adapters

Workarounds

  1. 80% success Increase connection pool size and add idle timeout. In Python requests: session = requests.Session(); adapter = requests.adapters.HTTPAdapter(pool_connections=100, pool_maxsize=100, max_retries=3); session.mount('https://', adapter); session.mount('http://', adapter) 
    Increase connection pool size and add idle timeout. In Python requests: session = requests.Session(); adapter = requests.adapters.HTTPAdapter(pool_connections=100, pool_maxsize=100, max_retries=3); session.mount('https://', adapter); session.mount('http://', adapter)
  2. 75% success Enable connection reuse with keepalive and reduce request timeout. For Node.js: const agent = new http.Agent({ keepAlive: true, maxSockets: 25, timeout: 60000 }); 
    Enable connection reuse with keepalive and reduce request timeout. For Node.js: const agent = new http.Agent({ keepAlive: true, maxSockets: 25, timeout: 60000 });
  3. 70% success Add retry with exponential backoff for 503 errors to allow connections to be released. 
    Add retry with exponential backoff for 503 errors to allow connections to be released.

中文步骤

  1. Increase connection pool size and add idle timeout. In Python requests: session = requests.Session(); adapter = requests.adapters.HTTPAdapter(pool_connections=100, pool_maxsize=100, max_retries=3); session.mount('https://', adapter); session.mount('http://', adapter)
  2. Enable connection reuse with keepalive and reduce request timeout. For Node.js: const agent = new http.Agent({ keepAlive: true, maxSockets: 25, timeout: 60000 });
  3. Add retry with exponential backoff for 503 errors to allow connections to be released.

Dead Ends

Common approaches that don't work:

  1. 60% fail

    Increasing max_connections arbitrarily without addressing slow backend responses leads to memory exhaustion and worse performance.

  2. 70% fail

    Restarting the application without adjusting timeout settings causes the pool to exhaust again quickly under load.