Squid Web Cache wiki

Squid Web Cache documentation

🔗 Too Many Queued Requests

🔗 Synopsis

Squid crashes and maybe restarts immediately. Logging complains about too many queued requests.

🔗 Symptoms

🔗 Explanation

Squid uses helper processes to perform certain actions such as authentication checks. The number of each helper is configurable by the proxy admin. As can be expected these helpers have a limit to how many actions they can process each second. Most of them handle only one client request at a time.

This message is displayed once there are more simultaneous client requests waiting to be handled than helpers available to process the load. If you configure N helpers, this warning appears when 2N+1 clients are waiting for replies. Depending on the squid version the factor may be 2 or 5 queued per helper.

This warning is most often seen with NTLM authenticators. Due to the nature of NTLM it locks one helper for the relatively long NTLM handshake period. This radically reduces the number of concurrent client requests that can be sent through Squid. Winbind places a maximum capacity somewhere around 256 simultaneous NTLM handshakes. Higher client connection rates require some skills organising fast handshakes and managing multiple DC. Negotiate can handle many more handshakes, but also has an annoyingly low capacity.

🔗 Workaround

Categories: KnowledgeBase

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