Slow Squid Requests with a Crashing URL Rewriter

If Squid accepts connections but takes a long time to send requests onward, inspect any URL rewriter on that path. In Squid 5–7, url_rewrite_program names an external program consulted after initial access checks. It can delay the request before the destination receives it.

1. Read the effective rewriter command, including wrapper and arguments.
2. Match the affected transaction with helper diagnostics. Repeated child exits, malformed replies and a growing queue are distinct leads.
3. Check whether one URL pattern triggers the failure. Preserve a redacted example of that input rather than changing unrelated resolver settings.

The helper has a line-oriented request/reply contract. Wrapper progress text on standard output can break it. Running the script successfully as an administrator also does not reproduce Squid's input stream, environment or permissions. This path is separate from password verification.

Only after the exchange works should you treat it as a capacity problem. url_rewrite_children controls processes and related queue behavior, but more children cannot repair input-triggered crashes. Its concurrency option introduces channel identifiers and requires a helper implementing that conversation.

An authorized comparison without the rewriter can isolate its contribution. Leaving it bypassed on overload can change the routing or filtering it enforces, so that is a policy choice. Compare the observed helper wait with DNS and onward-connection evidence before attributing the whole delay to network latency.