varnish

varnish/troubleshoot.md

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+### Varnish replies with 503 status for no apparent reason
+
+- Cause : Header receive from the backend are too big for the http_resp_hdr_len parameter.
+- Resolve : Increase http_resp_hdr_len parameter live to confirm and in systemd service to make it permanent
+
+```bash
+ExecStart=/usr/sbin/varnishd \
+          -j unix,user=vcache \
+          -F \
+          -a 0.0.0.0:6081 \
+          -T localhost:6082 \
+          -f /etc/varnish/default.vcl \
+          -S /etc/varnish/secret \
+          -s malloc,3G \
+          -p http_resp_hdr_len=16384
+```