.. Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. .. _admin-plugins-fq-pacing: FQ Pacing Plugin ================== This is a remap plugin that allows ATS to rate limit an individual TCP connection. It is based on Linux support for the Fair Queuing qdisc. FQ and SO_MAX_PACING_RATE is available in RedHat/Centos 7.2+, Debian 8+, and any other Linux distro with a kernel 3.18 or greater. How it Works ------------ When activated during remap processing, this plugin calls ``setsockopt(SO_MAX_PACING_RATE)`` on the client socket. To prevent the rate from leaking to other remap rules the client may access in future requests, a hook is set to deactivate the pacing when the current transaction completes. Installation ------------ First, enable the FQ qdisc by setting ``net.core.default_qdisc=fq`` in ``/etc/sysctl.conf`` and rebooting. The `FQ Pacing` plugin is a :term:`remap plugin`. Enable it by adding ``fq_pacing.so`` to your :file:`remap.config` file. Provide a ``--rate=BytesPerSec`` option to set the maxmimum rate of a TCP connection matching that remap line. Here is an example remap.config entry: :: map http://reverse-fqdn.com http://origin.com @plugin=fq_pacing.so @pparam=--rate=100000