randall commented on a change in pull request #7623: URL: https://github.com/apache/trafficserver/pull/7623#discussion_r607965112
########## File path: plugins/experimental/rate_limit/limiter.cc ########## @@ -0,0 +1,159 @@ +/* + * 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. + */ +#include "limiter.h" + +/////////////////////////////////////////////////////////////////////////////// +// This is the continuation that gets scheduled perdiocally to process the Review comment: periodically ########## File path: doc/admin-guide/plugins/rate_limit.en.rst ########## @@ -0,0 +1,115 @@ +.. 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-rate-limit: + +Rate Limit Plugin +******************** + +The :program:`rate_limit` plugin provides basic mechanism for how much +traffic a particular service (remap rule) is allowed to do. Currently, +the only implementation is a limit on how many active client transactions +a service can have. However, it would be easy to refactor this plugin to +allow for adding new limiter policies later on. + +The limit counters and queues are per remap rule only, i.e. there is +(currently) no way to group transaction limits from different remap rules +into a single rate limiter. + +All configuration is done via :file:`remap.config`, and the following options +are available: + +.. program:: rate-limit + +.. option:: --limit + + The maximum number of active client transactions. + +.. option:: --queue + + When the limit (above) has been reached, all new transactions are placed + on a FIFO queue. This option (optional) sets an upper bound on how many + queued transactions we will allow. When this threshold is reached, all + additional transactions are immediately served with an error message. + + The queue is effectively disabled if this is set to `0`, which implies + that when the transaction limit is reached, we immediately start serving + error responses. + + The default queue size is `UINT_MAX`, which is essentially unlimited. + +.. option:: --error + + An optional HTTP status error code, to be used together with the + :option:`--queue` option above. The default is `429`. + +.. option:: --retry + + An optional retry-after value, which if set will cause rejected (e.g. `429`) + responses to also include a header `Retry-After`. + +.. option:: --header + + This is an optional HTTP header name, which will be added to the client + request header IF the transaction was delayed (queued). The value of the + header is the delay, in milliseconds. This can be useful to for example + log the delays for later analysis. + + It is recommended that an `@` header is used here, e.g. `@RateLimit-Delay`, + since this header will not leave the ATS server instance. + +.. option:: --maxage + + An optional `max-age` for how long a transaction can sit in the delay queue. + The value (default 0) is the age in milliseconds. + +Examples +-------- + +This example shows a simple rate limiting of `128` concurently active client Review comment: concurrently -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected]
