| // ======================================================================== |
| // Copyright (c) 1995-2017 Mort Bay Consulting Pty. Ltd. |
| // ======================================================================== |
| // All rights reserved. This program and the accompanying materials |
| // are made available under the terms of the Eclipse Public License v1.0 |
| // and Apache License v2.0 which accompanies this distribution. |
| // |
| // The Eclipse Public License is available at |
| // http://www.eclipse.org/legal/epl-v10.html |
| // |
| // The Apache License v2.0 is available at |
| // http://www.opensource.org/licenses/apache2.0.php |
| // |
| // You may elect to redistribute this code under either of these licenses. |
| // ======================================================================== |
| |
| [[limit-load]] |
| === Limiting Load |
| |
| To achieve optimal fair handling for all users of a server, it can be necessary to limit the resources that each user/connection can utilize so as to maximize throughput for the server or to ensure that the entire server runs within the limitations of it's runtime. |
| |
| ==== Low Resources Monitor |
| |
| An instance of link:{JDURL}/org/eclipse/jetty/server/LowResourcesMonitor.html[LowResourcesMonitor] may be added to a Jetty server to monitor for low resources situations and to take action to limit the number of idle connections on the server. |
| To configure the low resources monitor, you can enable the the `lowresources.mod` on the command line, which has the effect of including the following XML configuration: |
| |
| [source, xml, subs="{sub-order}"] |
| ---- |
| include::{SRCDIR}/jetty-server/src/main/config/etc/jetty-lowresources.xml[] |
| ---- |
| |
| The monitor is configured with a period in milliseconds at which it will scan the server looking for a low resources condition, which may be one of: |
| |
| * If `monitorThreads` is configured as true and a connectors Executor is an instance of link:{JDURL}/org/eclipse/jetty/util/thread/ThreadPool.html[ThreadPool], then its `isLowOnThreads()` method is used to detect low resources. |
| * If `maxConnections` is configured to a number >0 then if the total number of connections from all monitored connectors exceeds this value, then low resources state is entered. |
| * If the `maxMemory` field is configured to a number of bytes >0 then if the JVMs total memory minus its idle memory exceeds this value, then low resources state is entered. |
| |
| Once low resources state is detected, then the monitor will iterate over all existing connections and set their `IdleTimeout` to its configured `lowResourcesIdleTimeout` in milliseconds. |
| This allows the idle time of existing connections to be reduced so that the connection is quickly closed if no further request are received. |
| |
| If the low resources state persists longer than the time in milliseconds configured for the `maxLowResourcesTime` field, the the `lowResourcesIdleTimeout` is repeatedly applied so that new connections as well as existing connections will be limited. |
