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65 lines
3.7 KiB
HTML
65 lines
3.7 KiB
HTML
<!--
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Copyright JS Foundation and other contributors, http://js.foundation
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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<script type="text/html" data-help-name="delay">
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<p>Delays each message passing through the node or limits the rate at which they can pass.</p>
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<h3>Inputs</h3>
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<dl class="message-properties">
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<dt class="optional">delay <span class="property-type">number</span></dt>
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<dd>Sets the delay, in milliseconds, to be applied to the message. This
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option only applies if the node is configured to allow the message to
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override the configured default delay interval.</dd>
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<dt class="optional">rate <span class="property-type">number</span></dt>
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<dd>Sets the rate value in milliseconds between messages.
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This node overwrites the existing rate value defined in the node configuration
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when it receives the message which contains <code>msg.rate</code> value in milliSeconds.
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This option only applies if the node is configured to allow the message to
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override the configured default rate interval.</dd>
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<dt class="optional">reset</dt>
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<dd>If the received message has this property set to any value, all
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outstanding messages held by the node are cleared without being sent.</dd>
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<dt class="optional">flush</dt>
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<dd>If the received message has this property set to a numeric value then that many messages
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will be released immediately. If set to any other type (e.g. boolean), then all
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outstanding messages held by the node are sent immediately.</dd>
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<dt class="optional">toFront</dt>
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<dd>When in rate limit mode, if the received message has this property set to boolean <code>true</code>,
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then the message is pushed to the front of the queue and will be released next.
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This can be used in combination with <code>msg.flush=1</code> to resend immediately.
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</dd>
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</dl>
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<h3>Details</h3>
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<p>When configured to delay messages, the delay interval can be a fixed value,
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a random value within a range or dynamically set for each message.
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Each message is delayed independently of any other message, based on
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the time of its arrival.
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</p>
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<p>When configured to rate limit messages, their delivery is spread across
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the configured time period. The status shows the number of messages currently in the queue.
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It can optionally discard intermediate messages as they arrive.</p>
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</p>
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<p>If set to allow override of the rate, the new rate will be applied immediately,
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and will remain in effect until changed again, the node is reset, or the flow is restarted.</p>
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<p>The rate limiting can be applied to all messages, or group them according to
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their <code>msg.topic</code> value. When grouping, intermediate messages are
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automatically dropped. At each time interval, the node can either release
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the most recent message for all topics, or release the most recent message
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for the next topic.
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</p>
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<p><b>Note</b>: In rate limit mode the maximum queue depth can be set by a property in your
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<i>settings.js</i> file. For example <code>nodeMessageBufferMaxLength: 1000,</code>
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</script>
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