Delay node - rate limit strange behaviour. Confusing limit rates. Is it lying us (a little)?

ortegafernando · 21 December 2025 09:35

Hi everyone,

I’m having a question about the Delay node in Node-RED when using the rate limit option. (Node red version 4.0.8)

For example, I configured the node to 10 messages per minute, but the behavior is not what I expected.

Instead of allowing up to 10 messages anywhere within the minute, the node seems to allow one message every 6 seconds, as if it were converting the rate limit into a fixed interval. I don't know exactly if it does maths in seconds, miliseconds, ...

In other words:

What I expected: a maximum of 10 messages in any 60-second window
What I get: (see and test example below)

The result is not what I expect, since I need to allow short bursts as long as the total per day is not exceeded.

Is this the expected behavior of the Delay node?
Is there a native way (or a recommended alternative) in Node-RED to implement a true sliding-window rate limit, instead of this strange behaviour?

Thanks in advance for any help.

Example:

The attached flow is a minimal example to show the behavior I’m seeing.
Use two inject nodes.
If you send 5 msg at 1 msg each 7 seconds, all messages are correctly sent to 1st output in delay node
If you send 5 msg at 1 msg each 5 seconds, same of them are sent to 2nd output despite the rate is less than 10 msg/minute.
the 10msg/min node has an strange behaviour, hasn't it?

[
    {
        "id": "5704b41a79567472",
        "type": "tab",
        "label": "Flow 2",
        "disabled": false,
        "info": "",
        "env": []
    },
    {
        "id": "60c6aa58e443d024",
        "type": "debug",
        "z": "5704b41a79567472",
        "name": "debug",
        "active": true,
        "tosidebar": true,
        "console": false,
        "tostatus": false,
        "complete": "true",
        "targetType": "full",
        "statusVal": "",
        "statusType": "auto",
        "x": 1170,
        "y": 260,
        "wires": []
    },
    {
        "id": "fc774e569bf24db2",
        "type": "change",
        "z": "5704b41a79567472",
        "name": "",
        "rules": [
            {
                "t": "set",
                "p": "out",
                "pt": "msg",
                "to": "2nd",
                "tot": "str"
            }
        ],
        "action": "",
        "property": "",
        "from": "",
        "to": "",
        "reg": false,
        "x": 1030,
        "y": 320,
        "wires": [
            [
                "60c6aa58e443d024"
            ]
        ]
    },
    {
        "id": "c67a43335950adbe",
        "type": "delay",
        "z": "5704b41a79567472",
        "name": "10/min",
        "pauseType": "rate",
        "timeout": "5",
        "timeoutUnits": "seconds",
        "rate": "10",
        "nbRateUnits": "1",
        "rateUnits": "minute",
        "randomFirst": "1",
        "randomLast": "5",
        "randomUnits": "seconds",
        "drop": true,
        "allowrate": false,
        "outputs": 2,
        "x": 810,
        "y": 320,
        "wires": [
            [
                "60c6aa58e443d024"
            ],
            [
                "fc774e569bf24db2"
            ]
        ]
    },
    {
        "id": "f9d520e7e8f322f3",
        "type": "inject",
        "z": "5704b41a79567472",
        "name": "",
        "props": [
            {
                "p": "timestamp",
                "v": "",
                "vt": "date"
            }
        ],
        "repeat": "",
        "crontab": "",
        "once": false,
        "onceDelay": 0.1,
        "topic": "",
        "x": 270,
        "y": 320,
        "wires": [
            [
                "455b795e61c69190"
            ]
        ]
    },
    {
        "id": "8eca9fe9dfbcd446",
        "type": "delay",
        "z": "5704b41a79567472",
        "name": "",
        "pauseType": "rate",
        "timeout": "7",
        "timeoutUnits": "seconds",
        "rate": "1",
        "nbRateUnits": "7",
        "rateUnits": "second",
        "randomFirst": "1",
        "randomLast": "5",
        "randomUnits": "seconds",
        "drop": false,
        "allowrate": false,
        "outputs": 1,
        "x": 640,
        "y": 320,
        "wires": [
            [
                "c67a43335950adbe"
            ]
        ]
    },
    {
        "id": "455b795e61c69190",
        "type": "function",
        "z": "5704b41a79567472",
        "name": "send 5 msg",
        "func": "const messages = [];\nfor(let i = 0; i < 5; i++){\n    messages.push({\n        nr: i+1\n    });\n}\nreturn [messages];",
        "outputs": 1,
        "timeout": 0,
        "noerr": 0,
        "initialize": "",
        "finalize": "",
        "libs": [],
        "x": 430,
        "y": 320,
        "wires": [
            [
                "8eca9fe9dfbcd446"
            ]
        ]
    },
    {
        "id": "99f7af637ff2c8f1",
        "type": "inject",
        "z": "5704b41a79567472",
        "name": "",
        "props": [
            {
                "p": "timestamp",
                "v": "",
                "vt": "date"
            }
        ],
        "repeat": "",
        "crontab": "",
        "once": false,
        "onceDelay": 0.1,
        "topic": "",
        "x": 270,
        "y": 400,
        "wires": [
            [
                "7ca23bbaf6e198c4"
            ]
        ]
    },
    {
        "id": "2db82a9f2d0c4fbd",
        "type": "delay",
        "z": "5704b41a79567472",
        "name": "",
        "pauseType": "rate",
        "timeout": "7",
        "timeoutUnits": "seconds",
        "rate": "1",
        "nbRateUnits": "5",
        "rateUnits": "second",
        "randomFirst": "1",
        "randomLast": "5",
        "randomUnits": "seconds",
        "drop": false,
        "allowrate": false,
        "outputs": 1,
        "x": 640,
        "y": 400,
        "wires": [
            [
                "c67a43335950adbe"
            ]
        ]
    },
    {
        "id": "7ca23bbaf6e198c4",
        "type": "function",
        "z": "5704b41a79567472",
        "name": "send 5 msg",
        "func": "const messages = [];\nfor(let i = 0; i < 5; i++){\n    messages.push({\n        nr: i+1\n    });\n}\nreturn [messages];",
        "outputs": 1,
        "timeout": 0,
        "noerr": 0,
        "initialize": "",
        "finalize": "",
        "libs": [],
        "x": 430,
        "y": 400,
        "wires": [
            [
                "2db82a9f2d0c4fbd"
            ]
        ]
    }
]

ortegafernando · 21 December 2025 09:47

Related: The Rate Limit node is lying to you (a little)
@waquete
@HaroldPetersInskipp
Have you found any solution?

dceejay · 21 December 2025 10:04

You are correct in that it converts everything into a single fixed interval. It uses a simple single timer to decide to block or allow the next message through.

ortegafernando · 21 December 2025 10:21

Thanks, I think this behavior is quite confusing given the node’s configuration options and the description in its help text. Even we don't know how it converts: minutes? seconds? miliseconds?

Would it make sense to reconsider or adjust how this works? Unfortunately, I’m not able to implement such a change myself.

mudwalker · 21 December 2025 10:46

You could use a simple gate, open the gate, allow a count of 10 messages to go through, close the gate and then open the gate again after 1 minute (that minute starting when you decide it's reference). You could count the time in milliseconds from the timestamp, when at one minute open gate.

dceejay · 21 December 2025 14:39

A simple function node is a workaround for now

[{"id":"5395ba2ccbd9c367","type":"function","z":"beff51c13e9e8c28","name":"burst filter","func":"const timeout = 10000;  // 10 seconds in milliseconds\nconst burst = 3;        // number in burst\n\nlet inflight = context.inflight || 0;\n\nif (inflight >= burst) { \n    node.status({ fill: \"red\", shape: \"dot\", text: burst });\n    return; \n}\n\ninflight += 1;\n\nsetTimeout(function() {\n    let v = context.inflight\n    v -= 1;\n    context.inflight = v;\n    node.status({ fill: \"green\", shape: \"ring\", text: v });\n}, timeout)\n\ncontext.inflight = inflight;\nnode.status({ fill: \"green\", shape: \"ring\", text: inflight });\n\nreturn msg;","outputs":1,"timeout":0,"noerr":0,"initialize":"","finalize":"","libs":[],"x":285,"y":112.5,"wires":[["343936e38ee83572"]]}]

edit the constants at the top as you desire

ortegafernando · 21 December 2025 17:01

@dceejay Thanks a lot for your proposal. I have found two solutions:

This one: @cameo69/node-red-ratelimit
And yours by adding a 2nd output (in my case it is what I want). I need a daily rate limit that I exactly dont know (api calls) it works. I am not sure if it resets every day at 00:00, or it is like your code (lets say a 24hours timer that reduces inflight counter). But I am going to start your code (it will be easy to change with a first code that checks if we have "changed" the day since de previous call).

It is a pitty not to have this implemented in the delay node itself.

Thanks a lot.

const timeout = 1000*60;  // 60 seconds in milliseconds
const burst = 10;         // number in burst

let inflight = context.inflight || 0;

if (inflight >= burst) { 
    node.status({ fill: "red", shape: "dot", text: burst });
    return [null, msg]; 
}

inflight += 1;

setTimeout(function() {
    let v = context.inflight
    v -= 1;
    context.inflight = v;
    node.status({ fill: "green", shape: "ring", text: v });
}, timeout)

context.inflight = inflight;
node.status({ fill: "green", shape: "ring", text: inflight });

return [msg, null];

dceejay · 21 December 2025 19:48

but maybe...

github.com/node-red/node-red

add burst mode to delay node

dev ← add-burst-mode-to-delay-node

opened 07:46PM - 21 Dec 25 UTC

dceejay

+131 -5

and tests - [ ] Bugfix (non-breaking change which fixes an issue) - [x] …New feature (non-breaking change which adds functionality) ## Proposed changes Adds a burst mode to the delay node as per this discussion - https://discourse.nodered.org/t/delay-node-rate-limit-strange-behaviour-confusing-limit-rates-is-it-lying-us-a-little/100005 - It has also been mentioned several times before that we don't handle bursts so the present implementation is confusing. This PR - add a new mode - burst - (vs the old mode, evenly spaced) - which allows the number of msgs specified through then blocks - using a sliding time window specified to unlock as required... messages can be dropped or sent to the second output. ## Checklist - [x] I have read the [contribution guidelines](https://github.com/node-red/node-red/blob/master/CONTRIBUTING.md) - [x] For non-bugfix PRs, I have discussed this change on the forum/slack team. - [x] I have run `npm run test` to verify the unit tests pass - [x] I have added suitable unit tests to cover the new/changed functionality

ortegafernando · 21 December 2025 23:13

Great, thanks a lot @dceejay! I have just marked this as the solution. (If anyone reads this before the PR is merged, please check the previous post for a temporary solution.)

cameo69 · 22 December 2025 08:12

Hi, you can save the hassle and use the rate limit note. It does exactly what you want. It gives you exactly the number of messages you specify in a sliding window.

Topic		Replies	Views
Delay node set to rate limit omits messages unexpectedly in case of bursts General	23	427	16 March 2023
Delay node- rate limit extension Feature Requests	17	181	2 March 2025
Delay node with rate limit by x msg / x time unit Feature Requests delay , function-node	12	339	8 April 2023
Delay node - rate limit not working for all messages? General delay	26	300	16 December 2024
[enhancement]to Rate limiting in Delay node to work in milliseconds Feature Requests	3	2184	23 August 2018

Delay node - rate limit strange behaviour. Confusing limit rates. Is it lying us (a little)?

Related topics