# Weird happening with subflows. Help needed to make sure what is happening

**URL:** <https://discourse.nodered.org/t/weird-happening-with-subflows-help-needed-to-make-sure-what-is-happening/59338>\
**Category:** General\
**Created:** [4 March 2022 01:45 UTC](https://discourse.nodered.org/t/weird-happening-with-subflows-help-needed-to-make-sure-what-is-happening/59338 "2022-03-04T01:45:01Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![Trying\_to\_learn](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/trying_to_learn/32/28400_2.png) [@Trying\_to\_learn](https://discourse.nodered.org/u/Trying_to_learn)\
**Post date:** [4 March 2022 01:45 UTC](https://discourse.nodered.org/t/weird-happening-with-subflows-help-needed-to-make-sure-what-is-happening/59338/1 "2022-03-04T01:45:01Z")

</div>

Sorry, this is not a nice picture.

Slightly birthed from my MQTT thread. But this is now a whole different scenario.

I have a subflow to give me a _userfriendly_ time output.  
3 options:  
For use in log files. The time/date are formatted for ease of reading.  
The second one passes the payload and adds a `msg.time` for use as you want.  
The third is formatted to be used to create file names. (So no `/`'s or `:`'s in it.)

Cutting to the chase:  
The subflow first:

```auto
[{"id":"98a12d23.4caf","type":"subflow","name":"Time Stamp","info":" **3 outputs. 1 - msg.payload holds the time. 2 - msg.time holds the time in a way to be used for reading time in a log file. 3 - outputs nsg.time in a format usable for file names**","category":"","in":[{"x":80,"y":100,"wires":[{"id":"b51453d8.f777"}]}],"out":[{"x":640,"y":180,"wires":[{"id":"537f67d0.440958","port":0},{"id":"b51453d8.f777","port":0}]},{"x":640,"y":230,"wires":[{"id":"b51453d8.f777","port":0},{"id":"436ec434.1175cc","port":0}]},{"x":640,"y":280,"wires":[{"id":"c77ad598.3b98e8","port":0},{"id":"b51453d8.f777","port":0}]}],"env":[],"color":"#FF8888","outputLabels":["For logging use","msg.time","For filename use"],"icon":"node-red/timer.svg"},{"id":"537f67d0.440958","type":"moment","z":"98a12d23.4caf","name":"","topic":"","input":"payload","inputType":"msg","inTz":"Australia/Sydney","adjAmount":0,"adjType":"days","adjDir":"add","format":"YYYY-MM-DD HH:mm:ss","locale":"en_AU","output":"payload","outputType":"msg","outTz":"Australia/Sydney","x":390,"y":180,"wires":[["c77ad598.3b98e8","9a6e708b.c8249"]]},{"id":"c77ad598.3b98e8","type":"string","z":"98a12d23.4caf","name":"","methods":[{"name":"replaceAll","params":[{"type":"str","value":":"},{"type":"str","value":""}]}],"prop":"payload","propout":"payload","object":"msg","objectout":"msg","x":440,"y":280,"wires":[[]]},{"id":"9a6e708b.c8249","type":"change","z":"98a12d23.4caf","name":"TOPIC","rules":[{"t":"move","p":"payload","pt":"msg","to":"time","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":220,"y":230,"wires":[["436ec434.1175cc"]]},{"id":"204888d7.8b194","type":"change","z":"98a12d23.4caf","name":"Save","rules":[{"t":"set","p":"payload","pt":"flow","to":"payload","tot":"msg","dc":true}],"action":"","property":"","from":"","to":"","reg":false,"x":220,"y":140,"wires":[["93239165.b7976"]]},{"id":"436ec434.1175cc","type":"change","z":"98a12d23.4caf","name":"Get","rules":[{"t":"set","p":"payload","pt":"msg","to":"payload","tot":"flow"}],"action":"","property":"","from":"","to":"","reg":false,"x":440,"y":230,"wires":[[]]},{"id":"b51453d8.f777","type":"switch","z":"98a12d23.4caf","name":"check topic","property":"topic","propertyType":"msg","rules":[{"t":"eq","v":"TIMESTAMP","vt":"str"},{"t":"else"}],"checkall":"true","repair":false,"outputs":2,"x":200,"y":100,"wires":[[],["204888d7.8b194"]]},{"id":"93239165.b7976","type":"change","z":"98a12d23.4caf","name":"TimeStamp","rules":[{"t":"set","p":"payload","pt":"msg","to":"","tot":"date"}],"action":"","property":"","from":"","to":"","reg":false,"x":200,"y":180,"wires":[["537f67d0.440958"]]},{"id":"87a8a491.9b6fa8","type":"subflow:98a12d23.4caf","z":"c56bddee.ca0a18","name":"","x":780,"y":3020,"wires":[[],["1b15d15.3819a2f"],[]]}]

```

I finally noticed messages being changed when passing through.  
But not all the time and not all messages. So this really took a lot of chasing to catch.  
(But have I really caught it, or it is just a ghost?)

(Added later one)  
I made the flow below that basically does what happens in the real flow.  
But, it doesn't error/have the bad thing happen.

I hope this is the right link.  
[Post 52](https://discourse.nodered.org/t/mqtt-messages-from-offline-devices/59036/52)

I stuck `debug` nodes all long the flow.  
The messages going into the `timestamp` node are not the same as the ones coming out, and in a critical way different.

The post pretty well shows that as the messages going in are changed coming out.

But not consistently or always.  
So I've maybe found something is _broken_.  
I'm not sure.

Example flow:

```auto
[{"id":"98a12d23.4caf","type":"subflow","name":"Time Stamp","info":" **3 outputs. 1 - msg.payload holds the time. 2 - msg.time holds the time in a way to be used for reading time in a log file. 3 - outputs nsg.time in a format usable for file names**","category":"","in":[{"x":80,"y":100,"wires":[{"id":"b51453d8.f777"}]}],"out":[{"x":640,"y":180,"wires":[{"id":"537f67d0.440958","port":0},{"id":"b51453d8.f777","port":0}]},{"x":640,"y":230,"wires":[{"id":"b51453d8.f777","port":0},{"id":"436ec434.1175cc","port":0}]},{"x":640,"y":280,"wires":[{"id":"c77ad598.3b98e8","port":0},{"id":"b51453d8.f777","port":0}]}],"env":[],"color":"#FF8888","outputLabels":["For logging use","msg.time","For filename use"],"icon":"node-red/timer.svg"},{"id":"537f67d0.440958","type":"moment","z":"98a12d23.4caf","name":"","topic":"","input":"payload","inputType":"msg","inTz":"Australia/Sydney","adjAmount":0,"adjType":"days","adjDir":"add","format":"YYYY-MM-DD HH:mm:ss","locale":"en_AU","output":"payload","outputType":"msg","outTz":"Australia/Sydney","x":390,"y":180,"wires":[["c77ad598.3b98e8","9a6e708b.c8249"]]},{"id":"c77ad598.3b98e8","type":"string","z":"98a12d23.4caf","name":"","methods":[{"name":"replaceAll","params":[{"type":"str","value":":"},{"type":"str","value":""}]}],"prop":"payload","propout":"payload","object":"msg","objectout":"msg","x":440,"y":280,"wires":[[]]},{"id":"9a6e708b.c8249","type":"change","z":"98a12d23.4caf","name":"TOPIC","rules":[{"t":"move","p":"payload","pt":"msg","to":"time","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":220,"y":230,"wires":[["436ec434.1175cc"]]},{"id":"204888d7.8b194","type":"change","z":"98a12d23.4caf","name":"Save","rules":[{"t":"set","p":"payload","pt":"flow","to":"payload","tot":"msg","dc":true}],"action":"","property":"","from":"","to":"","reg":false,"x":220,"y":140,"wires":[["93239165.b7976"]]},{"id":"436ec434.1175cc","type":"change","z":"98a12d23.4caf","name":"Get","rules":[{"t":"set","p":"payload","pt":"msg","to":"payload","tot":"flow"}],"action":"","property":"","from":"","to":"","reg":false,"x":440,"y":230,"wires":[[]]},{"id":"b51453d8.f777","type":"switch","z":"98a12d23.4caf","name":"check topic","property":"topic","propertyType":"msg","rules":[{"t":"eq","v":"TIMESTAMP","vt":"str"},{"t":"else"}],"checkall":"true","repair":false,"outputs":2,"x":200,"y":100,"wires":[[],["204888d7.8b194"]]},{"id":"93239165.b7976","type":"change","z":"98a12d23.4caf","name":"TimeStamp","rules":[{"t":"set","p":"payload","pt":"msg","to":"","tot":"date"}],"action":"","property":"","from":"","to":"","reg":false,"x":200,"y":180,"wires":[["537f67d0.440958"]]},{"id":"91100cee56080bc8","type":"subflow:98a12d23.4caf","z":"c56bddee.ca0a18","name":"","x":830,"y":3440,"wires":[[],["8ad1490198aa65dd"],[]]},{"id":"10e10d6dddcb6f09","type":"inject","z":"c56bddee.ca0a18","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":525.5555267333984,"y":3398.8888206481934,"wires":[["eaa79608a1039501"]]},{"id":"8ad1490198aa65dd","type":"debug","z":"c56bddee.ca0a18","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","statusVal":"","statusType":"auto","x":990,"y":3440,"wires":[]},{"id":"eaa79608a1039501","type":"function","z":"c56bddee.ca0a18","name":"","func":"msg.payload = {\n \"Foo1\":\"This is message 1\"\n}\n\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":665.5555267333984,"y":3398.8888206481934,"wires":[["91100cee56080bc8"]]},{"id":"ed43a81d6c1eb613","type":"function","z":"c56bddee.ca0a18","name":"","func":"msg.payload = {\n \"Foo1\":\"This is message 2\"\n}\n\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":665.5555267333984,"y":3448.8888206481934,"wires":[["91100cee56080bc8"]]},{"id":"be45998c047525f9","type":"inject","z":"c56bddee.ca0a18","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":525.5555267333984,"y":3448.8888206481934,"wires":[["ed43a81d6c1eb613"]]},{"id":"88811bb87213f436","type":"function","z":"c56bddee.ca0a18","name":"1","func":"msg = {\"topic\":\"STATUS/WIFIDEVICEID\",\"payload\":\"{\\\"WIFI_DEVICE\\\":\\\"TimePi\\\",\\\"IP_Address\\\":\\\"192.168.0.99\\\",\\\"Sent\\\":\\\"2022-03-04 11:52:02\\\"}\"}\nreturn msg;\n","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":655.5555267333984,"y":3528.8888206481934,"wires":[["91100cee56080bc8"]]},{"id":"1bbfb630a83eb34a","type":"function","z":"c56bddee.ca0a18","name":"2","func":"msg = {\"topic\":\"STATUS/WIFIDEVICEID\",\"payload\":\"{\\\"WIFI_DEVICE\\\":\\\"BedPi\\\",\\\"IP_Address\\\":\\\"192.168.0.83\\\",\\\"Sent\\\":\\\"2022-03-04 11:52:02\\\"}\"}\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":655.5555267333984,"y":3568.8888206481934,"wires":[["91100cee56080bc8"]]},{"id":"1a774c1781552d6d","type":"function","z":"c56bddee.ca0a18","name":"3","func":"msg = {\"topic\":\"STATUS/WIFIDEVICEID\",\"payload\":\"{\\\"WIFI_DEVICE\\\":\\\"TelePi\\\",\\\"IP_Address\\\":\\\"192.168.0.93\\\",\\\"Sent\\\":\\\"2022-03-04 11:52:02\\\"}\"}\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":655.5555267333984,"y":3608.8888206481934,"wires":[["91100cee56080bc8"]]},{"id":"296a72c2f5c45660","type":"function","z":"c56bddee.ca0a18","name":"4","func":"msg = {\"topic\":\"STATUS/WIFIDEVICEID\",\"payload\":\"{\\\"WIFI_DEVICE\\\":\\\"GPS\\\",\\\"IP_Address\\\":\\\"192.168.0.155\\\"}\"}\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":655.5555267333984,"y":3648.8888206481934,"wires":[["91100cee56080bc8"]]},{"id":"6fe7813002dffefd","type":"inject","z":"c56bddee.ca0a18","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":515.5555267333984,"y":3528.8888206481934,"wires":[["88811bb87213f436"]]},{"id":"40e742fb36ea6bda","type":"inject","z":"c56bddee.ca0a18","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":515.5555267333984,"y":3568.8888206481934,"wires":[["1bbfb630a83eb34a"]]},{"id":"69a1bf2fc28e46b2","type":"inject","z":"c56bddee.ca0a18","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":515.5555267333984,"y":3608.8888206481934,"wires":[["1a774c1781552d6d"]]},{"id":"1acd745e3149e010","type":"inject","z":"c56bddee.ca0a18","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":515.5555267333984,"y":3648.8888206481934,"wires":[["296a72c2f5c45660"]]},{"id":"e04ed4f11944f815","type":"comment","z":"c56bddee.ca0a18","name":"Proof of concept","info":"","x":610,"y":3360,"wires":[]},{"id":"099b1cf6c1d7d1c9","type":"comment","z":"c56bddee.ca0a18","name":"Problems","info":"","x":580,"y":3490,"wires":[]}]

```

What I saw happening is that there were the 4 messages going into the node.  
But when they came out their _device name_ was not the same as it was going in.

This has caused me a lot of grief.

The top two `inject` nodes show you a _Proof of concept_ and a _complex_ message gets through unchanged.

The lower 4 `inject` nodes are copies of the messages going in.

On testing a couple of times (of course) they worked.

But to _put it out there_.....

And looking at that link/thread...  
What else could I be missing?

Best I can see it is something to do with the subflow.

I sat there for about 20 minutes and a text editor collating the messages from the side window.  
After all that, I saw that what was going in was NOT what was coming out and parts of the message had been changed - for reason/s unknown to me.

Thanks very much in advance for help.

---

<div class="post-metadata">

**Author:** ![Steve-Mcl](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/steve-mcl/32/4826_2.png) [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)\
**Post date:** [4 March 2022 08:14 UTC](https://discourse.nodered.org/t/weird-happening-with-subflows-help-needed-to-make-sure-what-is-happening/59338/2 "2022-03-04T08:14:13Z")

</div>

Hi Andrew, this is a common pitfall of using context + asynchronous processes - when it is not necessary.

In simple terms, when 2 `msg`s arrive in your subflow in quick concession, the `payload` you store in `flow.payload` is updated by the 2nd `msg` and is then applied to the 1st `msg`

PROOF Your subflow vs my modified version (not using context)...

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/c/c/cc5fd303d85fcff420f1d53490b51919caa34697.png)

## Updated Subflow

Items changed ...

- change node 'save'
- change node 'get'

```auto
[{"id":"ea4c0247439a4f0a","type":"subflow","name":"Time Stamp (2)","info":" **3 outputs. 1 - msg.payload holds the time. 2 - msg.time holds the time in a way to be used for reading time in a log file. 3 - outputs nsg.time in a format usable for file names**","category":"","in":[{"x":80,"y":100,"wires":[{"id":"c652c017772e746d"}]}],"out":[{"x":640,"y":180,"wires":[{"id":"11d31e72e9e6efd2","port":0},{"id":"c652c017772e746d","port":0}]},{"x":640,"y":230,"wires":[{"id":"c652c017772e746d","port":0},{"id":"b87362142aacfecb","port":0}]},{"x":640,"y":280,"wires":[{"id":"0bfc1ccb9e5a2129","port":0},{"id":"c652c017772e746d","port":0}]}],"env":[],"color":"#FF8888","outputLabels":["For logging use","msg.time","For filename use"],"icon":"node-red/timer.svg"},{"id":"11d31e72e9e6efd2","type":"moment","z":"ea4c0247439a4f0a","name":"","topic":"","input":"payload","inputType":"msg","inTz":"Australia/Sydney","adjAmount":0,"adjType":"days","adjDir":"add","format":"YYYY-MM-DD HH:mm:ss","locale":"en_AU","output":"payload","outputType":"msg","outTz":"Australia/Sydney","x":390,"y":180,"wires":[["0bfc1ccb9e5a2129","6d98c0e06ccb6ad8"]]},{"id":"0bfc1ccb9e5a2129","type":"string","z":"ea4c0247439a4f0a","name":"","methods":[{"name":"replaceAll","params":[{"type":"str","value":":"},{"type":"str","value":""}]}],"prop":"payload","propout":"payload","object":"msg","objectout":"msg","x":440,"y":280,"wires":[[]]},{"id":"6d98c0e06ccb6ad8","type":"change","z":"ea4c0247439a4f0a","name":"TOPIC","rules":[{"t":"move","p":"payload","pt":"msg","to":"time","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":220,"y":230,"wires":[["b87362142aacfecb"]]},{"id":"be17b2ddd2419f8d","type":"change","z":"ea4c0247439a4f0a","name":"Save","rules":[{"t":"set","p":"origPayload","pt":"msg","to":"payload","tot":"msg","dc":true}],"action":"","property":"","from":"","to":"","reg":false,"x":220,"y":140,"wires":[["4ef466d92e42d925"]]},{"id":"b87362142aacfecb","type":"change","z":"ea4c0247439a4f0a","name":"Get","rules":[{"t":"set","p":"payload","pt":"msg","to":"origPayload","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":440,"y":230,"wires":[[]]},{"id":"c652c017772e746d","type":"switch","z":"ea4c0247439a4f0a","name":"check topic","property":"topic","propertyType":"msg","rules":[{"t":"eq","v":"TIMESTAMP","vt":"str"},{"t":"else"}],"checkall":"true","repair":false,"outputs":2,"x":200,"y":100,"wires":[[],["be17b2ddd2419f8d"]]},{"id":"4ef466d92e42d925","type":"change","z":"ea4c0247439a4f0a","name":"TimeStamp","rules":[{"t":"set","p":"payload","pt":"msg","to":"","tot":"date"}],"action":"","property":"","from":"","to":"","reg":false,"x":200,"y":180,"wires":[["11d31e72e9e6efd2"]]},{"id":"d2b6a96451037ba7","type":"subflow:ea4c0247439a4f0a","z":"bd35015ba96e019f","name":"","x":1900,"y":800,"wires":[[],["e7ffd856ca1c2d0f"],[]]}]

```

---

<div class="post-metadata">

**Author:** ![Trying\_to\_learn](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/trying_to_learn/32/28400_2.png) [@Trying\_to\_learn](https://discourse.nodered.org/u/Trying_to_learn)\
**Post date:** [4 March 2022 12:31 UTC](https://discourse.nodered.org/t/weird-happening-with-subflows-help-needed-to-make-sure-what-is-happening/59338/3 "2022-03-04T12:31:08Z")

</div>

{{@Steve-Mcl }}

Thanks.

I was suspicious but wasn't confident enough to really believe that.

I _thought_ (and you know what _he_ did....) that subflows kind of looked after themselves.

But I guess there are limits.

I can't sleep and it is 23:30 local here.

I'll download your modified subflow and learn from it.

---

<div class="post-metadata">

**Author:** ![Trying\_to\_learn](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/trying_to_learn/32/28400_2.png) [@Trying\_to\_learn](https://discourse.nodered.org/u/Trying_to_learn)\
**Post date:** [4 March 2022 12:34 UTC](https://discourse.nodered.org/t/weird-happening-with-subflows-help-needed-to-make-sure-what-is-happening/59338/4 "2022-03-04T12:34:50Z")

</div>

Very good!

I was _suspicious_ that may be how you did it.  
😉

Too easy.

Now rolling the changes out to all the machines.

---

<div class="post-metadata">

**Author:** ![Steve-Mcl](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/steve-mcl/32/4826_2.png) [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)\
**Post date:** [4 March 2022 12:35 UTC](https://discourse.nodered.org/t/weird-happening-with-subflows-help-needed-to-make-sure-what-is-happening/59338/5 "2022-03-04T12:35:55Z")

</div>

> [@Trying\_to\_learn](#):
>
> I _thought_ (and you know what _he_ did....) that subflows kind of looked after themselves.

Well they do. but if you misuse context, this is the result.

In order to understand the issue you need to either be aware of what happens under the hood OR follow best practices.

1st best practice : "Dont use context unless there is no other way"  
2nd best practice : "If you use context, consider what would happen if 2 or more messages arrive in quick succession"

---

<div class="post-metadata">

**Author:** ![Trying\_to\_learn](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/trying_to_learn/32/28400_2.png) [@Trying\_to\_learn](https://discourse.nodered.org/u/Trying_to_learn)\
**Post date:** [4 March 2022 12:39 UTC](https://discourse.nodered.org/t/weird-happening-with-subflows-help-needed-to-make-sure-what-is-happening/59338/6 "2022-03-04T12:39:56Z")

</div>

I do agree.

I didn't think - at the time - to _move_ the `payload` to another name and just keep it with the message.

And please understand this subflow was written probably a few years ago when I was REALLY at the bottom of the learning curve.

I guess this (problem) has been sneaking up on me for a while now as I have been getting weird messages slowly more and more.

Probably because every now and then I would get a burst of messages and it would throw that subflow.

Again: Thanks for that. It is probably a page one mistake. But I guess sometimes you have to make the mistake to learn from it.

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [18 March 2022 12:40 UTC](https://discourse.nodered.org/t/weird-happening-with-subflows-help-needed-to-make-sure-what-is-happening/59338/7 "2022-03-18T12:40:35Z")

</div>

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