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I tried the file nodes to write and read some JSON. While it works on regular NR it fails when running on the MCU:
flow.jsonOn the MCU this results in: |
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Replies: 3 comments 12 replies
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Thanks for reporting this. It is an interesting problem. This is a continuation of a thread that began here. In summary, the problem is due to having multiple nodes that access the same file. The LittleFS file system used on microcontrollers does not synchronize across concurrent instantiations of a file. That means that bytes written by one node may not be immediately available to another node. In Node-RED on a computer, this is taken care of outside Node-RED. I'm unsure about the best way to provide the behavior on an MCU. It may be that having a single shared instance of the file is the most reliable approach, but it will be some work to investigate that fully and implement. |
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The file-out nodes are set to "overwrite", so from the test cases an exception is only valid for case 5. Also in NR case 1 to 4 does not cause any exceptions on my side. For case 5 NR of course throws: The important difference is that the flow just happily continues to run after the exception, so one could use a catch-node and thus do a test if a certain file exists or not. |
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OK, I'll take a look.
That makes sense. Just out of curiosity, did you confirm that the catch-node is triggered on the error? I ask because, in my experience, there is a some inconsistency in the features each Node-RED node implements. |
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Yes, works nicely. |
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I made a few fixes. The tests now all pass. And Catch Nodes should receive the "file not found" error. The File Node behaviors are complicated, not so much because of Node-RED, but because of how sophisticated file systems are on computers. There may still be differences in some edge cases. But, perhaps it is closer now. |
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I can confirm that it is now working. Again, thanks so much
This still breaks hard upon reading a non existing file.
In a release build, the flow just freezes. In NR you do not get an exception at all when using the catch-node. This node just "eats" the exception and outputs the original payload leading to the exception. |
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By "breaks hard", I understand you to mean "stops on the exception in the debugger." By default, the xsbug does stop on exceptions. That can be disabled if you like.
I'm not sure that the presence of catch-node is responsible for Node-RED not showing an exception. My impression is that Node-RED developers don't generally run connected to a JavaScript debugger, so they won't get a break. Am I misunderstanding? It is easy enough to eliminate this exception by checking if the file exists before instantiating it. I've committed that change. It isn't realistic to expect to eliminate every exception from the runtime though. It is a feature of the language that is commonly used. |
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I was just trying to verify the catch-node stuff. I never used a JS debugger (certainly interesting to watch, you know "Yep, that's the engine") In vanilla NR:When reading from a non existing file without the catch-node: When reading from a non existing file with the catch-node: With you latest change:
Please don't get me wrong. I'm just dabbling around and reporting my findings. If I'm too much of a pain in your neck just tell me. |
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What do you mean by "Vanilla NR"? I assumed you meant "Node-RED running a computer", e.g. nothing to do with an MCU or the implementation of this repository. But... you show that it throws an XS error from the "ralphwetzel\node-red-mcu-plugin" repository. |
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Yes
Was a copy / paste mess up, sorry. Should have read |
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I've taken another look at this. Here's the flow I used. flows.json[
{
"id": "abd95de12314b6a2",
"type": "tab",
"label": "file catch",
"disabled": false,
"info": "",
"env": [],
"_mcu": {
"mcu": false
}
},
{
"id": "0e8f652363aa2a4a",
"type": "inject",
"z": "abd95de12314b6a2",
"name": "",
"props": [
{
"p": "payload"
}
],
"repeat": "",
"crontab": "",
"once": true,
"onceDelay": 0.1,
"topic": "",
"payload": "meaningless payload",
"payloadType": "str",
"_mcu": {
"mcu": false
},
"x": 240,
"y": 160,
"wires": [
[
"cfee59bed1c65735",
"b57a8a76e5c8a9d3"
]
]
},
{
"id": "b00d10e1309ca360",
"type": "catch",
"z": "abd95de12314b6a2",
"name": "catcher",
"scope": [
"cfee59bed1c65735"
],
"uncaught": false,
"_mcu": {
"mcu": false
},
"x": 290,
"y": 320,
"wires": [
[
"b57a8a76e5c8a9d3"
]
]
},
{
"id": "b57a8a76e5c8a9d3",
"type": "debug",
"z": "abd95de12314b6a2",
"name": "debug 85",
"active": true,
"tosidebar": true,
"console": true,
"tostatus": false,
"complete": "true",
"targetType": "full",
"statusVal": "",
"statusType": "auto",
"_mcu": {
"mcu": false
},
"x": 510,
"y": 320,
"wires": []
},
{
"id": "cfee59bed1c65735",
"type": "file in",
"z": "abd95de12314b6a2",
"name": "filer",
"filename": "missing.txt",
"filenameType": "str",
"format": "utf8",
"chunk": false,
"sendError": false,
"encoding": "none",
"allProps": false,
"_mcu": {
"mcu": false
},
"x": 430,
"y": 160,
"wires": [
[]
]
}
]In the Node-RED Editor, here's what it shows.
Using the Node-RED MCU Edition, here are the same messages in xsbug.
They are functionally equivalent. Notes on the differences:
I think these are close enough that we can consider this issue closed for practical purposes. |
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I agree :-) |
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I've taken another look at this. Here's the flow I used.
flows.json
[ { "id": "abd95de12314b6a2", "type": "tab", "label": "file catch", "disabled": false, "info": "", "env": [], "_mcu": { "mcu": false } }, { "id": "0e8f652363aa2a4a", "type": "inject", "z": "abd95de12314b6a2", "name": "", "props": [ { "p": "payload" } ], "repeat": "", "crontab": "", "once": true, "onceDelay": 0.1, "topic": "", "payload": "meaningless payload", "payloadType": "str", "_mcu"…