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Analysing Performance
As mentioned on the Discourse forum, this page can be used to pull together information, hints and tips aimed at analysing and improving the performance of Node-RED systems.
Please feel free to add links to other articles as well as direct hints and tips. If you have queries about this page, please raise them in Discourse or on the Docs channel of Slack.
Before starting more detailed analysis, the first thing to do is to look at the platform being used to run Node-RED.
Often, something like a Raspberry Pi or other single-board computer (SBC) is being used. They have very limited resources and often slow storage (e.g. SD-Cards). So it is very easy to overload them and kill performance.
To analyse this, you need to use a tool such as top. Better still, get something a bit more comprehensive such as glances. Either way, these will tell you how much CPU and memory (RAM) is being used and by what. Start by looking at the three 'load' values, these should all be fairly low, if they are going over about 2-3 regularly then you have an issue.
Next look at the 'swap'. If this is being used regularly, you will have a performance bottleneck because memory (RAM) is being overused. To fix this, you have to unload some services. If using the glances tool, it will show a warning if the memory is swapping.
The easiest way to remove load is likely to be turning off the 'desktop'. This gives you a GUI that you directly interact with via keyboard and monitor. Removing this will remove lots of load on memory and CPU. Have a look at articles that explain how to run your device 'headless'. You will need to be able to connect to your device over the network from another device.
After that, if there are still issues, you need to look at taking off services that you don't actually need running.
Finally, if you still have issues, you will need to think about splitting services between multiple devices or using a more powerful device.
TBC
For any browser performance issues, you firstly need to ensure that the problem is actually coming from something related to Node-RED. So you should turn off any browser extensions before continuing. An extension such as SimpleExtManager for Chromium browsers will assist with easily turning on/off extensions.
It should be noted that the debug panel does have some limitations regarding performance. Though much improved in recent versions of Node-RED, you may still wish to limit the amount of debug output, especially more complex objects such as from the http-in node which can be very large and complex.
Using your browser's developer tools, you are able to record and analyse a performance analysis. The Chromium developer tools have three tabs to help with this. Performance, Memory and Application.
The Performance tab is perhaps the easiest to get going with. Click on that tab and then start profiling. Leave that for an amount of time that you estimate will let you see any ongoing performance issues. That might be just a few seconds or a few minutes. You will want to tick the "memory" option and probably don't need the "Screenshots" option.
The thing to look at first is likely to be the memory utilisation. There is a graph 1/2 way down the display that shows you some important metrics including the "JS Heap". See how big that is getting by hovering over the line. Also look at how fast it is growing. You should see that the heap reduces periodically as the JavaScript engine does a 'garbage collection'.
You can also do multiple recordings and compare the heap over a longer period.
TBC
Some nodes that might help with overall analysis of flow performance:
- node-red-contrib-msg-speed - shows the speed at which messages are flowing.
- node-red-contrib-gc - Analyses the V8 JavaScript engine's garbage collection routines.