Just saw this trick, how you can do a for…of loop which also checks if the iterator is null or undefined. Normally, you would check this by another if statement before starting the for..of loop, like here
const d = undefined
if (d) {
for (const x of d ) {
console.log(x)
}
}
or by using a try...catch
try {
for (const x of d) {
console.log(value)
}
} catch (e) {
console.error(e) // TypeError: undefined is not iterable
}
But instead of if or try...catch, you could use d || [], to check if d is Falsy, and if it’s false, no iterations are performed and no errors are thrown. The disadvantage of this approach is that you create an unneeded array and the readability may be poor depending on the situation.
for (const x of d || []) {
console.log(x)
}
Of course, the first and the last option can also be done in one line
if (d) for (const x of d ) console.log(x)
for (const x of d || []) console.log(x)
In my application, I have a function that can take quite a long time to process, depending on the data selected. Two external systems were involved in the processing, so a lot of round trips were made. Of course, I tried to parallelize the calls to the external systems as much as possible, but it still took a long time. During the development in BAS everything worked fine, but during the deployment in BTP I encountered some errors, depending on the amount of data selected.
In the console I could see, that it was a 504 Gateway Timeout.
Luckily, the CAP docs are already explaining the possible reason for this. The approuter has a default timeout of 30 seconds for destinations. This matched my observation, that this issue only occurred when deployed.
In my case, the destination for my backend service is configured in the mta.yaml directly on the approuter. By simply adding the timeout property and by increasing the timeout from 30 seconds to 2 minutes, I could get rid of the errors.
I now noticed that you can also use the original request object and the getSubdomain function of the authInfo object. It’s provided by @sap/xssec and is only available when using XSUAA, means not with mocked authentication. This way you can get the subdomain in a single line:
In your mta.yaml you can define environment variables, which are filled during deployment. They can be filled with MTA Development and Deployment Parameters. Click here for an overview.
To get the URL of your deployed CAP service, simply use the ${default-url} parameter and pass the value to a variable below the properties attribute, e.g. SRV_URL. The approuter has to provide its default-url, which can then be used in the service for a variable, e.g. APPROUTER_URL.
After deployment, you can now access the URL via process.env.SRV_URL in a service handler. During development, simply use the .env file to provide the SRV_URL value.
You can check all the variables via the BTP Cockpit: Subaccount → Space → Select application → User-Provided Variables
Suddenly, some weeks ago, devices in my Zigbee network started to become sometimes unavailable and did not respond. This occurred at random times and on random devices. When checking the Zigbee2MQTT logs, it was flooded with MAC channel access failure error messages.
When searching for this error message, this GitHub issue pointed me to the potential issue: Network Interferences (probably Wi-Fi). See also the official docs here.
I have two ZigBee networks in parallel. One using ZHA and the Conbee II stick running on channel 20. And one using Zigbee2MQTT using a Sonoff ZBDongle-P (CC2652P) running on channel 11, which had the network issues. Without further investigation, I thought, let’s check what channel my own Wi-Fi is using and if it is on channel 11, simply change it to something else (which turned out to be a completely wrong approach). In my FritzBox router, the channel selection was configured as “auto”. So no specific channel set. That made sense to me, as the ZigBee issues randomly appeared, so perhaps only when the Wi-Fi switched to a channel, ZigBee was already using.
Without further investigation, I simply set the Wi-Fi channel to 1, so that it does not interact with Zigbee channel 11 (just to mention it here again: this is completely incorrect!). But things got worse, instead of better.
After reading this great blog post about building a stable Zigbee network and seeing the graph from Metageek about Wi-Fi and Zigbee channels, I noticed my issue…
Wi-Fi Channel 11 <> Zigbee Channel 11
By simply looking at the Metageethek graph, I understood why I made things even worse. My newly selected Wi-Fi channel 1 interfered directly with Zigbee2MQTT channel 11. SmartHomeScene is recommending the following channel settings in their blog post:
Zigbee channel 11, Wi-Fi channel 6 or 11
Zigbee channel 15, Wi-Fi channel 11
Zigbee channel 20, Wi-Fi channel 1
Zigbee channel 25, Wi-Fi channel 1 or 6
So I tried switching my WI-FI to channel to 11, which should not interference with ZigBee channel 11. And yes, Zigbee2MQTT was now running fine, but suddenly the MAC channel access failure error messages appeared on ZHA. Seems like the ZHA ZigBee channel 20 was sill too close to WI-FI channel 11. So I thought, why not using a WI-FI channel, which is completely out of the ZigBee range. I switched my Wi-Fi from channel 11 to channel 13, and everything runs smooth since then. Finally, my ZigBee network is “rock solid”! 🙂
Update 19.04.2024: The Zigbee network was now working without issues for a few days, but suddenly my ESP Devices started to drop off the WI-FI network… When searching, I found this blog post, where it’s recommended to avoid channel 12-14 when using ESP devices. As I didn’t want to get into conflict with the Zigbee network again, I changed the channel from 13 to 12 as a test. And after a few days, I can now say that Zigbee and ESP devices are running smoothly. Finally!
Use the attachLogoutEvent of the ushell container to trigger your approuter logout endpoint, that needs to be configured in your xs-app.json. The code in my launchpad.html looks like this:
