I’m unclear on how setting an environment variable impacts starting an Express server. For instance, what does executing TRACE=appServer:* yarn launch exactly do?
using debug=myapp:* tells the app to show extra debug log messages. it basically turns on console logs for modules whose id match that pattern instead of starting the server silently, so u can get more info while troubleshooting.
Using device DEBUG=myapp:* upon starting the server essentially signals the debug module to activate detailed log output for only those components that match the given pattern. In my experience, this is incredibly useful when trying to zero in on specific issues in a large application without being overwhelmed by logs from every module. I’ve often used this approach when troubleshooting Express-based setups, and it has helped pinpoint problems that would otherwise be hidden in standard logs. It effectively lets you control the verbosity on a per-module basis, making debugging considerably more efficient.
Setting DEBUG=myapp:* before starting your Express server tells the application to output selective debug messages that match the myapp:* pattern. From personal experience, this is especially useful in larger applications where you want to reduce the amount of logged information to focus only on specific components or issues. The environment variable is read by the debug library used in the project, and it filters out unrelated logs. This approach allows for efficient troubleshooting, as only the device-specific logs are shown upon startup, thereby simplifying the debugging process.
running npm start with DEBUG=myapp:* tells the appl to only print logs from modules tagged with myapp:. its a smart way to see just the debug messge you need, without the clutter of all other logs.