A simple, cross-platform, lightweight logging framework powered by Swift's built-in features (like print and FileHandle).
This framework was built for both out-of-the-box simplicity when you just need logging, and powerful extensibility for when your enterprise app has specific logging needs.
Six severity levels are defined in this package, but you can define more if you please:
- đŦ
verbose- The lowest builtin priority; anything and everything might be logged at this level - đŠđžâđģ
debug- Usually not included in user-facing logs, but helpful messages for debugging issues in the field - âšī¸
info- Usually the lowest level that appears in user logs, information for power-users who look at logs â ī¸ warning- Describing potential future problems. "Future" might be the next line, the next release, etc.- đ
error- Problems that just happened. A server log might only print lines of this severity or higher. - đ¨
fatal- The only fatal lines in a log file should be the last lines, in the event of a crash
This package also pairs these with some convenient global-scope functions for quick logging:
log(verbose: "Starting...")
log(debug: "TODO: Implement startup procedure")
log(info: "Startup done")
log(warning: "Future versions won't support the `--magically-work` flag")
if username == "BenLeggiero" {
log(error: "You aren't allowed in here")
return
}
if system.environment.isInvalid {
log(fatal: "Environment is invalid")
fatalError()
}Example output, with a channel which allows all messages:
2020-05-19 22:30:06.362Z đŦ Starting...
2020-05-19 22:30:06.362Z đŠđžâđģ TODO: Implement statup procedure
2020-05-19 22:30:06.362Z âšī¸ Startup done
2020-05-19 22:30:06.362Z â ī¸ Future versions won't support the `--magically-work` flag
2020-05-19 22:30:06.362Z đ¨ Environment is invalid
If you want, you can also specify these (and any you make) explicitly:
log(severity: .trace, "\(i) iterations so far")log(severity: .critical, "The system is down!")By default, severities are represented by emoji (like âšī¸ for info and đ for error) so a human can more-easily skim a log. Each can also be represented by a plaintext character or long name (for example, debug's names are đŠđžâđģ, "d", and "debug"). You can set this this per-channel, in case your channel can't handle UTF-16, or in case you just don't like that.
By default, this just logs to the same place as Swift's print statement. Because enterprise apps have different needs, it can also log to stdout, stderr, and any FileHandle. Arbitrarily many of these can operate simultaneously. You can also specify this per-log-call or for all log calls.
If none is specified, the lowest allowed severity is info, since that's the lowest built-in severity which users might care about if they're looking at the logs, but not debugging the code itself.
LogManager.defaultChannels += [
try LogChannel(name: "General Log File", location: .file(path: "/tmp/com.acme.AwesomeApp/general.log")),
try LogChannel(name: "Debug Log File", location: .file(path: "/tmp/com.acme.AwesomeApp/debug.log"), lowestAllowedSeverity: .debug),
try LogChannel(name: "Error Log File", location: .file(path: "/tmp/com.acme.AwesomeApp/errors.log"), lowestAllowedSeverity: .error, logSeverityNameStyle: .short),
]In the above example, info and up log messages will go to Swift's print target, and to a general log file, whereas error and up log messages will go to a specific error log file (which won't contain emoji), and debug log messages (and up) go to a specific debug log file. All channels will receive all error and up log messages. For example:
log(verbose: "This is thrown away")
log(debug: "This only goes to the debug log channel")
log(info: "This goes to most of the log channels")
log(warning: "Same here")
log(error: "This is the first item in the error log; everything gets this")
log(fatal: "Everything gets this too")The above lines will result in these logs:
Everywhere Swift's print usually goes:
2020-05-19 22:30:06.362Z âšī¸ This goes to most of the log channels 2020-05-19 22:30:06.362Z â ī¸ Same here 2020-05-19 22:30:06.362Z đ This is the first item in the error log; everything gets this 2020-05-19 22:30:06.362Z đ¨ Everything gets this too |
/tmp/com.acme.AwesomeApp/general.log
2020-05-19 22:30:06.362Z âšī¸ This goes to most of the log channels 2020-05-19 22:30:06.362Z â ī¸ Same here 2020-05-19 22:30:06.362Z đ This is the first item in the error log; everything gets this 2020-05-19 22:30:06.362Z đ¨ Everything gets this too |
/tmp/com.acme.AwesomeApp/debug.log
2020-05-19 22:30:06.362Z đŠđžâđģ This only goes to the debug log channel 2020-05-19 22:30:06.362Z âšī¸ This goes to most of the log channels 2020-05-19 22:30:06.362Z â ī¸ Same here 2020-05-19 22:30:06.362Z đ This is the first item in the error log; everything gets this 2020-05-19 22:30:06.362Z đ¨ Everything gets this too |
/tmp/com.acme.AwesomeApp/errors.log
2020-05-19 22:30:06.362Z đ This is the first item in the error log; everything gets this 2020-05-19 22:30:06.362Z đ¨ Everything gets this too |
When tracing through code in your logs, it's common to put log statements when a scope is entered and when it's exited. This framework makes such an action first-class and quite easy:
func notable() {
logEntry(); defer { logExit() }
MyApp.notableOperation()
}func longAsyncOperation() {
logEntry(); defer { logExit() }
DispatchQueue.main.async {
logEntry(); defer { logExit() }
longOperation()
}
}