Kermit Crash Logging - AppCenter

With the kermit-appcenter module, you can setup kermit to automatically send handled exceptions and crash reports to AppCenter.

Setup the AppCenterLogWriter with your Logger. The constructor for both platforms is the same, so in shared code, or in platform-specific Kotlin, run the following:

Logger.addLogWriter(AppCenterLogWriter(Severity.Error, Severity.Error, true))

(Static Config would be similar)

On either platform, you should make sure logging is configured immediately after AppCenter is initialized, to avoid a gap where some other failure may happen but logging is not capturing info.

iOS

For iOS, besides regular logging, you will also want to configure Kotlin's uncaught exception handling. kermit-appcenter provides the setupAppCenterExceptionHook helper function to handle this for you.

If you don't need to make kermit logging calls from Swift/Objective C code, we recommend not exporting Kermit in the framework exposed to your iOS app. To setup Kermit configuration you can make a top level helper method in the iosMain sourceset that you call from Swift code to avoid binary bloat. The same rule of thumb applies to kermit-appcenter and since the added api is only needed for configuration, a Kotlin helper method is almost always the best option. Here is a basic example.

// in Kermit/AppInit.kt
fun setupKermit() {
    Logger.addLogWriter(AppCenterLogWriter(Severity.Error, Severity.Error, true))
    setupAppCenterExceptionHook(Logger)
}

// in AppDelegate.swift
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    ...
    func application(
        _ application: UIApplication, 
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
    ) -> Bool {
        // Note: This MUST be the first two statement, in this order, for Kermit and AppCenter
        // to handle any crashes in your app launch. 
        // If the app crashes before these calls run, it will not show up properly in the dashboard
        AppCenter.start(withAppSecret: "API SECRET", services: [Crashes.self])
        AppInitKt.setupKermit()
        //...
    }
}

If providing instances built from a base Logger via DI, you need to make sure that the setupAppCenterExceptionHook call happens immediately on app launch, not lazily inside a lambda given to your DI framework. Example for Koin:

// in iosMain
fun initKoinIos() {
    val baseLogger = Logger(StaticConfig(logWriterList = listOf(platformLogWriter(), AppCenterLogWriter())))
    // Note that this runs sequentially, not in the lambda pass to the module function
    setupAppCenterExceptionHook(log)

    return initKoin(
        module { 
            factory { (tag: String?) -> if (tag != null) baseLogger.withTag(tag) else baseLogger }
        }
    )
}

// in AppDelegate.swift
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    ...
    func application(
        _ application: UIApplication, 
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
    ) -> Bool {
        // Note: This MUST be the first two statement, in this order, for Kermit and AppCenter
        // to handle any crashes in your app launch. 
        // If the app crashes before these calls run, it will not show up properly in the dashboard
        AppCenter.start(withAppSecret: "API SECRET", services: [Crashes.self])
        MyKoinKt.initKoinIos()
        //...
    }
}

Reading iOS Crash Logs

When a crash occurs in Kotlin code, the stack trace in AppCenter gets lost at the Swift-Kotlin barrier, which can make it difficult to determine the root cause of a crash that happens in Kotlin.

To remedy this, kermit-appcenter reports unhandled Kotlin exceptions as separate, non-fatal exceptions, which will show up in AppCenter with a readable stack trace.

aclassen/kermit-appcenter

Kermit Crash Logging - AppCenter

iOS

Reading iOS Crash Logs