A trace is a report of performance data captured between two points in time in your app. Performance Monitoring automatically provides the following types of traces:
App start traces — measure the time between when the user opens the app and when the app is responsive.
Screen traces — span the lifetime of a screen and measure slow and frozen frames.
App in background traces — measure the time when the app is running in the background.
App in foreground traces — measure the time when the app is running in the foreground and available to the user.
Automatic trace definitions
Performance Monitoring uses method calls and notifications in your app to determine when each type of automatic trace starts and stops.
App start traces
iOS
Starts when the application loads the first Object to memory.
Stops after the first successful run loop that occurs after the application
receives the UIApplicationDidBecomeActiveNotification notification.
Android
Starts when the app's FirebasePerfProvider ContentProvider completes its
onCreate method.
Stops when the first activity's onResume() method is called.
Note that if the app was not cold-started by an activity (for example, by a service or broadcast receiver), no trace is generated.
Screen traces
iOS
Starts for every UIViewController in the keyWindow when the app calls
viewDidAppear:.
Stops when the app calls viewDidDisappear:.
Note that screen traces don't capture canonical container view controllers.
Android
Starts for every Activity class when the app calls onActivityStarted().
Stops when the app calls onActivityStopped().
App in background traces
iOS
Starts when the application receives the
UIApplicationWillResignActiveNotification notification.
Stops when it receives the UIApplicationDidBecomeActiveNotification
notification.
Android
Starts when the last activity to leave the foreground has its onStop()
method called.
Stops when the first activity to reach the foreground has its onResume()
method called.
App in foreground traces
iOS
Starts when the application receives the
UIApplicationDidBecomeActiveNotification notification.
Stops when it receives the
UIApplicationWillResignActiveNotification notification.
Android
Starts when the first activity to reach the foreground has its onResume()
method called.
Stops when the last activity to leave the foreground has its onStop()
method called.
View more details on trace samples
You can deep dive into segments of specific traces or network requests in the Firebase console. A random sampling of recorded sessions shows the following information:
CPU: How much user time and system time your app consumes.
Memory: How much heap memory your app uses. Heap memory is the memory used for dynamic allocations, including objects created, objects deallocated, and objects that the app is actively using.
Individual information: Detailed information about a single instance of a trace or network request, including start time, end time, duration, request size, and response size.
Concurrent instances: Information about traces or network requests that happened at the same time.
Device attributes: Information about the device, including app version, model, OS version, radio, and custom attributes.
To see these detailed samples in the Firebase console, you can either:
Open one of your app's traces or network requests, then click See sessions.
Click the link for an attribute's sessions from the specific attribute.
Filter sessions by percentile
The sessions that Performance Monitoring collects are distributed into percentiles for each metric. Sessions in lower percentile ranges have a lower value for the metric than sessions in higher percentile ranges.
To filter the available sessions by percentile, use the percentiles dropdown above the sessions details.
