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Traces

Custom traces allow you to measure the duration of specific operations in your app, providing insights into performance and behavior of code paths that matter to your business. Traces are implemented using spans from the OpenTelemetry standard.

What are Traces and Spans?​

In OpenTelemetry:

  • A trace represents the entire journey of a request or operation through your system
  • Spans are the building blocks of a trace, representing individual units of work or operations

Each span:

  • Has a name and type
  • Tracks when the operation started and ended
  • Can include attributes (key-value pairs) that provide context
  • Can record errors that occurred during the operation
  • Can have parent-child relationships with other spans
  • Must be ended to properly capture the operation's duration and avoid memory leaks

Embrace uses spans to visualize and analyze the performance of operations in your app.

Creating Spans​

Embrace provides several ways to create custom spans depending on your needs:

Basic Span Creation​

Create a span using the buildSpan method:

let span = Embrace.client?.buildSpan(
    name: "image_processing", 
    type: .performance
).startSpan()

// Your code here
performImageProcessing()

span.end()

Using Closures​

For operations contained within a single function, you can use the closure-based API:

let result = Embrace.recordSpan(
    name: "data_calculation", 
    type: .performance
) { span in
    // Your code here
    let result = performCalculation()

    // Add attributes to the span
    span?.setAttribute(key: "calculation_result", value: result.description)

    return result
}

Async Operations​

For asynchronous operations, start the span before the operation begins and end it when the operation completes:

let span = Embrace.client?.buildSpan(
    name: "network_request", 
    type: .performance
).startSpan()

performAsyncOperation { result, error in
    if let error = error {
        span.recordError(error)
        span.setStatus(.error)
    } else {
        span.setAttribute(key: "result_count", value: result.count.description)
    }
    span.end()
}

Span Attributes​

Add context to your spans with attributes:

let span = Embrace.client?.buildSpan(
    name: "checkout_process", 
    type: .performance
).startSpan()

span.setAttribute(key: "cart_item_count", value: "5")
span.setAttribute(key: "total_amount", value: "99.99")
span.setAttribute(key: "payment_method", value: "credit_card")

// Complete checkout process

span.end()

You can add attributes at any point before the span is ended.

Span Hierarchy​

Create parent-child relationships between spans to represent nested operations:

let parentSpan = Embrace.client?.buildSpan(
    name: "data_sync", 
    type: .performance
).startSpan()

// Start a child span
let childSpan = Embrace.client?.buildSpan(
    name: "fetch_remote_data", 
    type: .performance
)
.setParent(parentSpan)
.startSpan()

fetchRemoteData { result in
    childSpan.end()

    // Create another child span
    let processSpan = Embrace.client?.buildSpan(
        name: "process_data", 
        type: .performance
    )
    .setParent(parentSpan)
    .startSpan()
    
    processData(result) { success in
        processSpan.end()
        parentSpan.end()
    }
}

This creates a hierarchy that helps visualize the relationship between operations.

Custom Span Types​

You can specify a span type to categorize different kinds of operations:

let span = Embrace.client?.buildSpan(
    name: "payment_processing",
    type: .performance // Use SpanType enum values like .performance, .ux, .system
).startSpan()

// Process payment

span.end()

Available span types include:

  • .performance - For performance monitoring
  • .ux - For user experience tracking
  • .system - For system-level operations

Best Practices​

Naming Conventions​

Use clear, descriptive names for your spans. Consider a naming convention such as:

  • Use camelCase for span names to maintain consistency with Swift naming conventions
  • Include the general category followed by the specific operation
  • Be consistent across your codebase

Good examples:

  • networkFetchUserProfile
  • databaseSavePreferences
  • renderingProductList

Granularity​

Choose an appropriate level of granularity for your spans:

  • Too coarse: app_startup (better to break into component parts)
  • Too fine-grained: increment_counter (likely too small to be useful)
  • Just right: image_cache_lookup, user_authentication

Resource Management​

Always end your spans to avoid memory leaks. Consider using Swift's defer statement for safety:

let span = Embrace.client?.buildSpan(
    name: "important_operation", 
    type: .performance
).startSpan()
defer { span.end() }

// Your code here, even if it throws an exception, span will be ended

Capturing Meaningful Data​

Add attributes that would be useful for troubleshooting:

span.setAttribute(key: "user_tier", value: "premium")
span.setAttribute(key: "data_size", value: dataSize.description)
span.setAttribute(key: "retry_count", value: retryCount.description)

Common Use Cases​

API Client Instrumentation​

func fetchUserProfile(userId: String, completion: @escaping (Result<UserProfile, Error>) -> Void) {
    let span = Embrace.client?.buildSpan(
        name: "api_fetch_user_profile", 
        type: .performance
    ).startSpan()
    span.setAttribute(key: "user_id", value: userId)

    apiClient.get("/users/\(userId)") { result in
        switch result {
        case .success(let data):
            span.setAttribute(key: "data_size", value: data.count.description)
            span.end()
            // Process data and call completion
        case .failure(let error):
            span.setAttribute(key: "error.message", value: error.localizedDescription)
            span.status = .error(description: "API request failed")
            span.end()
            completion(.failure(error))
        }
    }
}

Database Operations​

func saveUserPreferences(preferences: Preferences) throws {
    let span = Embrace.client?.buildSpan(
        name: "db_save_preferences", 
        type: .performance
    ).startSpan()
    defer { span.end() }

    span.setAttribute(key: "preference_count", value: preferences.count.description)

    do {
        try database.write { transaction in
            transaction.setObject(preferences, forKey: "user_preferences")
        }
    } catch let error {
        span.setAttribute(key: "error.message", value: error.localizedDescription)
        span.status = .error(description: "Database save failed")
        throw error
    }
}

Performance-Critical Algorithms​

func processFeed(posts: [Post]) -> [ProcessedPost] {
    let span = Embrace.client?.buildSpan(
        name: "algorithm_feed_processing", 
        type: .performance
    ).startSpan()
    span.setAttribute(key: "post_count", value: posts.count.description)

    // Measure the main processing algorithm
    let result = performFeedProcessing(posts)

    span.setAttribute(key: "processed_count", value: result.count.description)
    span.end()

    return result
}

Complex User Flow Examples​

Track user navigation through your app with hierarchical spans:

class NavigationFlowTracker {
    private var userJourneySpan: Span?
    
    func startUserJourney(from startScreen: String) {
        userJourneySpan = Embrace.client?.buildSpan(
            name: "user_journey",
            type: .ux,
            attributes: [
                "journey.start_screen": startScreen,
                "journey.session_id": Embrace.client?.currentSessionId() ?? "unknown"
            ]
        ).startSpan()
    }
    
    func trackScreenTransition(from: String, to: String) {
        let transitionSpan = Embrace.client?.buildSpan(
            name: "screen_transition",
            type: .ux,
            attributes: [
                "transition.from": from,
                "transition.to": to
            ]
        )
        .setParent(userJourneySpan)
        .startSpan()
        
        // Track the transition duration
        defer { transitionSpan?.end() }
        
        // Add transition-specific events
        transitionSpan?.addEvent(name: "transition_started")
        
        // Simulate transition work
        performTransition(from: from, to: to) { success in
            if success {
                transitionSpan?.addEvent(name: "transition_completed")
            } else {
                transitionSpan?.status = .error(description: "Navigation failed")
                transitionSpan?.addEvent(name: "transition_failed")
            }
        }
    }
    
    func endUserJourney(reason: String) {
        userJourneySpan?.setAttribute(key: "journey.end_reason", value: reason)
        userJourneySpan?.end()
        userJourneySpan = nil
    }
}

Game or Interaction Flow Measurement​

Track complex multi-stage user interactions:

class GameFlowTracker {
    private var gameSpan: Span?
    private var roundSpan: Span?
    private var currentRound = 0
    
    func startGame(gameType: String) {
        gameSpan = Embrace.client?.buildSpan(
            name: "game_session",
            type: .ux,
            attributes: [
                "game.type": gameType,
                "game.start_time": ISO8601DateFormatter().string(from: Date())
            ]
        ).startSpan()
    }
    
    func startRound() {
        currentRound += 1
        
        // End previous round if exists
        roundSpan?.end()
        
        // Start new round as child of game span
        roundSpan = Embrace.client?.buildSpan(
            name: "game_round",
            type: .ux,
            attributes: [
                "round.number": String(currentRound),
                "round.start_time": ISO8601DateFormatter().string(from: Date())
            ]
        )
        .setParent(gameSpan)
        .startSpan()
    }
    
    func recordUserAction(action: String, isCorrect: Bool, reactionTime: TimeInterval) {
        let actionSpan = Embrace.client?.buildSpan(
            name: "user_action",
            type: .ux,
            attributes: [
                "action.type": action,
                "action.correct": String(isCorrect),
                "action.reaction_time_ms": String(Int(reactionTime * 1000))
            ]
        )
        .setParent(roundSpan)
        .startSpan()
        
        if !isCorrect {
            actionSpan?.status = .error(description: "Incorrect user action")
        }
        
        actionSpan?.end()
    }
    
    func endRound(score: Int, success: Bool) {
        roundSpan?.setAttribute(key: "round.score", value: String(score))
        roundSpan?.setAttribute(key: "round.success", value: String(success))
        
        if !success {
            roundSpan?.status = .error(description: "Round failed")
        }
        
        roundSpan?.end()
        roundSpan = nil
    }
    
    func endGame(finalScore: Int, totalRounds: Int) {
        gameSpan?.setAttribute(key: "game.final_score", value: String(finalScore))
        gameSpan?.setAttribute(key: "game.total_rounds", value: String(totalRounds))
        gameSpan?.setAttribute(key: "game.average_score", value: String(finalScore / max(totalRounds, 1)))
        gameSpan?.end()
        gameSpan = nil
    }
}

E-commerce Checkout Flow​

Track a complete user purchase journey:

class CheckoutFlowTracker {
    private var checkoutSpan: Span?
    
    func startCheckout(cartValue: Double, itemCount: Int) {
        checkoutSpan = Embrace.client?.buildSpan(
            name: "checkout_flow",
            type: .ux,
            attributes: [
                "checkout.cart_value": String(format: "%.2f", cartValue),
                "checkout.item_count": String(itemCount),
                "checkout.started_at": ISO8601DateFormatter().string(from: Date())
            ]
        ).startSpan()
    }
    
    func trackCheckoutStep(step: String, duration: TimeInterval? = nil) {
        let stepSpan = Embrace.client?.buildSpan(
            name: "checkout_step",
            type: .ux,
            attributes: [
                "step.name": step,
                "step.timestamp": ISO8601DateFormatter().string(from: Date())
            ]
        )
        .setParent(checkoutSpan)
        .startSpan()
        
        if let duration = duration {
            stepSpan?.setAttribute(key: "step.duration_ms", value: String(Int(duration * 1000)))
        }
        
        return stepSpan
    }
    
    func trackPaymentFlow(paymentMethod: String) {
        let paymentSpan = Embrace.client?.buildSpan(
            name: "payment_processing",
            type: .ux,
            attributes: [
                "payment.method": paymentMethod
            ]
        )
        .setParent(checkoutSpan)
        .startSpan()
        
        // Track payment validation
        let validationSpan = Embrace.client?.buildSpan(
            name: "payment_validation",
            type: .performance
        )
        .setParent(paymentSpan)
        .startSpan()
        
        // Simulate payment processing
        DispatchQueue.main.asyncAfter(deadline: .now() + 2.0) {
            validationSpan?.end()
            
            // Track payment completion
            paymentSpan?.setAttribute(key: "payment.status", value: "completed")
            paymentSpan?.end()
        }
    }
    
    func completeCheckout(orderId: String, success: Bool, error: Error? = nil) {
        if success {
            checkoutSpan?.setAttribute(key: "checkout.order_id", value: orderId)
            checkoutSpan?.setAttribute(key: "checkout.status", value: "completed")
        } else {
            checkoutSpan?.setAttribute(key: "checkout.status", value: "failed")
            if let error = error {
                checkoutSpan?.setAttribute(key: "error.message", value: error.localizedDescription)
                checkoutSpan?.status = .error(description: "Checkout failed")
            }
        }
        
        checkoutSpan?.end()
        checkoutSpan = nil
    }
}

SwiftUI Navigation with Embrace Integration​

Track navigation in SwiftUI apps with automatic and manual instrumentation:

struct ShoppingAppView: View {
    @State private var selectedTab = 0
    @State private var showingProductDetail = false
    
    var body: some View {
        TabView(selection: $selectedTab) {
            ProductListView()
                .tabItem { Label("Products", systemImage: "list.bullet") }
                .tag(0)
                .onAppear {
                    trackTabSelection("products")
                }
            
            CartView()
                .tabItem { Label("Cart", systemImage: "cart") }
                .tag(1)
                .onAppear {
                    trackTabSelection("cart")
                }
        }
        .onChange(of: selectedTab) { newTab in
            trackTabChange(to: newTab)
        }
    }
    
    private func trackTabSelection(_ tabName: String) {
        Embrace.recordSpan(
            name: "tab_selection",
            type: .ux,
            attributes: [
                "tab.name": tabName,
                "tab.selection_time": ISO8601DateFormatter().string(from: Date())
            ]
        ) { span in
            // Tab tracking logic here
        }
    }
    
    private func trackTabChange(to newTab: Int) {
        let tabNames = ["products", "cart"]
        guard newTab < tabNames.count else { return }
        
        try? Embrace.client?.metadata.addProperty(
            key: "current_tab",
            value: tabNames[newTab],
            lifespan: .session
        )
    }
}

These examples demonstrate how to create comprehensive trace structures that provide deep insights into user behavior, performance bottlenecks, and application flow patterns.