Telemetry module for Swift (#369)

Sources/Segment/Analytics.swift

@@ -87,6 +87,15 @@ public class Analytics {
 
         // Get everything running
         platformStartup()
+
+        Telemetry.shared.increment(metric: Telemetry.INVOKE_METRIC) {it in 
+            it["message"] = "configured"
+            it["apihost"] = configuration.values.apiHost
+            it["cdnhost"] = configuration.values.cdnHost
+            it["flush"] =
+                "at:\(configuration.values.flushAt) int:\(configuration.values.flushInterval) pol:\(configuration.values.flushPolicies.count)"
+            it["config"] = "seg:\(configuration.values.autoAddSegmentDestination) ua:\(configuration.values.userAgent ?? "N/A")"
+        }
     }
 
     deinit {

Sources/Segment/Errors.swift

@@ -73,6 +73,12 @@ extension Analytics {
         if fatal {
             exceptionFailure("A critical error occurred: \(translatedError)")
         }
+        Telemetry.shared.error(metric: Telemetry.INVOKE_ERROR_METRIC, log: Thread.callStackSymbols.joined(separator: "\n")) { 
+                (_ it: inout [String: String]) in
+                it["error"] = "\(translatedError)"
+                it["writekey"] = configuration.values.writeKey
+                it["caller"] = Thread.callStackSymbols[3]
+            }
     }
 
     static public func reportInternalError(_ error: Error, fatal: Bool = false) {
@@ -83,5 +89,9 @@ extension Analytics {
         if fatal {
             exceptionFailure("A critical error occurred: \(translatedError)")
         }
+        Telemetry.shared.error(metric: Telemetry.INVOKE_ERROR_METRIC, log: Thread.callStackSymbols.joined(separator: "\n")) { 
+                (_ it: inout [String: String]) in
+                it["error"] = "\(translatedError)"
+            }
     }
 }

Sources/Segment/Plugins/StartupQueue.swift

@@ -20,6 +20,9 @@ public class StartupQueue: Plugin, Subscriber {
             analytics?.store.subscribe(self) { [weak self] (state: System) in
                 self?.runningUpdate(state: state)
             }
+            if let store = analytics?.store {
+                Telemetry.shared.subscribe(store)
+            }
         }
     }
 

Sources/Segment/Timeline.swift

@@ -65,10 +65,20 @@ public class Timeline {
 internal class Mediator {
     internal func add(plugin: Plugin) {
         plugins.append(plugin)
+        Telemetry.shared.increment(metric: Telemetry.INTEGRATION_METRIC) {
+            (_ it: inout [String: String]) in
+            it["message"] = "added"
+            it["plugin"] = "\(plugin.type)-\(String(describing: plugin))"
+        }
     }
 
     internal func remove(plugin: Plugin) {
         plugins.removeAll { (storedPlugin) -> Bool in
+            Telemetry.shared.increment(metric: Telemetry.INTEGRATION_METRIC) {
+                (_ it: inout [String: String]) in
+                it["message"] = "removed"
+                it["plugin"] = "\(plugin.type)-\(String(describing: plugin))"
+            }
             return plugin === storedPlugin
         }
     }
@@ -86,6 +96,11 @@ internal class Mediator {
                 } else {
                     result = plugin.execute(event: r)
                 }
+                Telemetry.shared.increment(metric: Telemetry.INTEGRATION_METRIC) {
+                    (_ it: inout [String: String]) in
+                    it["message"] = "event-\(r.type ?? "unknown")"
+                    it["plugin"] = "\(plugin.type)-\(String(describing: plugin))"
+                }
             }
         }
 

Sources/Segment/Utilities/Telemetry.swift

@@ -0,0 +1,313 @@
+import Foundation
+import Sovran
+
+public struct RemoteMetric: Codable {
+    let type: String
+    let metric: String
+    var value: Int
+    let tags: [String: String]
+    let log: [String: String]?
+
+    init(type: String, metric: String, value: Int, tags: [String: String], log: [String: String]? = nil) {
+        self.type = type
+        self.metric = metric
+        self.value = value
+        self.tags = tags
+        self.log = log
+    }
+}
+
+private let METRIC_TYPE = "Counter"
+
+func logError(_ error: Error) {
+    Analytics.reportInternalError(error)
+}
+
+/// A class for sending telemetry data to Segment.
+/// This system is used to gather usage and error data from the SDK for the purpose of improving the SDK.
+/// It can be disabled at any time by setting Telemetry.shared.enable to false.
+/// Errors are sent with a write key, which can be disabled by setting Telemetry.shared.sendWriteKeyOnError to false.
+/// All data is downsampled and no PII is collected.
+public class Telemetry: Subscriber {
+    public static let shared = Telemetry(session: HTTPSessions.urlSession())
+    private static let METRICS_BASE_TAG = "analytics_mobile"
+    public static let INVOKE_METRIC = "\(METRICS_BASE_TAG).invoke"
+    public static let INVOKE_ERROR_METRIC = "\(METRICS_BASE_TAG).invoke.error"
+    public static let INTEGRATION_METRIC = "\(METRICS_BASE_TAG).integration.invoke"
+    public static let INTEGRATION_ERROR_METRIC = "\(METRICS_BASE_TAG).integration.invoke.error"
+
+    init(session: any HTTPSession) {
+        self.session = session
+    }
+
+    /// A Boolean value indicating whether to enable telemetry.
+    #if DEBUG
+    public var enable: Bool = false { // Don't collect data in debug mode (i.e. test environments)
+        didSet {
+            if enable {
+                start()
+            }
+        }
+    }
+    #else
+    public var enable: Bool = true {
+        didSet {
+            if enable {
+                start()
+            }
+        }
+    }
+    #endif
+
+    /// A Boolean value indicating whether to send the write key with error metrics.
+    public var sendWriteKeyOnError: Bool = true
+    /// A Boolean value indicating whether to send the error log data with error metrics.
+    public var sendErrorLogData: Bool = false
+    /// A Callback for reporting errors that occur during telemetry.
+    public var errorHandler: ((Error) -> Void)? = logError
+
+    internal var session: any HTTPSession
+    internal var host: String = HTTPClient.getDefaultAPIHost()
+    var sampleRate: Double = 0.10
+    private var flushTimer: Int = 30 * 1000
+    internal var maxQueueSize: Int = 20
+    var errorLogSizeMax: Int = 4000
+
+    static private let MAX_QUEUE_BYTES = 28000
+    var maxQueueBytes: Int = MAX_QUEUE_BYTES {
+        didSet {
+            maxQueueBytes = min(maxQueueBytes, Telemetry.MAX_QUEUE_BYTES)
+        }
+    }
+
+    internal var queue = [RemoteMetric]()
+    private var queueBytes = 0
+    private var queueSizeExceeded = false
+    private var seenErrors = [String: Int]()
+    internal var started = false
+    private var rateLimitEndTime: TimeInterval = 0
+    private var telemetryQueue = DispatchQueue(label: "telemetryQueue")
+    private var telemetryTimer: Timer?
+
+    /// Starts the Telemetry send loop. Requires both `enable` to be set and a configuration to be retrieved from Segment.
+    func start() {
+        guard enable, !started, sampleRate > 0.0 && sampleRate <= 1.0 else { return }
+        started = true
+
+        if Double.random(in: 0...1) > sampleRate {
+            resetQueue()
+        }
+
+        telemetryTimer = Timer.scheduledTimer(withTimeInterval: TimeInterval(flushTimer) / 1000.0, repeats: true) { [weak self] _ in
+            if (!(self?.enable ?? false)) {
+                self?.started = false
+                self?.telemetryTimer?.invalidate()
+            }
+            self?.flush()
+        }
+    }
+
+    /// Resets the telemetry state, including the queue and seen errors.
+    func reset() {
+        telemetryTimer?.invalidate()
+        resetQueue()
+        seenErrors.removeAll()
+        started = false
+        rateLimitEndTime = 0
+    }
+
+    /// Increments a metric with the provided tags.
+    /// - Parameters:
+    ///   - metric: The metric name.
+    ///   - buildTags: A closure to build the tags dictionary.
+    func increment(metric: String, buildTags: (inout [String: String]) -> Void) {
+        var tags = [String: String]()
+        buildTags(&tags)
+
+        guard enable, sampleRate > 0.0 && sampleRate <= 1.0, metric.hasPrefix(Telemetry.METRICS_BASE_TAG), !tags.isEmpty, queueHasSpace() else { return }
+        if Double.random(in: 0...1) > sampleRate { return }
+
+        addRemoteMetric(metric: metric, tags: tags)
+    }
+
+    /// Logs an error metric with the provided log data and tags.
+    /// - Parameters:
+    ///   - metric: The metric name.
+    ///   - log: The log data.
+    ///   - buildTags: A closure to build the tags dictionary.
+    func error(metric: String, log: String, buildTags: (inout [String: String]) -> Void) {
+        var tags = [String: String]()
+        buildTags(&tags)
+
+        guard enable, sampleRate > 0.0 && sampleRate <= 1.0, metric.hasPrefix(Telemetry.METRICS_BASE_TAG), !tags.isEmpty, queueHasSpace() else { return }
+
+        var filteredTags = tags
+        if (!sendWriteKeyOnError) {
+            filteredTags = tags.filter { $0.key.lowercased() != "writekey" }
+        }
+
+        var logData: String? = nil
+        if (sendErrorLogData) {
+            logData = String(log.prefix(errorLogSizeMax))
+        }
+
+        if let errorKey = tags["error"] {
+            if let count = seenErrors[errorKey] {
+                seenErrors[errorKey] = count + 1
+                if Double.random(in: 0...1) > sampleRate { return }
+                addRemoteMetric(metric: metric, tags: filteredTags, value: Int(Double(count) * sampleRate), log: logData)
+                seenErrors[errorKey] = 0
+            } else {
+                addRemoteMetric(metric: metric, tags: filteredTags, log: logData)
+                flush()
+                seenErrors[errorKey] = 0
+            }
+        } else {
+            addRemoteMetric(metric: metric, tags: filteredTags, log: logData)
+        }
+    }
+
+    /// Flushes the telemetry queue, sending the metrics to the server.
+    internal func flush() {
+        guard enable else { return }
+
+        telemetryQueue.sync {
+            guard !queue.isEmpty else { return }
+            if rateLimitEndTime > Date().timeIntervalSince1970 {
+                return
+            }
+            rateLimitEndTime = 0
+
+            do {
+                try send()
+                queueBytes = 0
+            } catch {
+                errorHandler?(error)
+                sampleRate = 0.0
+            }
+        }
+    }
+
+    private func send() throws {
+        guard sampleRate > 0.0 && sampleRate <= 1.0 else { return }
+
+        var sendQueue = [RemoteMetric]()
+        while !queue.isEmpty {
+            var metric = queue.removeFirst()
+            metric.value = Int(Double(metric.value) / sampleRate)
+            sendQueue.append(metric)
+        }
+        queueBytes = 0
+        queueSizeExceeded = false
+
+        let payload = try JSONEncoder().encode(["series": sendQueue])
+        var request = upload(apiHost: host)
+        request.httpBody = payload
+
+        let task = session.dataTask(with: request) { data, response, error in
+            if let error = error {
+                self.errorHandler?(error)
+                return
+            }
+
+            if let httpResponse = response as? HTTPURLResponse, httpResponse.statusCode == 429 {
+                if let retryAfter = httpResponse.allHeaderFields["Retry-After"] as? String, let retryAfterSeconds = TimeInterval(retryAfter) {
+                    self.rateLimitEndTime = retryAfterSeconds + Date().timeIntervalSince1970
+                }
+            }
+        }
+        task.resume()
+    }
+
+    private var additionalTags: [String: String] {
+        var osVersion = ProcessInfo.processInfo.operatingSystemVersionString
+        let osRegex = try! NSRegularExpression(pattern: "[0-9]+", options: [])
+        if let match = osRegex.firstMatch(in: osVersion, options: [], range: NSRange(location: 0, length: osVersion.utf16.count)) {
+            osVersion = (osVersion as NSString).substring(with: match.range)
+        }
+        #if os(iOS)
+        osVersion = "iOS-\(osVersion)"
+        #elseif os(macOS)
+        osVersion = "macOS-\(osVersion)"
+        #elseif os(tvOS)
+        osVersion = "tvOS-\(osVersion)"
+        #elseif os(watchOS)
+        osVersion = "watchOS-\(osVersion)"
+        #else
+        osVersion = "unknown-\(osVersion)"
+        #endif
+
+        return [
+            "os": "\(osVersion)",
+            "library": "analytics.swift",
+            "library_version": __segment_version
+        ]
+    }
+
+    private func addRemoteMetric(metric: String, tags: [String: String], value: Int = 1, log: String? = nil) {
+        let fullTags = tags.merging(additionalTags) { (_, new) in new }
+
+        telemetryQueue.sync {
+            if var found = queue.first(where: { $0.metric == metric && $0.tags == fullTags }) {
+                found.value += value
+                return
+            }
+
+            let newMetric = RemoteMetric(
+                type: METRIC_TYPE,
+                metric: metric,
+                value: value,
+                tags: fullTags,
+                log: log != nil ? ["timestamp": Date().iso8601() , "trace": log!] : nil
+            )
+            let newMetricSize = String(describing: newMetric).data(using: .utf8)?.count ?? 0
+            if queueBytes + newMetricSize <= maxQueueBytes {
+                queue.append(newMetric)
+                queueBytes += newMetricSize
+            } else {
+                queueSizeExceeded = true
+            }
+        }
+    }
+
+    /// Subscribes to the given store to receive system updates.
+    /// - Parameter store: The store on which a sampleRate setting is expected.
+    public func subscribe(_ store: Store) {
+        store.subscribe(self,
+            initialState: true,
+            queue: telemetryQueue,
+            handler: systemUpdate
+        )
+    }
+
+    private func systemUpdate(system: System) {
+        if let settings = system.settings, let sampleRate = settings.metrics?["sampleRate"]?.doubleValue {
+            self.sampleRate = sampleRate
+            start()
+        }
+    }
+
+    private func upload(apiHost: String) -> URLRequest {
+        var request = URLRequest(url: URL(string: "https://\(apiHost)/m")!)
+        request.setValue("text/plain", forHTTPHeaderField: "Content-Type")
+        request.httpMethod = "POST"
+
+        return request
+    }
+
+    private func queueHasSpace() -> Bool {
+        var under = false
+        telemetryQueue.sync {
+            under = queue.count < maxQueueSize
+        }
+        return under
+    }
+
+    private func resetQueue() {
+        telemetryQueue.sync {
+            queue.removeAll()
+            queueBytes = 0
+            queueSizeExceeded = false
+        }
+    }
+}