Introduce sampling to session events. (#10516)

visumickey · web-flow · commit 611511b0ef3a · 2022-11-28T10:38:37.000-08:00
diff --git a/FirebaseSessions/ProtoSupport/Protos/sessions.proto b/FirebaseSessions/ProtoSupport/Protos/sessions.proto
@@ -79,7 +79,7 @@ message DataCollectionStatus {
   DataCollectionState crashlytics = 2;
   // Any sampling rate being applied to these events on device.
   // 1.0 implies no sampling.
-  float session_sampling_rate = 3;
+  double session_sampling_rate = 3;
 }
 
 // Enum denoting all possible states for SDK data collection.
diff --git a/FirebaseSessions/Protogen/nanopb/sessions.nanopb.c b/FirebaseSessions/Protogen/nanopb/sessions.nanopb.c
@@ -45,7 +45,7 @@ const pb_field_t firebase_appquality_sessions_SessionInfo_fields[6] = {
 const pb_field_t firebase_appquality_sessions_DataCollectionStatus_fields[4] = {
     PB_FIELD(  1, UENUM   , SINGULAR, STATIC  , FIRST, firebase_appquality_sessions_DataCollectionStatus, performance, performance, 0),
     PB_FIELD(  2, UENUM   , SINGULAR, STATIC  , OTHER, firebase_appquality_sessions_DataCollectionStatus, crashlytics, performance, 0),
-    PB_FIELD(  3, FLOAT   , SINGULAR, STATIC  , OTHER, firebase_appquality_sessions_DataCollectionStatus, session_sampling_rate, crashlytics, 0),
+    PB_FIELD(  3, DOUBLE  , SINGULAR, STATIC  , OTHER, firebase_appquality_sessions_DataCollectionStatus, session_sampling_rate, crashlytics, 0),
     PB_LAST_FIELD
 };
 
@@ -104,4 +104,10 @@ PB_STATIC_ASSERT((pb_membersize(firebase_appquality_sessions_SessionEvent, sessi
 #endif
 
 
+/* On some platforms (such as AVR), double is really float.
+ * These are not directly supported by nanopb, but see example_avr_double.
+ * To get rid of this error, remove any double fields from your .proto.
+ */
+PB_STATIC_ASSERT(sizeof(double) == 8, DOUBLE_MUST_BE_8_BYTES)
+
 /* @@protoc_insertion_point(eof) */
diff --git a/FirebaseSessions/Protogen/nanopb/sessions.nanopb.h b/FirebaseSessions/Protogen/nanopb/sessions.nanopb.h
@@ -93,7 +93,7 @@ typedef struct _firebase_appquality_sessions_AppleApplicationInfo {
 typedef struct _firebase_appquality_sessions_DataCollectionStatus {
     firebase_appquality_sessions_DataCollectionState performance;
     firebase_appquality_sessions_DataCollectionState crashlytics;
-    float session_sampling_rate;
+    double session_sampling_rate;
 /* @@protoc_insertion_point(struct:firebase_appquality_sessions_DataCollectionStatus) */
 } firebase_appquality_sessions_DataCollectionStatus;
 
@@ -182,7 +182,7 @@ extern const pb_field_t firebase_appquality_sessions_AppleApplicationInfo_fields
 /* Maximum encoded size of messages (where known) */
 /* firebase_appquality_sessions_SessionEvent_size depends on runtime parameters */
 /* firebase_appquality_sessions_SessionInfo_size depends on runtime parameters */
-#define firebase_appquality_sessions_DataCollectionStatus_size 9
+#define firebase_appquality_sessions_DataCollectionStatus_size 13
 /* firebase_appquality_sessions_ApplicationInfo_size depends on runtime parameters */
 /* firebase_appquality_sessions_AndroidApplicationInfo_size depends on runtime parameters */
 /* firebase_appquality_sessions_AppleApplicationInfo_size depends on runtime parameters */
diff --git a/FirebaseSessions/Sources/Development/DevEventConsoleLogger.swift b/FirebaseSessions/Sources/Development/DevEventConsoleLogger.swift
@@ -39,6 +39,7 @@ class DevEventConsoleLogger: EventGDTLoggerProtocol {
         data_collection_status
           crashlytics: \(proto.session_data.data_collection_status.crashlytics)
           performance: \(proto.session_data.data_collection_status.performance)
+          session_sampling_rate: \(proto.session_data.data_collection_status.session_sampling_rate)
       application_info
         app_id: \(proto.application_info.app_id.description)
         device_model: \(proto.application_info.device_model.description)
diff --git a/FirebaseSessions/Sources/FirebaseSessions.swift b/FirebaseSessions/Sources/FirebaseSessions.swift
@@ -55,7 +55,11 @@ protocol SessionsProvider {
     let fireLogger = EventGDTLogger(googleDataTransport: googleDataTransport!)
 
     let identifiers = Identifiers(installations: installations)
-    let coordinator = SessionCoordinator(identifiers: identifiers, fireLogger: fireLogger)
+    let coordinator = SessionCoordinator(
+      identifiers: identifiers,
+      fireLogger: fireLogger,
+      sampler: SessionSampler()
+    )
     let initiator = SessionInitiator()
     let appInfo = ApplicationInfo(appID: appID)
     let settings = Settings(appInfo: appInfo)
diff --git a/FirebaseSessions/Sources/FirebaseSessionsError.swift b/FirebaseSessions/Sources/FirebaseSessionsError.swift
@@ -0,0 +1,21 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import Foundation
+
+/// Contains the list of errors that are localized for Firebase Sessions Library
+enum FirebaseSessionsError: Error {
+  /// Event sampling related error
+  case SessionSamplingError
+}
diff --git a/FirebaseSessions/Sources/SessionCoordinator.swift b/FirebaseSessions/Sources/SessionCoordinator.swift
@@ -21,29 +21,40 @@ import Foundation
 class SessionCoordinator {
   let identifiers: IdentifierProvider
   let fireLogger: EventGDTLoggerProtocol
+  let sampler: SessionSamplerProtocol
 
-  init(identifiers: IdentifierProvider, fireLogger: EventGDTLoggerProtocol) {
+  init(identifiers: IdentifierProvider, fireLogger: EventGDTLoggerProtocol,
+       sampler: SessionSamplerProtocol) {
     self.identifiers = identifiers
     self.fireLogger = fireLogger
+    self.sampler = sampler
   }
 
   // Begins the process of logging a SessionStartEvent to FireLog, while taking into account Data Collection, Sampling, and fetching Settings
   func attemptLoggingSessionStart(event: SessionStartEvent,
                                   callback: @escaping (Result<Void, Error>) -> Void) {
-    event.setInstallationID(identifiers: identifiers)
+    if sampler.shouldSendEventForSession(sessionId: identifiers.sessionID) {
+      event.setInstallationID(identifiers: identifiers)
 
-    fireLogger.logEvent(event: event) { result in
-      switch result {
-      case .success():
-        Logger.logInfo("Successfully logged Session Start event to GoogleDataTransport")
-        callback(.success(()))
-      case let .failure(error):
-        Logger
-          .logError(
-            "Error logging Session Start event to GoogleDataTransport: \(error)."
-          )
-        callback(.failure(error))
+      fireLogger.logEvent(event: event) { result in
+        switch result {
+        case .success():
+          Logger.logInfo("Successfully logged Session Start event to GoogleDataTransport")
+          callback(.success(()))
+        case let .failure(error):
+          Logger
+            .logError(
+              "Error logging Session Start event to GoogleDataTransport: \(error)."
+            )
+          callback(.failure(error))
+        }
       }
+    } else {
+      Logger
+        .logInfo(
+          "Session event dropped due to sampling."
+        )
+      callback(.failure(FirebaseSessionsError.SessionSamplingError))
     }
   }
 }
diff --git a/FirebaseSessions/Sources/SessionSampler.swift b/FirebaseSessions/Sources/SessionSampler.swift
@@ -0,0 +1,43 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import Foundation
+
+protocol SessionSamplerProtocol {
+  /// Sampling rate that has to be applied across sessions.
+  /// Ranges from 0 to 1 in Double.
+  var sessionSamplingRate: Double { get set }
+
+  /// Determines if a provided sessionID should be sampled or not.
+  /// Note: Sample means allowed. A return of true means the event should be allowed, else dropped.
+  func shouldSendEventForSession(sessionId: String) -> Bool
+}
+
+class SessionSampler: SessionSamplerProtocol {
+  var sessionSamplingRate: Double
+
+  /// TODO: Update this to a sampling logic once we have the configuration flags in place.
+  /// Currently defaulted to 1.0 where no events are dropped.
+  init(sessionSamplingRate: Double = 1.0) {
+    self.sessionSamplingRate = sessionSamplingRate
+  }
+
+  func shouldSendEventForSession(sessionId: String) -> Bool {
+    let randomValue = Double.random(in: 0 ... 1)
+    if randomValue > sessionSamplingRate {
+      return false
+    }
+    return true
+  }
+}
diff --git a/FirebaseSessions/Sources/SessionStartEvent.swift b/FirebaseSessions/Sources/SessionStartEvent.swift
@@ -60,6 +60,10 @@ class SessionStartEvent: NSObject, GDTCOREventDataObject {
     proto.session_data.firebase_installation_id = makeProtoString(identifiers.installationID)
   }
 
+  func setSamplingRate(samplingRate: Double) {
+    proto.session_data.data_collection_status.session_sampling_rate = samplingRate
+  }
+
   // MARK: - GDTCOREventDataObject
 
   func transportBytes() -> Data {
diff --git a/FirebaseSessions/Tests/Unit/SessionCoordinatorTests.swift b/FirebaseSessions/Tests/Unit/SessionCoordinatorTests.swift
@@ -22,13 +22,19 @@ class SessionCoordinatorTests: XCTestCase {
   var time = MockTimeProvider()
   var fireLogger = MockGDTLogger()
   var appInfo = MockApplicationInfo()
+  var sampler = SessionSampler()
 
   var coordinator: SessionCoordinator!
 
   override func setUp() {
     super.setUp()
 
-    coordinator = SessionCoordinator(identifiers: identifiers, fireLogger: fireLogger)
+    coordinator = SessionCoordinator(
+      identifiers: identifiers,
+      fireLogger: fireLogger,
+      sampler: sampler
+    )
+    sampler.sessionSamplingRate = 1.0
   }
 
   func test_attemptLoggingSessionStart_logsToGDT() throws {
@@ -84,4 +90,43 @@ class SessionCoordinatorTests: XCTestCase {
     XCTAssertEqual(fireLogger.loggedEvent, event)
     XCTAssertFalse(resultSuccess)
   }
+
+  func test_eventNotDropped_handlesAllEventsAllowed() throws {
+    identifiers.mockAllValidIDs()
+
+    let event = SessionStartEvent(identifiers: identifiers, appInfo: appInfo, time: time)
+
+    sampler.sessionSamplingRate = 1.0
+    var resultSuccess = true
+    coordinator.attemptLoggingSessionStart(event: event) { result in
+      switch result {
+      case .success(()):
+        resultSuccess = true
+      case .failure:
+        resultSuccess = false
+      }
+    }
+
+    XCTAssertTrue(resultSuccess)
+  }
+
+  func test_eventDropped_handlesZeroSamplingRate() throws {
+    identifiers.mockAllValidIDs()
+
+    let event = SessionStartEvent(identifiers: identifiers, appInfo: appInfo, time: time)
+
+    sampler.sessionSamplingRate = 0.0
+
+    var resultSuccess = true
+    coordinator.attemptLoggingSessionStart(event: event) { result in
+      switch result {
+      case .success(()):
+        resultSuccess = true
+      case .failure:
+        resultSuccess = false
+      }
+    }
+
+    XCTAssertFalse(resultSuccess)
+  }
 }
diff --git a/FirebaseSessions/Tests/Unit/SessionSamplerTests.swift b/FirebaseSessions/Tests/Unit/SessionSamplerTests.swift
@@ -0,0 +1,40 @@
+//
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import XCTest
+
+@testable import FirebaseSessions
+
+class SessionSamplerTests: XCTestCase {
+  /// Validates if the default sampling rate is to allow all events.
+  func test_defaultSamplingRate() {
+    let localSampler = SessionSampler()
+    XCTAssertEqual(localSampler.sessionSamplingRate, 1.0)
+  }
+
+  /// Validates if the events are disabled when the sampling rate is Zero.
+  func test_disablesEventCollection_samplingRateZero() {
+    let localSampler = SessionSampler(sessionSamplingRate: 0.0)
+    XCTAssertEqual(localSampler.shouldSendEventForSession(sessionId: "random"), false)
+    XCTAssertEqual(localSampler.shouldSendEventForSession(sessionId: "anyEvent"), false)
+  }
+
+  /// Validates if the events are allowed when the sampling rate is One.
+  func test_allowsEventCollection_samplingRateOne() {
+    let localSampler = SessionSampler(sessionSamplingRate: 1.0)
+    XCTAssertEqual(localSampler.shouldSendEventForSession(sessionId: "random"), true)
+    XCTAssertEqual(localSampler.shouldSendEventForSession(sessionId: "anyEvent"), true)
+  }
+}

Original file line number	Diff line number	Diff line change
`@@ -79,7 +79,7 @@ message DataCollectionStatus {`
`79`	`79`	`DataCollectionState crashlytics = 2;`
`80`	`80`	`// Any sampling rate being applied to these events on device.`
`81`	`81`	`// 1.0 implies no sampling.`
`82`		`- float session_sampling_rate = 3;`
	`82`	`+ double session_sampling_rate = 3;`
`83`	`83`	`}`
`84`	`84`
`85`	`85`	`// Enum denoting all possible states for SDK data collection.`
Original file line number	Diff line number	Diff line change
`@@ -60,6 +60,10 @@ class SessionStartEvent: NSObject, GDTCOREventDataObject {`
`60`	`60`	`proto.session_data.firebase_installation_id = makeProtoString(identifiers.installationID)`
`61`	`61`	`}`
`62`	`62`
	`63`	`+ func setSamplingRate(samplingRate: Double) {`
	`64`	`+ proto.session_data.data_collection_status.session_sampling_rate = samplingRate`
	`65`	`+ }`
	`66`	`+`
`63`	`67`	`// MARK: - GDTCOREventDataObject`
`64`	`68`
`65`	`69`	`func transportBytes() -> Data {`