feat: bootstrap initial local evaluation flags (#41)

amplitude · Nov 30, 2023 · 7c5c995 · 7c5c995
1 parent 3d5db9d
commit 7c5c995
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Showing 3 changed files with 76 additions and 0 deletions.
diff --git a/Sources/Experiment/ExperimentClient.swift b/Sources/Experiment/ExperimentClient.swift
@@ -90,6 +90,7 @@ internal class DefaultExperimentClient : NSObject, ExperimentClient {
         self.variants.load()
         self.flags = getFlagStorage(apiKey: self.apiKey, instanceName: self.config.instanceName, storage: storage)
         self.flags.load()
+        self.flags.mergeInitialFlagsWithStorage(config.initialFlags)
     }
 
     public func start(_ user: ExperimentUser? = nil, completion: ((Error?) -> Void)? = nil) -> Void {
@@ -408,6 +409,7 @@ internal class DefaultExperimentClient : NSObject, ExperimentClient {
                         self.flags.clear()
                         self.flags.putAll(values: flags)
                         self.flags.store()
+                        self.flags.mergeInitialFlagsWithStorage(self.config.initialFlags)
                     }
                     completion?(nil)
                 case .failure(let error):
@@ -718,3 +720,19 @@ internal extension EvaluationVariant {
         return Variant(self.value as? String, payload: self.payload, expKey: experimentKey, key: self.key, metadata: metadata)
     }
 }
+
+private extension LoadStoreCache<EvaluationFlag> {
+    func mergeInitialFlagsWithStorage(_ initialFlagsString: String?) {
+        guard let initialFlagsData = initialFlagsString?.data(using: .utf8) else {
+            return
+        }
+        guard let initialFlags = try? JSONDecoder().decode([EvaluationFlag].self, from: initialFlagsData) else {
+            return
+        }
+        for flag in initialFlags {
+            if self.get(key: flag.key) == nil {
+                self.put(key: flag.key, value: flag)
+            }
+        }
+    }
+}
diff --git a/Sources/Experiment/ExperimentConfig.swift b/Sources/Experiment/ExperimentConfig.swift
@@ -22,6 +22,7 @@ import Foundation
     @objc public let debug: Bool
     @objc public let instanceName: String
     @objc public let fallbackVariant: Variant
+    @objc public let initialFlags: String?
     @objc public let initialVariants: [String: Variant]
     @objc public let source: Source
     @objc public let serverUrl: String
@@ -42,6 +43,7 @@ import Foundation
         self.debug = ExperimentConfig.Defaults.debug
         self.instanceName = ExperimentConfig.Defaults.instanceName
         self.fallbackVariant = ExperimentConfig.Defaults.fallbackVariant
+        self.initialFlags = ExperimentConfig.Defaults.initialFlags
         self.initialVariants = ExperimentConfig.Defaults.initialVariants
         self.source = ExperimentConfig.Defaults.source
         self.serverUrl = ExperimentConfig.Defaults.serverUrl
@@ -62,6 +64,7 @@ import Foundation
         self.debug = builder.debug
         self.instanceName = builder.instanceName
         self.fallbackVariant = builder.fallbackVariant
+        self.initialFlags = builder.initialFlags
         self.initialVariants = builder.initialVariants
         self.source = builder.source
         self.serverUrl = builder.serverUrl
@@ -82,6 +85,7 @@ import Foundation
         self.debug = builder.debug
         self.instanceName = builder.instanceName
         self.fallbackVariant = builder.fallbackVariant
+        self.initialFlags = builder.initialFlags
         self.initialVariants = builder.initialVariants
         self.source = builder.source
         self.serverUrl = builder.serverUrl
@@ -102,6 +106,7 @@ import Foundation
         static let debug: Bool = false
         static let instanceName: String = "$default_instance"
         static let fallbackVariant: Variant = Variant()
+        static let initialFlags: String? = nil
         static let initialVariants: [String: Variant] = [:]
         static let source: Source = Source.LocalStorage
         static let serverUrl: String = "https://api.lab.amplitude.com"
@@ -124,6 +129,7 @@ import Foundation
         internal var debug: Bool = ExperimentConfig.Defaults.debug
         internal var instanceName = ExperimentConfig.Defaults.instanceName
         internal var fallbackVariant: Variant = ExperimentConfig.Defaults.fallbackVariant
+        internal var initialFlags: String? = ExperimentConfig.Defaults.initialFlags
         internal var initialVariants: [String: Variant] = ExperimentConfig.Defaults.initialVariants
         internal var source: Source = ExperimentConfig.Defaults.source
         internal var serverUrl: String = ExperimentConfig.Defaults.serverUrl
@@ -161,6 +167,12 @@ import Foundation
             return self
         }
 
+        @discardableResult
+        public func initialFlags(_ initialFlags: String?) -> Builder {
+            self.initialFlags = initialFlags
+            return self
+        }
+
         @discardableResult
         public func initialVariants(_ initialVariants: [String: Variant]) -> Builder {
             self.initialVariants = initialVariants
@@ -268,6 +280,7 @@ import Foundation
             .debug(self.debug)
             .instanceName(self.instanceName)
             .fallbackVariant(self.fallbackVariant)
+            .initialFlags(self.initialFlags)
             .initialVariants(self.initialVariants)
             .source(self.source)
             .serverUrl(self.serverUrl)
@@ -293,6 +306,7 @@ import Foundation
     internal var debug: Bool = ExperimentConfig.Defaults.debug
     internal var instanceName: String = ExperimentConfig.Defaults.instanceName
     internal var fallbackVariant: Variant = ExperimentConfig.Defaults.fallbackVariant
+    internal var initialFlags: String? = ExperimentConfig.Defaults.initialFlags
     internal var initialVariants: [String: Variant] = ExperimentConfig.Defaults.initialVariants
     internal var source: Source = ExperimentConfig.Defaults.source
     internal var serverUrl: String = ExperimentConfig.Defaults.serverUrl
@@ -326,6 +340,12 @@ import Foundation
         return self
     }
 
+    @discardableResult
+    @objc public func initialFlags(_ initialFlags: String?) -> ExperimentConfigBuilder {
+        self.initialFlags = initialFlags
+        return self
+    }
+
     @discardableResult
     @objc public func initialVariants(_ initialVariants: [String: Variant]) -> ExperimentConfigBuilder {
         self.initialVariants = initialVariants

diff --git a/Tests/ExperimentTests/ExperimentClientTests.swift b/Tests/ExperimentTests/ExperimentClientTests.swift
@@ -1149,6 +1149,44 @@ class ExperimentClientTests: XCTestCase {
         client.fetchBlocking(user: user)
         XCTAssertEqual(1, client.fetchCalls)
     }
+
+    func testInitialflags() {
+        let initialFlags = """
+            [
+                {"key":"sdk-ci-test-local","metadata":{"deployed":true,"evaluationMode":"local","flagType":"release","flagVersion":1},"segments":[{"metadata":{"segmentName":"All Other Users"},"variant":"off"}],"variants":{"off":{"key":"off","metadata":{"default":true}},"on":{"key":"on","value":"on"}}},
+                {"key":"sdk-ci-test-local-2","metadata":{"deployed":true,"evaluationMode":"local","flagType":"release","flagVersion":1},"segments":[{"metadata":{"segmentName":"All Other Users"},"variant":"on"}],"variants":{"off":{"key":"off","metadata":{"default":true}},"on":{"key":"on","value":"on"}}}
+            ]
+        """
+        let storage = InMemoryStorage()
+        let config = ExperimentConfigBuilder()
+            .initialFlags(initialFlags)
+            .build()
+        let client = DefaultExperimentClient(apiKey: API_KEY, config: config, storage: storage)
+        let user = ExperimentUserBuilder()
+            .userId("user_id")
+            .deviceId("device_id")
+            .build()
+        client.setUser(user)
+        // before start, should get result from initial flags
+        var variant = client.variant("sdk-ci-test-local")
+        var variant2 = client.variant("sdk-ci-test-local-2")
+        XCTAssertEqual("off", variant.key!)
+        XCTAssertEqual("on", variant2.key!)
+        client.startBlocking(user: user)
+        // After start, should get result from downloaded flag, fallback on initial flag
+        variant = client.variant("sdk-ci-test-local")
+        variant2 = client.variant("sdk-ci-test-local-2")
+        XCTAssertEqual("on", variant.key!)
+        XCTAssertEqual("on", variant2.key!)
+        // Initialize a second client with the same storage to simulate an app restart
+        let client2 = DefaultExperimentClient(apiKey: API_KEY, config: config, storage: storage)
+        client2.setUser(user)
+        // Should get downloaded flag persisted in storage without calling start
+        variant = client2.variant("sdk-ci-test-local")
+        variant2 = client2.variant("sdk-ci-test-local-2")
+        XCTAssertEqual("on", variant.key!)
+        XCTAssertEqual("on", variant2.key!)
+    }
 }
 
 class TestAnalyticsProvider : ExperimentAnalyticsProvider {