chore: cache flags, distinct id and anon id in memory to avoid file I…

…O every time (#177)
PostHog · Sep 2, 2024 · ba8b00e · ba8b00e
1 parent a54c525
commit ba8b00e
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Showing 5 changed files with 80 additions and 19 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,5 +1,7 @@
 ## Next
 
+- chore: cache flags, distinct id and anon id in memory to avoid file IO every time ([#177](https://github.com/PostHog/posthog-ios/pull/177))
+
 ## 3.8.1 - 2024-08-30
 
 - fix: do not clear events when reset is called ([#175](https://github.com/PostHog/posthog-ios/pull/175))

diff --git a/PostHog/PostHogFeatureFlags.swift b/PostHog/PostHogFeatureFlags.swift
@@ -17,6 +17,9 @@ class PostHogFeatureFlags {
     private var loadingFeatureFlags = false
     private var sessionReplayFlagActive = false
 
+    private var featureFlags: [String: Any]?
+    private var featureFlagPayloads: [String: Any]?
+
     private let dispatchQueue = DispatchQueue(label: "com.posthog.FeatureFlags",
                                               target: .global(qos: .utility))
 
@@ -94,18 +97,18 @@ class PostHogFeatureFlags {
 
                 self.featureFlagsLock.withLock {
                     if errorsWhileComputingFlags {
-                        let cachedFeatureFlags = self.storage.getDictionary(forKey: .enabledFeatureFlags) as? [String: Any] ?? [:]
-                        let cachedFeatureFlagsPayloads = self.storage.getDictionary(forKey: .enabledFeatureFlagPayloads) as? [String: Any] ?? [:]
+                        let cachedFeatureFlags = self.getCachedFeatureFlags() ?? [:]
+                        let cachedFeatureFlagsPayloads = self.getCachedFeatureFlagPayload() ?? [:]
 
                         let newFeatureFlags = cachedFeatureFlags.merging(featureFlags) { _, new in new }
                         let newFeatureFlagsPayloads = cachedFeatureFlagsPayloads.merging(featureFlagPayloads) { _, new in new }
 
                         // if not all flags were computed, we upsert flags instead of replacing them
-                        self.storage.setDictionary(forKey: .enabledFeatureFlags, contents: newFeatureFlags)
-                        self.storage.setDictionary(forKey: .enabledFeatureFlagPayloads, contents: newFeatureFlagsPayloads)
+                        self.setCachedFeatureFlags(newFeatureFlags)
+                        self.setCachedFeatureFlagPayload(newFeatureFlagsPayloads)
                     } else {
-                        self.storage.setDictionary(forKey: .enabledFeatureFlags, contents: featureFlags)
-                        self.storage.setDictionary(forKey: .enabledFeatureFlagPayloads, contents: featureFlagPayloads)
+                        self.setCachedFeatureFlags(featureFlags)
+                        self.setCachedFeatureFlagPayload(featureFlagPayloads)
                     }
                 }
 
@@ -129,7 +132,7 @@ class PostHogFeatureFlags {
     func getFeatureFlags() -> [String: Any]? {
         var flags: [String: Any]?
         featureFlagsLock.withLock {
-            flags = self.storage.getDictionary(forKey: .enabledFeatureFlags) as? [String: Any]
+            flags = self.getCachedFeatureFlags()
         }
 
         return flags
@@ -138,7 +141,7 @@ class PostHogFeatureFlags {
     func isFeatureEnabled(_ key: String) -> Bool {
         var flags: [String: Any]?
         featureFlagsLock.withLock {
-            flags = self.storage.getDictionary(forKey: .enabledFeatureFlags) as? [String: Any]
+            flags = self.getCachedFeatureFlags()
         }
 
         let value = flags?[key]
@@ -158,16 +161,40 @@ class PostHogFeatureFlags {
     func getFeatureFlag(_ key: String) -> Any? {
         var flags: [String: Any]?
         featureFlagsLock.withLock {
-            flags = self.storage.getDictionary(forKey: .enabledFeatureFlags) as? [String: Any]
+            flags = self.getCachedFeatureFlags()
         }
 
         return flags?[key]
     }
 
+    private func getCachedFeatureFlagPayload() -> [String: Any]? {
+        if featureFlagPayloads == nil {
+            featureFlagPayloads = storage.getDictionary(forKey: .enabledFeatureFlagPayloads) as? [String: Any]
+        }
+        return featureFlagPayloads
+    }
+
+    private func setCachedFeatureFlagPayload(_ featureFlagPayloads: [String: Any]) {
+        self.featureFlagPayloads = featureFlagPayloads
+        storage.setDictionary(forKey: .enabledFeatureFlagPayloads, contents: featureFlagPayloads)
+    }
+
+    private func getCachedFeatureFlags() -> [String: Any]? {
+        if featureFlags == nil {
+            featureFlags = storage.getDictionary(forKey: .enabledFeatureFlags) as? [String: Any]
+        }
+        return featureFlags
+    }
+
+    private func setCachedFeatureFlags(_ featureFlags: [String: Any]) {
+        self.featureFlags = featureFlags
+        storage.setDictionary(forKey: .enabledFeatureFlags, contents: featureFlags)
+    }
+
     func getFeatureFlagPayload(_ key: String) -> Any? {
         var flags: [String: Any]?
         featureFlagsLock.withLock {
-            flags = self.storage.getDictionary(forKey: .enabledFeatureFlagPayloads) as? [String: Any]
+            flags = getCachedFeatureFlagPayload()
         }
 
         let value = flags?[key]

diff --git a/PostHog/PostHogStorageManager.swift b/PostHog/PostHogStorageManager.swift
@@ -14,20 +14,28 @@ class PostHogStorageManager {
     private let distinctLock = NSLock()
     private let idGen: (UUID) -> UUID
 
+    private var distinctId: String?
+    private var cachedDistinctId = false
+    private var anonymousId: String?
+
     init(_ config: PostHogConfig) {
         storage = PostHogStorage(config)
         idGen = config.getAnonymousId
     }
 
     public func getAnonymousId() -> String {
-        var anonymousId: String?
         anonLock.withLock {
-            anonymousId = storage.getString(forKey: .anonymousId)
-
             if anonymousId == nil {
-                let uuid = UUID.v7()
-                anonymousId = idGen(uuid).uuidString
-                setAnonId(anonymousId ?? "")
+                var anonymousId = storage.getString(forKey: .anonymousId)
+
+                if anonymousId == nil {
+                    let uuid = UUID.v7()
+                    anonymousId = idGen(uuid).uuidString
+                    setAnonId(anonymousId ?? "")
+                } else {
+                    // update the memory value
+                    self.anonymousId = anonymousId
+                }
             }
         }
 
@@ -41,29 +49,53 @@ class PostHogStorageManager {
     }
 
     private func setAnonId(_ id: String) {
+        anonymousId = id
         storage.setString(forKey: .anonymousId, contents: id)
     }
 
     public func getDistinctId() -> String {
         var distinctId: String?
         distinctLock.withLock {
-            distinctId = storage.getString(forKey: .distinctId) ?? getAnonymousId()
+            if self.distinctId == nil {
+                // since distinctId is nil until its identified, no need to read from
+                // cache every single time, otherwise anon users will never used the
+                // cached values
+                if !cachedDistinctId {
+                    distinctId = storage.getString(forKey: .distinctId)
+                    cachedDistinctId = true
+                }
+
+                // do this to not assign the AnonymousId to the DistinctId, its just a fallback
+                if distinctId == nil {
+                    distinctId = getAnonymousId()
+                } else {
+                    // update the memory value
+                    self.distinctId = distinctId
+                }
+            } else {
+                // read from memory
+                distinctId = self.distinctId
+            }
         }
         return distinctId ?? ""
     }
 
     public func setDistinctId(_ id: String) {
         distinctLock.withLock {
+            distinctId = id
             storage.setString(forKey: .distinctId, contents: id)
         }
     }
 
     public func reset() {
         distinctLock.withLock {
             storage.remove(key: .distinctId)
+            distinctId = nil
+            cachedDistinctId = false
         }
         anonLock.withLock {
             storage.remove(key: .anonymousId)
+            anonymousId = nil
         }
     }
 }
diff --git a/PostHogExample/AppDelegate.swift b/PostHogExample/AppDelegate.swift
@@ -31,7 +31,7 @@ class AppDelegate: NSObject, UIApplicationDelegate {
 //        PostHogSDK.shared.capture("App started!")
 //        PostHogSDK.shared.reset()
 
-        PostHogSDK.shared.identify("Manoel")
+//        PostHogSDK.shared.identify("Manoel")
 
         let defaultCenter = NotificationCenter.default
 

diff --git a/PostHogExample/ContentView.swift b/PostHogExample/ContentView.swift
@@ -63,7 +63,7 @@ class FeatureFlagsModel: ObservableObject {
 
 struct ContentView: View {
     @State var counter: Int = 0
-    @State private var name: String = "Tim"
+    @State private var name: String = "Max"
     @State private var showingSheet = false
     @State private var showingRedactedSheet = false
     @StateObject var api = Api()