Add separate thread for processing logevents (#35)

* Add separate thread for processing logevents

gradle.properties

@@ -1,3 +1,3 @@
 android.useAndroidX=true
-libraryVersion=4.1.0
+libraryVersion=4.2.0
 kotlinVersion=1.5.0

src/main/java/com/statsig/androidsdk/Statsig.kt

@@ -17,6 +17,7 @@ import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.flow.launchIn
 import kotlinx.coroutines.flow.onEach
 import kotlinx.coroutines.launch
+import kotlinx.coroutines.runBlocking
 import kotlinx.coroutines.withContext
 import java.util.*
 
@@ -158,6 +159,7 @@ object Statsig {
         lifecycleListener = StatsigActivityLifecycleListener()
         application.registerActivityLifecycleCallbacks(lifecycleListener)
         logger = StatsigLogger(
+            statsigScope,
             sdkKey,
             options.api,
             statsigMetadata,
@@ -331,16 +333,23 @@ object Statsig {
         pollForUpdates()
     }
 
+    @JvmSynthetic
+    suspend fun shutdownSuspend() {
+        enforceInitialized("shutdown")
+        pollingJob?.cancel()
+        logger.shutdown()
+    }
+
     /**
      * Informs the Statsig SDK that the client is shutting down to complete cleanup saving state
      * @throws IllegalStateException if the SDK has not been initialized
      */
     @JvmStatic
     fun shutdown() {
-        enforceInitialized("shutdown")
-        pollingJob?.cancel()
-        statsigScope.launch {
-            logger.flush()
+        runBlocking {
+            withContext(Dispatchers.Main.immediate) {
+                shutdownSuspend()
+            }
         }
     }
 
@@ -435,7 +444,9 @@ object Statsig {
 
         override fun onActivityStopped(activity: Activity) {
             currentActivity = null
-            shutdown()
+            statsigScope.launch {
+                logger.flush()
+            }
         }
 
         override fun onActivitySaveInstanceState(activity: Activity, outState: Bundle) {

src/main/java/com/statsig/androidsdk/StatsigLogger.kt

@@ -1,13 +1,12 @@
 package com.statsig.androidsdk
 
 import com.google.gson.Gson
+import java.util.concurrent.Executors
 import android.content.SharedPreferences
 import com.google.gson.annotations.SerializedName
-import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.delay
-import kotlinx.coroutines.withContext
+import kotlinx.coroutines.*
 
-internal const val MAX_EVENTS: Int = 500
+internal const val MAX_EVENTS: Int = 10
 internal const val FLUSH_TIMER_MS: Long = 60000
 
 internal const val CONFIG_EXPOSURE = "statsig::config_exposure"
@@ -19,33 +18,37 @@ internal data class LogEventData(
 )
 
 internal class StatsigLogger(
+    coroutineScope: CoroutineScope,
     private val sdkKey: String,
     private val api: String,
     private val statsigMetadata: StatsigMetadata,
     private val statsigNetwork: StatsigNetwork
 ) {
     private val gson = Gson()
 
-    // Since these collections are not thread-safe, they will be modified in a single thread only
+    private val executor = Executors.newSingleThreadExecutor();
+    private val singleThreadDispatcher = executor.asCoroutineDispatcher()
+    private val timer = coroutineScope.launch {
+        while (coroutineScope.isActive) {
+            delay(FLUSH_TIMER_MS)
+            flush()
+        }
+    }
+    // Modify in a single thread only
     internal var events = arrayListOf<LogEvent>()
 
     suspend fun log(event: LogEvent) {
-        withContext(Dispatchers.Main.immediate) { // Run on main thread if not already in it
+        withContext(singleThreadDispatcher) {
             events.add(event)
 
             if (events.size >= MAX_EVENTS) {
                 flush()
             }
-
-            if (events.size == 1) {
-                delay(FLUSH_TIMER_MS)
-                flush()
-            }
         }
     }
 
     suspend fun flush() {
-        withContext(Dispatchers.Main.immediate) {
+        withContext(singleThreadDispatcher) {
             if (events.size == 0) {
                 return@withContext
             }
@@ -57,7 +60,7 @@ internal class StatsigLogger(
 
     suspend fun logGateExposure(gateName: String, gateValue: Boolean, ruleID: String,
                                 secondaryExposures: Array<Map<String, String>>, user: StatsigUser?) {
-        withContext(Dispatchers.Main.immediate) {
+        withContext(singleThreadDispatcher) {
             var event = LogEvent(GATE_EXPOSURE)
             event.user = user
             event.metadata =
@@ -73,12 +76,18 @@ internal class StatsigLogger(
 
     suspend fun logConfigExposure(configName: String, ruleID: String, secondaryExposures: Array<Map<String, String>>,
                                   user: StatsigUser?) {
-        withContext(Dispatchers.Main.immediate) {
+        withContext(singleThreadDispatcher) {
             var event = LogEvent(CONFIG_EXPOSURE)
             event.user = user
             event.metadata = mapOf("config" to configName, "ruleID" to ruleID)
             event.secondaryExposures = secondaryExposures
             log(event)
         }
     }
+
+    suspend fun shutdown() {
+        timer.cancel()
+        flush()
+        executor.shutdown()
+    }
 }