Avoid starting sync service twice

Author: simolus3

demos/supabase-todolist/androidBackgroundSync/build.gradle.kts

@@ -3,6 +3,7 @@ plugins {
     alias(libs.plugins.kotlinAndroid)
     alias(libs.plugins.compose.compiler)
     id("org.jetbrains.compose")
+    alias(libs.plugins.kotlin.atomicfu)
 }
 
 android {

demos/supabase-todolist/androidBackgroundSync/src/main/java/com/powersync/demo/backgroundsync/SyncService.kt

@@ -14,6 +14,7 @@ import com.powersync.PowerSyncDatabase
 import com.powersync.connector.supabase.SupabaseConnector
 import com.powersync.sync.SyncStatusData
 import io.github.jan.supabase.auth.status.SessionStatus
+import kotlinx.atomicfu.atomic
 import kotlinx.coroutines.CancellationException
 import kotlinx.coroutines.launch
 import org.koin.android.ext.android.inject
@@ -22,14 +23,20 @@ class SyncService: LifecycleService() {
 
     private val connector: SupabaseConnector by inject()
     private val database: PowerSyncDatabase by inject()
+    private var holdsServiceLock = false
 
     private val notificationManager get()= NotificationManagerCompat.from(this)
 
     override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
         super.onStartCommand(intent, flags, startId)
 
-        createNotificationChannel()
+        holdsServiceLock = SERVICE_RUNNING.compareAndSet(false, true)
+        if (!holdsServiceLock) {
+            stopSelf()
+            return START_NOT_STICKY
+        }
 
+        createNotificationChannel()
         ServiceCompat.startForeground(
             this,
             startId,
@@ -44,6 +51,7 @@ class SyncService: LifecycleService() {
         lifecycleScope.launch {
             database.currentStatus.asFlow().collect {
                 try {
+                    Logger.i("Sync service received status $it")
                     notificationManager.notify(startId, buildNotification(it))
                 } catch (e: SecurityException) {
                     Logger.d("Ignoring security exception when updating notification", e)
@@ -82,6 +90,14 @@ class SyncService: LifecycleService() {
         stopSelf(startId)
     }
 
+    override fun onDestroy() {
+        if (holdsServiceLock) {
+            SERVICE_RUNNING.value = false
+        }
+
+        super.onDestroy()
+    }
+
     private fun createNotificationChannel() {
         val channel = NotificationChannelCompat.Builder(CHANNEL_ID, NotificationManagerCompat.IMPORTANCE_LOW)
             .setName(getString(R.string.background_channel_name))
@@ -101,6 +117,7 @@ class SyncService: LifecycleService() {
     }.build()
 
     private companion object {
-        private val CHANNEL_ID = "background_sync"
+        val CHANNEL_ID = "background_sync"
+        val SERVICE_RUNNING = atomic(false)
     }
 }

demos/supabase-todolist/build.gradle.kts

@@ -6,4 +6,5 @@ plugins {
     alias(libs.plugins.kotlinMultiplatform) apply false
     alias(libs.plugins.kotlinAndroid) apply false
     alias(libs.plugins.cocoapods) apply false
+    alias(libs.plugins.kotlin.atomicfu) apply false
 }

demos/supabase-todolist/gradle/libs.versions.toml

@@ -4,6 +4,7 @@ android-minSdk = "24"
 android-targetSdk = "35"
 android-compileSdk = "35"
 java = "17"
+atomicfu = "0.27.0"
 
 # Dependencies
 kotlin = "2.1.10"
@@ -74,5 +75,6 @@ kotlinMultiplatform = { id = "org.jetbrains.kotlin.multiplatform", version.ref =
 kotlinAndroid = { id = "org.jetbrains.kotlin.android", version.ref = "kotlin" }
 compose-compiler = { id = "org.jetbrains.kotlin.plugin.compose", version.ref = "kotlin" }
 buildKonfig = { id = "com.codingfeline.buildkonfig", version.ref = "buildKonfig" }
+kotlin-atomicfu = { id = "org.jetbrains.kotlinx.atomicfu", version.ref = "atomicfu" }
 
 [bundles]