Add SessionMaintainerFollower and create in FirebaseSessions when…

firebase-sessions/src/main/kotlin/com/google/firebase/sessions/EventGDTLogger.kt

@@ -21,6 +21,7 @@ import com.google.android.datatransport.Encoding
 import com.google.android.datatransport.Event
 import com.google.android.datatransport.TransportFactory
 import com.google.firebase.inject.Provider
+import com.google.firebase.sessions.leader.SessionEvent
 
 /**
  * The [EventGDTLoggerInterface] is for testing purposes so that we can mock EventGDTLogger in other

firebase-sessions/src/main/kotlin/com/google/firebase/sessions/FirebaseSessions.kt

@@ -25,6 +25,8 @@ import com.google.firebase.ktx.Firebase
 import com.google.firebase.ktx.app
 import com.google.firebase.sessions.api.FirebaseSessionsDependencies
 import com.google.firebase.sessions.api.SessionSubscriber
+import com.google.firebase.sessions.follower.SessionMaintainerFollower
+import com.google.firebase.sessions.follower.SessionsDataRepository
 import com.google.firebase.sessions.leader.SessionMaintainerLeader
 import kotlinx.coroutines.CoroutineDispatcher
 
@@ -39,21 +41,35 @@ internal constructor(
   backgroundDispatcher: CoroutineDispatcher,
   blockingDispatcher: CoroutineDispatcher,
   transportFactoryProvider: Provider<TransportFactory>,
+  processDetails: ProcessDetails = AndroidProcessDetails(firebaseApp.applicationContext)
 ) {
 
   private val sessionMaintainer: SessionMaintainer
   private val tag = "FirebaseSessions"
-
+  private val sessionsDataRepository: SessionsDataRepository
   init {
-    // TODO(rothbutter): create a different maintainer based on the characteristics of this process
+    Log.d(tag, "Initializing data repository")
+    sessionsDataRepository = SessionsDataRepository(firebaseApp.applicationContext)
+
+    Log.d(
+      tag,
+      "Initializing data maintainer. Default process is: ${processDetails.defaultProcessName}"
+    )
     sessionMaintainer =
-      SessionMaintainerLeader(
-        firebaseApp,
-        firebaseInstallations,
-        backgroundDispatcher,
-        blockingDispatcher,
-        transportFactoryProvider
-      )
+      if (AndroidProcessDetails.shouldProcessGenerateNewSession(processDetails)) {
+        Log.d(tag, "Initializing leader maintainer on process: ${processDetails.processName}")
+        SessionMaintainerLeader(
+          firebaseApp,
+          firebaseInstallations,
+          backgroundDispatcher,
+          blockingDispatcher,
+          transportFactoryProvider,
+          sessionsDataRepository
+        )
+      } else {
+        Log.d(tag, "Initializing follower maintainer on process: ${processDetails.processName}")
+        SessionMaintainerFollower(sessionsDataRepository)
+      }
 
     sessionMaintainer.start(backgroundDispatcher)
   }

firebase-sessions/src/main/kotlin/com/google/firebase/sessions/ProcessDetails.kt

@@ -30,6 +30,12 @@ internal interface ProcessDetails {
 
   /** Whether the current process is running in the foreground or not. */
   val isForegroundProcess: Boolean
+
+  /** Name of this process */
+  val processName: String?
+
+  /** Name of the default process */
+  val defaultProcessName: String
 }
 
 /** Android implementation of [ProcessDetails]. */
@@ -40,23 +46,23 @@ internal class AndroidProcessDetails(context: Context) : ProcessDetails {
    * This is the app's package name unless the app overrides the android:process attribute in the
    * application block of its Android manifest file.
    */
-  private val defaultProcessName: String = context.applicationInfo.processName
+  override val defaultProcessName: String = context.applicationInfo.processName
 
-  /** The name of the current process, or null if it couldn't be found. */
-  private val currentProcessName: String? =
+  /** The name of this process, or null if it couldn't be found. */
+  override val processName: String? =
     if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
       Application.getProcessName()
     } else {
       findProcessName(context, Process.myPid())
     }
 
-  override val isDefaultProcess: Boolean = currentProcessName == defaultProcessName
+  override val isDefaultProcess: Boolean = processName == defaultProcessName
 
   override val isForegroundProcess: Boolean
     get() {
       val runningAppProcessInfo = RunningAppProcessInfo()
       ActivityManager.getMyMemoryState(runningAppProcessInfo)
-      return runningAppProcessInfo.importance == RunningAppProcessInfo.IMPORTANCE_FOREGROUND
+      return runningAppProcessInfo.importance <= RunningAppProcessInfo.IMPORTANCE_FOREGROUND_SERVICE
     }
 
   /** Finds the process name for the given pid, or returns null if not found. */

firebase-sessions/src/main/kotlin/com/google/firebase/sessions/SessionEvents.kt

@@ -21,6 +21,13 @@ import com.google.firebase.FirebaseApp
 import com.google.firebase.encoders.DataEncoder
 import com.google.firebase.encoders.json.JsonDataEncoderBuilder
 import com.google.firebase.sessions.api.SessionSubscriber
+import com.google.firebase.sessions.leader.AutoSessionEventEncoder
+import com.google.firebase.sessions.leader.DataCollectionState
+import com.google.firebase.sessions.leader.DataCollectionStatus
+import com.google.firebase.sessions.leader.EventType
+import com.google.firebase.sessions.leader.SessionDetails
+import com.google.firebase.sessions.leader.SessionEvent
+import com.google.firebase.sessions.leader.SessionInfo
 import com.google.firebase.sessions.settings.SessionsSettings
 
 /** Contains functions for [SessionEvent]s. */

firebase-sessions/src/main/kotlin/com/google/firebase/sessions/follower/SessionMaintainerFollower.kt

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2023 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.
+ */
+
+package com.google.firebase.sessions.follower
+
+import android.util.Log
+import com.google.firebase.sessions.SessionMaintainer
+import com.google.firebase.sessions.api.FirebaseSessionsDependencies
+import com.google.firebase.sessions.api.SessionSubscriber
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.launch
+
+class SessionMaintainerFollower(private val sessionsDataRepository: SessionsDataRepository) :
+  SessionMaintainer {
+  val tag = "SessionMaintainerFollow"
+
+  override fun register(subscriber: SessionSubscriber) {
+    // NOOP
+  }
+
+  override fun start(backgroundDispatcher: CoroutineDispatcher) {
+    CoroutineScope(backgroundDispatcher).launch {
+      sessionsDataRepository.firebaseSessionDataFlow.collect {
+        if (it.sessionId == null) {
+          Log.d(
+            tag,
+            "No session data available in shared storage." + " subscribers will not be notified."
+          )
+        } else {
+          Log.d(
+            tag,
+            "Follower process has observed a change to the repository and will notify subscribers. New session id is ${it.sessionId}"
+          )
+          notifySubscribers(it.sessionId)
+        }
+      }
+    }
+  }
+
+  private suspend fun notifySubscribers(sessionId: String) {
+    val subscribers = FirebaseSessionsDependencies.getRegisteredSubscribers()
+    if (subscribers.isEmpty()) {
+      Log.d(tag, "Sessions SDK did not have any subscribers. Events will not be sent.")
+    } else {
+      subscribers.values.forEach { subscriber ->
+        // Notify subscribers, irregardless ;) of sampling and data collection state.
+        Log.d(tag, "Sending session id $sessionId to subscriber $subscriber.")
+        subscriber.onSessionChanged(SessionSubscriber.SessionDetails(sessionId))
+      }
+    }
+  }
+}

firebase-sessions/src/main/kotlin/com/google/firebase/sessions/follower/SessionsDataRepository.kt

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2023 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.
+ */
+
+package com.google.firebase.sessions.follower
+
+import android.content.Context
+import android.util.Log
+import androidx.datastore.core.DataStore
+import androidx.datastore.preferences.core.Preferences
+import androidx.datastore.preferences.core.edit
+import androidx.datastore.preferences.core.emptyPreferences
+import androidx.datastore.preferences.core.stringPreferencesKey
+import androidx.datastore.preferences.preferencesDataStore
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.catch
+import kotlinx.coroutines.flow.map
+
+data class FirebaseSessionsData(val sessionId: String?)
+
+/** Persists session data that needs to be synchronized across processes */
+class SessionsDataRepository(private val context: Context) {
+  private val tag = "FirebaseSessionsRepo"
+
+  private object FirebaseSessionDataKeys {
+    val SESSION_ID = stringPreferencesKey("session_id")
+  }
+
+  val firebaseSessionDataFlow: Flow<FirebaseSessionsData> =
+    context.dataStore.data
+      .catch { exception ->
+        Log.e(tag, "Error reading stored session data.", exception)
+        emit(emptyPreferences())
+      }
+      .map { preferences -> mapSessionsData(preferences) }
+
+  suspend fun updateSessionId(sessionId: String) {
+    context.dataStore.edit { preferences ->
+      preferences[FirebaseSessionDataKeys.SESSION_ID] = sessionId
+    }
+  }
+
+  private fun mapSessionsData(preferences: Preferences): FirebaseSessionsData =
+    FirebaseSessionsData(preferences[FirebaseSessionDataKeys.SESSION_ID])
+}
+
+const val SESSION_CONFIGS_NAME = "firebase_session_settings"
+
+private val Context.dataStore: DataStore<Preferences> by
+  preferencesDataStore(name = SESSION_CONFIGS_NAME)

firebase-sessions/src/main/kotlin/com/google/firebase/sessions/SessionCoordinator.kt → firebase-sessions/src/main/kotlin/com/google/firebase/sessions/leader/SessionCoordinator.kt

@@ -14,10 +14,11 @@
  * limitations under the License.
  */
 
-package com.google.firebase.sessions
+package com.google.firebase.sessions.leader
 
 import android.util.Log
 import com.google.firebase.installations.FirebaseInstallationsApi
+import com.google.firebase.sessions.EventGDTLoggerInterface
 import kotlinx.coroutines.tasks.await
 
 /**

firebase-sessions/src/main/kotlin/com/google/firebase/sessions/SessionEvent.kt → firebase-sessions/src/main/kotlin/com/google/firebase/sessions/leader/SessionEvent.kt

@@ -14,10 +14,11 @@
  * limitations under the License.
  */
 
-package com.google.firebase.sessions
+package com.google.firebase.sessions.leader
 
 import com.google.firebase.encoders.annotations.Encodable
 import com.google.firebase.encoders.json.NumberedEnum
+import com.google.firebase.sessions.ApplicationInfo
 
 /**
  * Contains the relevant information around a Firebase Session Event.

firebase-sessions/src/main/kotlin/com/google/firebase/sessions/SessionGenerator.kt → firebase-sessions/src/main/kotlin/com/google/firebase/sessions/leader/SessionGenerator.kt

@@ -14,8 +14,9 @@
  * limitations under the License.
  */
 
-package com.google.firebase.sessions
+package com.google.firebase.sessions.leader
 
+import com.google.firebase.sessions.TimeProvider
 import java.util.UUID
 
 /**

firebase-sessions/src/main/kotlin/com/google/firebase/sessions/SessionInitiateListener.kt → firebase-sessions/src/main/kotlin/com/google/firebase/sessions/leader/SessionInitiateListener.kt

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package com.google.firebase.sessions
+package com.google.firebase.sessions.leader
 
 /** Interface for listening to the initiation of a new session. */
 internal interface SessionInitiateListener {

firebase-sessions/src/main/kotlin/com/google/firebase/sessions/SessionInitiator.kt → firebase-sessions/src/main/kotlin/com/google/firebase/sessions/leader/SessionInitiator.kt

@@ -14,11 +14,12 @@
  * limitations under the License.
  */
 
-package com.google.firebase.sessions
+package com.google.firebase.sessions.leader
 
 import android.app.Activity
 import android.app.Application.ActivityLifecycleCallbacks
 import android.os.Bundle
+import com.google.firebase.sessions.TimeProvider
 import com.google.firebase.sessions.settings.SessionsSettings
 import kotlin.coroutines.CoroutineContext
 import kotlinx.coroutines.CoroutineScope