fix: use duration and exponential backoff

Author: jmattheis

app/src/main/kotlin/com/github/gotify/service/WebSocketConnection.kt

@@ -12,6 +12,10 @@ import com.github.gotify.client.model.Message
 import java.util.Calendar
 import java.util.concurrent.TimeUnit
 import java.util.concurrent.atomic.AtomicLong
+import kotlin.math.pow
+import kotlin.time.Duration
+import kotlin.time.Duration.Companion.minutes
+import kotlin.time.Duration.Companion.seconds
 import okhttp3.HttpUrl.Companion.toHttpUrlOrNull
 import okhttp3.OkHttpClient
 import okhttp3.Request
@@ -25,8 +29,8 @@ internal class WebSocketConnection(
     settings: SSLSettings,
     private val token: String?,
     private val alarmManager: AlarmManager,
-    private val reconnectInterval: Int,
-    private val disableBackoff: Boolean
+    private val reconnectDelay: Duration,
+    private val exponentialBackoff: Boolean
 ) {
     companion object {
         private val ID = AtomicLong(0)
@@ -130,19 +134,19 @@ internal class WebSocketConnection(
         state = State.Disconnected
     }
 
-    fun scheduleReconnectNow(seconds: Long) = scheduleReconnect(ID.get(), seconds)
+    fun scheduleReconnectNow(scheduleIn: Duration) = scheduleReconnect(ID.get(), scheduleIn)
 
     @Synchronized
-    fun scheduleReconnect(id: Long, seconds: Long) {
+    fun scheduleReconnect(id: Long, scheduleIn: Duration) {
         if (state == State.Connecting || state == State.Connected) {
             return
         }
         state = State.Scheduled
 
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
-            Logger.info("WebSocket: scheduling a restart in $seconds second(s) (via alarm manager)")
+            Logger.info("WebSocket: scheduling a restart in $scheduleIn (via alarm manager)")
             val future = Calendar.getInstance()
-            future.add(Calendar.SECOND, seconds.toInt())
+            future.add(Calendar.SECOND, scheduleIn.inWholeSeconds.toInt())
 
             alarmManagerCallback?.run(alarmManager::cancel)
             val cb = OnAlarmListener { syncExec(id) { start() } }
@@ -155,11 +159,11 @@ internal class WebSocketConnection(
                 null
             )
         } else {
-            Logger.info("WebSocket: scheduling a restart in $seconds second(s)")
+            Logger.info("WebSocket: scheduling a restart in $scheduleIn")
             handlerCallback?.run(reconnectHandler::removeCallbacks)
             val cb = Runnable { syncExec(id) { start() } }
             handlerCallback = cb
-            reconnectHandler.postDelayed(cb, TimeUnit.SECONDS.toMillis(seconds))
+            reconnectHandler.postDelayed(cb, scheduleIn.inWholeMilliseconds)
         }
     }
 
@@ -206,16 +210,15 @@ internal class WebSocketConnection(
                 closed()
 
                 errorCount++
-                val seconds = if (disableBackoff) {
-                    reconnectInterval
-                } else {
-                    ((errorCount * 2 - 1) * reconnectInterval)
-                        .coerceAtMost(TimeUnit.MINUTES.toSeconds(20).toInt())
+
+                var scheduleIn = reconnectDelay
+                if (exponentialBackoff) {
+                    scheduleIn *= 2.0.pow(errorCount - 1)
                 }
+                scheduleIn = scheduleIn.coerceIn(5.seconds..20.minutes)
 
-                val rounded = seconds.coerceAtLeast(5)
-                onFailure.execute(response?.message ?: "unreachable", rounded)
-                scheduleReconnect(id, rounded.toLong())
+                onFailure.execute(response?.message ?: "unreachable", scheduleIn)
+                scheduleReconnect(id, scheduleIn)
             }
             super.onFailure(webSocket, t, response)
         }
@@ -229,7 +232,7 @@ internal class WebSocketConnection(
     }
 
     internal fun interface OnNetworkFailureRunnable {
-        fun execute(status: String, seconds: Int)
+        fun execute(status: String, reconnectIn: Duration)
     }
 
     internal enum class State {

app/src/main/kotlin/com/github/gotify/service/WebSocketService.kt

@@ -40,6 +40,11 @@ import com.github.gotify.messages.MessagesActivity
 import io.noties.markwon.Markwon
 import java.util.concurrent.ConcurrentHashMap
 import java.util.concurrent.atomic.AtomicLong
+import kotlin.time.Duration
+import kotlin.time.Duration.Companion.minutes
+import kotlin.time.Duration.Companion.seconds
+import kotlin.time.DurationUnit
+import kotlin.time.toDuration
 import org.tinylog.kotlin.Logger
 
 internal class WebSocketService : Service() {
@@ -111,29 +116,28 @@ internal class WebSocketService : Service() {
         val cm = getSystemService(CONNECTIVITY_SERVICE) as ConnectivityManager
         val alarmManager = getSystemService(ALARM_SERVICE) as AlarmManager
         val sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this)
-        var reconnectInterval = sharedPreferences
-            .getString(getString(R.string.setting_key_reconnect_interval), "60")
-            ?.trim()
-            ?.toIntOrNull() ?: 60
-
-        reconnectInterval = reconnectInterval.coerceIn(5, 60)
-
-        val disableBackoff = sharedPreferences.getBoolean(
-            getString(R.string.setting_key_backoff),
-            false
+        val reconnectDelay =
+            sharedPreferences.getString(
+                getString(R.string.setting_key_reconnect_delay),
+                null
+            )?.toIntOrNull()?.toDuration(DurationUnit.SECONDS) ?: 1.minutes
+
+        val exponentialBackoff = sharedPreferences.getBoolean(
+            getString(R.string.setting_key_exponential_backoff),
+            true
         )
 
         connection = WebSocketConnection(
             settings.url,
             settings.sslSettings(),
             settings.token,
             alarmManager,
-            reconnectInterval,
-            disableBackoff
+            reconnectDelay,
+            exponentialBackoff
         )
             .onOpen { onOpen() }
             .onClose { onClose() }
-            .onFailure { status, seconds -> onFailure(status, seconds) }
+            .onFailure { status, reconnectIn -> onFailure(status, reconnectIn) }
             .onMessage { message -> onMessage(message) }
             .onReconnected { notifyMissedNotifications() }
             .start()
@@ -194,24 +198,14 @@ internal class WebSocketService : Service() {
     }
 
     private fun doReconnect() {
-        connection?.scheduleReconnectNow(15)
+        connection?.scheduleReconnectNow(15.seconds)
     }
 
-    private fun onFailure(status: String, seconds: Int) {
+    private fun onFailure(status: String, reconnectIn: Duration) {
         val title = getString(R.string.websocket_error, status)
-        val intervalUnit = if (seconds >= 60) {
-            val minutes = seconds / 60
-            resources.getQuantityString(R.plurals.websocket_retry_interval, minutes, minutes)
-        } else {
-            resources.getQuantityString(
-                R.plurals.websocket_retry_interval_seconds,
-                seconds,
-                seconds
-            )
-        }
         showForegroundNotification(
             title,
-            "${getString(R.string.websocket_reconnect)} $intervalUnit"
+            getString(R.string.websocket_reconnect, reconnectIn.toString())
         )
     }
 

app/src/main/kotlin/com/github/gotify/settings/SettingsActivity.kt

@@ -21,6 +21,7 @@ import androidx.preference.SwitchPreferenceCompat
 import com.github.gotify.R
 import com.github.gotify.Utils
 import com.github.gotify.databinding.SettingsActivityBinding
+import com.github.gotify.service.WebSocketService
 import com.google.android.material.dialog.MaterialAlertDialogBuilder
 
 internal class SettingsActivity :
@@ -75,28 +76,23 @@ internal class SettingsActivity :
                 )?.isEnabled = true
             }
             findPreference<androidx.preference.EditTextPreference>(
-                getString(R.string.setting_key_reconnect_interval)
-            )?.let {
-                it.setOnBindEditTextListener { editText ->
-                    editText.inputType = android.text.InputType.TYPE_CLASS_NUMBER
-                }
-                it.onPreferenceChangeListener =
-                    Preference.OnPreferenceChangeListener { _, newValue ->
-                        val value = (newValue as String).trim().toIntOrNull() ?: 60
-                        if (value < 5 || value > 60) {
-                            Utils.showSnackBar(
-                                requireActivity(),
-                                "Please enter a value between 5 and 60"
-                            )
-                            return@OnPreferenceChangeListener false
-                        }
-
-                        requestWebSocketRestart()
-                        true
+                getString(R.string.setting_key_reconnect_delay)
+            )?.onPreferenceChangeListener =
+                Preference.OnPreferenceChangeListener { _, newValue ->
+                    val value = (newValue as String).trim().toIntOrNull() ?: 60
+                    if (value !in 5..1200) {
+                        Utils.showSnackBar(
+                            requireActivity(),
+                            "Please enter a value between 5 and 1200"
+                        )
+                        return@OnPreferenceChangeListener false
                     }
-            }
+
+                    requestWebSocketRestart()
+                    true
+                }
             findPreference<SwitchPreferenceCompat>(
-                getString(R.string.setting_key_backoff)
+                getString(R.string.setting_key_exponential_backoff)
             )?.onPreferenceChangeListener =
                 Preference.OnPreferenceChangeListener { _, _ ->
                     requestWebSocketRestart()
@@ -105,8 +101,7 @@ internal class SettingsActivity :
         }
 
         private fun requestWebSocketRestart() {
-            val intent =
-                Intent(requireContext(), com.github.gotify.service.WebSocketService::class.java)
+            val intent = Intent(requireContext(), WebSocketService::class.java)
             requireContext().startService(intent)
         }
 

app/src/main/res/values/strings.xml

@@ -115,22 +115,14 @@
     <string name="action_dialog_button_cancel">Cancel</string>
 
     <string name="websocket_error">Error %s (see logs)</string>
-    <string name="websocket_reconnect">Trying to reconnect</string>
-    <plurals name="websocket_retry_interval">
-        <item quantity="one">in %d minute</item>
-        <item quantity="other">in %d minutes</item>
-    </plurals>
-    <plurals name="websocket_retry_interval_seconds">
-        <item quantity="one">in %d second</item>
-        <item quantity="other">in %d seconds</item>
-    </plurals>
-    <string name="setting_reconnect_interval">Reconnect Interval (Seconds)</string>
-    <string name="setting_key_reconnect_interval">reconnect_interval</string>
+    <string name="websocket_reconnect">Trying to reconnect in %s</string>
+    <string name="setting_reconnect_delay">Reconnect Delay (Seconds)</string>
+    <string name="setting_key_reconnect_delay">reconnect_delay</string>
     <string name="setting_connection">Connection</string>
-    <string name="setting_reconnect_interval_summary">Wait time between connection attempts</string>
-    <string name="setting_backoff_title">Constant Retry Interval</string>
-    <string name="setting_backoff_summary">Do not increase wait time between retries</string>
-    <string name="setting_key_backoff">reconnect_backoff</string>
+    <string name="setting_reconnect_interval_summary">Delay between reconnect attempts</string>
+    <string name="setting_exponential_backoff_title">Exponential Backoff</string>
+    <string name="setting_exponential_backoff_summary">Exponentially increase the reconnect delay for each reconnect attempt</string>
+    <string name="setting_key_exponential_backoff">reconnect_exponential_backoff</string>
 
     <string name="notification_channel_title_foreground">Gotify foreground notification</string>
     <string name="notification_channel_title_min">Min priority messages (&lt;1)</string>

app/src/main/res/xml/root_preferences.xml

@@ -54,14 +54,15 @@
     <PreferenceCategory app:title="@string/setting_connection">
         <EditTextPreference
             android:defaultValue="60"
-            android:key="@string/setting_key_reconnect_interval"
-            android:title="@string/setting_reconnect_interval"
+            android:inputType="numberSigned"
+            android:key="@string/setting_key_reconnect_delay"
+            android:title="@string/setting_reconnect_delay"
             android:summary="@string/setting_reconnect_interval_summary" />
         <SwitchPreferenceCompat
-            android:key="@string/setting_key_backoff"
-            android:title="@string/setting_backoff_title"
-            android:summary="@string/setting_backoff_summary"
-            android:defaultValue="false" />
+            android:key="@string/setting_key_exponential_backoff"
+            android:title="@string/setting_exponential_backoff_title"
+            android:summary="@string/setting_exponential_backoff_summary"
+            android:defaultValue="true" />
     </PreferenceCategory>
 
 </PreferenceScreen>