fix: retry Open-Meteo on 429/5xx and show why loading failed

Co-Authored-By: Claude Opus 5.5 <[email protected]>

wetter/app/src/main/java/app/wetter/data/OpenMeteo.kt

@@ -17,6 +17,7 @@ import okhttp3.HttpUrl.Companion.toHttpUrl
 import okhttp3.OkHttpClient
 import okhttp3.Request
 import java.io.IOException
+import kotlinx.coroutines.delay
 import java.time.LocalDate
 import java.time.LocalDateTime
 import java.time.ZoneId
@@ -154,13 +155,25 @@ class OpenMeteo(private val http: OkHttpClient = defaultClient()) {
         return Air(c.int("european_aqi"), c.num("pm2_5"), c.num("pm10"), pollen)
     }
 
+    /** Open-Meteo answers 429/5xx ("service is overloaded") now and then; retry those twice with backoff. */
     private suspend fun get(url: String): String = withContext(Dispatchers.IO) {
         val request = Request.Builder().url(url).header("User-Agent", USER_AGENT).build()
+        var attempt = 0
+        while (true) {
+            val result = runCatching {
                 http.newCall(request).execute().use { response ->
-            if (!response.isSuccessful) throw IOException("HTTP ${response.code}")
+                    if (!response.isSuccessful) throw HttpException(response.code)
                     response.body?.string() ?: throw IOException("empty body")
                 }
             }
+            val error = result.exceptionOrNull() ?: return@withContext result.getOrThrow()
+            val retryable = error is IOException && (error !is HttpException || error.code == 429 || error.code >= 500)
+            if (!retryable || attempt >= 2) throw error
+            delay(600L * (attempt + 1) * (attempt + 1))
+            attempt++
+        }
+        @Suppress("UNREACHABLE_CODE") error("unreachable")
+    }
 
     companion object {
         const val USER_AGENT = "Wetter/0.1 (private, non-commercial)"
@@ -189,3 +202,5 @@ private fun JsonObject.int(key: String) = num(key)?.toInt()
 private fun JsonObject.arr(key: String): JsonArray = this[key]?.jsonArray ?: JsonArray(emptyList())
 private fun JsonObject.numAt(key: String, i: Int) = arr(key).getOrNull(i)?.takeUnless { it is JsonNull }?.jsonPrimitive?.doubleOrNull
 private fun JsonObject.intAt(key: String, i: Int) = numAt(key, i)?.toInt() ?: arr(key).getOrNull(i)?.takeUnless { it is JsonNull }?.jsonPrimitive?.intOrNull
+
+class HttpException(val code: Int) : IOException("HTTP $code")

wetter/app/src/main/java/app/wetter/ui/screens/HomeScreen.kt

@@ -152,12 +152,12 @@ private fun LocationPage(
     val repo = Graph.repo
     val forecast by remember(location.id) { repo.forecast(location.id) }.collectAsState(initial = null)
     var refreshing by remember { mutableStateOf(false) }
-    var failed by remember { mutableStateOf(false) }
+    var error by remember { mutableStateOf<Throwable?>(null) }
     val scope = rememberCoroutineScope()
     val refresh: (Boolean) -> Unit = { force ->
         scope.launch {
             refreshing = force
-            failed = repo.refresh(location, force) is RefreshResult.Failed
+            error = (repo.refresh(location, force) as? RefreshResult.Failed)?.error
             refreshing = false
         }
     }
@@ -172,7 +172,7 @@ private fun LocationPage(
         settings = settings,
         animate = animate,
         refreshing = refreshing,
-        failed = failed,
+        error = error,
         onRefresh = { refresh(true) },
         navigation = {
             IconButton(onClick = onOpenLocations) { Icon(Icons.Rounded.FormatListBulleted, stringResource(R.string.open_locations)) }
@@ -195,7 +195,7 @@ fun ForecastPage(
     settings: Settings,
     animate: Boolean,
     refreshing: Boolean,
-    failed: Boolean,
+    error: Throwable?,
     onRefresh: () -> Unit,
     navigation: @Composable () -> Unit,
     actions: @Composable () -> Unit,
@@ -208,6 +208,7 @@ fun ForecastPage(
         ?: SceneSpec(app.wetter.data.Condition.CLOUDY, true)
     val listState = rememberLazyListState()
     val fg = spec.onScene
+    val failed = error != null
 
     Box(Modifier.fillMaxSize()) {
         WeatherScene(spec, animate = animate && settings.animations, scroll = {
@@ -237,7 +238,7 @@ fun ForecastPage(
                     item(key = "loading") {
                         Column(Modifier.padding(top = 120.dp), horizontalAlignment = Alignment.CenterHorizontally) {
                             if (failed) {
-                                Text(stringResource(R.string.loading_error), color = fg, style = WType.body)
+                                Text(stringResource(errorText(error)), color = fg, style = WType.body, textAlign = TextAlign.Center)
                                 TextButton(onClick = onRefresh) { Text(stringResource(R.string.retry), color = fg) }
                             } else CircularProgressIndicator(color = fg)
                         }
@@ -310,3 +311,10 @@ private fun PermissionPrompt(onAllow: () -> Unit, onSearch: () -> Unit, asked: B
         }
     }
 }
+
+@androidx.annotation.StringRes
+private fun errorText(error: Throwable?): Int = when {
+    error is app.wetter.data.HttpException && (error.code == 429 || error.code >= 500) -> R.string.loading_error_busy
+    error is java.net.UnknownHostException || error is java.net.ConnectException || error is java.net.SocketTimeoutException -> R.string.loading_error_offline
+    else -> R.string.loading_error
+}

wetter/app/src/main/java/app/wetter/ui/screens/PreviewScreen.kt

@@ -25,12 +25,12 @@ import kotlinx.coroutines.launch
 @Composable
 fun PreviewScreen(place: Place, settings: Settings, onBack: () -> Unit, onSaved: (Long) -> Unit) {
     var forecast by remember { mutableStateOf<Forecast?>(null) }
-    var failed by remember { mutableStateOf(false) }
+    var error by remember { mutableStateOf<Throwable?>(null) }
     var attempt by remember { mutableStateOf(0) }
     val scope = rememberCoroutineScope()
     LaunchedEffect(place, attempt) {
-        failed = false
-        runCatching { Graph.repo.preview(place) }.onSuccess { forecast = it }.onFailure { failed = true }
+        error = null
+        runCatching { Graph.repo.preview(place) }.onSuccess { forecast = it }.onFailure { error = it }
     }
     ForecastPage(
         title = place.name,
@@ -39,7 +39,7 @@ fun PreviewScreen(place: Place, settings: Settings, onBack: () -> Unit, onSaved:
         settings = settings,
         animate = true,
         refreshing = false,
-        failed = failed,
+        error = error,
         onRefresh = { attempt++ },
         navigation = { IconButton(onClick = onBack) { Icon(Icons.AutoMirrored.Rounded.ArrowBack, stringResource(R.string.back)) } },
         actions = {

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

@@ -93,6 +93,8 @@
     <string name="perm_allow">Standort erlauben</string>
     <string name="perm_search">Lieber einen Ort suchen</string>
     <string name="loading_error">Wetterdaten konnten nicht geladen werden</string>
+    <string name="loading_error_busy">Der Wetterdienst ist gerade überlastet. Bitte gleich noch einmal versuchen.</string>
+    <string name="loading_error_offline">Keine Verbindung zum Internet</string>
 
     <string name="set_units">Einheiten</string>
     <string name="set_temp">Temperatur</string>

wetter/app/src/test/java/app/wetter/ScreenshotTest.kt

@@ -62,7 +62,7 @@ class ScreenshotTest {
     @Composable
     private fun Home(f: Forecast, title: String = "Berlin", preview: Boolean = false) = ForecastPage(
         title = title, isCurrent = !preview, forecast = f, settings = Settings(), animate = false,
-        refreshing = false, failed = false, onRefresh = {},
+        refreshing = false, error = null, onRefresh = {},
         navigation = { IconButton(onClick = {}) { Icon(Icons.Rounded.FormatListBulleted, null) } },
         actions = {
             if (preview) FilledTonalButton(onClick = {}) { Text("Speichern") }

wetter/app/src/test/resources/newyork_forecast.json

@@ -0,0 +1 @@
+{"reason":"The service is overloaded","error":true}