Hacktoberfest 2026：メンテナが10月に向けて印を付けた、オープンで初心者向けの issue。 Hacktoberfest の issue を見る

[firebase_messaging]: Android: a burst of background messages starts a FlutterEngine per service start, and can lose all of them

クローズ
  • 何か問題がありますか？
#18,789 コメント 1 件 リアクション 0 件 担当者 0 名 GitHub で見る

メンテナーはふだん 1 日以内に返信

@SelaseKay がすでに取り組んでいます。

2026年10月13日 から。

  • #18791 @SelaseKay による — オープン

評価

難易度
1/5
見積もり時間
1時間未満
初心者へのやさしさ
45/100
issue の種類
バグ
明瞭さ
明確に書かれている
活発さ
活発
技術スタック
android, dart, flutter
領域
backend, mobile

調査の方向性

Read FlutterFirebaseMessagingBackgroundExecutor.java around line 140 and trace how startBackgroundIsolate() assigns the engine before the queued callback runs. Reproduce with a burst of background data messages on Android, then check that only one engine is created and every queued message is handled. The issue reports a one-line fix and a successful 12-message run, though it does not name a test file.

索引モデルが issue の本文から書いたものです。

説明

Needs Attention platform: android plugin: messaging reproduced type: bug
Is there an existing issue for this?
  • I have searched the existing issues.
Which plugins are affected?

Messaging

Which platforms are affected?

Android

Description

When several data messages reach an app that isn't running (a device switched on, or back online, after missing a few), FlutterFirebaseMessagingBackgroundExecutor creates a background FlutterEngine for every FlutterFirebaseMessagingBackgroundService start that lands before the first engine exists, instead of one.

Expected: one background engine, and every message handled.

Actual: one engine per early service start. On a profile build, 12 messages held while the device was off, then boot: 6 × Creating background FlutterEngine instance. and 6 × FlutterFirebaseMessagingBackgroundService started! in one process. On a debug build, 22 held messages: 22 engines, then the low-memory killer, and no notification shown.

Cause: onCreate calls startBackgroundIsolate(), whose guard is if (backgroundFlutterEngine != null) return;. But the engine is only assigned inside the callback that method posts to the main looper after ensureInitializationCompleteAsync. Every service start before then posts another callback. The callback checks only isNotRunning(), which stays true until Dart sends MessagingBackground#initialized, so each one creates a new engine, overwrites backgroundFlutterEngine and backgroundChannel, and starts another isolate. The queued intents drain only in onInitialized. Their work was already completed, so if the process dies first (memory pressure from N engines) they are lost.

Fix (FlutterFirebaseMessagingBackgroundExecutor.java, L140 on 16.7.0 and on main at 90c22c8dd9):

-                if (isNotRunning()) {
+                if (isNotRunning() && backgroundFlutterEngine == null) {

onCreate, the posted runnable and its callback all run on the main looper, so once the first callback assigns the engine, every later one skips. With that change, the same 12-message boot burst makes one engine and shows all 12 notifications.

Reproducing the issue
  1. Register a handler with FirebaseMessaging.onBackgroundMessage.
  2. Power the device off.
  3. Send ≥10 high-priority, data-only messages to it.
  4. Boot the device without opening the app.
  5. Count Creating background FlutterEngine instance. in logcat: one per early service start, not one.

A profile or release build shows the duplicate engines cleanly. On a debug build the first engine's kernel load on the main thread (7–10 s) can also trip a background ANR on the pending FCM broadcast, which is a separate, debug-only effect.

Firebase Core version

4.15.0

Flutter Version

3.47.7

Relevant Log Output
# Profile build, 12 held data messages, device booted without opening the app (one process):
I FLTFireBGExecutor: Creating background FlutterEngine instance.     (×6)
I FLTFireMsgService: FlutterFirebaseMessagingBackgroundService started!     (×6)

# The same burst with the one-line fix:
I FLTFireBGExecutor: Creating background FlutterEngine instance.     (×1)
I FLTFireMsgService: FlutterFirebaseMessagingBackgroundService started!     (×1)
Flutter dependencies

firebase_messaging 16.7.0, firebase_core 4.15.0.

Additional context and comments
  • Versions: firebase_messaging 16.7.0 and main at 90c22c8dd9. Earlier 16.x releases (checked: 16.4.2, 16.4.3, 16.6.0) have the same isNotRunning()-only check in the callback.
  • Tested on an Android 16 emulator.
  • We're carrying the one-line change above as a build-time patch until a fix ships, and we're happy to open a PR with it if that helps.
主要言語
Dart
スター
9.3k
フォーク
4.1k
平均マージ
1日 15時間
マージ済み PR（30日）
82

環境構築

はじめの一歩

  1. issue を最後まで読み、次にプロジェクトのコントリビューションガイドを読みます。
  2. 着手することを issue にコメントします — 二人が同じ作業をするのを防げます。
  3. リポジトリをフォークし、ブランチを切って変更します。
  4. issue 番号を参照したプルリクエストを送ります。

firebase/flutterfire のほかの issue

firebase/flutterfire の issue をすべて見る

似ている issue

Dart の issue をもっと見る

新しい issue をメールで受け取る

初心者向けの GitHub issue を短くまとめたダイジェスト。