Question

我尝试使用Firestore来为集合设置实时侦听器。每当在集合中添加，修改或删除文档时，我都希望调用该侦听器。我的代码目前正在为一个集合工作，但是当我在较大的集合上尝试相同的代码时，它会因错误而失败：

侦听失败：com.google.cloud.firestore.FirestoreException：后端结束侦听流：数据存储区操作超时，或者数据暂时不可用。

这是我的实际听众代码：

/**
 * Sets up a listener at the given collection reference. When changes are made in this collection, it writes a flat
 * text file for import into backend.
 * @param collectionReference The Collection Reference that we want to listen to for changes.
 */
public static void listenToCollection(CollectionReference collectionReference) {

    AtomicBoolean initialUpdate = new AtomicBoolean(true);

    System.out.println("Initializing listener for: " + collectionReference.getId());

    collectionReference.addSnapshotListener(new EventListener<QuerySnapshot>() {
        @Override
        public void onEvent(@Nullable QuerySnapshot queryDocumentSnapshots, @Nullable FirestoreException e) {
            // Error Handling
            if (e != null) {
                System.err.println("Listen failed: " + e);
                return;
            }

            // If this is the first time this function is called, it's simply reading everything in the collection
            // We don't care about the initial value, only the updates, so we simply ignore the first call
            if (initialUpdate.get()) {
                initialUpdate.set(false);
                System.out.println("Initial update complete...\nListener active for " + collectionReference.getId() + "...");
                return;
            }

            // A document has changed, propagate this back to backend by writing text file.
            for (DocumentChange dc : queryDocumentSnapshots.getDocumentChanges()) {

                String docId = dc.getDocument().getId();
                Map<String, Object> docData = dc.getDocument().getData();

                String folderPath = createFolderPath(collectionReference, docId, docData);

                switch (dc.getType()) {
                    case ADDED:
                        System.out.println("Document Created: " + docId);
                        writeMapToFile(docData, folderPath, "CREATE");
                        break;
                    case MODIFIED:
                        System.out.println("Document Updated: " + docId);
                        writeMapToFile(docData, folderPath, "UPDATE");
                        break;
                    case REMOVED:
                        System.out.println("Document Deleted: " + docId);
                        writeMapToFile(docData, folderPath, "DELETE");
                        break;
                    default:
                        break;
                }
            }

        }
    });
}

在我看来，该集合太大，并且该集合的初始下载超时。我是否可以使用某种工作来实时获取此集合的更新？

Answer 1

我联系了Firebase团队，他们目前正在回答这个问题。与此同时，我可以通过基于 Last Updated timestamp属性查询集合来减小侦听器的大小。我只查看了最近更新过的文档，并且只要进行了更改，我的应用就会更改此属性。

FirestoreException：后端结束了Listen Stream

1 个答案: