I understand that data is cached locally and synced with a server, but it is unclear from the docs how long data is saved on the local machine.
If I quit my browser, do I need to re-download my data the next time I visit the app? Is the local data persisted permanently, syncing with the server-data like a git repository?
Thanks.
While Firebase has offline disk persistence available for the iOS client, there is currently no offline storage out-of-the-box in the browser. If you quit your browser or navigate away from the page, only the user's authentication state / session is persisted while all application data will be re-synced.
Related
To use a firestore bundle, does the client need to have persistence enabled for the offline cache. If persistence is enabled, does it mean that the offline cache and the bundle are retained when the app or browser is closed and don't have to be re-downloaded when the app or browser window starts up again.
According to the firebase website, for the web, offline persistence is supported only by chrome, safari and firefox. Is this information up to date - is it possible that Edge, Opera and Brave browsers support persistent cache.
For the web, if cache persistence isn't available, is it possible to cache the firestore bundle locally some other way?
If the app requests to ead a document from the local cache and it's not there, will the document be read from the cloud if the device is online?
When you enable disk persistence, your app writes the data locally to the device so your app can maintain state while offline, even if the user or operating system restarts the app.
By enabling persistence, any data that the Firebase Realtime Database client would sync while online persists to disk and is available offline, even when the user or operating system restarts the app. This means your app works as it would online by using the local data stored in the cache. Listener callbacks will continue to fire for local updates.
Check the section here for more information on Handling Transactions Offline
Even with persistence enabled, transactions are not persisted across app restarts. So you cannot rely on transactions done offline being committed to your Firebase Realtime Database. To provide the best user experience, your app should show that a transaction has not been saved into your Firebase Realtime Database yet, or make sure your app remembers them manually and executes them again after an app restart.
As per the official documentation ,Offline persistence is supported only in Android, Apple, and web apps.For the web version, offline persistence is supported only by the Chrome, Safari, and Firefox web browsers
For the web, offline persistence is disabled by default. To enable persistence, call the enablePersistence method.
While network access is disabled, all snapshot listeners and document requests retrieve results from the cache. Write operations are queued until network access is re-enabled.
Also , check the following for similar implementations examples:
Firebase Offline persistence Upfront Caching
Firebase Offline possibilities
What happens when an offline device goes online
I have a clarifying question about Cloud Firestore and Flutter:
I am making an app that users can create log entries of sort, which will be saved on Firebase. But they might make up to 30 entries offline, before they have internet connection again.
And I know that Firestore has an offline feature, with which any created documents can be viewed offline because it is saved in the order of logging, and then synced with the database when internet connection is gained. But it is absolutely crucial that these logs cannot be lost in my app before having a chance of uploading it. Is there a way to ensure that my app will not lose this data before connecting to Firebase again, or should I create a Sembast database on the device, and save a copy of everything, and then check that once in a while against the database?
Does Firestore have offline contingency for if the phone's battery dies before it could sync with Firestore?
Or is there another solution I am unaware of?
For Android and iOS, offline persistence is enabled by default.
You don't have to do anything in your code.
Note there is a default cache size of 100 MB. This can be changed though, eg
let settings = Firestore.firestore().settings
settings.cacheSizeBytes = FirestoreCacheSizeUnlimited
Firestore.firestore().settings = settings
Does Firestore have offline contingency for if the phone's battery dies before it could sync with Firestore?
When Firestore's offline persistence is enabled, it stores data that your app has recently read, as well as any pending writes, to a database on the local device or browser. This disk based cache will survive restarts of the app/reloads of the page.
For new version of use below code -
FirebaseFirestore.instance.settings =
Settings(cacheSizeBytes: Settings.CACHE_SIZE_UNLIMITED);
Using
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
Is this guarantee to download the data only one time across the App life/App restarts even if the user has good connection?
N.B: The official docs isn't clear ( at least for me) at this point.
By enabling persistence, any data that the Firebase Realtime Database client would sync while online persists to disk and is available offline, even when the user or operating system restarts the app. This means your app works as it would online by using the local data stored in the cache. Listener callbacks will continue to fire for local updates.
The sole goal of enabling persistence is to ensure that the app continues to work, even when the user starts it when they don't have a connection to the Firebase servers.
The client does send tree of hash values of its restored local state to the server when it connects, which the server then uses to only send the modified segments back. But there is no guarantee on how much data this sends or saves.
If you want to learn more about what Firebase actually does under the hood, I highly recommend enabling debug logging and studying its output on logcat.
For more on the topic, see these questions on Firebase's synchronization strategy.
Assuming my rules are setup to user read/write on owned object only, I want to know what data does firebase client (IOS/Android) store in devices? In this example, does it download the data that doesn't belongs to the user as well on the device but just blocked it? or only object owned by user will be downloaded on device.
Is there a way to just have some of the child object saved in the cloud only but not locally? I am worried about the db size getting too large in the devices.
Thanks!
Your Firebase app will only have access to data in the database that the rules permit. Security is handled by the Firebase Realtime Database (not the app) so only data that the user is allowed to access will be downloaded.
In order for your app to work with data stored in the database, it needs to be downloaded to the device. By default, data is cached so that your app still works even if your device temporarily loses its network connection. The app only stores this locally if you enable offline capabilities to allow the app to continue working when no network is available.
Firebase apps automatically handle temporary network interruptions. Cached data is available while offline and Firebase resends any writes when network connectivity is restored.
When you enable disk persistence, your app writes the data locally to the device so your app can maintain state while offline, even if the user or operating system restarts the app.
The Firebase app will automatically handle all of this functionality for you.
The size of the local cache will rarely be large enough to worry about, unless you are storing or downloading huge amounts of data, which is not recommended. If your database is large, you should implement strategies to restrict queries to only retrieve relevant data by filtering or paginating your queries.
In Realm Browser and in my App I can watch how rows get deleted, modified and created when I log in with a Sync User, like it is getting synced slowly, when I login my app I would like to know when this sync ends, or better, get only the latest data at once and not the whole history of it.
I don't know if is a setting in Realm Object Server (Ubuntu) or in my App (iOS Swift)
Realm Mobile Platform syncs your data automatically in background, it allows you to work with the Realm url the same way you work with the local one.
So you can just use any type of Notifications to handle any data changes.