Offline Firebase

问题

I am implementing an AngularJS web app with Firebase as a backend; it should work offline, too; multi-user sync issues should be very limited, since the app - by design - will only allow new data entries when offline.

I understand Firebase has offline capabilities, in the sense that a client can withstand temporary network connection failures: any write operation will be delayed and cached until network comes up again.

I ask if any possibility does exist (or does any plan to implement it) to extend Firebase offline capabilities to enable clients to locally cache a snapshot of (some of) the data on the server, to be able to offer clients a complete offline experience, with read operations available, too.

I see a third part Firebase wrapper exists, but it's documentation is quite 'limited' (to be kind... :-). A native solution should be preferred...

UPDATE: After Frank van Puffelen comment, I better qualify my question:

*Does Firebase natively support offline data access in its Web API, or will it any time soon?*

回答1:

An alternative to Firebase that solves this problem for JS apps is CouchDb (server) <=> PouchDb (JS client). If you've implemented a nice clean Service layer for your AngularJS app then porting to PouchDb should be fairly straight forward since both are NoSQL/JSON databases.

PouchDb is a Javascript API that implements a fully offline CouchDb client. It can auto detect and use either _local storage_, _IndexDb_ or _WebSQL_ to permanently persist local data while online or offline. The PouchDb API can be used to access either your local or remote databases (just change the URL) and wire up full syncing or filtered syncing between the two. There are many useful PouchDb plugins, code samples and a small wrapper library to support AngularJS's Q promises API.

Using PouchDb, you can safely start up your app while offline and then days later restart your app and sync all your CUD data changes to the server. This can result in update collisions so CouchDb supports record versioning that is designed to detect and track this. Consequently, you'll likely need server side logic to resolve these collisions. This is unavoidable for distributed systems with offline synchronization and a key feature of CouchDb (not quite true ... see comments)

PouchDb is basically a reimplementation of Apache CouchDb including it's efficient synchronization protocol. Both CouchDb and PouchDb are well tested, free and open source. Being open source means that a CouchDb server can also be deployed as an Intranet service - optionally syncing to an external cloud service. There are a number of CouchDb hosting providers.

The Cloudant hosting team recently added their BigCouch clustering features to Apache CouchDb 2.0 project so now you can scale from Micro Db (PouchDb) => Single Server => Multi-Master (Replicated) => Big Couch Clustered / Geo Clustered. Unlike MongoDb, CouchDb safely supports single server deployment.

NOTE: PouchDb can also sync to CouchBase using the same protocol but Couchbase !== CouchDb. It's a commercial product.

How to code your CouchDb and PouchDb replication for mobile or web apps.

CouchDb Hosters:

Cloudant
Iris Couch
Smileupps

DIY

How To Install CouchDB and Futon on Ubuntu 12.04 - Digital Ocean
Secure CouchDB by using SSL/HTTPS

Docker + CouchDb:

Dockerizing a CouchDB Service
GitHub: Yet Another Dockerized CouchDB
Dockerized CouchDB 1.6.0 with stud SSL terminator

Truck load of Plugins

PouchDb has a number of extension points and growing list plugins (37 last count):

Plugins and External Projects

Security Model

One issue you'll need to consider when migrating to CouchDb is that it has a more limited access control model. This is partly due to it's replication algorithm. This blog post covers this in detail (better than the real definitive guide).

Matt Woodward's Definitive Guide to CouchDB Authentication and Security
CouchDB Security Overview
Superlogin - Client and server authentication APIs based on PassportJS to use OAuth2 or local signup/logins to a CouchDb server. Optional Angular API and a nice Demo reference app. Replaces weaker basic authentication in CouchDb with a randomly generated username and password for each login session (like an auth token) after authentication via PassportJS which supports over 300 auth plugins.

回答2:

According to the Firebase docs, it does: https://www.firebase.com/docs/web/guide/offline-capabilities.html

From the site: Firebase provides some simple primitives that allows data to be written when a client disconnects from the Firebase servers. These updates will occur whether the client disconnects cleanly or not, so we can rely on them to clean up data even if a connection is dropped or a client crashes. All Firebase write operations, including setting, updating, and removing, can be performed upon a disconnection.

Am I interpreting the question incorrectly ?

I almost deleted my post but when I clicked on the link OP had given, I saw that the third party package does exactly the same thing as what Firebase itself does, maybe it was done before Firebase improved sync ?

When I deleted the post, I thought the OP might have wanted a selective set of data only, not 'active data' which is what FB stores locally until connection is restored

来源：https://stackoverflow.com/questions/25990048/offline-firebase

标签

angularjs