I am developing a multi-user Windows Store client app. The app's main screen displays data that can be updated by users at any time. Any changes made by a user needs to be pushed onto all clients in order to update the data displayed on the main screens of all the other users.
Would Azure's Notification Hubs apply to my scenario? The demos I've seen so far only show the pushing of "toast" notifications. In my case, I need to push notifications to client application code for programmatic processing rather than for direct display to the user.
My client app is programmed in a way that requires an object/relational mapping tool sitting between it and the database. It appears that Azure's Mobile Services includes support for Entity Framework and so can facilitate this. Is it possible to leverage Notification Hubs to achieve the goal of keeping all clients updated with the latest database changes? If so, then how would I accomplish each event in the following sequence?
Inform the mobile service that the database has changed.
Notify all the clients about the changes.
Materialize the changes on each client as objects via the O/R mapper.
Related
We are generating the Primary Keys from(GUID) from client side and passing to server.
From some of the articles and blogs we came to know that Azure client sdk pushes the records in random order.
We have created a 2 tables with relations and tested this in offline mode and it works well. So we would like to confirm if the latest client side sdk has done some code fix to send the records in some order.
I wonder why can't they create a queue so that it will push the first in first out manner.
Since we have foriegn key relations in server side we need to push the inserts in an orderly manner, is there any mechanism to make this pushes to server in a specified order?
is there any mechanism to make this pushes to server in a specified order?
We could get the answer from this book-chapter3/relationships/.
The former is generally handled for you. If you InsertAsync a tag in offline mode, it will be placed into the operations queue prior to anything that uses it. Since the operations queue is processed in order, the tag will be sent to the backend prior to any record updates that would use it.
Note: Prefer handling tables individually and handling relationship management on the mobile client manually. This causes more code on the mobile client but makes the server much simpler by avoiding most of the complexity of relationships.
I would like to create an app that retrieves events (similar to calendar events) from a remote database and shows them in a View, create, edit and delete new or existing events; currently I’m using EventKit framework to access iOS calendar, I read this docs and tried SimpleEKDemo:
https://developer.apple.com/library/ios/documentation/DataManagement/Conceptual/EventKitProgGuide/Introduction/Introduction.html#//apple_ref/doc/uid/TP40009765
I actually can get events from server through an HTTP POST request (a NSMutableURLRequest) with JSON response and show them in a tableView, when I tap on an event I can edit it, update the remote db entry and if I switch to iOS calendar I see the event (so writing in calendar database is successful);
the most important thing is that all events must be synchronized with remote database, so the core problem occurs when user leaves my app, opens iOS calendar and edits an event previously created through my app: in this case the synch does not occur and the data are inconsistent.
I was thinking at these possible ways:
Is there a way to hook at iOS Calendar so I can perform update in remote db, only for a subset of events?
Or can I create an event only editable through my app?
Maybe do I have to quit EventKit and create a custom calendar with custom update functions?
I read also these questions:
Create a calendar in iOS
How to identify EKEvent uniquely with Sync across the devices
Sync database on ipad with remote database
but I don't know if I'am on the right track.
Any help is appreciated, thank you.
EDIT: with "synchronized" I mean that all data on the app database must be the same as server database
At least today you cannot create a custom protocol provider for the iOS calendar, which I think is what you are asking for (you would like to feed the calendar backend with your JSON-like protocol, or some app extension translating that).
There are three options:
a) keep the remote database in sync using an application
b) write your own calendar UI
c) implement CalDAV on the server side, or in a proxy
It sounds like a) is what you are doing today. You would need to sync the EventKit database when your app starts (to pickup changes done in other EventKit apps like Calendar). Obviously the user needs to start your app once in a while to get the sync going ... (as a hack you might also be able to trigger your app using a push)
Depending on your needs b) is a lot of work and you have zero platform integration.
I think implementing CalDAV in your server, or adding a proxy which translates between your server's JSON and CalDAV is probably the best way to go. You can then just add your server as a CalDAV account to iOS. As a bonus you can use any other client doing CalDAV with your server ...
I have a database (MySQL) to which data is being written to. I need to push new records and changed records to UI. A few constraints here: I do not have control on the code which writes to this database and I cannot modify it to write to a queue.
So far, I am reading the DB periodically for changes and new additions (using a last update timestamp) and pushing that data to a mongo db (as I do not want to hit main MySQL server for every request). Then I push these changes to frontend using cramp (ruby framework) and server sent events. To maintain per user queue, I have redis in the mix.
I realize that this is a convulated way of doing realtime push. I was wondering if there is a more neat solution to this mess.
If you want to push data realtime from the server, then make use of technologies that provide real time access. I would recommend you to make use of Websockets.
The only issue is websockets is not supported by all the browsers, to take care of this you can use the available frameworks built over websockets that provide fallback to protocols supported by the browsers such as long polling, streaming etc. Following are the frameworks which I would suggest to use:
Atmosphere framework - https://github.com/Atmosphere/atmosphere
Play framework! - http://www.playframework.org/
I've got a database on my server which is about 3mb big. I'd like to ship that with my iphone application.
The most important thing is that I'd like to promote changes to the database (insert, updates, deletes) to the iphone. What's the best way of doing that? I mean - what is necessary on
- the server
- the client (= iphone)
- between; how to transfer this data?
I'm pretty free in using technologies serverside; right now, I've got an sqlite-database on the server filled with the data I'd like to sync to the iphones.
How often do you need the database to be updated, and how urgent are the changes?
If the database updates are infrequent and non-urgent, I'd have the app check for a new version of the database on startup, and if it has changed, download the entire new file.
The app would always download a small metadata file from a known URL on startup. The metadata file contains an version identifier for the latest version and a location where that version of the database can be downloaded. If the version identifier has changed from the version the app already has, will download the new version. If the version identifier has not changed, or if it can't check, the app can keep using the version it has.
Pro tip: if you want to show a progress bar for the download, include the size of the database in the metadata file. Cell networks often have transparent proxies that strip out the Content-Length header from HTTP responses.
Try using web hooks.
The concept of a WebHook is simple. A
WebHook is an HTTP callback: an HTTP
POST that occurs when something
happens; a simple event-notification
via HTTP POST.
A web application implementing
WebHooks will POST a message to a URL
when certain things happen. When a web
application enables users to register
their own URLs, the users can then
extend, customize, and integrate that
application with their own custom
extensions or even with other
applications around the web. For the
user, WebHooks are a way to receive
valuable information when it happens,
rather than continually polling for
that data and receiving nothing
valuable most of the time. WebHooks
have enormous potential and are
limited only by your imagination! (No,
it can't wash the dishes. Yet.)
You can find out more on Webhooks here:
http://www.webhooks.org/ and http://webhooks.pbworks.com/
Wonder if you have considered using a Sync Framework to manage the synchronization. If that interests you can take a look at the open source project, OpenMobster's Sync service. You can do the following sync operations
two-way
one-way client
one-way device
bootup
Besides that, all modifications are automatically tracked and synced with the Cloud. You can have your app offline when network connection is down. It will track any changes and automatically in the background synchronize it with the cloud when the connection returns. It also provides synchronization like iCloud across multiple devices
Also, modifications in the Cloud are synched using Push notifications, so the data is always current even if it is stored locally.
Here is a link to the open source project: http://openmobster.googlecode.com
Here is a link to iPhone App Sync: http://code.google.com/p/openmobster/wiki/iPhoneSyncApp
I'm looking into building an application which works just as well offline as it does online. Since the application cannot communicate with the server while in offline, there is some level of synchronization which needs to take place.
What are some good tools to read about and start thinking about when planning offline operations with synchronization for your iPhone?
What tools would I have to create on my own, versus tools that apple already provides to help with this particular issue?
I've been working on an app that handles this exact behavior for the last 2 months or so. It has a small subset of functions which are online only and a large set of functionality that is offline/online.
I'm using sqlite for local storage as suggested here with a modified version of the sqlitepersistentobjects library. The base version of sqlitepersistentobjects is not thread safe so watch out if you are using it. (check out objectiverecord in: objectivesync for a thread safe alternative but be prepared to dig into the code). If you are willing to develop for the 3.0 sdk then core data is another possibility for a sqlite library.
The overall architecture is simple enough I have modeled local storage using sqlite and remote interaction using objective resource against a rails app and REST api. It can use either xml or json for data serialization.
When an object is modified locally the change is first saved to the sqlite database record for that object and then added to a queue which is serialized and stored in the local sqlite db as well. (The queue can then be processed at any time)
If there is a connection available any queued local changes are deserialized and added to an NSOperationQueue which then processes them in the background.
In order to make this all work I've subclassed NSOperation so that it can support several types of remote queue operations - create, update, delete essentially using objective resource to make the remote requests.
The nice thing about using NSOperationQueue and NSOperation is that they handle the background threading for you so I'd highly recommend having a look at the apple docs for those classes and also at the apple threading guide.
When the application loads there is a bit of remote checking done and processed in the background to pull down the latest data - although to be honest I am still changing the way this behaves a bit.
That's a quick overview of what I've had to deal with so far...hope it helps a little.
there are plenty of application on the app store which rely on both online as well as offline data
what you should really be doing is on start of your app, run a background thread (which runs silently so your user never sees any delay). this thread downloads the latest data from your server and pushes it into your local database (sqlite is the best choice)
make sure you implement some kind of data versioning so that your app only downloads data which is actually changed since last download - else you would unnecessarily be downloading the entire dataset which can be quite huge (depending upon your app requirements)
also make sure to test for internet connectivity when doing this. if no internet is available, alert the user for sure
this way you get the best of both worlds. users when away from internet can still use your app with their local sqlite data
in iphone os 3.0 apple has introduced push services - where you can simply "PUSH" your data instead of doing a "PULL" however this is not available in the current iPhone OS (2.x.x)
Push is probably not a viable option here, since the amount of data you can push is miniscule, and basically comes back to "tell my app to make a server call". We use an online/offline model in Satchel. Whenever we have to communicate with the server, we bundle that communication (a URL and possibly some POST data) and store it to a database. If we're online, we pull it right back out, send it, and when we get a valid response back, we remove the record from the database. If we're offline, those rows build up, and the next time we ARE online, they get sent out. This is not a workable model in all situations, but can be adapted to most.
In 3.0, you've got access to CoreData, which is a great data management tool. Other than that, the NSURLXXX family is your friend.
I would store all the information I gather while offline in a SQLite database. Then, on user 's request, you can SYNC all the stored information with a server using HTTP or a custom TCP/IP protocol you can come up with.
I have been using this approach on Palm OS applications for almost 10 years now, and they do work very effectively.
As far as I know, the only "tool" you will have to accomplish this is plain old OBJECTIVE-C with Cocoa Touch. Although you could use some TCP/IP C++ libraries that will make your life easier if you decide to implement your own protocol.
Wonder if you have considered using a Sync Framework to manage the synchronization. If that interests you can take a look at the open source project, OpenMobster's Sync service. You can do the following sync operations
two-way
one-way client
one-way device
bootup
Besides that, all modifications are automatically tracked and synced with the Cloud. You can have your app offline when network connection is down. It will track any changes and automatically in the background synchronize it with the cloud when the connection returns. It also provides synchronization like iCloud across multiple devices
Also, modifications in the Cloud are synched using Push notifications, so the data is always current even if it is stored locally.
Here is a link to the open source project: http://openmobster.googlecode.com
Here is a link to iPhone App Sync: http://code.google.com/p/openmobster/wiki/iPhoneSyncApp