I am using following method to sync Azure DB local table with server table but the changes which I made on my local DB are not reflecting to the Azure server,
public async Task PushDataAsync()
{
try
{
await _mobileService.SyncContext.PushAsync();
}
catch (Exception exc)
{
throw exc;
}
}
While using above method I am getting Error :-
Push Operation Fail.
Any Help will appreciated.
you are using right method to sync your offline store with server which is :-
await _mobileService.SyncContext.PushAsync();
I would suggest you to wrote few line of code in catch block which will help you to find out the reasons why the operations are not performed on server side
please use code bellow in catch block:-
public async Task PushDataAsync()
{
try
{
await _mobileService.SyncContext.PushAsync();
}
catch (MobileServicePushFailedException exc)
{
if (exc.PushResult != null)
{
syncErrors = exc.PushResult.Errors;
}
}
// Simple error/conflict handling.
if (syncErrors != null)
{
foreach (var error in syncErrors)
{
if (error.OperationKind == MobileServiceTableOperationKind.Update && error.Result != null || error.OperationKind == MobileServiceTableOperationKind.Insert && error.Result != null || error.OperationKind == MobileServiceTableOperationKind.Delete && error.Result != null)
{
//Update failed, reverting to server's copy.
await error.CancelAndUpdateItemAsync(error.Result);
}
else
{
// Discard local change.
await error.CancelAndDiscardItemAsync();
}
Debug.WriteLine(#"Error executing sync {2} operation. Item: {0} ({1}). Operation discarded.",
error.TableName, error.Item["id"], error.OperationKind);
}
}
}
Remember that PushAsync() pushes ALL changes from your local store to the cloud and that PullAsync first performs a Push. I would get rid of the service variable for each table and just use the service as a singleton class across your app. Here is my initialization. After this method returns, my local db is synced with the cloud and I can start using my tables:
public async Task InitializeStoreAsync()
{
try
{
var sqliteStore = _platform.MobileServiceSqliteStore;
sqliteStore.DefineTable<Memory>();
sqliteStore.DefineTable<User> ();
sqliteStore.DefineTable<Comment> ();
sqliteStore.DefineTable<Status>();
await _zumoClient.SyncContext.InitializeAsync(sqliteStore);
_memoryTable = _zumoClient.GetSyncTable<Memory> ();
_userTable = _zumoClient.GetSyncTable<User> ();
_commentTable = _zumoClient.GetSyncTable<Comment> ();
_statusTable = _zumoClient.GetSyncTable<Status>();
await _userTable.PullAsync ();
await _memoryTable.PullAsync ();
await _commentTable.PullAsync ();
await _statusTable.PullAsync();
}
catch (Exception ex)
{
Debug.WriteLine ("Initialize Store failed: {0}", ex.Message);
}
}
https://adrianhall.github.io/develop-mobile-apps-with-csharp-and-azure/chapter3/client/ search for "Handling Conflict Resolution"
Related
I have implemented the Azure - Offline Sync based on the documentation / Sample provided by Microsoft Sample in my Xamarin Forms Application.
In the sample / documentation provided, they are using the default Service Handler.
// Simple error/conflict handling. A real application would handle the various errors like network conditions,server conflicts and others via the IMobileServiceSyncHandler.
Since I need to implement a retry logic for 3 times if the Pull / Push fails. As per the documentation I have created a custom Service Handler(IMobileServiceSyncHandler).
Please find my code logic here.
public class CustomSyncHandler : IMobileServiceSyncHandler
{
public async Task<JObject> ExecuteTableOperationAsync(IMobileServiceTableOperation operation)
{
MobileServiceInvalidOperationException error = null;
Func<Task<JObject>> tryExecuteAsync = operation.ExecuteAsync;
int retryCount = 3;
for (int i = 0; i < retryCount; i++)
{
try
{
error = null;
var result = await tryExecuteAsync();
return result;
}
catch (MobileServiceConflictException e)
{
error = e;
}
catch (MobileServicePreconditionFailedException e)
{
error = e;
}
catch (MobileServiceInvalidOperationException e)
{
error = e;
}
catch (Exception e)
{
throw e;
}
if (error != null)
{
if(retryCount <=3) continue;
else
{
//Need to implement
//Update failed, reverting to server's copy.
}
}
}
return null;
}
public Task OnPushCompleteAsync(MobileServicePushCompletionResult result)
{
return Task.FromResult(0);
}
}
But I am not sure how to handle / revert server copy in case all the 3 retry failed.
In the TODO sample they where reverting it based on the
MobileServicePushFailedException. But which is available when we implement IMobileServiceSyncHandler.
More over if we include custom IMobileServiceSyncHandler it wont execute the code after PushAsync / PullAsync. Even the try catch wont fire in case any exception.
try
{
await this.client.SyncContext.PushAsync();
await this.todoTable.PullAsync(
//The first parameter is a query name that is used internally by the client SDK to implement incremental sync.
//Use a different query name for each unique query in your program
"allTodoItems",
this.todoTable.CreateQuery());
}
catch (MobileServicePushFailedException exc)
{
if (exc.PushResult != null)
{
syncErrors = exc.PushResult.Errors;
}
}
// Simple error/conflict handling. A real application would handle the various errors like network conditions,
// server conflicts and others via the IMobileServiceSyncHandler.
if (syncErrors != null)
{
foreach (var error in syncErrors)
{
if (error.OperationKind == MobileServiceTableOperationKind.Update && error.Result != null)
{
//Update failed, reverting to server's copy.
await error.CancelAndUpdateItemAsync(error.Result);
}
else
{
// Discard local change.
await error.CancelAndDiscardItemAsync();
}
Debug.WriteLine(#"Error executing sync operation. Item: {0} ({1}). Operation discarded.", error.TableName, error.Item["id"]);
}
}
}
Note
In my application I am only trying to achieve retry for 3 time in case any server error. I am not looking for to resolve conflicts. Thant is the reason I haven't added the code for the same.
If someone came across similar issues and resolved it please help.
Stez.
You say you aren't trying to resolve conflicts, but you need to resolve them one way or another (without telling the user what's going on, perhaps) by accepting the server version of the object or updating the client operation. Otherwise it will just keep telling you about the same conflict each time it retries the operation.
You need to have a subclass of the Microsoft.WindowsAzure.MobileServices.Sync.MobileServiceSyncHandler class, which overrides OnPushCompleteAsync() in order to handle conflicts and other errors. Let's call the class SyncHandler:
public class SyncHandler : MobileServiceSyncHandler
{
public override async Task OnPushCompleteAsync(MobileServicePushCompletionResult result)
{
foreach (var error in result.Errors)
{
await ResolveConflictAsync(error);
}
await base.OnPushCompleteAsync(result);
}
private static async Task ResolveConflictAsync(MobileServiceTableOperationError error)
{
Debug.WriteLine($"Resolve Conflict for Item: {error.Item} vs serverItem: {error.Result}");
var serverItem = error.Result;
var localItem = error.Item;
if (Equals(serverItem, localItem))
{
// Items are the same, so ignore the conflict
await error.CancelAndUpdateItemAsync(serverItem);
}
else // check server item and local item or the error for criteria you care about
{
// Cancels the table operation and discards the local instance of the item.
await error.CancelAndDiscardItemAsync();
}
}
}
Include an instance of this SyncHandler() when you initialize your MobileServiceClient:
await MobileServiceClient.SyncContext.InitializeAsync(store, new SyncHandler()).ConfigureAwait(false);
Read up on the MobileServiceTableOperationError to see other conflicts you can handle as well as its methods to allow resolving them.
The exception carries with it a copy of the server version. In my implementation of IMobileServiceSyncHandler I therefore just return error.Value and this seems to work.
A more extensive example of this kind of logic can be found in this MSDN blog.
The same author has another example where he shows how you can resolve the conflict in favour of the server copy or the client copy, here.
I have windows desktop application which commands or automates VMware functionalities. I want to rename existing snapshot and update same with following flow, but i don't see any vmware API to rename existing snapshot. Can anyone provide me info on how to rename vmware snapshot?
Thanks
Click on ‘Register and initiate snapshot’-> Initiate Guest VM
Shutdown->Rename Current Snapshot- SS1 to Temp-SS1->Take New Snapshot
with current snapshot name(i.e. SS1)->delete previous renamed
snapshot(i.e. Temp-SS1).
Above can be done by simple following two methods:
public bool CreateSnapShot(string vmName, string snapShotName, string snapShotDescription, bool replaceSnapShot, string currentSnapShotName)
{
try
{
NameValueCollection filter = new NameValueCollection();
filter.Add(Constants.VM_FILTER_NAME, vmName);
ManagedObjectReference snapShotMor = null;
VirtualMachine vmObject = (VirtualMachine) vimClient.FindEntityViews(typeof(VirtualMachine), null, filter, null).FirstOrDefault();
if (vmObject != null)
{
if (vmObject.Runtime.PowerState == VirtualMachinePowerState.poweredOn)
vmObject.ShutdownGuest();
while (vmObject.Runtime.PowerState == VirtualMachinePowerState.poweredOn)
{
Thread.Sleep(5000);
vmObject.UpdateViewData();//This will refresh VM object state
}
if (replaceSnapShot && currentSnapShotName!= "")
{
if (RenameSnapshot(snapShotName, vmObject))
snapShotMor = vmObject.CreateSnapshot(snapShotName, snapShotDescription, false, false);
}
else snapShotMor = vmObject.CreateSnapshot(snapShotName, snapShotDescription, false, false);
if (snapShotMor != null)
return true;
else return false;
}
else return false;
}
catch (Exception ex)
{
return false;
}
}
Snapshot rename can be done by following method:
public bool RenameSnapshot(string snapShotName, VirtualMachine vmObject)
{
try
{
ManagedObjectReference snapshotObject = vmObject.Snapshot.CurrentSnapshot;
VirtualMachineSnapshot currentSnapshotName = new VirtualMachineSnapshot(vimClient, snapshotObject);
currentSnapshotName.RenameSnapshot("Temp-" + snapShotName, "Renamed for deletion");
return true;
}
catch (Exception ex)
{
return false;
}
}
After above two steps you can delete renamed(Temp) snapshot.
Working with an Azure Mobile App with Node.js backend. I got everything working, kind of. After setting up Offline Sync it is taking about 8 minutes to sync what should be 30 seconds.
After debugging the app I found everything client side is working great. Reviewing the logs on the website I see the "read script" running repeatedly. It literally runs the read script every second, up until it finally finishes.
Is this behavior expected?
It hangs in SyncAsync() while awaiting LocalCards.PullAsync
Read Script
var table = module.exports = require('azure-mobile-apps').table();
table.read(function (context)
{
console.log('Attempting table read');
return context.execute();
});
App Code
private async Task InitLocalStoreAsync()
{
if (!App.MobileService.SyncContext.IsInitialized)
{
var store = new MobileServiceSQLiteStore("localsync32.db");
store.DefineTable<Nname>();
await App.MobileService.SyncContext.InitializeAsync(store);
}
await SyncAsync();
await RefreshNcards();
}
private async Task SyncAsync()
{
String errorString = null;
string unique = DateTime.Now.Ticks.ToString() + DateTime.UtcNow.TimeOfDay.ToString();
try
{
await LocalCards.PullAsync("Nnames "+unique,LocalCards.CreateQuery()); // first param is query ID, used for incremental sync
}
catch (Exception ex)
{
errorString = "Pull failed: " + ex.Message +
"\n\nIf you are still in an offline scenario, " +
"you can try your Pull again when connected with your Mobile Serice.";
}
if (errorString != null)
{
MessageDialog d = new MessageDialog(errorString);
await d.ShowAsync();
}
}
Apparently the PullAsync() command limits the query results to 50 per trip. So in my code I was only pulling 50 items at a time. To fix I added a pull options Param with a max page size:
private async Task SyncAsync()
{
String errorString = null;
PullOptions pageSize = new PullOptions { MaxPageSize =1000 };
try
{
await LocalCards.PullAsync("Nname",LocalCards.CreateQuery(), pullOptions: pageSize); // first param is query ID, used for incremental sync
}
catch (Exception ex)
{
errorString = "Pull failed: " + ex.Message +
"\n\nIf you are still in an offline scenario, " +
"you can try your Pull again when connected with your Mobile Serice.";
}
if (errorString != null)
{
MessageDialog d = new MessageDialog(errorString);
await d.ShowAsync();
}
}
I am working on a Windows Universal App. I Want to get the Data from a Bluetooth Device to the Windows Phone. I am Using the Concept of RFCommCommunicationTrigger for this Purpose.
Here's the code Snippet I am Using
var rfTrigger = new RfcommConnectionTrigger();
// Specify what the service ID is
rfTrigger.InboundConnection.LocalServiceId = RfcommServiceId.FromUuid(new Guid("<some_base_guid>"));
//Register RFComm trigger
var rfReg = RegisterTaskOnce(
"HWRFCommTrigger",
"BackgroundLibrary.RFBackgroundTask",
rfTrigger, null
);
SetCompletedOnce(rfReg, OnTaskCompleted);
Here the Function of RegisterTaskOnce
static private IBackgroundTaskRegistration RegisterTaskOnce(string taskName, string entryPoint, IBackgroundTrigger trigger, params IBackgroundCondition[] conditions)
{
// Validate
if (string.IsNullOrEmpty(taskName)) throw new ArgumentException("taskName");
if (string.IsNullOrEmpty(entryPoint)) throw new ArgumentException("entryPoint");
if (trigger == null) throw new ArgumentNullException("trigger");
// Look to see if the name is already registered
var existingReg = (from reg in BackgroundTaskRegistration.AllTasks
where reg.Value.Name == taskName
select reg.Value).FirstOrDefault();
Debug.WriteLine("Background task "+ taskName+" is already running in the Background");
// If already registered, just return the existing registration
if (existingReg != null)
{
return existingReg;
}
// Create the builder
var builder = new BackgroundTaskBuilder();
builder.TaskEntryPoint = entryPoint;
builder.Name = taskName;
builder.SetTrigger(trigger);
// Conditions?
if (conditions != null)
{
foreach (var condition in conditions)
{
builder.AddCondition(condition);
}
}
// Register
return builder.Register();
}
Here's the code for SetCompletedOnce this will add a Handler only once
static private void SetCompletedOnce(IBackgroundTaskRegistration reg, BackgroundTaskCompletedEventHandler handler)
{
// Validate
if (reg == null) throw new ArgumentNullException("reg");
if (handler == null) throw new ArgumentNullException("handler");
// Unsubscribe in case already subscribed
reg.Completed -= handler;
// Subscribe
reg.Completed += handler;
}
I have also Written the BackgroundLibrary.RFBackgroundTask.cs
public sealed class RFBackgroundTask : IBackgroundTask
{
public async void Run(IBackgroundTaskInstance taskInstance)
{
BackgroundTaskDeferral deferral = taskInstance.GetDeferral();
try
{
Debug.WriteLine(taskInstance.TriggerDetails.GetType());
taskInstance.Canceled += new BackgroundTaskCanceledEventHandler(OnCanceled);
Debug.WriteLine("RFComm Task Running");
Debug.WriteLine(taskInstance.TriggerDetails.GetType().ToString());
}
catch (System.Exception e)
{
Debug.WriteLine("RFComm Task Error: {0}", e.Message);
}
deferral.Complete();
}
}
The Run Method is Invoked Every Time The Device tries to Open the Connection.
The type of the Trigger that is obtained (the type I am debugging in the run method of the RFBackgroundTask.cs) is printed as
Windows.Devices.Bluetooth.Background.RfcommConnectionTriggerDetails
But I am Unable use that because I dont have this Class in the BackgroundLibrary project.
The Documentation says that this Provides information about the Bluetooth device that caused this trigger to fire.
It has Variables like Socket,RemoteDevice etc.
I think I am Missing something very simple
Can you please help me out .
Once your background task is launched, simply cast the TriggerDetails object to an RfcommConnectionTriggerDetails object:
public sealed class RFBackgroundTask : IBackgroundTask
{
public async void Run(IBackgroundTaskInstance taskInstance)
{
BackgroundTaskDeferral deferral = taskInstance.GetDeferral();
try
{
taskInstance.Canceled += new BackgroundTaskCanceledEventHandler(OnCanceled);
RfcommConnectionTriggerDetails details = (RfcommConnectionTriggerDetails)taskInstance.TriggerDetails;
StreamSocket = details.Socket; // Rfcomm Socket
// Access other properties...
}
catch (System.Exception e)
{
Debug.WriteLine("RFComm Task Error: {0}", e.Message);
}
deferral.Complete();
}
}
I'm using EMDK 2.5 (VS2008 and VC# and .NetCF3.5) Barcode2 class from the library to write a sample application to scan bar codes. I followed the samples available in EMDK namely CS_Barcode2Sample1 project.Every time I hardware trigger the scan the notification "E_SCN_READINCOMPATIBLE" is thrown and not able to retrieve the scanned data. The documentation doesn't say much about the cause of E_SCN_READINCOMPATIBLE notification and no luck from Google search. I tried several options including making use of Symbol.Barcode and the outcome is same.
I also tried EMDK 2.3 but the result is same.
I've pasted the whole code here....
public partial class Form1 : Form
{
private Barcode2 myBarcode2 = null;
public Form1()
{
InitializeComponent();
InitBarcode();
}
public bool InitBarcode()
{
// If the Barcode2 object is already initialized then fail the initialization.
if (myBarcode2 != null)
{
return false;
}
else // Else initialize the reader.
{
try
{
Symbol.Barcode2.Device[] AvailableDevices = Symbol.Barcode2.Devices.SupportedDevices;
if (AvailableDevices.Length == 0)
{
return false;
}
if (AvailableDevices.Length == 1)
{
//get the first available scanner in the list
Symbol.Barcode2.Device MyDevice = AvailableDevices[0];
// Create the reader, based on selected device.
myBarcode2 = new Barcode2(MyDevice);
// Attach a scan notification handler.
//this.myScanNotifyHandler = new Barcode2.OnScanHandler(myBarcode2_ScanNotify);
myBarcode2.OnScan += myBarcode2_ScanNotify;
// Attach a status notification handler.
//this.myStatusNotifyHandler = new Barcode2.OnStatusHandler(myBarcode2_StatusNotify);
myBarcode2.OnStatus += myBarcode2_StatusNotify;
myBarcode2.Config.TriggerMode = TRIGGERMODES.HARD;
// Submit a scan.
myBarcode2.Scan(5000);
}
}
catch (OperationFailureException ex)
{
MessageBox.Show("Exception Raised 1");
return false;
}
catch (InvalidRequestException ex)
{
MessageBox.Show("Exception Raised 2");
return false;
}
catch (InvalidIndexerException ex)
{
MessageBox.Show("Exception Raised 3");
return false;
}
}
return false;
}
private void myBarcode2_ScanNotify(ScanDataCollection scanDataCollection)
{
// Checks if the BeginInvoke method is required because the OnScan delegate is called by a different thread
if (this.InvokeRequired)
{
// Executes the OnScan delegate asynchronously on the main thread
this.BeginInvoke(new Barcode2.OnScanHandler(myBarcode2_ScanNotify), new object[] { scanDataCollection });
}
else
{
// Get ScanData
ScanData scanData = scanDataCollection.GetFirst;
int i;
switch (scanData.Result)
{
case Symbol.Barcode2.Results.SUCCESS:
String str = scanData.Text;
myBarcode2.Config.TriggerMode = TRIGGERMODES.HARD;
myBarcode2.Scan(5000);
break;
case Symbol.Barcode2.Results.E_SCN_READTIMEOUT:
break;
case Symbol.Barcode2.Results.CANCELED:
break;
case Symbol.Barcode2.Results.E_SCN_DEVICEFAILURE:
i = 93;
break;
default:
if (scanData.Result == Symbol.Barcode2.Results.E_SCN_READINCOMPATIBLE)
{
// If the failure is E_SCN_READINCOMPATIBLE, exit the application.
MessageBox.Show("Fatal Error");
this.Close();
return;
}
break;
}
}
}
private void myBarcode2_StatusNotify(StatusData statusData)
{
// Checks if the Invoke method is required because the OnStatus delegate is called by a different thread
if (this.InvokeRequired)
{
// Executes the OnStatus delegate on the main thread
this.Invoke(new Barcode2.OnStatusHandler(myBarcode2_StatusNotify), new object[] { statusData });
}
else
{
int i;
switch (statusData.State)
{
case States.IDLE:
break;
case States.READY:
break;
default:
break;
}
}
}
}
}
I've went thru this recently also, as I observed, it probably due to the scanner device is occupied by other application, where the scan request has been queued already, you can go to memory management, and kill the suspect app, and try your app again.
Refer to the Symbol FAQ