I'm having a huge issue that I've been trying for days to get through. I have a scenario in which I'm trying to handle an Insert Conflict in my Xamarin project. The issue is that the record in the Cloud DB doesn't exist because there was an issue with a foreign key constraint so I'm in a scenario in which the sync conflict handler needs to delete the local record along with the record in the __operations table in SQLite. I've tried everything. Purge with the override set to 'true' so that it should delete the local record and all operations associated. Doesn't work. I've been just trying to force delete it by accessing the SQL store manually:
var id = localItem[MobileServiceSystemColumns.Id];
var operationQuery = await store.ExecuteQueryAsync("__operations", $"SELECT * FROM __operations WHERE itemId = '{id}'", null).ConfigureAwait(false);
var syncOperation = operationQuery.FirstOrDefault();
var tableName = operation.Table.TableName;
await store.DeleteAsync(tableName, new List<string>(){ id.ToString() });
if (syncOperation != null)
{
await store.DeleteAsync("__operations", new List<string>() { syncOperation["id"].ToString() }).ConfigureAwait(false);
}
I am able to query the __operations table and I can see the ID of the item I want to delete. The DeleteAsync method runs without exception but no status is returned so I have no idea if this worked or not. When I try to sync again the operation stubbornly exists. This seems ridiculous. How do I just delete an operation without having to sync with the web service? I'm about to dig down further and try to force it even harder by using the SQLiteRaw library but I'm really really hoping I'm missing something obvious? Can anyone help? THANKS!
You need to have a subclass of the Microsoft.WindowsAzure.MobileServices.Sync.MobileServiceSyncHandler class, which overrides OnPushCompleteAsync() in order to handle conflicts and other errors. Let's call the class SyncHandler:
public class SyncHandler : MobileServiceSyncHandler
{
public override async Task OnPushCompleteAsync(MobileServicePushCompletionResult result)
{
foreach (var error in result.Errors)
{
await ResolveConflictAsync(error);
}
await base.OnPushCompleteAsync(result);
}
private static async Task ResolveConflictAsync(MobileServiceTableOperationError error)
{
Debug.WriteLine($"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.
Related
this function takes a ServicePoint object as argument, which has the following attributes:
adminId (String)
name (String)
serviceType (enum)
I want this function to create a new Table with name: "name+adminId". This is achieved.
Also I want this function to create a new Table (if it is not there already) by the name ServicePoints.
ServicePoints stores the relationship between user (with objectId = adminId) and the new Table.
To achieve this, I set "serviceTable" attribute with value as the new Table created, acting as a pointer.
When I run the code first time, I achieve the required tables. But, when I run the function second time, it doesn't add the new row/record to ServicePoints table.
I don't know why.
UPDATE I found that set ParseObject operation is the culprit. But, to my surprize, it executes successfully for the very first time. But fails every next time. This is really absurd behaviour from parse_server_sdk_flutter.
Future<bool> createServicePoint(ServicePoint servicePoint) async {
String newServicePointName = servicePoint.name + servicePoint.adminId;
var newServiceTable = ParseObject(newServicePointName);
var response = await newServiceTable.save();
if (response.success) {
print('Now adding new row to ServicePoints table');
var servicePointsTable = ParseObject('ServicePoints')
..set<String>("serviceName", servicePoint.name)
..set<String>("adminId", servicePoint.adminId)
..set<String>("serviceType", _typeToLabel[servicePoint.serviceType])
..set<ParseObject>("serviceTable", newServiceTable);
var recentResponse = await servicePointsTable.save();
return recentResponse.success;
} else {
return false;
}
}
If anyone runs into this problem, you need to check the result after saving the ParseObject. If there is error like "Can't save into non-existing class/table", then just go to the dashboard and create the table first.
I'm facing an issue in the Reliable Dictionary where I update a particular entry, but do not commit the transaction. It appears that the transaction abort does not reset the updated entry.
In my logic, I have to check if a few seats are available in a reliable dictionary. If they are, I assign them to the Order. If one of them isn't available, I'd ideally like to abort the transaction ensuring that the previously assigned seats would roll back to their original state, since I didn't commit the transaction.
Could I be doing something wrong here?
Here is the code I'm building:
var unavailableSeats = new List<string>();
using (var tx = StateManager.CreateTransaction())
{
foreach (var requestSeat in request.Seats)
{
var match = await dict.Value.TryGetValueAsync(tx, requestSeat.ToString(), LockMode.Update);
if (!match.HasValue)
{
response.SetError($"No Seat found matching the Seat Key: {requestSeat} provided.");
return response;
}
var seatEntry = match.Value;
if (seatEntry.IsAvailable())
{
seatEntry.AssignToOrder(request.OrderId, request.RequestId.ToString());
await dict.Value.SetAsync(tx, requestSeat.ToString(), seatEntry, TimeSpan.FromSeconds(4),
cancellationToken);
}
else
{
unavailableSeats.Add(requestSeat.ToString());
}
}
if (!unavailableSeats.Any())
{
await tx.CommitAsync();
response.Success = true;
response.RequestId = request.RequestId;
return response;
}
tx.Abort();
}
You are modifying the in memory entity which is what is stored in the dictionary. You need to make a copy of the object before you modify any property. This is documented in a few places, but specifically mentioned in this article https://learn.microsoft.com/en-us/azure/service-fabric/service-fabric-work-with-reliable-collections in the common pitfalls section.
Instead of
var seatEntry = match.Value
do
var seatEntry = new SeatEntryType(match.Value) // assuming copy constructor
How to handle high frequency updateOrCreate requests with Waterline in Sails for a Postgresql database ?
I tried to use findOrCreate and then update the item, I tried findOne and then update or create the item, I tried to put a beforeCreate, a beforeValidation hook method to check if the item exists but without any success.
Should I add an error handler to get errors from the unique index and try again?
In the Waterline docs, there is a warning about it but no direction to solve this problem.
Thank you for any tips.
Should I add an error handler to get errors from the unique index and try again?
That's going to be the only option until such time as Waterline implements transactions. Something like:
// This will hold the found or created user
var user;
// Keep repeating until we find or create a user, or get an error we dont expect
async.doUntil(
function findOrCreate(cb) {
// Try findOrCreate
User.findOrCreate(criteria, values).exec(function(err, _user) {
// If we get an error that is not a uniqueness error on the
// attribute we expect collisions on, bail out of the doUntil
if (err &&
(
!err.invalidAttributes["myUniqueAttribute"] ||
!_.find(err.invalidAttributes["myUniqueAttribute"], {rule: 'unique'})
)
) {
return cb(err);
}
// Otherwise set the user var
// It may still be undefined if a uniqueness error occurred;
// this will just cause doUntil to run this function again
else {
user = _user;
return cb();
}
},
// If we have a user, we are done. Otherwise go again.
function test() {return user},
// We are done!
function done(err) {
if (err) {return res.serverError(err);}
// "user" now contains the found or created user
}
});
Not the prettiest, but it should do the trick.
I would like to update a column in a specific row in Azure Mobile Services using server side code (node.js).
The idea is that the column A (that stores a number) will increase its count by 1 (i++) everytime a user runs a read query from my mobile apps.
Please, how can I accomplish that from the read script in Azure Mobile Services.
Thanks in advance,
Check out the examples in the online reference. In the table Read script for the table you're tracking you will need to do something like this. It's not clear whether you're tracking in the same table the user is reading, or in a separate counts table, but the flow is the same.
Note that if you really want to track this you should log read requests to another table and tally them after the fact, or use an external analytics system (Google Analytics, Flurry, MixPanel, Azure Mobile Engagement, etc.). This way of updating a single count field in a record will not be accurate if multiple phones read from the table at the same time -- they will both read the same value x from the tracking table, increment it, and update the record with the same value x+1.
function read(query, user, request) {
var myTable = tables.getTable('counting');
myTable.where({
tableName: 'verses'
}).read({
success: updateCount
});
function updateCount(results) {
if (results.length > 0) {
// tracking record was found. update and continue normal execution.
var trackingRecord = results[0];
trackingRecord.count = trackingRecord.count + 1;
myTable.update(trackingRecord, { success: function () {
request.execute();
});
} else {
console.log('error updating count');
request.respond(500, 'unable to update read count');
}
}
};
Hope this helps.
Edit: fixed function signature and table names above, adding another example below
If you want to track which verses were read (if your app can request one at a time) you need to do the "counting" request and update after the "verses" request, because the script doesn't tell you up front which verse records the user requested.
function read(query, user, request) {
request.execute( { success: function(verseResults) {
request.respond();
if (verseResults.length === 1) {
var countTable = tables.getTable('counting');
countTable.where({
verseId: verseResults[0].id
}).read({
success: updateCount
});
function updateCount(results) {
if (results.length > 0) {
// tracking record was found. update and continue normal execution.
var trackingRecord = results[0];
trackingRecord.count = trackingRecord.count + 1;
countTable.update(trackingRecord);
} else {
console.log('error updating count');
}
}
}
});
};
Another note: make sure your counting table has an index on the column you're selecting by (tableName in the first example, verseId in the second).
I've got a mySql db with non-standard IDs and field names, so I was trying to use both jsonResultsAdapterProvider and setRestangularFields. Here's the code in my app.config file:
RestangularProvider.setBaseUrl(remoteServiceName);
RestangularProvider.setRestangularFields({id: 'personID'});
RestangularProvider.addResponseInterceptor(function(data, operation, what, url, response, deferred) {
if (data.error) {
return data.error;
}
var extractedData = data.result;
return jsonResultsAdapterProvider.$get().camelizeKeys(extractedData);
});
RestangularProvider.addRequestInterceptor(function(elem, operation, what, url) {
return jsonResultsAdapterProvider.$get().decamelizeKeys(elem);
});
It's all good until I try to do a put/save. When I look at the request payload within the browser dev tools, it's: {"undefined":12842} (but the url is correct, so I know the id is set) If I don't use the ResultsAdapter and change the id field to Person_ID, payload looks good, so I know I'm making the right calls to Get and Save the Restangular objects. But for what it's worth, here's the code:
$scope.tests = Restangular.all('members').getList().$object;
vm.testEdit = function () {
$scope.test = Restangular.one('members', 12842).get().then(function(test) {
var copy = Restangular.copy(test);
copy.title = 'xxxx';
copy.put(); // payload was: undefined: 12842
});
}
// I also tried customPUT...
// copy.customPUT(copy, '', {}, {'Content-Type':'application/x-www-form-urlencoded'});
I tried "fixing" the id other ways too, too. like this:
Restangular.extendModel('members', function(model) {
model.id = model.personID;
return model;
});
but that messed up the urls, causing missing ids. And I tried getIdFromElem, but it only got called for my objects created with Restangular.one(), not with Restangular.all()
Restangular.configuration.getIdFromElem = function(elem) {
console.log('custom getIdFromElem called');
if (elem.route === 'members') { // this was never true
return elem[personID];
}
};
It seems like Restangular needs to substitute 'personID' most of the time, but maybe it needs 'Person_ID' at some point during the Save? Any ideas on what I could try to get the Save working?
I finally figured it out! The problem was in my config code and in the way I was decamelizing. Because of inconsistencies in my db field names (most use underscores, but some are already camelCase), I was storing the server's original elem names in an array within the jsonResultsAdapterProvider. But since I was calling jsonResultsAdapterProvider.$get().camelizeKeys(extractedData); within the interceptors, I was reinstantiating the array each time I made a new request. So, the undefined in the PUT request was coming from my decamelizeKeys() method.
My updated config code fixed the problem:
RestangularProvider.setBaseUrl(remoteServiceName);
RestangularProvider.setRestangularFields({id: 'personID'});
var jsonAdapter = jsonResultsAdapterProvider.$get();
RestangularProvider.addResponseInterceptor(function(data, operation, what, url, response, deferred) {
if (data.error) {
return data.error;
}
var extractedData = data.result;
// return extractedData;
return jsonAdapter.camelizeKeys(extractedData);
});
RestangularProvider.addRequestInterceptor(function(elem, operation, what, url) {
return jsonAdapter.decamelizeKeys(elem);
});