MongoDB official drivers automatically cache this resume token, and in the case of network transient error the driver will retry once. The _id of change event output is a resume token. For example, a change stream cursor opened against a 3-shard sharded cluster returns change events respecting the total order of those changes across all three shards.ĭue to the ordering characteristic, change streams are also inherently resumable. MongoDB guarantees the order of changes are preserved and change events can be safely interpreted in the order received. Provide a total ordering of changes across shards by utilising a global logical clock. Applications don’t need to handle data rollback in the event of failover. This means the change events that are sent to the client are durable. While the entries in Oplog may change between MongoDB major versions.Ĭhange events that are returned as part of change streams are at least committed to the majority of the replica set. Also, all of the official MongoDB drivers follow the same specifications when implementing change streams interface. The change events output that are returned by change streams are well documented. Provide a well defined API that are reliable. Applications can only open change streams against collections they have read access to. Utilise the built-in MongoDB Role-Based Access Control.
Key benefits of Change Streams over tailing Oplog are: In addition, Change Stream is more than just tailing the Oplog. See also MongoDB Specifications: Change Streams for more information on MongoDB driver specs on Change Stream implementation. Depending on the use case, this potentially could be more efficient in terms of data round trips.
#CHANGE CURSOR FULL#
It’s a cursor that will wait for a few seconds after returning a full result set, so that it can capture and return additional data added during a query. If more data is seen, iteration of the cursor will continue from the last document seen.Ĭhange Stream utilises TAILABLE_AWAIT, which is a tailable cursor with an await option set. Which basically a cursor that is not closed when the last data is retrieved but are kept open, the cursor location marks the final document position.
#CHANGE CURSOR CODE#
Without knowing more of the your code implementation, you’re probably utilising TAILABLE cursor.
Mouse.OverrideCursor = DisplayArea.I was initially concerned with the get more command because our tailable curosr implementation of the Oplog issues a lot of get more commands, but in case of Change Streams it is proportion to the amount of change cursors opened ' use OverrideCursor to force the cursor for all elements ' if the cursor scope is set to the entire application Private Sub CursorTypeChanged(ByVal sender As Object, ByVal e As SelectionChangedEventArgs)ĭim item As String = CType(e.Source, ComboBox).() ' When the Radiobox changes, a new cursor type is set Mouse.OverrideCursor = DisplayArea.Cursor Use OverrideCursor to force the cursor for all elements If the cursor scope is set to the entire application Switch (())ĭisplayArea.Cursor = Cursors.AppStarting
Changing the cursor of the Border control private void CursorTypeChanged(object sender, SelectionChangedEventArgs e)ĬomboBoxItem selectedCursor = source.SelectedItem as ComboBoxItem This forces the cursor to change for the whole application. If the cursor change is set to "Entire Application", the OverrideCursor property is set to the Cursor property of the Border control. A switch statement filters on the cursor name and sets the Cursor property on the Border which is named DisplayArea. The following code behind creates a SelectionChanged event handler which is called when the cursor type is changed in the ComboBox. The user interface is created, which consists of a ComboBox to select the desired Cursor, a pair of RadioButton objects to determine if the cursor change applies to only a single element or applies to the entire application, and a Border which is the element that the new cursor is applied to. This example consists of a Extensible Application Markup Language (XAML) file and a code behind file.
#CHANGE CURSOR HOW TO#
This example shows how to change the Cursor of the mouse pointer for a specific element and for the application.