Changes API: How to Subscribe to Index Changes

C#JavaNode.js

Subscribe to index changes using ForIndex or ForAllIndexes.

The Subscribe method on the observable these methods return accepts only an IObserver object by default.
To instead subscribe with a delegate, like the change => ... lambda used in the examples below, add the System.Reactive package to your project.
This adds Subscribe overloads that take delegates, including ones with error and completion handlers.

• In this article:
  • ForIndex
  • ForAllIndexes
  • IndexChange and IndexChangeTypes syntax

ForIndex

Index changes for one index can be observed using ForIndex method.

Syntax

IChangesObservable<IndexChange> ForIndex(string indexName);

Parameters
indexName	string	Name of an index for which notifications will be processed.

Return Value
IChangesObservable<IndexChange>	Observable that allows to add subscriptions to notifications for index with given name.

Example

IDisposable subscription = store
    .Changes()
    .ForIndex("Orders/All")
    .Subscribe(
        change =>
        {
            switch (change.Type)
            {
                case IndexChangeTypes.None:
                    //Do someting
                    break;
                case IndexChangeTypes.BatchCompleted:
                    //Do someting
                    break;
                case IndexChangeTypes.IndexAdded:
                    //Do someting
                    break;
                case IndexChangeTypes.IndexRemoved:
                    //Do someting
                    break;
                case IndexChangeTypes.IndexDemotedToIdle:
                    //Do someting
                    break;
                case IndexChangeTypes.IndexPromotedFromIdle:
                    //Do someting
                    break;
                case IndexChangeTypes.IndexDemotedToDisabled:
                    //Do someting
                    break;
                case IndexChangeTypes.IndexMarkedAsErrored:
                    //Do someting
                    break;
                case IndexChangeTypes.SideBySideReplace:
                    //Do someting
                    break;
                case IndexChangeTypes.IndexPaused:
                    //Do someting
                    break;
                case IndexChangeTypes.LockModeChanged:
                    //Do someting
                    break;
                case IndexChangeTypes.PriorityChanged:
                    //Do someting
                    break;
                default:
                    throw new ArgumentOutOfRangeException();
            }
        });

ForAllIndexes

Index changes for all indexex can be observed using ForAllIndexes method.

Syntax

IChangesObservable<IndexChange> ForAllIndexes();

Return Value
IChangesObservable<IndexChange>	Observable that allows to add subscriptions to notifications for all indexes.

Example

IDisposable subscription = store
    .Changes()
    .ForAllIndexes()
    .Subscribe(change => Console.WriteLine("{0} on index {1}", change.Type, change.Name));

IndexChange and IndexChangeTypes syntax

• IndexChange
• IndexChangeTypes

The notification object delivered to subscribers when an index changes.

class IndexChange
{
    IndexChangeTypes Type
    string Name
}

Property	Type	Description
Type	IndexChangeTypes	Change type
Name	string	Index name

enum IndexChangeTypes
{
    None,
    BatchCompleted,
    IndexAdded,
    IndexRemoved,
    IndexDemotedToIdle,
    IndexPromotedFromIdle,
    IndexDemotedToDisabled,
    IndexMarkedAsErrored,
    SideBySideReplace,
    Renamed,
    IndexPaused,
    LockModeChanged,
    PriorityChanged,
    RollingIndexChanged,
}

Name	Value
None	0
BatchCompleted	1
IndexAdded	8
IndexRemoved	16
IndexDemotedToIdle	32
IndexPromotedFromIdle	64
IndexDemotedToDisabled	256
IndexMarkedAsErrored	512
SideBySideReplace	1024
Renamed	2048
IndexPaused	4096
LockModeChanged	8192
PriorityChanged	16384
RollingIndexChanged	65536