What Is the Changes API

The changes subscription is accessible by a document store through its IDatabaseChanges interface.

store.changes([database]);

Changes object interface extends IConnectableChanges interface that represents the connection. It exposes the following properties, methods and events.

To receive notifications regarding server-side events, subscribe using one of the following methods.

• forAllDocuments()
• forAllIndexes()
• forAllOperations()
• forDocument()
• forDocumentsInCollection()
• forDocumentsStartingWith()
• forIndex()
• forOperationId()

To end a subscription (stop listening for particular notifications) use dispose.

const changes = store.changes();

await changes.ensureConnectedNow();

const allDocsChanges = changes.forAllDocuments()
    .on("data", change => {
        console.log(change.type + " on document " + change.id);
    })
    .on("error", err => {
        // handle error
    });

// ...

try {
    // application code here
} finally {
    // dispose changes after use
    if (changes != null) {
        changes.dispose();
    }
}

Changes API and Database Timeout

One or more open Changes API connections will prevent a database from becoming idle and unloaded, regardless of the configuration value for database idle timeout.

Changes API and Method Overloads

Changes API and Data Subscription are services that a RavenDB Server provides subscribing clients.
Both services respond to events that take place on the server, by sending updates to their subscribers.

• Changes API is a Push Notifications Service.

  • Changes API subscribers receive notifications regarding events that took place on the server, without receiving the actual data entities affected by these events.
    For the modification of a document, for example, the client will receive a DocumentChange object with details like the document's ID and collection name.

  • The server does not keep track of sent notifications or checks clients' usage of them. It is a client's responsibility to manage its reactions to such notifications.

• Data Subscription is a Data Consumption Service.

  • A Data Subscription task keeps track of document modifications in the database and delivers the documents in an orderly fashion when subscribers indicate they are ready to receive them.
  • The process is fully managed by the server, leaving very little for the subscribers to do besides consuming the delivered documents.