Events

The Open API interface allows the client to subscribe to a variety of asynchronous events. These events fall in the following categories:

• Server events: server closed, server errors, events related to Persistent Queries
• Worker events: workers opened, workers closed, worker errors, log messages
• Table events: table update events and table snapshot events

Server Events

The client subscribes to server events by implementing the IOpenApiListener interface and passing that object to Connect. For the sake of implementation convenience we also provide the class AbstractOpenApiListener which provides default (no-op) implementations of all the interface methods; this frees the caller from having to implement every method in the interface: it can implement only the methods it cares about. We also provide the class OpenApiEventDispatcher for callers who prefer to use event rather than interface syntax.

Worker Events

The client subscribes to worker events by implementing the IWorkerListener interface and passing that object to the StartWorker, AttachWorkerByName, or AttachWorkerBySerial methods. For the sake of implementation convenience we also provide the class AbstractWorkerListener which provides default (no-op) implementations of all the interface methods; this frees the caller from having to implement every method in the interface: it can implement only the methods it cares about. We also provide the class WorkerEventDispatcher for callers who prefer to use event rather than interface syntax.

Table Update Events

Note: This interface is in flux and is subject to change. It currently exposes a low-level Deephaven protocol object to the client, Deephaven.OpenAPI.Shared.Data.DeltaUpdates. It is our intention to update this interface so it uses a higher-level object instead.

The client subscribes to table update events by attaching a callback to the OnTableUpdate event, for example with a lambda:

table.OnTableUpdate += (table, update) =>
{
    ...
};

table is of type IQueryTable and refers to the IQueryTable that is firing the event. udpate is of type ITableUpdate. It currently contains the single getter DeltaUpdates which is of type Deephaven.OpenAPI.Shared.Data.DeltaUpdates. As discussed above, this is currently a low-level protocol object. In a future version of the client, we will return a higher-level object instead.

Table Snapshot Events

The client subscribes to table snapshot events by attaching a callback to the OnTableSnapshot event, for example with a lambda:

table.OnTableSnapshot += (table, snapshot) =>
{
    ...
};

table is of type IQueryTable and refers to the IQueryTable that is firing the event. snapshot is of type ITableSnapshot. The definition of each of the properties of ITableSnapshot is provided in its API documentation.

What's Next

In the next chapter, we cover Asynchronous Programming.