Client
The MosaicClient class provides a base class for client implementation. Clients are responsible for publishing their data needs and performing data processing tasks—such as rendering a visualization—once data is provided by the coordinator.
If you are interested in creating your own Mosaic clients, see the Mosaic GitHub repository. For concrete examples, start with the source code of Mosaic inputs.
constructor
new MosaicClient(filterSelection)
Create a new client instance. If provided, the Selection-valued filterSelection argument will be exposed as the client's filterBy property.
filterBy
client.filterBy
Property getter for the Selection that should filter this client. The coordinator uses this property to provide automatic updates to the client upon selection changes.
filterStable
client.filterStable
Property getter for a Boolean value indicating if the client query can be safely optimized using a pre-aggregated materialized view. This property should return true if changes to the filterBy selection do not change the groupby (e.g., binning) values of the client query.
The MosaicClient base class will always return true. Subclasses should override the property getter to provide more nuanced results as needed.
fields
client.fields()
Return an array of field requests, called by the coordinator when the client is first connected. Each field request should be an object with table and column properties. The coordinator will then return column metadata via the client fieldInfo() method.
The MosaicClient base class will always return null, indicating no field metadata is needed. Subclasses should override this method to provide more nuanced results as needed.
fieldInfo
client.fieldInfo(info)
Called by the coordinator to set the field information for this client. The info argument will be an array of objects with the table name, column name, and type information.
The MosaicClient base class does nothing here. Subclasses should override this method to process and retain field information as needed.
query
client.query(filter)
Return a query specifying the data needed by this client, incorporating any requested filter criteria. If provided, the filter argument should consist of Boolean-valued SQL predicates, suitable for inclusion in a WHERE clause.
The MosaicClient base class simply returns null. Subclasses should override this method to provide a query, typically constructed using Mosaic SQL builder utilities.
queryPending
client.queryPending()
Called by the coordinator to inform the client that a query is pending. The info argument will be an array of objects with the table name, column name, and type information. This method should return the current client instance.
The MosaicClient base class does nothing here. Subclasses should override this method as needed.
queryResult
client.queryResult(data)
Called by the coordinator to return query results in the form of a data table. This method should return the current client instance.
The MosaicClient base class does nothing here. Subclasses should override this method as needed.
queryError
client.queryError(error)
Called by the coordinator to report that an error occurred during query processing. This method should return the current client instance.
The MosaicClient base class reports the error to console.error. Subclasses should override this method as needed.
update
client.update()
Requests that a client update using its current data, for example to (re-)render an interface component, and returns the current client instance. Called by the coordinator after returning data via the queryResult method.
The MosaicClient base class does nothing here. Subclasses should override this method as needed.
requestQuery
client.requestQuery(query)
Requests that the coordinator execute a query for this client, and returns a Promise that resolves upon query completion or error. If an explicit query is not provided, the client query method will be called, filtered by the current filterBy selection.
requestUpdate
client.requestUpdate()
Request that the coordinator perform a throttled update of this client using the default query provided by the query method. Unlike requestQuery, for which every call will result in an executed query, multiple calls to requestUpdate may be consolidated.