Cassandra Reader Component

The Cassandra Reader component is designed to execute a query against a database and pass along the results of the query. Each resulting row will be output as a separate entity.

Data Governance

The Cassandra Reader component will register every data item it returns with the Data Governance System. If the reader was triggered by a SignalData, the returned items are recorded as being derived from the SignalData.

Input Channels

execute — Receives a SignalData object that instructs the component to re-execute its query.  If the query is already executing, the message is ignored and logged.

Output Channels

default — Outputs each row returned by the query one-at-a-time as a DatabaseRowData. When the last record is returned, the isLast flag of the DatabaseRowData object will be set.

noResults— Outputs a SignalData object if the query executes, and no results are returned.

error — Outputs an ErrorOutput object if there is an error executing the query.

Parameters

resource — (CassandraResource) The resource defining the service to which this component should connect

query — (String) The CQL query to execute against the database

rowsToReturnPerCall — (int, default: 10) The number of rows to return per call to the database.  This defaults to 10 to limit the amount of data that is being read into memory at once.

executeOnstart — (String, default: true) Indicates whether the query should execute immediately upon start, or if it should wait for a signal before executing.

consistencyLevel — (String, default: ONE) The Consistency level to use when executing the query.  

requestTimeout — (int, default: 2) Maximum time, in seconds, before the request times out