Error Handling at Sink

Handling errors in sinks is crucial when external systems become unavailable or errors occur during event publication. The OnError.action property provides a standardized approach to manage these errors.

The following actions are supported for error handling at sink:

• log - Logs the error, and drops the message.
• stream - Forward the error and the event to fault stream. This stream, indicated as !<StreamName>, is created implicitly and captures both the event that led to the error and the error details. A fault stream will be composed of the base stream’s attributes, plus an _error attribute containing error details.
• wait - Wait for some time (i.e. 5 seconds) and then retry.

OnError.action Property

Apply the OnError.action property to a sink to handle errors.

CREATE SINK <stream name> WITH (type='<sink type>', OnError.action='<action>', <other properties>) (<attribute name> <attribute type>, ...);

Supported Sink Types

The OnError.action='stream' property is supported by various sink types including:

• database
• stream
• table
• jms
• http
• queryworker

Example: Sink with Fault Stream

-- Sink definition with OnError.action='stream' to manage errors
CREATE SINK HTTPSink WITH (
    type='http', 
    publisher.url='http://example.com/endpoint', 
    map.type='json',
    OnError.action='stream'
) (status string, count long, time long);

-- Automatically created fault stream schema
CREATE STREAM !HTTPSink (status string, count long, time long, _error object);

-- Error handling by inserting into the fault stream
INSERT INTO HTTPSinkErrorStream
SELECT status, count, time, convert(_error, 'string') as error
FROM !HTTPSink;

This example shows how to apply the OnError.action='stream' property to a sink, directing any errors encountered during event publication to a fault stream.