How to design a Sink
While the default implementation will create one
Sink per stream, this behavior can be
customized or overridden in a number of ways:
This is the default, where only one sink is active for each incoming stream name:
The exception to this rule is when a new STATE message is received for an already-active stream. In this case, the existing sink will be marked to be drained and a new sink will be initialized to receive the next incoming records.
In the case that a sink is archived because of a superseding STATE message, all prior version(s) of the stream’s sink are guaranteed to be drained in creation order.
Database sink example
A database-type target where each stream will land in a dedicated table. Each sink is of the same class, with a different target table based on stream_name.
SaaS sink example
A SaaS-type target where each stream will be uploaded to a different REST endpoint based on stream name. Each sink class is specialized based on the requirements of the target API endpoint.
In this scenario, the target intentionally creates multiple sinks per stream:
The developer may override
Target.get_sink()and use details within the record (or a randomization algorithm) to send records to multiple sinks all corresponding to the same stream.
Data lake ingestion example
1:many relationship may be used for a data lake target where output files should be pre-partitioned according to
one or more attributes within the record. Importing multiple smaller files, named according to
their partition key values are more efficient than loading fewer larger files.
In this scenario, the target intentionally sends all records to the same sink regardless of stream name:
The stream name will likely be made an attribute of the final output, but records do not need to be segregated by the stream name.
JSON file writer example
A json file writer where the desired output is a single combined json file with all records from all streams.