[KAFKA-3338] Add print and writeAsText functions to the Streams DSL

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.10.0.0
• Fix Version/s: 0.10.0.0
• Component/s: streams
• Labels: api newbie++
• Assignee: Bill Bejeck
• Reporter: Guozhang Wang
• Created: 05/Mar/16 02:15
• Updated: 22/Feb/17 01:06
• Resolved: 11/Apr/16 00:44

Description

We want to provide some REPL-like pattern for users for better debuggability. More concretely, we want to allow users to easily inspect their intermediate data streams in the topology while running the application. Theoretically this can be done by using a break point, or by calling System.out.println() inside the operator, or through a finer grained trace-level logging. But more user-friendly API would be to add a print() function to the KStream / KTable object like:

// Prints the elements in this stream to the stdout, i.e. "System.out" of the JVM
KStream#print(/* optional serde */);  
KTable#print(/* optional serde */);  

// Writes the stream as text file(s) to the specified location.
KStream#writeAsText(String filePath, /* optional serde */);
KTable#writeAsText(String filePath, /* optional serde */);

Issue Links

• relates to: KAFKA-3262 Make KafkaStreams debugging friendly