Status

Current state: Under Discussion Accepted

Discussion thread: http://mail-archives.apache.org/mod_mbox/samza-dev/201703.mbox/browser

JIRA: SAMZA-1126

Released:  0.13.0

Problem

In Samza 0.12, we introduced the StreamProcessor API to support Samza as a Library model. That introduced "processorId" that is synonymous to the logical "containerId" that Samza assigns in a fixed-set container model. 
However, having an "int" processorId is insufficient to uniquely identify a processor in various runtime environment(s). This proposal is to define proper semantics to processorId and how it will be used in the samza tech stack.

...

public interface JobCoordinator {
	...
 
	// Before
	// int getProcessorId();
 
	String getLocalProcessorIdgetProcessorId();
	...
}

New Interface

/**
  * To be used by the JobCoordinator to generator ProcessorId
  * It can be configured by using a configuration - app.processor-id-generator.class
  */
public interface ProcessorIdGenerator {
	/**
	* Generates a String representation to identify the processor instance
	* This value can be representative of its current executing environment. It can also be custom-managed by the user.
	* **Note**: processorId has to be unique among the processors within a job
	* @return String , identifier for the processor
	*/
	String generateProcessorId();
}
 
// Default (after 0.13+)
public class UUIDGenerator implements ProcessorIdGenerator {
	String generateProcessorId() {
	    return UUID.randomUUID();
	}
}

...

Existing users of StreamProcessor API should also set the processor.id config to the value previously assigned in the constructor.

Note: In In case of more than one StreamProcessor within the same JVM, it is still required to use unique processorId for each StreamProcessor instance. The custom ProcessorIdGenerator, then, should can contain a static counter which is incremented for each call to generateProcessorId and the counter value can be appended to the identifier. 

...