refac: Refactor Publish module to Improve code quality by removing implementation smell

[nakul3736]

Refactor for Improved Readability and Modularity

Changes

1. Simplified Complex Conditional in publishOutstandingBatch

   • Path: com.google.cloud.pubsub.v1
   • File: Publisher.java
   • Method: publishOutstandingBatch
   • Problem: The method contained a complex conditional (if (!activeAlarm.get() && outstandingBatch.orderingKey != null && !outstandingBatch.orderingKey.isEmpty())) mixing multiple checks, increasing cognitive load.
   • Change: Broke the conditional into a separate method shouldPublishMoreForKey(boolean isAlarmActive, String orderingKey) to isolate the logic and improve readability.
   • Impact: Reduces cyclomatic complexity and makes the intent clearer.

2. Extracted acquire Method into Modular Helper Methods

   • Path: com.google.cloud.pubsub.v1
   • File: Publisher.java (nested class MessageFlowController)
   • Method: acquire
   • Problem: The original method was long and handled multiple responsibilities (limit checking, message slot acquisition, byte space allocation, waiting), leading to high complexity and duplication.
   • Change: Refactored into five focused methods:
     • checkMessageLimit(): Validates message count against the limit.
     • checkByteLimit(long messageSize): Validates byte count against the limit.
     • acquireMessageSlot(): Acquires a message slot, waiting if necessary.
     • acquireByteSpace(long messageSize): Acquires byte space, handling partial allocation.
     • waitForResource(CountDownLatch waiter): Centralizes waiting logic with lock management.
   • Impact: Each method now has a single responsibility, reducing complexity, eliminating duplication (e.g., waiting logic), and improving testability.

3. Renamed Variables for Clarity and Consistency

   • Path: com.google.cloud.pubsub.v1
   • File: Publisher.java
   • Changes:
     • topicNameSize → serializedTopicNameSize: Reflects it’s the serialized size, not string length.
     • messagesBatches → batchesByOrderingKey: Clarifies it’s a map keyed by ordering keys.
     • activeAlarm → isBatchPublishScheduled: Indicates it tracks scheduled batch publishing.
     • messagesWaiter → pendingPublishesTracker: Specifies it tracks pending publishes.
     • outstandingMessages → inFlightMessages: Uses standard “in-flight” term for processing items.
     • outstandingBytes → inFlightBytes: Consistent with inFlightMessages.
     • batchedBytes → totalMessageBytesInBatch: Describes it’s the total byte size in a batch.
   • Impact: Improves readability and reduces ambiguity, making the code self-documenting.

4. Refactor SchemaServiceGrpc to Eliminate Duplicated Code (Extract Class)

• Change: Extracted duplicated MethodDescriptor creation logic from SchemaServiceGrpc into a new MethodDescriptorFactory class.
• Impact:
  • Reduces code duplication across 10 methods (e.g., getCreateSchemaMethod).
  • Adheres to DRY principles.
  • Simplifies future maintenance by centralizing descriptor creation.

5. Replace Conditionals with Polymorphism in OpenTelemetryPubsubTracer

• Change: Refactored startSubscribeRpcSpan in OpenTelemetryPubsubTracer to use an RpcOperationHandler interface and concrete handlers (AckHandler, ModAckHandler, NackHandler), eliminating conditional logic (if/switch statements).
• Impact:
  • Removes Conditional Logic Over Type smell.
  • Makes the method extensible (new operations require only a new handler).
  • Aligns with the Open/Closed Principle.

6. Move Field/Method in Publisher Class (acquire Method)

• Change: Moved the field and associated logic used in the acquire method of the Publisher class to a more appropriate class (e.g., a resource manager or semaphore wrapper).
• Impact:
  • Improves cohesion by relocating resource acquisition logic to a dedicated class.
  • Reduces the Publisher class’s responsibilities.
  • Enhances readability and maintainability.

Testing

• Verified that the refactored code maintains original behavior by running existing unit tests (assumed present in the codebase).
• Manually tested publishing scenarios with ordered and unordered messages to ensure flow control and batching work as expected.
• Code coverage is also not reduced in the mockPublisher class.

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