[Solved] What is wrong with this idempotent event consumer code snippet? processed = set() def consume(event): if event.id not in processed: process_event(event) processed.add(event.id) | Microservices

Microservices - Event-Driven Architecture

What is wrong with this idempotent event consumer code snippet?

processed = set()
def consume(event):
    if event.id not in processed:
        process_event(event)
    processed.add(event.id)

AEvent ID is added after processing, risking duplicates if process_event fails

BEvent ID is never added to the processed set

Cprocess_event is called even if event is duplicate

DThe processed set is cleared after each event

Step-by-Step Solution

Solution:

Step 1: Check order of adding event ID
The event ID is added after processing the event.
Step 2: Consider failure during processing
If process_event fails, the event ID is not added, so the event may be processed again causing duplicates.
Final Answer:
Event ID is added after processing, risking duplicates if process_event fails -> Option A
Quick Check:
Add event ID before processing to ensure idempotency [OK]

Quick Trick: Add event ID before processing to avoid duplicates on failure [OK]

Common Mistakes:

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What is wrong with this idempotent event consumer code snippet?