Event replay

As explained in Troubleshooting Java, Second Edition

Event replay is the technique of feeding previously recorded event messages back into a system to reproduce workflows or behavior.

Event replay feeds previously recorded event messages back into a system, usually in staging or testing, to reproduce workflows and investigate missing or out-of-order behavior. section 13.2.2

Use replay and event-log inspection to ask:

• Was the event published, when, and by which service? section 13.2.2
• Was it consumed, delayed, dropped, or sent to a dead-letter queue? section 13.2.2
• Does replaying the message reproduce the failed workflow without affecting real users or data? section 13.2.2

Missing welcome emails

Filter the Kafka user-events topic by affected user IDs, confirm that UserRegistered messages contain the expected data, then replay them in a test environment to check whether the email service consumes them correctly. section 13.2.2

Figure 13.6 A developer can choose to replay events to troubleshoot a certain scenario.

Shows how a developer selects recorded events for troubleshooting a specific scenario. section 13.2.2

How Troubleshooting Java, Second Edition covers it

How deep it goes

Explains message structure, replay location, and diagnostic questions, but stops short of implementation code.

Examples

Uses UserRegistered messages, Kafka user-events, missing welcome emails, and a staging or test environment.

What it assumes

Assumes event-driven services and recorded event logs while defining events, messages, metadata, and brokers.

What you can do after

Diagnose/debug workflow failures by inspecting event history and replaying selected messages safely.

How it connects

Connects event replay with event-driven architecture, message brokers, event logs, service consumers, and dead-letter queues.

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Related concepts

• monitoringuses · Monitoring is the ongoing observation and measurement of a system’s behavior, state, or operational signals to assess its condition and detect changes or problems.
• software artifactuses · A software artifact is a persistent work product or object produced or maintained during software development or a related workflow.
• clientused by · A client is a person, organization, device, or software component that receives or uses a product, service, resource, or functionality provided by another entity.
• event sourcingused by · Event sourcing is a persistence pattern in which state changes are recorded as an ordered sequence of events from which application state can be derived.
• kafka-console-consumerused by · kafka-console-consumer is an Apache Kafka command-line utility that reads records from topics or partitions and prints them to the console.
• auditabilityproduces · Auditability is the ability to trace, inspect, and verify a system’s actions, decisions, changes, or records using available evidence.

This explainer was generated by Manning's knowledge graph from the text of Troubleshooting Java, Second Edition. The section links point to the parts of the book it draws on.