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A synchronous communication pattern where a client sends a request to a service and waits for a response.
DESCRIPTION
The request-response pattern underpins client-server interactions, most notably HTTP and gRPC. A requester issues a request and blocks or awaits a response from the provider. It offers straightforward control flow and error handling. Drawbacks include tighter coupling, potential cascading latency, and backpressure under load. Resilience patterns like circuit breakers and retries mitigate risks. Request-response suits CRUD APIs, command operations, and interactive user flows. It complements asynchronous messaging when combined thoughtfully.
ALTERNATIVE DEFINITIONS
Wikipedia
Requestâresponse is a message exchange pattern in which a requestor sends a request message and waits for a response message.
Emphasizes waiting for a correlated response in a messaging exchange.
IETF
The Hypertext Transfer Protocol (HTTP) is a stateless request-response protocol in the client-server computing model.
Anchors the pattern within HTTPâs client-server model and statelessness.
Microsoft Learn
Use an asynchronous messaging system to decouple request and response processing for systems that require a response.
Shows a variation that decouples the pattern using asynchronous messaging.
RELATED TERMS
REST gRPC Synchronous Communication Circuit Breaker Pattern Service Mesh Timeout Retry with Backoff Idempotency Queue
COMPETING TERMS
KNOWLEDGE AREAS
Software Engineering Data Integration & Interoperability Cloud Real-time & Streaming Data
TARGET AUDIENCE
Software Developer DevOps Engineer Cloud Architect Data Engineer Data Architect
EXTERNAL SOURCES
- Wikipedia - Requestâresponse
- IETF - HTTP semantics request-response
- gRPC - gRPC request/response RPC model
- Microsoft - Resiliency for request-response
- NGINX - Reverse proxying request-response
TOP QUESTIONS
When should you use the Request-Response Pattern?
Use it for operations requiring immediate confirmation, such as CRUD APIs and user-initiated actions. Itâs suitable when latency is low and tight coordination is needed.
Category: Advice
What are the risks of the Request-Response Pattern?
Coupling and synchronous waits can cause cascading failures under load. Timeouts and retries must be tuned. Overuse can reduce resilience in distributed systems.
Category: Risks
How is the Request-Response Pattern typically implemented?
Common implementations include HTTP/REST and gRPC. Clients send requests and await replies. Infrastructure adds load balancers, service meshes, and tracing.
Category: Management
What is a common misunderstanding about the Request-Response Pattern?
People assume it must block threads. With async I/O, clients can await non-blockingly, preserving the request-response semantics without tying up resources.
Category: Misunderstanding
What are common mistakes with the Request-Response Pattern?
Missing timeouts and circuit breakers causes cascading failures. Ignoring idempotency makes retries dangerous. Lack of backoff amplifies thundering herds.
Category: Mistakes
What competes with the Request-Response Pattern?
Event-driven architectures compete by offering asynchronous decoupling. They suit high-throughput and loosely coupled workflows.
Category: Alternatives
How do you make Request-Response resilient?
Apply timeouts, retries with backoff, circuit breakers, and bulkheads. Use observabilityâtraces, logs, metricsâto diagnose latency and errors.
Category: Requirements
What is a good analogy for the Request-Response Pattern?
Itâs like a phone call: you dial (request) and wait for the person to answer (response).
Category: Example
What is currently a hot topic around Request-Response Pattern?
Using gRPC for efficient binary request-response and integrating service meshes for retries and timeouts are popular trends.
Category: Topic