API 组合模式架构

Architecture

API 组合架构图，组合器服务向多个微服务扇出并行请求，收集带超时处理的响应，并将结果合并为单一统一响应，支持部分降级。该模板模拟当单个客户端查询需要来自多个服务的数据时使用的 API 组合模式，避免直接的服务间调用。适合在微服务架构中构建聚合层的团队。

下载 .fz 文件

完整 FlowZap 代码

Client { # Client Application
n1: circle label:"Complex Query Request"
n2: rectangle label:"API Composer Service"
n3: rectangle label:"Receive Composed Response"
n4: circle label:"End"
n1.handle(right) -> n2.handle(left)
n2.handle(bottom) -> Composer.n5.handle(top) [label="Compose"]
n3.handle(right) -> n4.handle(left)
}
Composer { # API Composition Layer
n5: rectangle label:"Parse Query Requirements"
n6: rectangle label:"Fan-Out Parallel Requests"
n7: rectangle label:"Collect Responses"
n8: diamond label:"All Responses Received?"
n9: rectangle label:"Merge and Transform"
n10: rectangle label:"Return Partial with Fallback"
n5.handle(right) -> n6.handle(left) [label="Decompose"]
n6.handle(bottom) -> Services.n11.handle(top) [label="GET /users"]
n6.handle(bottom) -> Services.n12.handle(top) [label="GET /orders"]
n6.handle(bottom) -> Services.n13.handle(top) [label="GET /products"]
n7.handle(right) -> n8.handle(left)
n8.handle(right) -> n9.handle(left) [label="Yes"]
n8.handle(bottom) -> n10.handle(top) [label="Timeout"]
n9.handle(top) -> Client.n3.handle(bottom) [label="Composed JSON"]
n10.handle(top) -> Client.n3.handle(bottom) [label="Partial JSON"]
}
Services { # Microservices
n11: rectangle label:"User Service"
n12: rectangle label:"Order Service"
n13: rectangle label:"Product Service"
n14: rectangle label:"User Response"
n15: rectangle label:"Order Response"
n16: rectangle label:"Product Response"
n11.handle(right) -> n14.handle(left) [label="Query"]
n12.handle(right) -> n15.handle(left) [label="Query"]
n13.handle(right) -> n16.handle(left) [label="Query"]
n14.handle(top) -> Composer.n7.handle(bottom) [label="User Data"]
n15.handle(top) -> Composer.n7.handle(bottom) [label="Order Data"]
n16.handle(top) -> Composer.n7.handle(bottom) [label="Product Data"]
}

为什么需要这个工作流？

When a single UI view requires data from multiple microservices, having the client make multiple API calls increases latency and complexity. The API composition pattern provides a server-side aggregation layer that fans out requests in parallel, collects responses, and returns a single unified result.

工作原理

Step 1: The client sends a single query request to the API composer service.
Step 2: The composer parses the query requirements and identifies which services to call.
Step 3: Parallel requests are fanned out to User, Order, and Product services simultaneously.
Step 4: Responses are collected with timeout handling for slow services.
Step 5: If all responses arrive, they are merged into a single composed JSON response.
Step 6: If some services timeout, a partial response with fallback data is returned.

替代方案

GraphQL federation provides query-level composition without a custom aggregator. Client-side composition gives more control but increases latency. BFF pattern is similar but client-specific. This template shows the generic API composition approach.

Key Facts

Template Name	API 组合模式架构
Category	Architecture
Steps	6 workflow steps
Format	FlowZap Code (.fz file)