request-aggregation

Aggregating User, Order, and Recommendation Data in Parallel

A dashboard page needs the user profile, recent orders, and personalized recommendations -- but fetching them sequentially triples the page load time. This workflow uses FORK_JOIN to fetch all three in parallel, then merges the results into a single response.

Workflow

userId
  |
  v
  FORK_JOIN ----------------------------------+
  |                |                          |
  v                v                          v
+-----------------+ +------------------+ +------------------------+
| agg_fetch_user  | | agg_fetch_orders | | agg_fetch_             |
|                 | |                  | | recommendations        |
+-----------------+ +------------------+ +------------------------+
  name: "Alice"      recent orders list    items: ["Widget Pro",
  email: alice@co    from user history      "Gadget X"]
  tier: "premium"                           count: 2
  |                |                          |
  +------ JOIN ---+--------------------------+
               |
               v
     +---------------------+
     | agg_merge_results   |   combined from 3 services
     +---------------------+

Workers

FetchUserWorker -- Fetches user profile: name: "Alice", email: "alice@co.com", tier: "premium".

FetchOrdersWorker -- Fetches recent orders for the user.

FetchRecommendationsWorker -- Generates recommendations: items: ["Widget Pro", "Gadget X"], count: 2.

MergeResultsWorker -- Combines all three data sources into a single merged response.

Tests

31 unit tests cover user fetching, order fetching, recommendations, and result merging.

Running

See ../../RUNNING.md for setup and execution instructions.