Schedule delayed duplicate attempts

Launch a second safe read only when the delay expires before a winner.

Type: Build Languages: Go Stage: 2 of 4 Prerequisites: Basic functions, collections, JSON and the previous stages when applicable. Time: ~2 hours

What you build

Start the primary request and a delay timer. A valid primary result before the timer prevents the hedge. Otherwise launch at most one secondary. Apply a two-second ceiling under the parent context and perform GET only.

Worked example

The local primary sleeps 80ms; the secondary sleeps 5ms. A 10ms hedge delay can return around 15ms while creating a second service request. Exact observed times depend on the local scheduler.

Implement the contract

Hedged(parent context.Context,client *http.Client,endpoints []string,delay time.Duration)(Receipt,error). Accept one or two endpoints and delay from 0 to 1 second. Receipt contains launched attempt count, winner index, value and winner latency. Response validation is provided scaffolding for this stage.

Reject malformed input before producing a partial artifact. The tests include held-out records separate from the demonstration fixture.

Run your work

python3 scripts/project_test.py hedged-request-lab --init /tmp/hedged-request-lab-work
python3 scripts/project_test.py hedged-request-lab --stage 2 --path /tmp/hedged-request-lab-work --strict

Initialization copies cumulative scaffolding without replacing your work. Implement the TODO functions in the first-stage starter; later-stage starter notes describe the new behavior. Tests import the learner workspace. Run the command in the README against your own input after passing the stage.

Inspect and extend

Set delay above the primary latency. The second endpoint should receive no request, and launched must remain one.

Go standard library and Node standard library. All fixtures and implementations are original.