Timeouts, retries and pools · hard

Do not charge them twice

Three POSTs against an API that fails the first attempt. The client retries everything, which gets the requests through and delivers one of them to the origin twice. Fix it without giving up on retries.

How this is graded

Every request returns successfully inside 210 ms
Never delivers the same non-idempotent request twice
Spreads its retries rather than lining them up

The budget is measured, not chosen: it is what a configuration that solves this actually cost, plus a little room.

The client

Timeouts

connectTimeoutMsGetting a connection, handshake includedreadTimeoutMsIdle time waiting for bytes; restarts when some arrivetotalBudgetMsThe whole request, every retry and backoff included

Retries

maxAttemptsIncluding the first. 1 means no retriesjitterHow the delay is spread across clientsrespectRetryAfterWait as long as the server askedgenerateIdempotencyKeysAttach a key to non-idempotent requestshonourIdempotencyKeyRetry a non-idempotent request that carries oneretryPostTreat POST as safe to repeatretryOn429Treat 429 as worth another attempt

Pool

keepAliveReuse a connection for more than one requestmaxConnectionsHow many may be open at oncemaxPerHost…and how many to any one hostacquireTimeoutMsHow long a request waits for a free slot

Capture

Nothing has run yet. Configure the client and run it — the capture is what you will be graded on.