resilience 0.3.0 changelog

0.3.0 #

Behaviour change: Retry no longer retries CircuitOpenException by default. A breaker throws it without calling the action, so a retry wrapped around a breaker used to spend its whole budget, and sleep through every backoff delay, on calls that were never made. Measured in the new test: with maxAttempts: 10 and a breaker that opens after 3 failures, the old default ran 9 retries for 3 real calls; it now runs 3 and stops. The old behaviour had one real use, which is why it was the default: if the backoff can outlast the breaker's resetTimeout, a later attempt arrives after the circuit is willing to half-open. That needs delays of tens of seconds, so it is now opt-in — pass retryIf: (error) => true. The README says when that is worth doing.
The circuit breaker's reset timeout is now measured monotonically with a Stopwatch, so a system clock change cannot shorten or extend the open period. The doc comment promised this "in 0.2" and 0.2.1 still used the wall clock. Passing now still switches to a wall clock of your choosing, which is what a test wants; production no longer has one.

Declare the diagram in pubspec.yaml so pub.dev renders it on the package page. It was already in the repository and the README, but pub.dev shows only what the screenshots: field points at, so the page opened with prose where the picture should have been.

Add Hedge, which starts a second copy of a slow call rather than waiting for it and takes whichever finishes first. Retrying cannot help a call that is merely slow, since a retry only begins once the slow attempt has already failed. A failed attempt brings the next one forward instead of waiting out the delay, losers are ignored, and if every attempt fails the last error is thrown. Only hedge calls that are safe to run twice.
Add withFallback, which returns a substitute value when the policy around it still failed, for serving cached or default data instead of an exception. It is a function taking a policy rather than a policy itself: a fallback swallows the error, so inside a retry the retry would see success and never run again, and inside a circuit breaker the breaker would never learn the call is failing. The outermost position is the only correct one, so it is the only one the API offers, which also keeps the substitute typed to the action's result.

Docs: sharpen the pub.dev description to lead with the value and the terms people search.

Initial release.

Retry with Backoff.none, Backoff.fixed, and Backoff.exponential (factor, cap, and jitter), plus retryIf and onRetry hooks.
CircuitBreaker with consecutive failure threshold, lazy reset timeout, single half-open trial, countAs filter, and onStateChange hook.
Timeout built on Future.timeout.
RateLimiter: token bucket with steady refill, FIFO waiting, an optional queue bound, and dispose.
Bulkhead: concurrency limit with a bounded FIFO queue.
ResiliencePipeline for composing policies, outermost first.