kacerrandClaude Fable 5
7219eb5a23
Includes solved 02-worker-pool and 09-safe-counter (mutex, atomic, sharded). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01GbnJj9ZqEx9nUvzkjdwfMq
54 lines
1.7 KiB
Go
54 lines
1.7 KiB
Go
// Exercise 06 — Retry with Exponential Backoff + Jitter
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//
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// ASSIGNMENT
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// ----------
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// Implement Retry(ctx, attempts, base, fn):
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//
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// 1. Calls fn up to `attempts` times; returns nil on first success.
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// 2. Retries ONLY errors matching ErrRetryable (errors.Is — fn may wrap it).
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// Non-retryable errors are returned immediately.
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// 3. Between attempt i and i+1, sleeps a random duration in
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// [0, base * 2^i) — exponential backoff with FULL JITTER.
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// 4. The sleep must be interruptible by ctx: if ctx is cancelled mid-sleep,
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// return promptly with an error that matches ctx.Err() (errors.Is).
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// 5. If all attempts fail, return an error that wraps the last error from fn.
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// 6. Never sleep after the final attempt.
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//
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// Run the tests: go test -race ./06-retry-backoff/
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package main
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import (
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"context"
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"errors"
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"fmt"
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"time"
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)
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// ErrRetryable marks transient failures. fn returns errors wrapping this
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// to request a retry.
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var ErrRetryable = errors.New("retryable")
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// Retry runs fn with exponential backoff + full jitter.
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// TODO: implement me.
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func Retry(ctx context.Context, attempts int, base time.Duration, fn func(context.Context) error) error {
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// TODO:
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// - loop attempts times, call fn
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// - errors.Is(err, ErrRetryable) to classify
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// - backoff := base << i ; sleep := rand in [0, backoff)
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// - select { time.After(sleep) / ctx.Done() }
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// - wrap the final error with fmt.Errorf("... %w", err)
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return nil
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}
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func main() {
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i := 0
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err := Retry(context.Background(), 5, 50*time.Millisecond, func(ctx context.Context) error {
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i++
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if i < 3 {
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return fmt.Errorf("attempt %d flaked: %w", i, ErrRetryable)
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}
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return nil
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})
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fmt.Println("attempts:", i, "err:", err)
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}
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