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| 1 | +//go:build go1.18 |
| 2 | +// +build go1.18 |
| 3 | + |
| 4 | +package errorsext |
| 5 | + |
| 6 | +import ( |
| 7 | + "context" |
| 8 | + "time" |
| 9 | + |
| 10 | + . "github.com/go-playground/pkg/v5/values/result" |
| 11 | +) |
| 12 | + |
| 13 | +// MaxAttemptsMode is used to set the mode for the maximum number of attempts. |
| 14 | +// |
| 15 | +// eg. Should the max attempts apply to all errors, just ones not determined to be retryable, reset on retryable errors, etc. |
| 16 | +type MaxAttemptsMode uint8 |
| 17 | + |
| 18 | +const ( |
| 19 | + // MaxAttemptsNonRetryableReset will apply the max attempts to all errors not determined to be retryable, but will |
| 20 | + // reset the attempts if a retryable error is encountered after a non-retryable error. |
| 21 | + MaxAttemptsNonRetryableReset MaxAttemptsMode = iota |
| 22 | + |
| 23 | + // MaxAttemptsNonRetryable will apply the max attempts to all errors not determined to be retryable. |
| 24 | + MaxAttemptsNonRetryable |
| 25 | + |
| 26 | + // MaxAttempts will apply the max attempts to all errors, even those determined to be retryable. |
| 27 | + MaxAttempts |
| 28 | + |
| 29 | + // MaxAttemptsUnlimited will not apply a maximum number of attempts. |
| 30 | + MaxAttemptsUnlimited |
| 31 | +) |
| 32 | + |
| 33 | +// BackoffFn is a function used to apply a backoff strategy to the retryable function. |
| 34 | +// |
| 35 | +// It accepts `E` in cases where the amount of time to backoff is dynamic, for example when and http request fails |
| 36 | +// with a 429 status code, the `Retry-After` header can be used to determine how long to backoff. It is not required |
| 37 | +// to use or handle `E` and can be ignored if desired. |
| 38 | +type BackoffFn[E any] func(ctx context.Context, attempt int, e E) |
| 39 | + |
| 40 | +// IsRetryableFn2 is called to determine if the type E is retryable. |
| 41 | +type IsRetryableFn2[E any] func(ctx context.Context, e E) (isRetryable bool) |
| 42 | + |
| 43 | +// EarlyReturnFn is the function that can be used to bypass all retry logic, no matter the MaxAttemptsMode, for when the |
| 44 | +// type of `E` will never succeed and should not be retried. |
| 45 | +// |
| 46 | +// eg. If retrying an HTTP request and getting 400 Bad Request, it's unlikely to ever succeed and should not be retried. |
| 47 | +type EarlyReturnFn[E any] func(ctx context.Context, e E) (earlyReturn bool) |
| 48 | + |
| 49 | +// Retryer is used to retry any fallible operation. |
| 50 | +type Retryer[T, E any] struct { |
| 51 | + isRetryableFn IsRetryableFn2[E] |
| 52 | + isEarlyReturnFn EarlyReturnFn[E] |
| 53 | + maxAttemptsMode MaxAttemptsMode |
| 54 | + maxAttempts uint8 |
| 55 | + bo BackoffFn[E] |
| 56 | + timeout time.Duration |
| 57 | +} |
| 58 | + |
| 59 | +// NewRetryer returns a new `Retryer` with sane default values. |
| 60 | +// |
| 61 | +// The default values are: |
| 62 | +// - `MaxAttemptsMode` is `MaxAttemptsNonRetryableReset`. |
| 63 | +// - `MaxAttempts` is 5. |
| 64 | +// - `Timeout` is 0 no context timeout. |
| 65 | +// - `IsRetryableFn` will always return false as `E` is unknown until defined. |
| 66 | +// - `BackoffFn` will sleep for 200ms. It's recommended to use exponential backoff for production. |
| 67 | +// - `EarlyReturnFn` will be None. |
| 68 | +func NewRetryer[T, E any]() Retryer[T, E] { |
| 69 | + return Retryer[T, E]{ |
| 70 | + isRetryableFn: func(_ context.Context, _ E) bool { return false }, |
| 71 | + maxAttemptsMode: MaxAttemptsNonRetryableReset, |
| 72 | + maxAttempts: 5, |
| 73 | + bo: func(ctx context.Context, attempt int, _ E) { |
| 74 | + t := time.NewTimer(time.Millisecond * 200) |
| 75 | + defer t.Stop() |
| 76 | + select { |
| 77 | + case <-ctx.Done(): |
| 78 | + case <-t.C: |
| 79 | + } |
| 80 | + }, |
| 81 | + } |
| 82 | +} |
| 83 | + |
| 84 | +// IsRetryableFn sets the `IsRetryableFn` for the `Retryer`. |
| 85 | +func (r Retryer[T, E]) IsRetryableFn(fn IsRetryableFn2[E]) Retryer[T, E] { |
| 86 | + if fn == nil { |
| 87 | + fn = func(_ context.Context, _ E) bool { return false } |
| 88 | + } |
| 89 | + r.isRetryableFn = fn |
| 90 | + return r |
| 91 | +} |
| 92 | + |
| 93 | +// IsEarlyReturnFn sets the `EarlyReturnFn` for the `Retryer`. |
| 94 | +// |
| 95 | +// NOTE: If the `EarlyReturnFn` and `IsRetryableFn` are both set and a conflicting `IsRetryableFn` will take precedence. |
| 96 | +func (r Retryer[T, E]) IsEarlyReturnFn(fn EarlyReturnFn[E]) Retryer[T, E] { |
| 97 | + r.isEarlyReturnFn = fn |
| 98 | + return r |
| 99 | +} |
| 100 | + |
| 101 | +// MaxAttempts sets the maximum number of attempts for the `Retryer`. |
| 102 | +// |
| 103 | +// NOTE: Max attempts is optional and if not set will retry indefinitely on retryable errors. |
| 104 | +func (r Retryer[T, E]) MaxAttempts(mode MaxAttemptsMode, maxAttempts uint8) Retryer[T, E] { |
| 105 | + r.maxAttemptsMode, r.maxAttempts = mode, maxAttempts |
| 106 | + return r |
| 107 | +} |
| 108 | + |
| 109 | +// Backoff sets the backoff function for the `Retryer`. |
| 110 | +func (r Retryer[T, E]) Backoff(fn BackoffFn[E]) Retryer[T, E] { |
| 111 | + if fn == nil { |
| 112 | + fn = func(_ context.Context, _ int, _ E) {} |
| 113 | + } |
| 114 | + r.bo = fn |
| 115 | + return r |
| 116 | +} |
| 117 | + |
| 118 | +// Timeout sets the timeout for the `Retryer`. This is the timeout per `RetyableFn` attempt and not the entirety |
| 119 | +// of the `Retryer` execution. |
| 120 | +// |
| 121 | +// A timeout of 0 will disable the timeout and is the default. |
| 122 | +func (r Retryer[T, E]) Timeout(timeout time.Duration) Retryer[T, E] { |
| 123 | + r.timeout = timeout |
| 124 | + return r |
| 125 | +} |
| 126 | + |
| 127 | +// Do will execute the provided functions code and automatically retry using the provided retry function. |
| 128 | +func (r Retryer[T, E]) Do(ctx context.Context, fn RetryableFn[T, E]) Result[T, E] { |
| 129 | + var attempt int |
| 130 | + remaining := r.maxAttempts |
| 131 | + for { |
| 132 | + var result Result[T, E] |
| 133 | + if r.timeout == 0 { |
| 134 | + result = fn(ctx) |
| 135 | + } else { |
| 136 | + ctx, cancel := context.WithTimeout(ctx, r.timeout) |
| 137 | + result = fn(ctx) |
| 138 | + cancel() |
| 139 | + } |
| 140 | + if result.IsErr() { |
| 141 | + err := result.Err() |
| 142 | + isRetryable := r.isRetryableFn(ctx, err) |
| 143 | + if !isRetryable && r.isEarlyReturnFn != nil && r.isEarlyReturnFn(ctx, err) { |
| 144 | + return result |
| 145 | + } |
| 146 | + |
| 147 | + switch r.maxAttemptsMode { |
| 148 | + case MaxAttemptsUnlimited: |
| 149 | + goto RETRY |
| 150 | + case MaxAttemptsNonRetryableReset: |
| 151 | + if isRetryable { |
| 152 | + remaining = r.maxAttempts |
| 153 | + goto RETRY |
| 154 | + } else if remaining > 0 { |
| 155 | + remaining-- |
| 156 | + } |
| 157 | + case MaxAttemptsNonRetryable: |
| 158 | + if isRetryable { |
| 159 | + goto RETRY |
| 160 | + } else if remaining > 0 { |
| 161 | + remaining-- |
| 162 | + } |
| 163 | + case MaxAttempts: |
| 164 | + if remaining > 0 { |
| 165 | + remaining-- |
| 166 | + } |
| 167 | + } |
| 168 | + if remaining == 0 { |
| 169 | + return result |
| 170 | + } |
| 171 | + |
| 172 | + RETRY: |
| 173 | + r.bo(ctx, attempt, err) |
| 174 | + attempt++ |
| 175 | + continue |
| 176 | + } |
| 177 | + return result |
| 178 | + } |
| 179 | +} |
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