github.com/livekit/protocol@v1.39.3/utils/hedge.go (about)

     1  // Copyright 2023 LiveKit, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package utils
    16  
    17  import (
    18  	"context"
    19  	"errors"
    20  	"time"
    21  
    22  	"go.uber.org/multierr"
    23  )
    24  
    25  var ErrMaxAttemptsReached = errors.New("max attempts reached")
    26  
    27  type HedgeParams[T any] struct {
    28  	Timeout       time.Duration
    29  	RetryDelay    time.Duration
    30  	MaxAttempts   int
    31  	IsRecoverable func(err error) bool
    32  	Func          func(context.Context) (T, error)
    33  }
    34  
    35  // race retries if the function takes too long to return
    36  // |---------------- attempt 1 ----------------|
    37  // |    delay    |--------- attempt 2 ---------|
    38  func HedgeCall[T any](ctx context.Context, params HedgeParams[T]) (v T, err error) {
    39  	ctx, cancel := context.WithTimeout(ctx, params.Timeout)
    40  	defer cancel()
    41  
    42  	type result struct {
    43  		value T
    44  		err   error
    45  	}
    46  	ch := make(chan result, params.MaxAttempts)
    47  
    48  	race := func() {
    49  		value, err := params.Func(ctx)
    50  		ch <- result{value, err}
    51  	}
    52  
    53  	var attempt, done int
    54  	delay := time.NewTimer(0)
    55  	defer delay.Stop()
    56  
    57  	for {
    58  		select {
    59  		case <-delay.C:
    60  			go race()
    61  			if attempt++; attempt < params.MaxAttempts {
    62  				delay.Reset(params.RetryDelay)
    63  			}
    64  		case res := <-ch:
    65  			if res.err == nil {
    66  				return res.value, nil
    67  			}
    68  
    69  			err = multierr.Append(err, res.err)
    70  			if params.IsRecoverable != nil && !params.IsRecoverable(res.err) {
    71  				return
    72  			}
    73  			if done++; done == params.MaxAttempts {
    74  				err = multierr.Append(err, ErrMaxAttemptsReached)
    75  				return
    76  			}
    77  		case <-ctx.Done():
    78  			err = multierr.Append(err, ctx.Err())
    79  			return
    80  		}
    81  	}
    82  }