asteris-llc/converge

// Copyright © 2016 Asteris, LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package wait

import "time"

const (
    // DefaultInterval is the default amount of time to wait in between checks
    DefaultInterval = 5 * time.Second

    // DefaultGracePeriod is the amount of time to wait before running the first
    // check and after a successful check
    DefaultGracePeriod = time.Duration(0)

    // DefaultRetries is the default number of times to retry before failing
    DefaultRetries = 5
)

// Retrier can be included in resources to provide retry capabilities
type Retrier struct {
    GracePeriod time.Duration
    Interval    time.Duration
    MaxRetry    int
    RetryCount  int
    Duration    time.Duration
}

// RetryFunc is the function to retry
type RetryFunc func() (bool, error)

// RetryUntil implements a retry loop
func (r *Retrier) RetryUntil(retryFunc RetryFunc) (bool, error) {
    startTime := time.Now()

    for {
        ok, err := retryFunc()
        if err != nil {
            return false, err
        }

        if !ok {
            r.RetryCount++

            if r.RetryCount >= r.MaxRetry {
                return false, nil
            }
            time.Sleep(r.GracePeriod)
        } else {
            break
        }
    }

    r.Duration = time.Since(startTime)
    return true, nil
}

// PrepareRetrier generates a Retrier from preparer input
func PrepareRetrier(interval, gracePeriod *time.Duration, maxRetry *int) *Retrier {
    // set the default values for the retrier interval, grace period, and retries
    retrierInterval := DefaultInterval
    retrierGracePeriod := DefaultGracePeriod
    retrierMaxRetry := DefaultRetries

    // if any of the fields were set by the preparer, use those values instead of
    // the defaults
    if interval != nil {
        retrierInterval = *interval
    }

    if gracePeriod != nil {
        retrierGracePeriod = *gracePeriod
    }

    if maxRetry != nil {
        retrierMaxRetry = *maxRetry
    }

    return &Retrier{
        MaxRetry:    retrierMaxRetry,
        GracePeriod: retrierGracePeriod,
        Interval:    retrierInterval,
    }
}