refresh provider

refresh_provider.go

package main

import (
    "log"
    "sync"
    "time"

    "github.com/aws/aws-sdk-go/aws"
    "github.com/aws/aws-sdk-go/aws/credentials"
    "github.com/aws/aws-sdk-go/aws/session"
    "github.com/aws/aws-sdk-go/service/s3"
)

func main() {
    sess := session.New()

    // call credRefreshTicker.Stop() to stop the cred refresh
    // useful when the custom credential provider will not
    // be used for the lifetime of the app.
    credRefreshTicker := time.NewTicker(1 * time.Hour)
    s3Svc := s3.New(sess, &aws.Config{
        Credentials: credentials.NewCredentials(&RefreshProvider{
            Provider: customProvider,
            Ticker:   credRefreshTicker,
        }),
    })

    for {
        s3Svc.GetObject(&s3.GetObjectInput{
            Bucket: aws.String("bucket"),
            Key:    aws.String("key"),
        })

        <-time.Tick(5 * time.Hour)
    }

}

type RefreshProvider struct {
    // Nested Provider to call Retrieve and IsExpired on
    credentials.Provider
    // How often the credential provider should be refreshed.
    Ticker *time.Ticker

    creds      credentials.Value
    err        error
    mux        sync.RWMutex
    initRunner sync.Once
}

func (p *RefreshProvider) Retrieve() (credentials.Value, error) {
    p.initRunner.Do(func() {
        p.creds, p.err = p.Provider.Retrieve()
        go p.periodicRefresh()
    })

    p.mux.RLock()
    defer p.mux.RUnlock()

    return p.creds, p.err
}

func (p *RefreshProvider) periodicRefresh() {
    for {
        _, ok := <-p.Ticker.C
        if !ok {
            break
        }

        p.mux.Lock()
        // Probably want to log the returned error
        creds, err := p.Provider.Retrieve()
        if err != nil {
            if p.Provider.IsExpired() {
                // If the credentials have expired, and still unable
                // to retrieve new credentials set the error
                p.err = err
            }
            p.mux.Unlock()

            log.Println("ERROR: failed to refresh credentials provider,", err)
            continue
        }
        p.err = nil
        p.creds = creds
        p.mux.Unlock()
    }
}

func (p *RefreshProvider) IsExpired() bool {
    p.mux.RLock()
    defer p.mux.RUnlock()

    return p.Provider.IsExpired()
}