Add a retry mechanism

common/retry/retry.go

@@ -0,0 +1,44 @@
+package retry
+
+import (
+	"errors"
+	"time"
+)
+
+var (
+	RetryFailed = errors.New("All retry attempts failed.")
+)
+
+type RetryStrategy interface {
+	On(func() error) error
+}
+
+type retryer struct {
+	NextDelay func(int) int
+}
+
+func (r *retryer) On(method func() error) error {
+	attempt := 0
+	for {
+		err := method()
+		if err == nil {
+			return nil
+		}
+		delay := r.NextDelay(attempt)
+		if delay < 0 {
+			return RetryFailed
+		}
+		<-time.After(time.Duration(delay) * time.Millisecond)
+	}
+}
+
+func Timed(attempts int, delay int) RetryStrategy {
+	return &retryer{
+		NextDelay: func(attempt int) int {
+			if attempt >= attempts {
+				return -1
+			}
+			return delay
+		},
+	}
+}