Create packages client/internal/ retry and lhttp.

client/internal/retry/retry.go

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package retry
+
+import (
+        "io"
+        "time"
+)
+
+// Default defines the default retry parameters that should be used throughout
+// the program. It is fine to update this variable on start up.
+var Default = &Config{
+        10,
+        100 * time.Millisecond,
+        500 * time.Millisecond,
+        5 * time.Second,
+}
+
+// Config defines the retry properties.
+type Config struct {
+        MaxTries            int           // Maximum number of retries.
+        SleepMax            time.Duration // Maximum duration of a single sleep.
+        SleepBase           time.Duration // Base sleep duration.
+        SleepMultiplicative time.Duration // Incremental sleep duration for each additional try.
+}
+
+// Do runs a Retriable, potentially retrying it multiple times.
+func (c *Config) Do(r Retriable) (err error) {
+        defer func() {
+                if err2 := r.Close(); err == nil {
+                        err = err2
+                }
+        }()
+        for i := 0; i < c.MaxTries; i++ {
+                err = r.Do()
+                if _, ok := err.(Error); !ok {
+                        return err
+                }
+                if i != c.MaxTries-1 {
+                        s := c.SleepBase + time.Duration(i)*c.SleepMultiplicative
+                        if s > c.SleepMax {
+                                s = c.SleepMax
+                        }
+                        time.Sleep(s)
+                }
+        }
+        return
+}
+
+// Error is an error that can be retried.
+type Error struct {
+        Err error
+}
+
+func (e Error) Error() string {
+        return e.Err.Error()
+}
+
+// Retriable is a task that can be retried. It is important that Do be
+// idempotent.
+type Retriable interface {
+        io.Closer
+        Do() error
+}