Move retry and lhttp packages from client/internal to common/.

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
-}