chrome/browser/sync/retry_verifier.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "chrome/browser/sync/retry_verifier.h"
   6
   7 #include <algorithm>
   8
   9 #include "base/logging.h"
  10 #include "sync/internal_api/public/engine/polling_constants.h"
  11 #include "sync/internal_api/public/sessions/sync_session_snapshot.h"
  12
  13 namespace browser_sync {
  14
  15 namespace {
  16 // Given the current delay calculate the minimum and maximum wait times for
  17 // the next retry.
  18 DelayInfo CalculateDelay(int64 current_delay) {
  19   int64 backoff_s = std::max(static_cast<int64>(1), current_delay *
  20                              syncer::kBackoffRandomizationFactor);
  21
  22   DelayInfo delay_info;
  23   delay_info.min_delay = backoff_s + (-1 * current_delay/
  24                              syncer::kBackoffRandomizationFactor);
  25   delay_info.max_delay = backoff_s + current_delay/2;
  26
  27   delay_info.min_delay = std::max(static_cast<int64>(1),
  28       std::min(delay_info.min_delay, syncer::kMaxBackoffSeconds));
  29
  30   delay_info.max_delay = std::max(static_cast<int64>(1),
  31       std::min(delay_info.max_delay, syncer::kMaxBackoffSeconds));
  32
  33   return delay_info;
  34 }
  35
  36 // Fills the table with the maximum and minimum values for each retry, upto
  37 // |count| number of retries.
  38 void FillDelayTable(DelayInfo* delay_table, int count) {
  39   DCHECK(count > 1);
  40
  41   // We start off with the minimum value of 2 seconds.
  42   delay_table[0].min_delay = static_cast<int64>(2);
  43   delay_table[0].max_delay = static_cast<int64>(2);
  44
  45   for (int i = 1 ; i < count ; ++i) {
  46     delay_table[i].min_delay = CalculateDelay(delay_table[i-1].min_delay).
  47                                min_delay;
  48     delay_table[i].max_delay = CalculateDelay(delay_table[i-1].max_delay).
  49                                max_delay;
  50   }
  51 }
  52 }  // namespace
  53
  54 // Verifies if the current retry is on time. Note that we dont use the
  55 // maximum value of the retry range in verifying, only the minimum. Reason
  56 // being there is no guarantee that the retry will be on the dot. However in
  57 // practice it is on the dot. But making that assumption for all the platforms
  58 // would make the test flaky. However we have the global timeout for the
  59 // verification which would make sure all retries take place in a reasonable
  60 // amount of time. The global timeout is defined in profile sync service
  61 // harness as |kExponentialBackoffVerificationTimeoutMs|.
  62 bool IsRetryOnTime(DelayInfo* delay_table, int retry_count,
  63                    const base::TimeDelta& time_elapsed) {
  64   DVLOG(1) << "Retry Count : " << retry_count
  65            << " Time elapsed : " << time_elapsed.InSeconds()
  66            << " Retry table min: " << delay_table[retry_count].min_delay
  67            << " Retry table max: " << delay_table[retry_count].max_delay;
  68   return ((time_elapsed.InSeconds() >= delay_table[retry_count].min_delay));
  69 }
  70
  71 RetryVerifier::RetryVerifier() : retry_count_(0),
  72                                  success_(false),
  73                                  done_(false) {
  74   memset(&delay_table_, 0, sizeof(delay_table_));
  75 }
  76
  77 RetryVerifier::~RetryVerifier() {
  78 }
  79
  80 // Initializes the state for verification.
  81 void RetryVerifier::Initialize(
  82     const syncer::sessions::SyncSessionSnapshot& snap) {
  83   retry_count_ = 0;
  84   last_sync_time_ = snap.sync_start_time();
  85   FillDelayTable(delay_table_, kMaxRetry);
  86   done_ = false;
  87   success_ = false;
  88 }
  89
  90 void RetryVerifier::VerifyRetryInterval(
  91     const syncer::sessions::SyncSessionSnapshot& snap) {
  92   DCHECK(retry_count_ < kMaxRetry);
  93   if (retry_count_ == 0) {
  94     if (snap.sync_start_time() != last_sync_time_) {
  95       retry_count_++;
  96       last_sync_time_ = snap.sync_start_time();
  97     }
  98     success_ = true;
  99     return;
 100   }
 101
 102   // Check if the sync start time has changed. If so indicates a new sync
 103   // has taken place.
 104   if (snap.sync_start_time() != last_sync_time_) {
 105     base::TimeDelta delta = snap.sync_start_time() - last_sync_time_;
 106     success_ = IsRetryOnTime(delay_table_,retry_count_ -1, delta);
 107     last_sync_time_ = snap.sync_start_time();
 108     ++retry_count_;
 109     done_ = (retry_count_ >= kMaxRetry);
 110     return;
 111   }
 112 }
 113 }  // namespace browser_sync