Move chromeos symbols into brillo namespace

And move the include files into "brillo" directory instead of "chromeos"

BUG: 24872993
TEST=built aosp and brillo and unit tests pass on dragonoboard

Change-Id: Ieb979d1ebd3152921d36cd15acbd6247f02aae69

1 files changed, 167 insertions, 0 deletions

diff --git a/brillo/backoff_entry.cc b/brillo/backoff_entry.cc
new file mode 100644
index 0000000..acef714
--- /dev/null
+++ b/brillo/backoff_entry.cc
@@ -0,0 +1,167 @@
+// Copyright 2015 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <brillo/backoff_entry.h>
+
+#include <algorithm>
+#include <cmath>
+#include <limits>
+
+#include <base/logging.h>
+#include <base/numerics/safe_math.h>
+#include <base/rand_util.h>
+
+namespace brillo {
+
+BackoffEntry::BackoffEntry(const BackoffEntry::Policy* const policy)
+    : policy_(policy) {
+  DCHECK(policy_);
+  Reset();
+}
+
+void BackoffEntry::InformOfRequest(bool succeeded) {
+  if (!succeeded) {
+    ++failure_count_;
+    exponential_backoff_release_time_ = CalculateReleaseTime();
+  } else {
+    // We slowly decay the number of times delayed instead of
+    // resetting it to 0 in order to stay stable if we receive
+    // successes interleaved between lots of failures.  Note that in
+    // the normal case, the calculated release time (in the next
+    // statement) will be in the past once the method returns.
+    if (failure_count_ > 0)
+      --failure_count_;
+
+    // The reason why we are not just cutting the release time to
+    // ImplGetTimeNow() is on the one hand, it would unset a release
+    // time set by SetCustomReleaseTime and on the other we would like
+    // to push every request up to our "horizon" when dealing with
+    // multiple in-flight requests. Ex: If we send three requests and
+    // we receive 2 failures and 1 success. The success that follows
+    // those failures will not reset the release time, further
+    // requests will then need to wait the delay caused by the 2
+    // failures.
+    base::TimeDelta delay;
+    if (policy_->always_use_initial_delay)
+      delay = base::TimeDelta::FromMilliseconds(policy_->initial_delay_ms);
+    exponential_backoff_release_time_ = std::max(
+        ImplGetTimeNow() + delay, exponential_backoff_release_time_);
+  }
+}
+
+bool BackoffEntry::ShouldRejectRequest() const {
+  return exponential_backoff_release_time_ > ImplGetTimeNow();
+}
+
+base::TimeDelta BackoffEntry::GetTimeUntilRelease() const {
+  base::TimeTicks now = ImplGetTimeNow();
+  if (exponential_backoff_release_time_ <= now)
+    return base::TimeDelta();
+  return exponential_backoff_release_time_ - now;
+}
+
+base::TimeTicks BackoffEntry::GetReleaseTime() const {
+  return exponential_backoff_release_time_;
+}
+
+void BackoffEntry::SetCustomReleaseTime(const base::TimeTicks& release_time) {
+  exponential_backoff_release_time_ = release_time;
+}
+
+bool BackoffEntry::CanDiscard() const {
+  if (policy_->entry_lifetime_ms == -1)
+    return false;
+
+  base::TimeTicks now = ImplGetTimeNow();
+
+  int64 unused_since_ms =
+      (now - exponential_backoff_release_time_).InMilliseconds();
+
+  // Release time is further than now, we are managing it.
+  if (unused_since_ms < 0)
+    return false;
+
+  if (failure_count_ > 0) {
+    // Need to keep track of failures until maximum back-off period
+    // has passed (since further failures can add to back-off).
+    return unused_since_ms >= std::max(policy_->maximum_backoff_ms,
+                                       policy_->entry_lifetime_ms);
+  }
+
+  // Otherwise, consider the entry is outdated if it hasn't been used for the
+  // specified lifetime period.
+  return unused_since_ms >= policy_->entry_lifetime_ms;
+}
+
+void BackoffEntry::Reset() {
+  failure_count_ = 0;
+
+  // We leave exponential_backoff_release_time_ unset, meaning 0. We could
+  // initialize to ImplGetTimeNow() but because it's a virtual method it's
+  // not safe to call in the constructor (and the constructor calls Reset()).
+  // The effects are the same, i.e. ShouldRejectRequest() will return false
+  // right after Reset().
+  exponential_backoff_release_time_ = base::TimeTicks();
+}
+
+base::TimeTicks BackoffEntry::ImplGetTimeNow() const {
+  return base::TimeTicks::Now();
+}
+
+base::TimeTicks BackoffEntry::CalculateReleaseTime() const {
+  int effective_failure_count =
+      std::max(0, failure_count_ - policy_->num_errors_to_ignore);
+
+  // If always_use_initial_delay is true, it's equivalent to
+  // the effective_failure_count always being one greater than when it's false.
+  if (policy_->always_use_initial_delay)
+    ++effective_failure_count;
+
+  if (effective_failure_count == 0) {
+    // Never reduce previously set release horizon, e.g. due to Retry-After
+    // header.
+    return std::max(ImplGetTimeNow(), exponential_backoff_release_time_);
+  }
+
+  // The delay is calculated with this formula:
+  // delay = initial_backoff * multiply_factor^(
+  //     effective_failure_count - 1) * Uniform(1 - jitter_factor, 1]
+  // Note: if the failure count is too high, |delay_ms| will become infinity
+  // after the exponential calculation, and then NaN after the jitter is
+  // accounted for. Both cases are handled by using CheckedNumeric<int64_t> to
+  // perform the conversion to integers.
+  double delay_ms = policy_->initial_delay_ms;
+  delay_ms *= pow(policy_->multiply_factor, effective_failure_count - 1);
+  delay_ms -= base::RandDouble() * policy_->jitter_factor * delay_ms;
+
+  // Do overflow checking in microseconds, the internal unit of TimeTicks.
+  const int64_t kTimeTicksNowUs =
+      (ImplGetTimeNow() - base::TimeTicks()).InMicroseconds();
+  base::internal::CheckedNumeric<int64_t> calculated_release_time_us =
+      delay_ms + 0.5;
+  calculated_release_time_us *= base::Time::kMicrosecondsPerMillisecond;
+  calculated_release_time_us += kTimeTicksNowUs;
+
+  const int64_t kMaxTime = std::numeric_limits<int64_t>::max();
+  base::internal::CheckedNumeric<int64_t> maximum_release_time_us = kMaxTime;
+  if (policy_->maximum_backoff_ms >= 0) {
+    maximum_release_time_us = policy_->maximum_backoff_ms;
+    maximum_release_time_us *= base::Time::kMicrosecondsPerMillisecond;
+    maximum_release_time_us += kTimeTicksNowUs;
+  }
+
+  // Decide between maximum release time and calculated release time, accounting
+  // for overflow with both.
+  int64 release_time_us = std::min(
+      calculated_release_time_us.ValueOrDefault(kMaxTime),
+      maximum_release_time_us.ValueOrDefault(kMaxTime));
+
+  // Never reduce previously set release horizon, e.g. due to Retry-After
+  // header.
+  return std::max(
+      base::TimeTicks() + base::TimeDelta::FromMicroseconds(release_time_us),
+      exponential_backoff_release_time_);
+}
+
+}  // namespace brillo