ChromeOS: Implement periodic timezone refresh on geolocation data.

chromeos/timezone/timezone_resolver.cc

+// Copyright 2014 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.
+
+#include "chromeos/timezone/timezone_resolver.h"
+
+#include <math.h>
+
+#include <algorithm>
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/callback_helpers.h"
+#include "base/logging.h"
+#include "base/power_monitor/power_monitor.h"
+#include "base/power_monitor/power_observer.h"
+#include "base/strings/utf_string_conversions.h"
+#include "base/time/time.h"
+#include "chromeos/geolocation/geoposition.h"
+#include "chromeos/geolocation/simple_geolocation_provider.h"
+#include "chromeos/timezone/timezone_provider.h"
+#include "net/url_request/url_request_context_getter.h"
+#include "url/gurl.h"
+
+namespace chromeos {
+
+namespace {
+
+class TZRequest;
+
+// Total timezone resolving process timeout.
+const unsigned int kRefreshTimeZoneTimeoutSeconds = 60;
+
+// Initial delay (for the first request).
+const int64 kInitialRefreshIntervalMS = 3000;
+
+// Timezone refresh happens at least once each this interval.
+const int64 kMaximalRefreshIntervalMS = 6 * 3600 * 1000;  // 6 hours
+
+// Delay between refresh attempts depends on current number of requests and
+// this constant.
+// [interval = kInitialRefreshIntervalMS * (2 ^
+//                 (kRefreshIntervalRequestsCountMultiplier * requests_count))]
+// in seconds.

[Bernhard Bauer, 2015/01/16 10:56:11]

BTW, I just found out there's also net::BackoffEntry to implement exponential
backoff.

[Alexander Alekseev, 2015/01/16 20:42:44]

It implements back-off strategy to optimize for network errors.
We do not have erors here, so it seems to be too complicated.

I would better stay with this implementation.

+const unsigned long kRefreshIntervalRequestsCountMultiplier = 3;
+
+unsigned int MaxRequestsCountForInterval(const double interval_seconds) {
+  const base::TimeDelta initial_interval =
+      base::TimeDelta::FromMilliseconds(kInitialRefreshIntervalMS);
+  return log2(interval_seconds / initial_interval.InSecondsF()) /
+         kRefreshIntervalRequestsCountMultiplier;
+}
+
+unsigned int IntervalForNextRequest(const unsigned int requests) {
+  const base::TimeDelta initial_interval =
+      base::TimeDelta::FromMilliseconds(kInitialRefreshIntervalMS);
+  return static_cast<unsigned int>(
+      initial_interval.InSecondsF() *
+      (2 << (requests * kRefreshIntervalRequestsCountMultiplier)));
+}
+
+}  // anonymous namespace
+
+// This class periodically refreshes location and timezone.
+// It should be destroyed to stop refresh.
+class TimeZoneResolver::TimeZoneResolverImpl
+    : public base::PowerObserver,
+      public base::SupportsWeakPtr<TimeZoneResolver::TimeZoneResolverImpl> {
+ public:
+  TimeZoneResolverImpl(
+      net::URLRequestContextGetter* url_context_getter,
+      const GURL& url,
+      const TimeZoneResolver::ApplyTimeZoneCallback& apply_timezone,
+      const TimeZoneResolver::DelayNetworkCallClosure& delay_network_call);
+
+  ~TimeZoneResolverImpl() override;
+
+  // This is called once after the object is created.
+  void Start();
+
+  // PowerObserver implementation.
+  void OnResume() override;
+
+  // (Re)Starts timer.
+  void ScheduleRequest();
+
+  // Creates new TZRequest.
+  void CreateNewRequest();
+
+  // Called by TZRequest.
+  SimpleGeolocationProvider* geolocation_provider() {
+    return &geolocation_provider_;
+  }
+  TimeZoneProvider* timezone_provider() { return &timezone_provider_; }
+
+  // Update requests count and last request time.
+  void RecordAttempt();
+
+  // This is called by TZRequest. Destroys active request and starts a new one.
+  void RequestIsFinished();
+
+  void ApplyTimeZone(const TimeZoneResponseData* timezone);
+
+  TimeZoneResolver::DelayNetworkCallClosure delay_network_call() const {
+    return delay_network_call_;
+  }
+
+ private:
+  // Returns delay to next timezone update request
+  base::TimeDelta CalculateNextInterval();
+
+  net::URLRequestContextGetter* url_context_getter_;
+  const GURL url_;
+
+  const TimeZoneResolver::ApplyTimeZoneCallback apply_timezone_;
+  const TimeZoneResolver::DelayNetworkCallClosure delay_network_call_;
+
+  SimpleGeolocationProvider geolocation_provider_;
+  TimeZoneProvider timezone_provider_;
+
+  base::OneShotTimer<TimeZoneResolver::TimeZoneResolverImpl> refresh_timer_;
+
+  // Total number of request attempts.
+  unsigned int requests_count_;
+
+  // This is not NULL when update is in progress.
+  scoped_ptr<TZRequest> request_;
+
+  DISALLOW_COPY_AND_ASSIGN(TimeZoneResolverImpl);
+};
+
+namespace {
+
+// This class implements a single timezone refresh attempt.
+class TZRequest : public base::SupportsWeakPtr<TZRequest> {
+ public:
+  explicit TZRequest(TimeZoneResolver::TimeZoneResolverImpl* resolver)
+      : resolver_(resolver) {}
+
+  ~TZRequest();
+
+  // Starts request after specified delay.
+  void Start();
+
+  // Called from SimpleGeolocationProvider when location is resolved.
+  void OnLocationResolved(const Geoposition& position,
+                          bool server_error,
+                          const base::TimeDelta elapsed);
+
+  // TimeZoneRequest::TimeZoneResponseCallback implementation.
+  void OnTimezoneResolved(scoped_ptr<TimeZoneResponseData> timezone,
+                          bool server_error);
+
+ private:
+  // Schedules new request and destroys current object.
+  void RequestIsFinished();
+
+  // This is called by network detector when network is available.
+  void StartRequestOnNetworkAvailable();
+
+  TimeZoneResolver::TimeZoneResolverImpl* const resolver_;
+
+  DISALLOW_COPY_AND_ASSIGN(TZRequest);
+};
+
+TZRequest::~TZRequest() {
+}
+
+void TZRequest::StartRequestOnNetworkAvailable() {
+  resolver_->RecordAttempt();
+  resolver_->geolocation_provider()->RequestGeolocation(
+      base::TimeDelta::FromSeconds(kRefreshTimeZoneTimeoutSeconds),
+      base::Bind(&TZRequest::OnLocationResolved, AsWeakPtr()));
+}
+
+void TZRequest::Start() {
+  // call to chromeos::DelayNetworkCall
+  resolver_->delay_network_call().Run(
+      base::Bind(&TZRequest::StartRequestOnNetworkAvailable, AsWeakPtr()));
+}
+
+void TZRequest::OnLocationResolved(const Geoposition& position,
+                                   bool server_error,
+                                   const base::TimeDelta elapsed) {
+  base::ScopedClosureRunner on_request_finished(
+      base::Bind(&TZRequest::RequestIsFinished, base::Unretained(this)));
+
+  // Ignore invalid position.
+  if (!position.Valid())
+    return;
+
+  const base::TimeDelta timeout =
+      base::TimeDelta::FromSeconds(kRefreshTimeZoneTimeoutSeconds);
+
+  if (elapsed >= timeout) {
+    VLOG(1) << "Refresh TimeZone: got location after timeout ("
+            << elapsed.InSecondsF() << " seconds elapsed). Ignored.";
+    return;
+  }
+
+  resolver_->timezone_provider()->RequestTimezone(
+      position,
+      false,  // sensor
+      timeout - elapsed,
+      base::Bind(&TZRequest::OnTimezoneResolved, AsWeakPtr()));
+
+  // Prevent |on_request_finished| from firing here.
+  base::Closure unused = on_request_finished.Release();
+}
+
+void TZRequest::OnTimezoneResolved(scoped_ptr<TimeZoneResponseData> timezone,
+                                   bool server_error) {
+  base::ScopedClosureRunner on_request_finished(
+      base::Bind(&TZRequest::RequestIsFinished, base::Unretained(this)));
+
+  DCHECK(timezone);
+  VLOG(1) << "Refreshed local timezone={" << timezone->ToStringForDebug()
+          << "}.";
+
+  if (timezone->status != TimeZoneResponseData::OK) {
+    VLOG(1) << "Refresh TimeZone: failed to resolve timezone.";
+    return;
+  }
+
+  resolver_->ApplyTimeZone(timezone.get());
+}
+
+void TZRequest::RequestIsFinished() {

[Bernhard Bauer, 2015/01/16 09:25:05]

You only call this via a closure now, right? In that case, you could directly
bind TimeZoneResolverImpl::RequestIsFinished.

[Alexander Alekseev, 2015/01/16 20:42:44]

Done.

+  // This object is destroyed inside TimeZoneResolverImpl::RequestIsFinished().
+  resolver_->RequestIsFinished();
+}
+
+}  // anonymous namespace
+
+// ------------------------------------------------------------------------
+// TimeZoneResolver::TimeZoneResolverImpl implementation.
+
+TimeZoneResolver::TimeZoneResolverImpl::TimeZoneResolverImpl(
+    net::URLRequestContextGetter* url_context_getter,
+    const GURL& url,
+    const TimeZoneResolver::ApplyTimeZoneCallback& apply_timezone,
+    const TimeZoneResolver::DelayNetworkCallClosure& delay_network_call)
+    : url_context_getter_(url_context_getter),
+      url_(url),
+      apply_timezone_(apply_timezone),
+      delay_network_call_(delay_network_call),
+      geolocation_provider_(
+          url_context_getter,
+          SimpleGeolocationProvider::DefaultGeolocationProviderURL()),
+      timezone_provider_(url_context_getter, DefaultTimezoneProviderURL()),
+      requests_count_(0) {
+  DCHECK(!apply_timezone.is_null());
+  DCHECK(!delay_network_call.is_null());
+
+  base::PowerMonitor* power_monitor = base::PowerMonitor::Get();
+  power_monitor->AddObserver(this);
+}
+
+TimeZoneResolver::TimeZoneResolverImpl::~TimeZoneResolverImpl() {
+  base::PowerMonitor* power_monitor = base::PowerMonitor::Get();
+  if (power_monitor)
+    power_monitor->RemoveObserver(this);
+}
+
+void TimeZoneResolver::TimeZoneResolverImpl::Start() {
+  // Start() is usually called twice:
+  // - On device boot.
+  // - On user session start.
+  if (request_ || refresh_timer_.IsRunning())
+    return;
+
+  ScheduleRequest();
+}
+
+// Returns delay to next timezone update request
+base::TimeDelta
+TimeZoneResolver::TimeZoneResolverImpl::CalculateNextInterval() {
+  const base::TimeDelta initial_interval =
+      base::TimeDelta::FromMilliseconds(kInitialRefreshIntervalMS);
+  const base::TimeDelta maximum_interval =
+      base::TimeDelta::FromMilliseconds(kMaximalRefreshIntervalMS);
+
+  // This is initial request, which should be served immediately.
+  if (requests_count_ == 0)
+    return initial_interval;
+
+  // See comment to kRefreshIntervalRequestsCountMultiplier.
+  if (requests_count_ >=
+      MaxRequestsCountForInterval(maximum_interval.InSecondsF())) {
+    return maximum_interval;
+  }
+
+  const base::TimeDelta interval(
+      base::TimeDelta::FromSeconds(IntervalForNextRequest(requests_count_)));
+  DCHECK_LE(interval, maximum_interval);
+  return interval;
+}
+
+void TimeZoneResolver::TimeZoneResolverImpl::OnResume() {
+  requests_count_ = 0;
+  // Refresh timezone immediately.
+  request_.reset();
+  ScheduleRequest();
+}
+
+void TimeZoneResolver::TimeZoneResolverImpl::ScheduleRequest() {
+  if (request_)
+    return;
+
+  // base::OneShotTimer
+  base::TimeDelta interval = CalculateNextInterval();
+  refresh_timer_.Stop();
+  refresh_timer_.Start(
+      FROM_HERE, interval,
+      base::Bind(&TimeZoneResolver::TimeZoneResolverImpl::CreateNewRequest,
+                 AsWeakPtr()));
+}
+
+void TimeZoneResolver::TimeZoneResolverImpl::CreateNewRequest() {
+  if (request_)
+    return;
+
+  refresh_timer_.Stop();
+
+  request_.reset(new TZRequest(this));
+  request_->Start();
+}
+
+void TimeZoneResolver::TimeZoneResolverImpl::RecordAttempt() {
+  ++requests_count_;
+}
+
+void TimeZoneResolver::TimeZoneResolverImpl::RequestIsFinished() {
+  scoped_ptr<TZRequest> previous_request(request_.release());

[Bernhard Bauer, 2015/01/16 09:25:05]

Is it important now that the request is only destroyed at the end of the method?
If not, you could just reset() request.

[Alexander Alekseev, 2015/01/16 20:42:44]

Done.

+  ScheduleRequest();
+}
+
+void TimeZoneResolver::TimeZoneResolverImpl::ApplyTimeZone(
+    const TimeZoneResponseData* timezone) {
+  apply_timezone_.Run(timezone);
+}
+
+// ------------------------------------------------------------------------
+// TimeZoneResolver implementation
+
+TimeZoneResolver::TimeZoneResolver(
+    net::URLRequestContextGetter* context,
+    const GURL& url,
+    const ApplyTimeZoneCallback& apply_timezone,
+    const DelayNetworkCallClosure& delay_network_call)
+    : context_(context),
+      url_(url),
+      apply_timezone_(apply_timezone),
+      delay_network_call_(delay_network_call) {
+  DCHECK(!apply_timezone.is_null());
+}
+
+TimeZoneResolver::~TimeZoneResolver() {
+  Stop();
+}
+
+void TimeZoneResolver::Start() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  if (!implementation_) {
+    implementation_.reset(new TimeZoneResolverImpl(
+        context_, url_, apply_timezone_, delay_network_call_));
+    implementation_->Start();
+  }
+}
+
+void TimeZoneResolver::Stop() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  implementation_.reset();
+}
+
+unsigned int MaxRequestsCountForIntervalForTesting(
+    const double interval_seconds) {
+  return MaxRequestsCountForInterval(interval_seconds);
+}
+
+unsigned int IntervalForNextRequestForTesting(const unsigned int requests) {
+  return IntervalForNextRequest(requests);
+}
+
+}  // namespace chromeos