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// Copyright 2012 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 <map>
#include <memory>
#include <string>
#include "base/callback.h"
#include "base/cancelable_callback.h"
#include "base/compiler_specific.h"
#include "base/gtest_prod_util.h"
#include "base/macros.h"
#include "base/memory/linked_ptr.h"
#include "base/memory/weak_ptr.h"
#include "base/threading/non_thread_safe.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
#include "sync/base/sync_export.h"
#include "sync/engine/net/server_connection_manager.h"
#include "sync/engine/nudge_source.h"
#include "sync/engine/sync_scheduler.h"
#include "sync/engine/syncer.h"
#include "sync/internal_api/public/engine/polling_constants.h"
#include "sync/internal_api/public/util/weak_handle.h"
#include "sync/sessions/nudge_tracker.h"
#include "sync/sessions/sync_session.h"
#include "sync/sessions/sync_session_context.h"
namespace syncer {
class BackoffDelayProvider;
namespace sessions {
struct ModelNeutralState;
class SYNC_EXPORT SyncSchedulerImpl : public SyncScheduler,
public base::NonThreadSafe {
// |name| is a display string to identify the syncer thread. Takes
// |ownership of |syncer| and |delay_provider|.
SyncSchedulerImpl(const std::string& name,
BackoffDelayProvider* delay_provider,
sessions::SyncSessionContext* context,
Syncer* syncer);
// Calls Stop().
~SyncSchedulerImpl() override;
void Start(Mode mode, base::Time last_poll_time) override;
void ScheduleConfiguration(const ConfigurationParams& params) override;
void ScheduleClearServerData(const ClearParams& params) override;
void Stop() override;
void ScheduleLocalNudge(
ModelTypeSet types,
const tracked_objects::Location& nudge_location) override;
void ScheduleLocalRefreshRequest(
ModelTypeSet types,
const tracked_objects::Location& nudge_location) override;
void ScheduleInvalidationNudge(
syncer::ModelType type,
std::unique_ptr<InvalidationInterface> invalidation,
const tracked_objects::Location& nudge_location) override;
void ScheduleInitialSyncNudge(syncer::ModelType model_type) override;
void SetNotificationsEnabled(bool notifications_enabled) override;
void OnCredentialsUpdated() override;
void OnConnectionStatusChange() override;
// SyncSession::Delegate implementation.
void OnThrottled(const base::TimeDelta& throttle_duration) override;
void OnTypesThrottled(ModelTypeSet types,
const base::TimeDelta& throttle_duration) override;
bool IsCurrentlyThrottled() override;
void OnReceivedShortPollIntervalUpdate(
const base::TimeDelta& new_interval) override;
void OnReceivedLongPollIntervalUpdate(
const base::TimeDelta& new_interval) override;
void OnReceivedCustomNudgeDelays(
const std::map<ModelType, base::TimeDelta>& nudge_delays) override;
void OnReceivedClientInvalidationHintBufferSize(int size) override;
void OnSyncProtocolError(
const SyncProtocolError& sync_protocol_error) override;
void OnReceivedGuRetryDelay(const base::TimeDelta& delay) override;
void OnReceivedMigrationRequest(syncer::ModelTypeSet types) override;
// Returns true if the client is currently in exponential backoff.
bool IsBackingOff() const;
enum JobPriority {
// Non-canary jobs respect exponential backoff.
// Canary jobs bypass exponential backoff, so use with extreme caution.
enum PollAdjustType {
// Restart the poll interval.
// Restart the poll interval only if its length has changed.
friend class SyncSchedulerTest;
friend class SyncSchedulerWhiteboxTest;
friend class SyncerTest;
FRIEND_TEST_ALL_PREFIXES(SyncSchedulerTest, TransientPollFailure);
FRIEND_TEST_ALL_PREFIXES(SyncSchedulerTest, SuccessfulRetry);
FRIEND_TEST_ALL_PREFIXES(SyncSchedulerTest, FailedRetry);
FRIEND_TEST_ALL_PREFIXES(SyncSchedulerTest, ReceiveNewRetryDelay);
struct SYNC_EXPORT WaitInterval {
enum Mode {
// Uninitialized state, should not be set in practice.
// We enter a series of increasingly longer WaitIntervals if we experience
// repeated transient failures. We retry at the end of each interval.
// A server-initiated throttled interval. We do not allow any syncing
// during such an interval.
WaitInterval(Mode mode, base::TimeDelta length);
static const char* GetModeString(Mode mode);
Mode mode;
base::TimeDelta length;
static const char* GetModeString(Mode mode);
void SetDefaultNudgeDelay(base::TimeDelta delay_ms);
// Invoke the syncer to perform a nudge job.
void DoNudgeSyncSessionJob(JobPriority priority);
// Invoke the syncer to perform a configuration job.
void DoConfigurationSyncSessionJob(JobPriority priority);
void DoClearServerDataSyncSessionJob(JobPriority priority);
// Helper function for Do{Nudge,Configuration,Poll}SyncSessionJob.
void HandleSuccess();
// Helper function for Do{Nudge,Configuration,Poll}SyncSessionJob.
void HandleFailure(
const sessions::ModelNeutralState& model_neutral_state);
// Invoke the Syncer to perform a poll job.
void DoPollSyncSessionJob();
// Helper function to calculate poll interval.
base::TimeDelta GetPollInterval();
// Adjusts the poll timer to account for new poll interval, and possibly
// resets the poll interval, depedning on the flag's value.
void AdjustPolling(PollAdjustType type);
// Helper to restart waiting with |wait_interval_|'s timer.
void RestartWaiting();
// Determines if we're allowed to contact the server right now.
bool CanRunJobNow(JobPriority priority);
// Determines if we're allowed to contact the server right now.
bool CanRunNudgeJobNow(JobPriority priority);
// If the scheduler's current state supports it, this will create a job based
// on the passed in parameters and coalesce it with any other pending jobs,
// then post a delayed task to run it. It may also choose to drop the job or
// save it for later, depending on the scheduler's current state.
void ScheduleNudgeImpl(
const base::TimeDelta& delay,
const tracked_objects::Location& nudge_location);
// Helper to signal listeners about changed retry time.
void NotifyRetryTime(base::Time retry_time);
// Helper to signal listeners about changed throttled types.
void NotifyThrottledTypesChanged(ModelTypeSet types);
// Looks for pending work and, if it finds any, run this work at "canary"
// priority.
void TryCanaryJob();
// At the moment TrySyncSessionJob just posts call to TrySyncSessionJobImpl on
// current thread. In the future it will request access token here.
void TrySyncSessionJob();
void TrySyncSessionJobImpl();
// Transitions out of the THROTTLED WaitInterval then calls TryCanaryJob().
void Unthrottle();
// Called when a per-type throttling interval expires.
void TypeUnthrottle(base::TimeTicks unthrottle_time);
// Runs a normal nudge job when the scheduled timer expires.
void PerformDelayedNudge();
// Attempts to exit EXPONENTIAL_BACKOFF by calling TryCanaryJob().
void ExponentialBackoffRetry();
// Called when the root cause of the current connection error is fixed.
void OnServerConnectionErrorFixed();
// Creates a session for a poll and performs the sync.
void PollTimerCallback();
// Creates a session for a retry and performs the sync.
void RetryTimerCallback();
// Returns the set of types that are enabled and not currently throttled.
ModelTypeSet GetEnabledAndUnthrottledTypes();
// Called as we are started to broadcast an initial session snapshot
// containing data like initial_sync_ended. Important when the client starts
// up and does not need to perform an initial sync.
void SendInitialSnapshot();
// This is used for histogramming and analysis of ScheduleNudge* APIs.
// SyncScheduler is the ultimate choke-point for all such invocations (with
// and without InvalidationState variants, all NudgeSources, etc) and as such
// is the most flexible place to do this bookkeeping.
void UpdateNudgeTimeRecords(ModelTypeSet types);
// For certain methods that need to worry about X-thread posting.
WeakHandle<SyncSchedulerImpl> weak_handle_this_;
// Used for logging.
const std::string name_;
// Set in Start(), unset in Stop().
bool started_;
// Modifiable versions of kDefaultLongPollIntervalSeconds which can be
// updated by the server.
base::TimeDelta syncer_short_poll_interval_seconds_;
base::TimeDelta syncer_long_poll_interval_seconds_;
// Timer for polling. Restarted on each successful poll, and when entering
// normal sync mode or exiting an error state. Not active in configuration
// mode.
base::OneShotTimer poll_timer_;
// The mode of operation.
Mode mode_;
// Current wait state. Null if we're not in backoff and not throttled.
std::unique_ptr<WaitInterval> wait_interval_;
std::unique_ptr<BackoffDelayProvider> delay_provider_;
// The event that will wake us up.
base::OneShotTimer pending_wakeup_timer_;
// An event that fires when data type throttling expires.
base::OneShotTimer type_unthrottle_timer_;
// Storage for variables related to an in-progress configure request. Note
// that (mode_ != CONFIGURATION_MODE) \implies !pending_configure_params_.
std::unique_ptr<ConfigurationParams> pending_configure_params_;
std::unique_ptr<ClearParams> pending_clear_params_;
// If we have a nudge pending to run soon, it will be listed here.
base::TimeTicks scheduled_nudge_time_;
// Keeps track of work that the syncer needs to handle.
sessions::NudgeTracker nudge_tracker_;
// Invoked to run through the sync cycle.
std::unique_ptr<Syncer> syncer_;
sessions::SyncSessionContext* session_context_;
// A map tracking LOCAL NudgeSource invocations of ScheduleNudge* APIs,
// organized by datatype. Each datatype that was part of the types requested
// in the call will have its TimeTicks value updated.
typedef std::map<ModelType, base::TimeTicks> ModelTypeTimeMap;
ModelTypeTimeMap last_local_nudges_by_model_type_;
// Used as an "anti-reentrancy defensive assertion".
// While true, it is illegal for any new scheduling activity to take place.
// Ensures that higher layers don't break this law in response to events that
// take place during a sync cycle. We call this out because such violations
// could result in tight sync loops hitting sync servers.
bool no_scheduling_allowed_;
// TryJob might get called for multiple reasons. It should only call
// DoPollSyncSessionJob after some time since the last attempt.
// last_poll_reset_ keeps track of when was last attempt.
base::TimeTicks last_poll_reset_;
// next_sync_session_job_priority_ defines which priority will be used next
// time TrySyncSessionJobImpl is called. CANARY_PRIORITY allows syncer to run
// even if scheduler is in exponential backoff. This is needed for events that
// have chance of resolving previous error (e.g. network connection change
// after NETWORK_UNAVAILABLE error).
// It is reset back to NORMAL_PRIORITY on every call to TrySyncSessionJobImpl.
JobPriority next_sync_session_job_priority_;
// One-shot timer for scheduling GU retry according to delay set by server.
base::OneShotTimer retry_timer_;
base::WeakPtrFactory<SyncSchedulerImpl> weak_ptr_factory_;
// A second factory specially for weak_handle_this_, to allow the handle
// to be const and alleviate threading concerns.
base::WeakPtrFactory<SyncSchedulerImpl> weak_ptr_factory_for_weak_handle_;
} // namespace syncer