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// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CHROMEOS_ASH_COMPONENTS_PROCESS_SNAPSHOT_PROCESS_SNAPSHOT_SERVER_H_
#define CHROMEOS_ASH_COMPONENTS_PROCESS_SNAPSHOT_PROCESS_SNAPSHOT_SERVER_H_
#include "base/component_export.h"
#include "base/lazy_instance.h"
#include "base/memory/scoped_refptr.h"
#include "base/memory/weak_ptr.h"
#include "base/observer_list.h"
#include "base/observer_list_types.h"
#include "base/process/process_iterator.h"
#include "base/task/sequenced_task_runner.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
namespace ash {
// Provides an interface to regularly getting a full snapshot of the running
// processes on the system.
// The process snapshot will be refreshed at the highest refresh rate (i.e.
// lowest desired refresh time) requested by all clients.
// This system is useful for clients that regularly need a process snapshot but
// don't care if it's stale for a short amount of time. This is to avoid
// multiple clients building a separate process snapshot individually which can
// lead to performance issues.
// (See b/154362057 and https://crbug.com/).
// TODO(afakhry): Currently, this is only used by chome-os-specific task manager
// providers (for VM/Crostini and ARC++ tasks). Consider moving this server
// outside chrome/browser/chromeos/ so that other non-chrome-os clients can use
// it.
class COMPONENT_EXPORT(CHROMEOS_ASH_COMPONENTS_PROCESS_SNAPSHOT)
ProcessSnapshotServer {
public:
class Observer : public base::CheckedObserver {
public:
explicit Observer(base::TimeDelta desired_refresh_time);
base::TimeDelta desired_refresh_time() const {
return desired_refresh_time_;
}
// Called when the process |snapshot| is refreshed. This may be called with
// intervals shorter than |desired_refresh_time_| as there might be other
// observers demanding higher refresh rates.
virtual void OnProcessSnapshotRefreshed(
const base::ProcessIterator::ProcessEntries& snapshot) = 0;
protected:
~Observer() override = default;
private:
// The desired time between two successive refreshes of the process
// snapshot. The server will use the value from the observer which is
// minimum among all other observers.
const base::TimeDelta desired_refresh_time_;
};
ProcessSnapshotServer(const ProcessSnapshotServer&) = delete;
ProcessSnapshotServer& operator=(const ProcessSnapshotServer&) = delete;
~ProcessSnapshotServer();
static ProcessSnapshotServer* Get();
const base::ProcessIterator::ProcessEntries& snapshot() const {
return snapshot_;
}
// If the added |observer| has a lower |desired_refresh_time_| than all
// current observers, the refresh rate will be adjusted to match that,
// otherwise, the server will continue at the same current refresh rate.
//
// The first |observer| to be added will trigger an immediate refresh of the
// process snapshot regardless of the |desired_refresh_time_|.
void AddObserver(Observer* observer);
// If the removed |observer| used to have the lowset |desired_refresh_time_|,
// the refresh rate will be adjusted according to the remaining observers.
// If |observer| is the last one to be removed, then refreshing will stop.
void RemoveObserver(Observer* observer);
const base::RepeatingTimer& GetTimerForTesting() const { return timer_; }
private:
friend struct base::LazyInstanceTraitsBase<ProcessSnapshotServer>;
ProcessSnapshotServer();
// Triggers a refresh of the process snapshot on |task_runner_|.
void RefreshSnapshot();
// Called on the UI thread when the process snapshot is refreshed.
void OnSnapshotRefreshed(base::ProcessIterator::ProcessEntries snapshot);
// Updates the current refresh rate based on |new_refresh_time| which could
// also lead to stopping the timer if |base::TimeDelta::Max()| is provided.
void RefreshTimer(base::TimeDelta new_refresh_time);
// The current cached process snapshot. It's only valid if the |timer_| is
// running and it's being refreshed regularly. Depending on the current
// refresh rate, it can be too stale.
base::ProcessIterator::ProcessEntries snapshot_;
base::RepeatingTimer timer_;
base::ObserverList<Observer> observers_;
scoped_refptr<base::SequencedTaskRunner> task_runner_;
base::WeakPtrFactory<ProcessSnapshotServer> weak_ptr_factory_;
};
} // namespace ash
#endif // CHROMEOS_ASH_COMPONENTS_PROCESS_SNAPSHOT_PROCESS_SNAPSHOT_SERVER_H_
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