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rocksdb/thrift/lib/cpp/async/TAsyncTimeoutSet.h

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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
#ifndef THRIFT_ASYNC_TASYNCTIMEOUTSET_H_
#define THRIFT_ASYNC_TASYNCTIMEOUTSET_H_ 1
#include "thrift/lib/cpp/async/TAsyncTimeout.h"
#include "thrift/lib/cpp/async/TDelayedDestruction.h"
#include <chrono>
#include <cstddef>
#include <memory>
namespace apache { namespace thrift { namespace async {
/**
* TAsyncTimeoutSet exists for efficiently managing a group of timeouts events
* that always have the same timeout interval.
*
* TAsyncTimeoutSet takes advantage of the fact that the timeouts are always
* scheduled in sorted order. (Since each timeout has the same interval, when
* a new timeout is scheduled it will always be the last timeout in the set.)
* This avoids the need to perform any additional sorting of the timeouts
* within a single TAsyncTimeoutSet.
*
* TAsyncTimeoutSet is useful whenever you have a large group of objects that
* each need their own timeout, but with the same interval for each object.
* For example, managing idle timeouts for thousands of connection, or
* scheduling health checks for a large group of servers.
*/
class TAsyncTimeoutSet : private TAsyncTimeout, public TDelayedDestruction {
public:
typedef std::unique_ptr<TAsyncTimeoutSet, Destructor> UniquePtr;
/**
* A callback to be notified when a timeout has expired.
*
* TAsyncTimeoutSet::Callback is very similar to TAsyncTimeout. The primary
* distinction is that TAsyncTimeout can choose its timeout interval each
* time it is scheduled. On the other hand, TAsyncTimeoutSet::Callback
* always uses the timeout interval defined by the TAsyncTimeoutSet where it
* is scheduled.
*/
class Callback {
public:
Callback()
: timeoutSet_(NULL),
expiration_(0),
prev_(NULL),
next_(NULL) {}
virtual ~Callback();
/**
* timeoutExpired() is invoked when the timeout has expired.
*/
virtual void timeoutExpired() THRIFT_NOEXCEPT = 0;
/**
* Cancel the timeout, if it is running.
*
* If the timeout is not scheduled, cancelTimeout() does nothing.
*/
void cancelTimeout() {
if (timeoutSet_ == NULL) {
// We're not scheduled, so there's nothing to do.
return;
}
cancelTimeoutImpl();
}
/**
* Return true if this timeout is currently scheduled, and false otherwise.
*/
bool isScheduled() const {
return timeoutSet_ != NULL;
}
private:
// Get the time remaining until this timeout expires
std::chrono::milliseconds getTimeRemaining(
std::chrono::milliseconds now) const {
if (now >= expiration_) {
return std::chrono::milliseconds(0);
}
return expiration_ - now;
}
void setScheduled(TAsyncTimeoutSet* timeoutSet, Callback* prev);
void cancelTimeoutImpl();
TAsyncTimeoutSet* timeoutSet_;
std::chrono::milliseconds expiration_;
Callback* prev_;
Callback* next_;
// Give TAsyncTimeoutSet direct access to our members so it can take care
// of scheduling/cancelling.
friend class TAsyncTimeoutSet;
};
/**
* Create a new TAsyncTimeoutSet with the specified interval.
*/
TAsyncTimeoutSet(TEventBase* eventBase,
std::chrono::milliseconds intervalMS,
std::chrono::milliseconds atMostEveryN =
std::chrono::milliseconds(0));
/**
* Destroy the TAsyncTimeoutSet.
*
* Normally a TAsyncTimeoutSet should only be destroyed when there are no
* more callbacks pending in the set. If there are timeout callbacks pending
* for this set, destroying the TAsyncTimeoutSet will automatically cancel
* them. If you destroy a TAsyncTimeoutSet with callbacks pending, your
* callback code needs to be aware that the callbacks will never be invoked.
*/
virtual void destroy();
/**
* Get the interval for this TAsyncTimeoutSet.
*
* Returns the timeout interval in milliseconds. All callbacks scheduled
* with scheduleTimeout() will be invoked after this amount of time has
* passed since the call to scheduleTimeout().
*/
std::chrono::milliseconds getInterval() const {
return interval_;
}
/**
* Schedule the specified Callback to be invoked after the TAsyncTimeoutSet's
* specified timeout interval.
*
* If the callback is already scheduled, this cancels the existing timeout
* before scheduling the new timeout.
*/
void scheduleTimeout(Callback* callback);
/**
* Limit how frequently this TAsyncTimeoutSet will fire.
*/
void fireAtMostEvery(const std::chrono::milliseconds& ms) {
atMostEveryN_ = ms;
}
/**
* Get a pointer to the next Callback scheduled to be invoked (may be null).
*/
Callback* front() { return head_; }
const Callback* front() const { return head_; }
protected:
/**
* Protected destructor.
*
* Use destroy() instead. See the comments in TDelayedDestruction for more
* details.
*/
virtual ~TAsyncTimeoutSet();
private:
// Forbidden copy constructor and assignment operator
TAsyncTimeoutSet(TAsyncTimeoutSet const &) = delete;
TAsyncTimeoutSet& operator=(TAsyncTimeoutSet const &) = delete;
// Private methods to be invoked by TAsyncTimeoutSet::Callback
void headChanged();
// Methods inherited from TAsyncTimeout
virtual void timeoutExpired() THRIFT_NOEXCEPT;
std::chrono::milliseconds interval_;
std::chrono::milliseconds atMostEveryN_;
bool inTimeoutExpired_;
Callback* head_;
Callback* tail_;
};
}}} // apache::thrift::async
#endif // THRIFT_ASYNC_TASYNCTIMEOUTSET_H_