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/**
* Copyright (C) 2017 Mongodb Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects
* for all of the code used other than as permitted herein. If you modify
* file(s) with this exception, you may extend this exception to your
* version of the file(s), but you are not obligated to do so. If you do not
* wish to do so, delete this exception statement from your version. If you
* delete this exception statement from all source files in the program,
* then also delete it in the license file.
*/
#pragma once
#include "mongo/db/client.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/service_context.h"
#include "mongo/stdx/mutex.h"
namespace mongo {
/**
* OperationContextGroup maintains a collection of operation contexts so that they may all be killed
* on a common event (typically stepdown). Its public member functions serialize access to private
* data members.
*/
class OperationContextGroup {
OperationContextGroup(OperationContextGroup const&) = delete;
OperationContextGroup(OperationContextGroup&&) = delete;
void operator=(OperationContextGroup const&) = delete;
void operator=(OperationContextGroup&&) = delete;
public:
using UniqueOperationContext = ServiceContext::UniqueOperationContext;
class Context;
OperationContextGroup() = default;
~OperationContextGroup() {
invariant(isEmpty());
}
/**
* Makes an OperationContext on `client` and returns a Context object to track it. On
* destruction of the returned Context, the OperationContext is destroyed and its corresponding
* entry in *this is erased. If *this has been interrupted already, the new context will be
* interrupted immediately.
*/
Context makeOperationContext(Client& client);
/**
* Takes ownership of the OperationContext from `ctx`, and returns a Context object to track it.
* On destruction of the Context, its entry in *this is erased and its corresponding
* OperationContext is destroyed. If *this has been interrupted already, `ctx` will be
* interrupted immediately.
*/
Context adopt(UniqueOperationContext ctx);
/**
* Moves the OperationContext of `ctx` from its current OperationContextGroup into *this.
* Do this to protect an OperationContext from being interrupted along with the rest of its
* group, or to expose `ctx` to this->interrupt(). Taking from a Context already in *this is
* equivalent to moving from `ctx`. Taking a moved-from Context yields another moved-from
* Context.
*/
Context take(Context ctx);
/*
* Interrupts all the OperationContexts maintained in *this.
*/
void interrupt(ErrorCodes::Error);
/**
* Reports whether the group has any OperationContexts. This must be true before the destructor
* is called. Its usefulness is typically limited to invariants.
*/
bool isEmpty();
private:
friend class Context;
stdx::mutex _lock;
std::vector<UniqueOperationContext> _contexts;
}; // class OperationContextGroup
/**
* Context tracks one OperationContext*, and on destruction unregisters and destroys the associated
* OperationContext. May be used as if it were an OperationContext*.
*
* The lifetime of an OperationContextGroup::Context object must not exceed that of its
* OperationContextGroup, unless it has been moved from, taken from (see
* OperationContextGroup::take), or discarded.
*/
class OperationContextGroup::Context {
Context() = delete;
Context(Context const&) = delete;
void operator=(Context const&) = delete;
void operator=(Context&&) = delete;
public:
Context(Context&& ctx) : _opCtx(ctx._opCtx), _ctxGroup(ctx._ctxGroup) {
ctx._movedFrom = true;
}
~Context() {
discard();
}
/**
* Returns a pointer to the tracked OperationContext, or nullptr if *this has been moved from.
*/
OperationContext* opCtx() const {
return _movedFrom ? nullptr : &_opCtx;
}
/**
* These enable treating a Context as if it were an OperationContext*.
*/
operator OperationContext*() const {
dassert(!_movedFrom);
return &_opCtx;
}
OperationContext* operator->() const { // because op-> will not use the conversion
dassert(!_movedFrom);
return &_opCtx;
}
/**
* Destroys and unregisters the corresponding OperationContext. After this operation, *this is
* an xvalue, and can only be destroyed.
*/
void discard();
private:
friend class OperationContextGroup;
Context(OperationContext& ctx, OperationContextGroup& group);
bool _movedFrom = false;
OperationContext& _opCtx;
OperationContextGroup& _ctxGroup;
}; // class OperationContextGroup::Context
} // namespace mongo
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