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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* 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
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* 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 Server Side 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 <functional>
#include <string>
#include <vector>
#include "mongo/base/status.h"
namespace mongo {
/** Context of an initialization process. Passed as a parameter to initialization functions. */
class InitializerContext {
public:
explicit InitializerContext(std::vector<std::string> args) : _args(std::move(args)) {}
const std::vector<std::string>& args() const {
return _args;
}
private:
std::vector<std::string> _args;
};
/** Context of a deinitialization process. Passed as a parameter to deinitialization functions. */
class DeinitializerContext {
public:
DeinitializerContext(const DeinitializerContext&) = delete;
DeinitializerContext& operator=(const DeinitializerContext&) = delete;
};
/**
* An InitializerFunction implements the behavior of an initializer operation.
* It may inspect and mutate the supplied InitializerContext.
* Throws on failure.
*/
using InitializerFunction = std::function<void(InitializerContext*)>;
/**
* A DeinitializerFunction implements the behavior of a deinitializer operation.
* It may inspect and mutate the supplied DeinitializerContext.
* Throws on failure.
*/
using DeinitializerFunction = std::function<void(DeinitializerContext*)>;
/**
* Class representing an initialization process.
*
* Such a process is described by a directed acyclic graph of initialization operations, the
* InitializerDependencyGraph. One constructs an initialization process by adding nodes and
* edges to the graph. Then, one executes the process, causing each initialization operation to
* execute in an order that respects the programmer-established prerequistes.
*
* The initialize and delinitialize process can repeat, a features which
* supports embedded contexts. However, the graph cannot be modified with
* `addInitializer` after the first initialization. Latecomers are rejected.
*/
class Initializer {
public:
Initializer();
~Initializer();
/**
* Add a new initializer node, with the specified `name`, to the dependency graph, with the
* given behavior, `initFn`, `deinitFn`, and with the given `prerequisites` and `dependents`,
* which are the names of other initializers which will be in the graph when `topSort`
* is called. `initFn` must be non-null, but null-valued `deinitFn` are allowed.
*
* - Throws `ErrorCodes::BadValue` if `initFn` is null-valued.
*
* - Throws with `ErrorCodes::CannotMutateObject` if the graph has been frozen
* by a previous call to `executeInitializers`.
*/
void addInitializer(std::string name,
InitializerFunction initFn,
DeinitializerFunction deinitFn,
std::vector<std::string> prerequisites,
std::vector<std::string> dependents);
/**
* Execute the initializer process, using the given args as input.
* This call freezes the graph, so that addInitializer will reject any latecomers.
*
* Throws on initialization failures, or on invalid call sequences
* (double-init, double-deinit, etc) and the thing being initialized should
* be considered dead in the water.
*/
void executeInitializers(const std::vector<std::string>& args);
/**
* Executes all deinit functions in reverse order from init order.
* Note that this does not unfreeze the graph. Freezing is permanent.
*/
void executeDeinitializers();
/**
* Returns the function mapped to `name`, for testing only.
*
* Throws with `ErrorCodes::BadValue` if name is not mapped to a node.
*/
InitializerFunction getInitializerFunctionForTesting(const std::string& name);
private:
class Graph;
/**
* kNeverInitialized
* |
* +-> kUninitialized <----------+
* | |
* +-> kInitializing |
* | |
* +-> kInitialized |
* | |
* +-> kDeinitializing
*/
enum class State {
kNeverInitialized, ///< still accepting addInitializer calls
kUninitialized,
kInitializing,
kInitialized,
kDeinitializing,
};
void _transition(State expected, State next);
std::unique_ptr<Graph> _graph; // pimpl
std::vector<std::string> _sortedNodes;
State _lifecycleState = State::kNeverInitialized;
};
/**
* Get the process-global initializer object.
*/
Initializer& getGlobalInitializer();
/**
* Run the global initializers.
*
* It's a programming error for this to fail, but if it does it will return a status other
* than Status::OK.
*
* This means that the few initializers that might want to terminate the program by failing
* should probably arrange to terminate the process themselves.
*/
Status runGlobalInitializers(const std::vector<std::string>& argv);
/**
* Same as runGlobalInitializers(), except prints a brief message to std::cerr
* and terminates the process on failure.
*/
void runGlobalInitializersOrDie(const std::vector<std::string>& argv);
/**
* Run the global deinitializers. They will execute in reverse order from initialization.
*
* It's a programming error for this to fail, but if it does it will return a status other
* than Status::OK.
*
* This means that the few initializers that might want to terminate the program by failing
* should probably arrange to terminate the process themselves.
*/
Status runGlobalDeinitializers();
} // namespace mongo
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