SERVER-40811 make initializers throwy

- Consolidate init-related headers (just init.h and initializer.h)
- Factor out a separate DependencyGraph component
- Remove MONGO_DEFAULT_PREREQUISITES, MONGO_NO_PREREQUISITES, MONGO_NO_DEPENDENTS.
- Document the role of the "default" initializer.

1 files changed, 0 insertions, 167 deletions

diff --git a/src/mongo/base/initializer_dependency_graph.h b/src/mongo/base/initializer_dependency_graph.h
deleted file mode 100644
index 515f75cff26..00000000000
--- a/src/mongo/base/initializer_dependency_graph.h
+++ /dev/null
@@ -1,167 +0,0 @@
-/**
- *    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 <string>
-#include <utility>
-#include <vector>
-
-#include "mongo/base/initializer_function.h"
-#include "mongo/base/status.h"
-#include "mongo/stdx/unordered_map.h"
-#include "mongo/stdx/unordered_set.h"
-
-namespace mongo {
-
-class InitializerDependencyNode {
-    friend class InitializerDependencyGraph;
-
-public:
-    bool isInitialized() const {
-        return initialized;
-    }
-    void setInitialized(bool value) {
-        initialized = value;
-    };
-
-    InitializerFunction const& getInitializerFunction() const {
-        return initFn;
-    }
-    DeinitializerFunction const& getDeinitializerFunction() const {
-        return deinitFn;
-    }
-
-private:
-    InitializerFunction initFn;
-    DeinitializerFunction deinitFn;
-    stdx::unordered_set<std::string> prerequisites;
-    bool initialized{false};
-};
-
-/**
- * Representation of a dependency graph of "initialization operations."
- *
- * Each operation has a unique name, a function object implementing the operation's behavior,
- * and a set of prerequisite operations, which may be empty.  A legal graph contains no cycles.
- *
- * Instances of this class are used in two phases.  In the first phase, the graph is "unfrozen",
- * which permits it to be constructed by repeated calls to addInitializer().  In the second phase,
- * the graph is "frozen" by calling frozen(), which prevents the addition of any further
- * initializers to the graph.  A user can then call the topSort() method to produce an
- * initialization order that respects the dependencies among operations, and then uses the
- * getInitializerFunction() to get the behavior function for each operation, in turn.
- *
- * Concurrency Notes: The user is responsible for synchronization.  Multiple threads may
- * simultaneously call the const functions, getInitializerFunction and topSort, on the same instance
- * of InitializerDependencyGraph.  However, no thread may call addInitializer or freeze while any
- * thread is executing those functions, addInitializer or freeze on the same instance.
- */
-class InitializerDependencyGraph {
-    InitializerDependencyGraph(const InitializerDependencyGraph&) = delete;
-    InitializerDependencyGraph& operator=(const InitializerDependencyGraph&) = delete;
-
-public:
-    InitializerDependencyGraph();
-    ~InitializerDependencyGraph();
-
-    /**
-     * Add a new initializer node, named "name", to the dependency graph, with the given
-     * behavior, "fn", and the given "prerequisites" (input dependencies) and "dependents"
-     * (output dependencies).
-     *
-     * The graph must not be frozen.
-     *
-     * If "!fn" (fn is NULL in function pointer parlance), returns status with code
-     * ErrorCodes::badValue.  If "name" is a duplicate of a name already present in the graph,
-     * returns "ErrorCodes::duplicateKey".  Otherwise, returns Status::OK() and adds the new node
-     * to the graph.  Note that cycles in the dependency graph are not discovered in this phase.
-     * Rather, they're discovered by topSort, below.
-     */
-    Status addInitializer(std::string name,
-                          InitializerFunction initFn,
-                          DeinitializerFunction deinitFn,
-                          std::vector<std::string> prerequisites,
-                          std::vector<std::string> dependents);
-
-    /**
-     * Given a dependency operation node named "name", return its behavior function.  Returns
-     * a value that evaluates to "false" in boolean context, otherwise.
-     */
-    InitializerDependencyNode* getInitializerNode(const std::string& name);
-
-    /**
-     * Construct a topological sort of the dependency graph, and store that order into
-     * "sortedNames".  Returns Status::OK() on success.
-     *
-     * If the graph contains a cycle, returns ErrorCodes::graphContainsCycle, and "sortedNames"
-     * is an ordered sequence of nodes involved in a cycle.  In this case, the first and last
-     * element of "sortedNames" will be equal.
-     *
-     * If any node in the graph names a prerequisite that was never added to the graph via
-     * addInitializer, this function will return ErrorCodes::badValue.
-     *
-     * Any other return value indicates an internal error, and should not occur.
-     */
-    Status topSort(std::vector<std::string>* sortedNames) const;
-
-    /**
-     * Called to mark the end of the period when nodes are allowed to be added to the graph.
-     * The graph is effectively read-only after this point.
-     */
-    void freeze() {
-        _frozen = true;
-    }
-
-    /**
-     * Returns true if this graph has been frozen.
-     */
-    bool frozen() const {
-        return _frozen;
-    }
-
-private:
-    typedef stdx::unordered_map<std::string, InitializerDependencyNode> NodeMap;
-    typedef NodeMap::value_type Node;
-
-    /**
-     * Map of all named nodes.  Nodes named as prerequisites or dependents but not explicitly
-     * added via addInitializer will either be absent from this map or be present with
-     * NodeData::fn set to a false-ish value.
-     */
-    NodeMap _nodes;
-
-    /**
-     * If true, then the graph is "frozen" (ie. effectively read-only), and adding initializer nodes
-     * is not allowed.
-     */
-    bool _frozen{false};
-};
-
-}  // namespace mongo