mirror of
https://github.com/matrix-construct/construct
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234 lines
8.9 KiB
C++
234 lines
8.9 KiB
C++
// Matrix Construct
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//
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// Copyright (C) Matrix Construct Developers, Authors & Contributors
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// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
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//
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice is present in all copies. The
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// full license for this software is available in the LICENSE file.
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#pragma once
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#define HAVE_IRCD_M_VM_H
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/// Matrix Virtual Machine
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///
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/// This is the processing unit for matrix events. The front-end interface to
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/// m::vm consists of two parts: The query suite (observation) and the eval
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/// (modification). The back-end interface consists of modules which supply
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/// the features for the vm's logic. The m::vm operates primarily as a global
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/// singleton and facilitates synchronization between multiple ircd::ctx's
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/// using its interfaces.
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///
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/// The query suite tries to satisfy a query using the current state of the vm,
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/// the database, and may even use the network. An idea of a basic pseudo-
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/// query: was user X a member of room Y when event Z happened? Is X a member
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/// of Y right now? etc.
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///
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/// The vm::eval is the primary input receptacle for events. The eval of an
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/// event leads to its execution and will advance the global state of IRCd. That
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/// advance may broadcast its effects to clients of IRCd, federation servers,
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/// and alter the responses to future queries. Execution of an event is a
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/// unique phenomenon: it only happens once. IRCd has thenceforth borne witness
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/// to the event and will never execute it again unless it is forgotten by
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/// erasing the db. Simulation options allow for evals without execution.
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///
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/// The back-end provides the business logic and features for the above user
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/// interfaces.
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///
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namespace ircd::m::vm
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{
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IRCD_M_EXCEPTION(m::error, VM_ERROR, http::INTERNAL_SERVER_ERROR);
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IRCD_M_EXCEPTION(VM_ERROR, VM_FAULT, http::BAD_REQUEST);
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enum fault :uint;
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struct front;
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struct eval;
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struct opts;
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using closure = std::function<void (const event &)>;
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using closure_bool = std::function<bool (const event &)>;
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using dbs::where;
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using dbs::query;
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using dbs::cursor;
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extern struct log::log log;
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extern struct fronts fronts;
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extern uint64_t current_sequence;
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extern ctx::view<const event> inserted;
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bool test(const query<> &, const closure_bool &);
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bool test(const query<> &);
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bool until(const query<> &, const closure_bool &);
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bool until(const query<> &);
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void for_each(const query<> &, const closure &);
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void for_each(const closure &);
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size_t count(const query<> &, const closure_bool &);
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size_t count(const query<> &);
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event::id::buf commit(json::iov &event);
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event::id::buf commit(json::iov &event, const json::iov &content);
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}
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/// Evaluation Options
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struct ircd::m::vm::opts
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{
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/// Setting to false will disable the eval from exiting with a fault and
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/// instead consider all faults as errors which throw exceptions. If
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/// nothrow is also specified then the exception will be stored in the
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/// exception_ptr and #gp will be set.
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bool faults {true};
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/// Setting to true will prevent any exception throwing from an eval and
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/// instead only use the exception_ptr field. Note that eval does not make
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/// a noexcept guarantee with or without this option and it may still throw
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/// some rare or unexpected exception aborting the eval.
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bool nothrow {false};
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/// Setting to true will cause a successful eval to commit the result
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/// which writes to the db and has global effects for the server.
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/// False is the simulation mode to test evaluation without effects.
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bool commit {false};
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/// Setting to false will prevent the release sequence after a commit.
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/// This is a really bad thing to do. testing/debug/devel use only.
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bool release {true};
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/// Setting to true will force the eval to be aware of an m.room.create
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/// for a room for anything to succeed. There will be #ef's until found.
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bool genesis {false};
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/// Setting to true will cause #ef's until there is at least one unbroken
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/// link of events down to an m.room.create.
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bool cosmogonic {false};
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/// Setting to true will cause #ef's until the entire reference cone is
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/// known by the evaluation (if legit). i.e full history tree.
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bool fullcone {false};
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/// Setting to 1 forces evaluations to only proceed from oldest to newest
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/// events; the capstan will only operate using forward mode and positive
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/// accumulations. Because events only reference the past the machine won't
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/// always #ef, it will just stop. More events can be input. Setting to
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/// -1 is anti-causal: evaluations only proceed from newest to oldest and
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/// only negative accumulations are used. 0 is automatic and may use both.
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int causal {0};
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/// Option to skip event signature verification when false.
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bool verify_signature {true};
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};
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/// Individual evaluation state
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///
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/// Evaluation faults. These are reasons which evaluation has halted but may
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/// continue after the user defaults the fault. They are basically types of
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/// interrupts and traps, which are recoverable. Only the GENERAL protection
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/// fault (#gp) is an abort and is not recoverable. An exception_ptr will be
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/// set; aborts are otherwise just thrown as exceptions from eval. If any
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/// fault isn't handled properly that is an abort.
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///
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enum ircd::m::vm::fault
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:uint
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{
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ACCEPT, ///< No fault.
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DEBUGSTEP, ///< Debug step. (#db)
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BREAKPOINT, ///< Debug breakpoint. (#bp)
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GENERAL, ///< General protection fault. (#gp)
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EVENT, ///< Eval requires addl events in the ef register (#ef)
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STATE, ///< Required state is missing (#st)
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};
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/// Event Evaluation Device
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///
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/// This object conducts the evaluation of an event or a tape of multiple
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/// events. An event is evaluated in an attempt to execute it. Events which
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/// fail during evaluation won't be executed; such is the case for events which
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/// have already been executed, or events which are invalid or lead to invalid
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/// transitions or actions of the machine etc.
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///
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/// Basic usage of the eval is simply calling the ctor like a function with an
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/// event; with the default options this evaluates and executes the event
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/// throwing all errors. Advanced usage of eval takes the form of an instance
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/// constructed with options; the user then drives the eval in a loop,
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/// responding to its needs for more data or other issues, and then continuing
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/// the loop until satisfied.
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///
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/// The back-end interface consists of a set of modules which register with the
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/// vm::eval class and provide their piece of eval functionality to instances.
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///
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struct ircd::m::vm::eval
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{
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static const struct opts default_opts;
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const struct opts *opts;
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db::txn txn{*event::events};
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std::set<event::id> ef;
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uint64_t cs {0};
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fault operator()();
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fault operator()(const event &);
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fault operator()(const vector_view<const event> &);
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fault operator()(const json::vector &);
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fault operator()(const json::array &);
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template<class events> eval(const struct opts &, events&&);
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template<class events> eval(const events &);
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eval(const struct opts &);
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eval();
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friend string_view reflect(const fault &);
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};
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/// Convenience construction passes events through to operator().
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template<class events>
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ircd::m::vm::eval::eval(const events &event)
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:eval(default_opts)
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{
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operator()(event);
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}
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/// Convenience construction passes events through to operator().
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template<class events>
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ircd::m::vm::eval::eval(const struct opts &opts,
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events&& event)
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:eval(opts)
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{
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operator()(std::forward<events>(event));
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}
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/// The "event front" for a graph. This holds all of the childless events
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/// for a room. Each childless event may exist at a different depth, but
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/// we track the highest depth to increment it for issuing the next event.
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/// The contents of the front will then be used as the prev references for
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/// that new event. The front is then replaced by the new event. This is
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/// managed by the vm core.
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///
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struct ircd::m::vm::front
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{
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int64_t top {0};
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std::map<std::string, uint64_t, std::less<std::string_view>> map;
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};
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/// Singleton iface to all "event fronts" - the top depth in an active graph
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///
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/// This extern singleton is a fundamental structure which holds the highest
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/// depth events in a graph which have no children. The fronts collection
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/// itself is a map of rooms by ID, and one 'front' is held in RAM for each
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/// room. Each front is a collection of those events, which ideally, will
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/// become the prev references for the next event this server issues in the
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/// room.
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///
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/// This is managed by the vm core. The fronts interface is the root of the
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/// RAM footprint for a room known to IRCd. In other words, all room data is
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/// stored in the database except what is reachable through here.
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///
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struct ircd::m::vm::fronts
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{
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std::map<std::string, front, std::less<std::string_view>> map;
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friend front &fetch(const room::id &, front &, const event &);
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public:
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front &get(const room::id &, const event &);
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front &get(const room::id &);
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};
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