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// Copyright 2015 The Kyua Authors.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
// * Neither the name of Google Inc. nor the names of its contributors
// may be used to endorse or promote products derived from this software
// without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
/// \file utils/process/executor.hpp
/// Multiprogrammed process executor with isolation guarantees.
///
/// This module provides a mechanism to invoke more than one process
/// concurrently while at the same time ensuring that each process is run
/// in a clean container and in a "safe" work directory that gets cleaned
/// up automatically on termination.
///
/// The intended workflow for using this module is the following:
///
/// 1) Initialize the executor using setup(). Keep the returned object
/// around through the lifetime of the next operations. Only one
/// instance of the executor can be alive at once.
/// 2) Spawn one or more processes with spawn(). On the caller side, keep
/// track of any per-process data you may need using the returned
/// exec_handle, which is unique among the set of active processes.
/// 3) Call wait() or wait_any() to wait for completion of a process started
/// in the previous step. Repeat as desired.
/// 4) Use the returned exit_handle object by wait() or wait_any() to query
/// the status of the terminated process and/or to access any of its
/// data files.
/// 5) Invoke cleanup() on the exit_handle to wipe any stale data.
/// 6) Invoke cleanup() on the object returned by setup().
///
/// It is the responsibility of the caller to ensure that calls to
/// spawn() and spawn_followup() are balanced with wait() and wait_any() calls.
///
/// Processes executed in this manner have access to two different "unique"
/// directories: the first is the "work directory", which is an empty directory
/// that acts as the subprocess' work directory; the second is the "control
/// directory", which is the location where the in-process code may place files
/// that are not clobbered by activities in the work directory.
#if !defined(UTILS_PROCESS_EXECUTOR_HPP)
#define UTILS_PROCESS_EXECUTOR_HPP
#include "utils/process/executor_fwd.hpp"
#include <cstddef>
#include <memory>
#include "utils/datetime_fwd.hpp"
#include "utils/fs/path_fwd.hpp"
#include "utils/optional.hpp"
#include "utils/passwd_fwd.hpp"
#include "utils/process/child_fwd.hpp"
#include "utils/process/status_fwd.hpp"
namespace utils {
namespace process {
namespace executor {
namespace detail {
extern const char* stdout_name;
extern const char* stderr_name;
extern const char* work_subdir;
/// Shared reference counter.
typedef std::shared_ptr< std::size_t > refcnt_t;
void setup_child(const utils::optional< utils::passwd::user >,
const utils::fs::path&, const utils::fs::path&);
} // namespace detail
/// Maintenance data held while a subprocess is being executed.
///
/// This data structure exists from the moment a subprocess is executed via
/// executor::spawn() to when it is cleaned up with exit_handle::cleanup().
///
/// The caller NEED NOT maintain this object alive for the execution of the
/// subprocess. However, the PID contained in here can be used to match
/// exec_handle objects with corresponding exit_handle objects via their
/// original_pid() method.
///
/// Objects of this type can be copied around but their implementation is
/// shared. The implication of this is that only the last copy of a given exit
/// handle will execute the automatic cleanup() on destruction.
class exec_handle {
struct impl;
/// Pointer to internal implementation.
std::shared_ptr< impl > _pimpl;
friend class executor_handle;
exec_handle(std::shared_ptr< impl >);
public:
~exec_handle(void);
int pid(void) const;
utils::fs::path control_directory(void) const;
utils::fs::path work_directory(void) const;
const utils::fs::path& stdout_file(void) const;
const utils::fs::path& stderr_file(void) const;
};
/// Container for the data of a process termination.
///
/// This handle provides access to the details of the process that terminated
/// and serves as the owner of the remaining on-disk files. The caller is
/// expected to call cleanup() before destruction to remove the on-disk state.
///
/// Objects of this type can be copied around but their implementation is
/// shared. The implication of this is that only the last copy of a given exit
/// handle will execute the automatic cleanup() on destruction.
class exit_handle {
struct impl;
/// Pointer to internal implementation.
std::shared_ptr< impl > _pimpl;
friend class executor_handle;
exit_handle(std::shared_ptr< impl >);
detail::refcnt_t state_owners(void) const;
public:
~exit_handle(void);
void cleanup(void);
int original_pid(void) const;
const utils::optional< utils::process::status >& status(void) const;
const utils::optional< utils::passwd::user >& unprivileged_user(void) const;
const utils::datetime::timestamp& start_time() const;
const utils::datetime::timestamp& end_time() const;
utils::fs::path control_directory(void) const;
utils::fs::path work_directory(void) const;
const utils::fs::path& stdout_file(void) const;
const utils::fs::path& stderr_file(void) const;
};
/// Handler for the livelihood of the executor.
///
/// Objects of this type can be copied around (because we do not have move
/// semantics...) but their implementation is shared. Only one instance of the
/// executor can exist at any point in time.
class executor_handle {
struct impl;
/// Pointer to internal implementation.
std::shared_ptr< impl > _pimpl;
friend executor_handle setup(void);
executor_handle(void) throw();
utils::fs::path spawn_pre(void);
exec_handle spawn_post(const utils::fs::path&,
const utils::fs::path&,
const utils::fs::path&,
const utils::datetime::delta&,
const utils::optional< utils::passwd::user >,
std::unique_ptr< utils::process::child >);
void spawn_followup_pre(void);
exec_handle spawn_followup_post(const exit_handle&,
const utils::datetime::delta&,
std::unique_ptr< utils::process::child >);
public:
~executor_handle(void);
const utils::fs::path& root_work_directory(void) const;
void cleanup(void);
template< class Hook >
exec_handle spawn(Hook,
const datetime::delta&,
const utils::optional< utils::passwd::user >,
const utils::optional< utils::fs::path > = utils::none,
const utils::optional< utils::fs::path > = utils::none);
template< class Hook >
exec_handle spawn_followup(Hook,
const exit_handle&,
const datetime::delta&);
exit_handle wait(const exec_handle);
exit_handle wait_any(void);
exit_handle reap(const pid_t);
void check_interrupt(void) const;
};
executor_handle setup(void);
} // namespace executor
} // namespace process
} // namespace utils
#endif // !defined(UTILS_PROCESS_EXECUTOR_HPP)
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