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// Copyright (C) 2012-2015 Internet Systems Consortium, Inc. ("ISC")
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This file requires LOCKFILE_DIR to be defined. It points to the default
// directory where lockfile will be created.
#include <log/interprocess/interprocess_sync_file.h>
#include <string>
#include <cerrno>
#include <cstring>
#include <sstream>
#include <iostream>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
namespace isc {
namespace log {
namespace interprocess {
InterprocessSyncFile::~InterprocessSyncFile() {
if (fd_ != -1) {
// This will also release any applied locks.
close(fd_);
// The lockfile will continue to exist, and we must not delete
// it.
}
}
bool
InterprocessSyncFile::do_lock(int cmd, short l_type) {
// Open lock file only when necessary (i.e., here). This is so that
// if a default InterprocessSync object is replaced with another
// implementation, it doesn't attempt any opens.
if (fd_ == -1) {
std::string lockfile_path = LOCKFILE_DIR;
const char* const env = getenv("KEA_LOCKFILE_DIR");
if (env != NULL) {
lockfile_path = env;
}
lockfile_path += "/" + task_name_ + "_lockfile";
// Open the lockfile in the constructor so it doesn't do the access
// checks every time a message is logged.
const mode_t mode = umask(S_IXUSR | S_IXGRP | S_IXOTH); // 0111
fd_ = open(lockfile_path.c_str(), O_CREAT | O_RDWR,
S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP); // 0660
umask(mode);
if (fd_ == -1) {
std::stringstream tmp;
// We failed to create a lockfile. This means that the logging
// system is unusable. We need to report the issue using plain
// print to stderr.
tmp << "Unable to use interprocess sync lockfile ("
<< std::strerror(errno) << "): " << lockfile_path;
std::cerr << tmp.str() << std::endl;
// And then throw exception as usual.
isc_throw(InterprocessSyncFileError, tmp.str());
}
}
struct flock lock;
memset(&lock, 0, sizeof (lock));
lock.l_type = l_type;
lock.l_whence = SEEK_SET;
lock.l_start = 0;
lock.l_len = 1;
return (fcntl(fd_, cmd, &lock) == 0);
}
bool
InterprocessSyncFile::lock() {
if (is_locked_) {
return (true);
}
if (do_lock(F_SETLKW, F_WRLCK)) {
is_locked_ = true;
return (true);
}
return (false);
}
bool
InterprocessSyncFile::tryLock() {
if (is_locked_) {
return (true);
}
if (do_lock(F_SETLK, F_WRLCK)) {
is_locked_ = true;
return (true);
}
return (false);
}
bool
InterprocessSyncFile::unlock() {
if (!is_locked_) {
return (true);
}
if (do_lock(F_SETLKW, F_UNLCK)) {
is_locked_ = false;
return (true);
}
return (false);
}
} // namespace interprocess
} // namespace log
} // namespace isc
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