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#pragma once
#include <fcntl.h>
#include <sys/file.h>
#include <string>
#include <mutex>
#include <filesystem>
#include <Poco/Exception.h>
#include <IO/ReadBufferFromFileDescriptor.h>
#include <IO/WriteBufferFromFileDescriptor.h>
#include <IO/ReadHelpers.h>
#include <IO/WriteHelpers.h>
#include <Common/Exception.h>
#include <base/defines.h>
#include <base/types.h>
namespace DB
{
namespace ErrorCodes
{
extern const int CANNOT_OPEN_FILE;
extern const int CANNOT_READ_ALL_DATA;
extern const int ATTEMPT_TO_READ_AFTER_EOF;
}
}
namespace fs = std::filesystem;
/** Stores a number in the file.
* Designed for rare calls (not designed for performance).
*/
class CounterInFile
{
private:
static inline constexpr size_t SMALL_READ_WRITE_BUFFER_SIZE = 16;
public:
/// path - the name of the file, including the path
explicit CounterInFile(const std::string & path_) : path(path_) {}
/** Add `delta` to the number in the file and return the new value.
* If the `create_if_need` parameter is not set to true, then
* the file should already have a number written (if not - create the file manually with zero).
*
* To protect against race conditions between different processes, file locks are used.
* (But when the first file is created, the race condition is possible, so it's better to create the file in advance.)
*
* `locked_callback` is called when the counter file is locked. A new value is passed to it.
* `locked_callback` can be used to do something atomically with incrementing the counter (for example, renaming files).
*/
template <typename Callback>
Int64 add(Int64 delta, Callback && locked_callback, bool create_if_need = false)
{
std::lock_guard lock(mutex);
Int64 res = -1;
bool file_doesnt_exists = !fs::exists(path);
if (file_doesnt_exists && !create_if_need)
{
throw Poco::Exception("File " + path + " does not exist. "
"You must create it manually with appropriate value or 0 for first start.");
}
int fd = ::open(path.c_str(), O_RDWR | O_CREAT | O_CLOEXEC, 0666);
if (-1 == fd)
DB::throwFromErrnoWithPath("Cannot open file " + path, path, DB::ErrorCodes::CANNOT_OPEN_FILE);
try
{
int flock_ret = flock(fd, LOCK_EX);
if (-1 == flock_ret)
DB::throwFromErrnoWithPath("Cannot lock file " + path, path, DB::ErrorCodes::CANNOT_OPEN_FILE);
if (!file_doesnt_exists)
{
DB::ReadBufferFromFileDescriptor rb(fd, SMALL_READ_WRITE_BUFFER_SIZE);
try
{
DB::readIntText(res, rb);
}
catch (const DB::Exception & e)
{
/// A more understandable error message.
if (e.code() == DB::ErrorCodes::CANNOT_READ_ALL_DATA || e.code() == DB::ErrorCodes::ATTEMPT_TO_READ_AFTER_EOF)
throw DB::ParsingException(e.code(), "File {} is empty. You must fill it manually with appropriate value.", path);
else
throw;
}
}
else
res = 0;
if (delta || file_doesnt_exists)
{
res += delta;
DB::WriteBufferFromFileDescriptor wb(fd, SMALL_READ_WRITE_BUFFER_SIZE);
wb.seek(0, SEEK_SET);
wb.truncate(0);
DB::writeIntText(res, wb);
DB::writeChar('\n', wb);
wb.sync();
}
locked_callback(res);
}
catch (...)
{
int err = close(fd);
chassert(!err || errno == EINTR);
throw;
}
int err = close(fd);
chassert(!err || errno == EINTR);
return res;
}
Int64 add(Int64 delta, bool create_if_need = false)
{
return add(delta, [](UInt64){}, create_if_need);
}
const std::string & getPath() const
{
return path;
}
/// Change the path to the file.
void setPath(std::string path_)
{
path = path_;
}
// Not thread-safe and not synchronized between processes.
void fixIfBroken(UInt64 value)
{
bool file_exists = fs::exists(path);
int fd = ::open(path.c_str(), O_RDWR | O_CREAT | O_CLOEXEC, 0666);
if (-1 == fd)
DB::throwFromErrnoWithPath("Cannot open file " + path, path, DB::ErrorCodes::CANNOT_OPEN_FILE);
try
{
bool broken = true;
if (file_exists)
{
DB::ReadBufferFromFileDescriptor rb(fd, SMALL_READ_WRITE_BUFFER_SIZE);
try
{
UInt64 current_value;
DB::readIntText(current_value, rb);
char c;
DB::readChar(c, rb);
if (rb.count() > 0 && c == '\n' && rb.eof())
broken = false;
}
catch (const DB::Exception & e)
{
if (e.code() != DB::ErrorCodes::CANNOT_READ_ALL_DATA && e.code() != DB::ErrorCodes::ATTEMPT_TO_READ_AFTER_EOF)
throw;
}
}
if (broken)
{
DB::WriteBufferFromFileDescriptor wb(fd, SMALL_READ_WRITE_BUFFER_SIZE);
wb.seek(0, SEEK_SET);
wb.truncate(0);
DB::writeIntText(value, wb);
DB::writeChar('\n', wb);
wb.sync();
}
}
catch (...)
{
int err = close(fd);
chassert(!err || errno == EINTR);
throw;
}
int err = close(fd);
chassert(!err || errno == EINTR);
}
private:
std::string path;
std::mutex mutex;
};
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