ClickHouse/src/IO/RemoteReadBufferCache.cpp

#include <fstream>
#include <memory>
#include <unistd.h>
#include <functional>
#include <Poco/Logger.h>
#include <Poco/JSON/JSON.h>
#include <Poco/JSON/Parser.h>
#include <base/logger_useful.h>
#include <base/sleep.h>
#include <base/errnoToString.h>
#include <Common/SipHash.h>
#include <Common/hex.h>
#include <Common/Exception.h>
#include <IO/RemoteReadBufferCache.h>
#include <IO/WriteHelpers.h>


namespace fs = std::filesystem;

namespace DB
{
namespace ErrorCodes
{
    extern const int BAD_ARGUMENTS;
    extern const int BAD_GET;
    extern const int LOGICAL_ERROR;
    extern const int CANNOT_CREATE_DIRECTORY;
}

std::shared_ptr<RemoteCacheController> RemoteCacheController::recover(
    const String & local_path_, std::function<void(RemoteCacheController *)> const & finish_callback)
{
    fs::path data_file = fs::path(local_path_) / "data.bin";
    fs::path meta_file = fs::path(local_path_) / "meta.txt";
    auto * log = &Poco::Logger::get("RemoteCacheController");
    if (!fs::exists(data_file) || !fs::exists(meta_file))
    {
        LOG_ERROR(log, "Directory {} or file {}, {} does not exist", local_path_, data_file.string(), meta_file.string());
        return nullptr;
    }

    std::ifstream meta_fs(meta_file);
    Poco::JSON::Parser meta_parser;
    auto meta_jobj = meta_parser.parse(meta_fs).extract<Poco::JSON::Object::Ptr>();
    auto remote_path = meta_jobj->get("remote_path").convert<String>();
    auto schema = meta_jobj->get("schema").convert<String>();
    auto cluster = meta_jobj->get("cluster").convert<String>();
    auto downloaded = meta_jobj->get("downloaded").convert<String>();
    auto modification_ts = meta_jobj->get("last_modification_timestamp").convert<UInt64>();
    if (downloaded == "false")
    {
        LOG_ERROR(log, "Local metadata for local path {} exists, but the data was not downloaded", local_path_);
        return nullptr;
    }
    auto file_size = fs::file_size(data_file);

    RemoteFileMetadata remote_file_meta(schema, cluster, remote_path, modification_ts, file_size);
    auto cache_controller = std::make_shared<RemoteCacheController>(remote_file_meta, local_path_, 0, nullptr, finish_callback);
    cache_controller->download_finished = true;
    cache_controller->current_offset = file_size;
    meta_fs.close();

    finish_callback(cache_controller.get());
    return cache_controller;
}

RemoteCacheController::RemoteCacheController(
    const RemoteFileMetadata & remote_file_meta,
    const String & local_path_,
    size_t cache_bytes_before_flush_,
    std::shared_ptr<ReadBuffer> read_buffer_,
    std::function<void(RemoteCacheController *)> const & finish_callback)
    : schema(remote_file_meta.schema)
    , cluster(remote_file_meta.cluster)
    , remote_path(remote_file_meta.path)
    , local_path(local_path_)
    , last_modify_time(remote_file_meta.last_modify_time)
    , valid(true)
    , local_cache_bytes_read_before_flush(cache_bytes_before_flush_)
    , download_finished(false)
    , current_offset(0)
    , remote_read_buffer(read_buffer_)
{
    /// readbuffer == nullptr if `RemoteCacheController` is created in `initOnce`, when metadata and local cache already exist.
    if (remote_read_buffer)
    {
        // setup local files
        out_file = std::make_unique<std::ofstream>(fs::path(local_path_) / "data.bin", std::ios::out | std::ios::binary);
        out_file->flush();

        Poco::JSON::Object jobj;
        jobj.set("schema", schema);
        jobj.set("cluster", cluster);
        jobj.set("remote_path", remote_path);
        jobj.set("downloaded", "false");
        jobj.set("last_modification_timestamp", last_modify_time);
        std::stringstream buf; // STYLE_CHECK_ALLOW_STD_STRING_STREAM
        jobj.stringify(buf);
        std::ofstream meta_file(fs::path(local_path_) / "meta.txt", std::ios::out);
        meta_file.write(buf.str().c_str(), buf.str().size());
        meta_file.close();

        backgroundDownload(finish_callback);
    }
}

RemoteReadBufferCacheError RemoteCacheController::waitMoreData(size_t start_offset_, size_t end_offset_)
{
    std::unique_lock lock{mutex};
    if (download_finished)
    {
        // finish reading
        if (start_offset_ >= current_offset)
        {
            lock.unlock();
            return RemoteReadBufferCacheError::END_OF_FILE;
        }
    }
    else // block until more data is ready
    {
        if (current_offset >= end_offset_)
        {
            lock.unlock();
            return RemoteReadBufferCacheError::OK;
        }
        else
            more_data_signal.wait(lock, [this, end_offset_] { return download_finished || current_offset >= end_offset_; });
    }
    lock.unlock();
    return RemoteReadBufferCacheError::OK;
}

void RemoteCacheController::backgroundDownload(std::function<void(RemoteCacheController *)> const & finish_callback)
{
    auto task = [this, finish_callback]()
    {
        size_t before_unflush_bytes = 0;
        size_t total_bytes = 0;
        while (!remote_read_buffer->eof())
        {
            size_t bytes = remote_read_buffer->available();

            out_file->write(remote_read_buffer->position(), bytes);
            remote_read_buffer->position() += bytes;
            total_bytes += bytes;
            before_unflush_bytes += bytes;
            if (before_unflush_bytes >= local_cache_bytes_read_before_flush)
            {
                std::unique_lock lock(mutex);
                current_offset += total_bytes;
                total_bytes = 0;
                flush();
                lock.unlock();
                more_data_signal.notify_all();
                before_unflush_bytes = 0;
            }
        }
        std::unique_lock lock(mutex);
        current_offset += total_bytes;
        download_finished = true;
        flush(true);
        out_file->close();
        out_file.reset();
        remote_read_buffer.reset();
        lock.unlock();
        more_data_signal.notify_all();
        finish_callback(this);
        LOG_TRACE(log, "Finish download from remote path: {} to local path: {}, file size:{} ", remote_path, local_path, current_offset);
    };
    RemoteReadBufferCache::instance().getThreadPool()->scheduleOrThrow(task);
}

void RemoteCacheController::flush(bool need_flush_meta_)
{
    if (out_file)
    {
        out_file->flush();
    }

    if (!need_flush_meta_)
        return;
    Poco::JSON::Object jobj;
    jobj.set("schema", schema);
    jobj.set("cluster", cluster);
    jobj.set("remote_path", remote_path);
    jobj.set("downloaded", download_finished ? "true" : "false");
    jobj.set("last_modification_timestamp", last_modify_time);
    std::stringstream buf; // STYLE_CHECK_ALLOW_STD_STRING_STREAM
    jobj.stringify(buf);

    std::ofstream meta_file(fs::path(local_path) / "meta.txt", std::ios::out);
    meta_file << buf.str();
    meta_file.close();
}

RemoteCacheController::~RemoteCacheController() = default;

void RemoteCacheController::close()
{
    LOG_TRACE(log, "Removing all local cache for remote path: {}, local path: {}", remote_path, local_path);
    fs::remove_all(local_path);
}

std::pair<FILE *, String> RemoteCacheController::allocFile()
{
    fs::path result_local_path;
    if (download_finished)
        result_local_path = fs::path(local_path) / "data.bin";

    FILE * fs = fopen((fs::path(local_path) / "data.bin").string().c_str(), "r");
    if (!fs)
        throw Exception(ErrorCodes::BAD_GET, "Alloc file failed, error code: {} local path: {}", errno, local_path);

    std::lock_guard lock{mutex};
    opened_file_streams.insert(fs);
    return {fs, result_local_path};
}

void RemoteCacheController::deallocFile(FILE * file_stream)
{
    {
        std::lock_guard lock{mutex};
        auto it = opened_file_streams.find(file_stream);
        if (it == opened_file_streams.end())
            throw Exception(
                ErrorCodes::BAD_ARGUMENTS,
                "Try to deallocate file with invalid handler remote path: {}, local path: {}",
                remote_path,
                local_path);
        opened_file_streams.erase(it);
    }
    fclose(file_stream);
}

LocalCachedFileReader::LocalCachedFileReader(RemoteCacheController * cache_controller_, size_t file_size_)
    : cache_controller(cache_controller_)
    , file_size(file_size_)
    , offset(0)
{
    std::tie(file_stream, local_path) = cache_controller->allocFile();
}

LocalCachedFileReader::~LocalCachedFileReader()
{
    cache_controller->deallocFile(file_stream);
}

size_t LocalCachedFileReader::read(char * buf, size_t size)
{
    auto wret = cache_controller->waitMoreData(offset, offset + size);
    if (wret != RemoteReadBufferCacheError::OK)
        return 0;
    std::lock_guard lock(mutex);
    auto ret_size = fread(buf, 1, size, file_stream);
    offset += ret_size;
    return ret_size;
}

off_t LocalCachedFileReader::seek(off_t off)
{
    cache_controller->waitMoreData(off, 1);
    std::lock_guard lock(mutex);
    auto ret = fseek(file_stream, off, SEEK_SET);
    if (ret < 0)
        throw Exception(
            ErrorCodes::BAD_ARGUMENTS, "Seek file {} with size {} to offset {} failed: {}", getPath(), getSize(), off, errnoToString(errno));

    offset = off;
    return off;
}

size_t LocalCachedFileReader::getSize()
{
    if (file_size != 0)
        return file_size;

    if (local_path.empty())
    {
        LOG_TRACE(log, "Empty local_path");
        return 0;
    }

    file_size = fs::file_size(local_path);
    return file_size;
}

// the size need be equal to the original buffer
RemoteReadBuffer::RemoteReadBuffer(size_t buff_size) : BufferWithOwnMemory<SeekableReadBufferWithSize>(buff_size)
{
}

RemoteReadBuffer::~RemoteReadBuffer() = default;

std::unique_ptr<RemoteReadBuffer> RemoteReadBuffer::create(const RemoteFileMetadata & remote_file_meta, std::unique_ptr<ReadBuffer> read_buffer)
{
    auto * log = &Poco::Logger::get("RemoteReadBuffer");
    size_t buff_size = DBMS_DEFAULT_BUFFER_SIZE;
    if (read_buffer)
        buff_size = read_buffer->internalBuffer().size();
    /*
     * in the new implement of ReadBufferFromHDFS, buffer size is 0.
     *
     * in the common case, we don't read bytes from readbuffer directly, so set buff_size = DBMS_DEFAULT_BUFFER_SIZE
     * is OK.
     *
     * we need be careful with the case  without local file reader.
     */
    if (buff_size == 0)
        buff_size = DBMS_DEFAULT_BUFFER_SIZE;

    const auto & remote_path = remote_file_meta.path;
    auto remote_read_buffer = std::make_unique<RemoteReadBuffer>(buff_size);
    auto * raw_rbp = read_buffer.release();
    std::shared_ptr<ReadBuffer> srb(raw_rbp);
    RemoteReadBufferCacheError error;
    int retry = 0;
    do
    {
        if (retry > 0)
            sleepForMicroseconds(20 * retry);

        std::tie(remote_read_buffer->file_reader, error) = RemoteReadBufferCache::instance().createReader(remote_file_meta, srb);
        retry++;
    } while (error == RemoteReadBufferCacheError::FILE_INVALID && retry < 10);
    if (remote_read_buffer->file_reader == nullptr)
    {
        LOG_ERROR(log, "Failed to allocate local file for remote path: {}, reason: {}", remote_path, error);
        remote_read_buffer->original_read_buffer = srb;
    }
    return remote_read_buffer;
}

bool RemoteReadBuffer::nextImpl()
{
    if (file_reader)
    {
        int bytes_read = file_reader->read(internal_buffer.begin(), internal_buffer.size());
        if (bytes_read)
            working_buffer.resize(bytes_read);
        else
            return false;
    }
    else 
    {
        // In the case we cannot use local cache, read from the original readbuffer directly
        if (!original_read_buffer)
            throw Exception(ErrorCodes::LOGICAL_ERROR, "Original read buffer is not initialized. It's a bug");

        auto status = original_read_buffer->next();
        // We don't need to worry about the memory buffer allocated in RemoteReadBuffer, since it is owned by
        // BufferWithOwnMemory, BufferWithOwnMemory would release it.
        if (status)
            BufferBase::set(original_read_buffer->buffer().begin(), original_read_buffer->buffer().size(), original_read_buffer->offset());
        return status;
    }
    return true;
}

off_t RemoteReadBuffer::seek(off_t offset, int whence)
{
    off_t pos_in_file = file_reader->getOffset();
    off_t new_pos;
    if (whence == SEEK_SET)
        new_pos = offset;
    else if (whence == SEEK_CUR)
        new_pos = pos_in_file - available() + offset;
    else
        throw Exception(ErrorCodes::BAD_ARGUMENTS, "Expects SEEK_SET or SEEK_CUR as whence but given {}", whence);

    /// Position is unchanged.
    if (off_t(new_pos + available()) == pos_in_file)
        return new_pos;

    if (new_pos <= pos_in_file && new_pos >= pos_in_file - static_cast<off_t>(working_buffer.size()))
    {
        /// Position is still inside buffer.
        pos = working_buffer.begin() + (new_pos - (pos_in_file - working_buffer.size()));
        return new_pos;
    }

    pos = working_buffer.end();
    auto ret_off = file_reader->seek(new_pos);
    return ret_off;
}

off_t RemoteReadBuffer::getPosition()
{
    return file_reader->getOffset() - available();
}

RemoteReadBufferCache::RemoteReadBufferCache() = default;

RemoteReadBufferCache::~RemoteReadBufferCache()
{
    thread_pool->wait();
}

RemoteReadBufferCache & RemoteReadBufferCache::instance()
{
    static RemoteReadBufferCache instance;
    return instance;
}

void RemoteReadBufferCache::recoverCachedFilesMeta(
    const fs::path & current_path,
    size_t current_depth,
    size_t max_depth,
    std::function<void(RemoteCacheController *)> const & finish_callback)
{
    if (current_depth >= max_depth)
    {
        for (auto const & dir : fs::directory_iterator{current_path})
        {
            std::string path = dir.path();
            auto cache_controller = RemoteCacheController::recover(path, finish_callback);
            if (!cache_controller)
                continue;
            auto & cell = caches[path];
            cell.cache_controller = cache_controller;
            cell.key_iterator = keys.insert(keys.end(), path);
        }
        return;
    }

    for (auto const & dir : fs::directory_iterator{current_path})
    {
        recoverCachedFilesMeta(dir.path(), current_depth + 1, max_depth, finish_callback);
    }
}

void RemoteReadBufferCache::initOnce(
    const String & root_dir_, size_t limit_size_, size_t bytes_read_before_flush_, size_t max_threads_)
{
    LOG_INFO(
        log, "Initializing local cache for remote data sources. Local cache root path: {}, cache size limit: {}", root_dir_, limit_size_);
    root_dir = root_dir_;
    limit_size = limit_size_;
    local_cache_bytes_read_before_flush = bytes_read_before_flush_;
    thread_pool = std::make_shared<FreeThreadPool>(max_threads_, 1000, 1000, false);

    /// create if root_dir not exists
    if (!fs::exists(fs::path(root_dir) / ""))
    {
        std::error_code ec;
        bool success = fs::create_directories(fs::path(root_dir) / "", ec);
        if (!success)
            throw Exception(
                ErrorCodes::CANNOT_CREATE_DIRECTORY, "Failed to create directories, error code:{} reason:{}", ec.value(), ec.message());
    }

    auto recover_task = [this]()
    {
        auto callback = [this](RemoteCacheController * cache_controller) { total_size += cache_controller->size(); };
        std::lock_guard lock(mutex);
        recoverCachedFilesMeta(root_dir, 1, 2, callback);
        initialized = true;
        LOG_TRACE(log, "Recovered from directory:{}", root_dir);
    };
    getThreadPool()->scheduleOrThrow(recover_task);
}

String RemoteReadBufferCache::calculateLocalPath(const RemoteFileMetadata & meta) const
{
    String full_path = meta.schema + ":" + meta.cluster + ":" + meta.path;
    UInt128 hashcode = sipHash128(full_path.c_str(), full_path.size());
    String hashcode_str = getHexUIntLowercase(hashcode);
    return fs::path(root_dir) / hashcode_str.substr(0, 3) / hashcode_str;
}

std::pair<std::shared_ptr<LocalCachedFileReader>, RemoteReadBufferCacheError>
RemoteReadBufferCache::createReader(const RemoteFileMetadata & remote_file_meta, std::shared_ptr<ReadBuffer> & read_buffer)
{
    // If something is wrong on startup, rollback to read from the original ReadBuffer
    if (!isInitialized())
    {
        LOG_ERROR(log, "RemoteReadBufferCache not initialized yet");
        return {nullptr, RemoteReadBufferCacheError::NOT_INIT};
    }

    auto remote_path = remote_file_meta.path;
    const auto & file_size = remote_file_meta.file_size;
    const auto & last_modification_timestamp = remote_file_meta.last_modify_time;
    auto local_path = calculateLocalPath(remote_file_meta);
    std::lock_guard lock(mutex);
    auto cache_iter = caches.find(local_path);
    if (cache_iter != caches.end())
    {
        // if the file has been update on remote side, we need to redownload it
        if (cache_iter->second.cache_controller->getLastModificationTimestamp() != last_modification_timestamp)
        {
            LOG_TRACE(
                log,
                "Remote file ({}) has been updated. Last saved modification time: {}, actual last modification time: {}",
                remote_path,
                std::to_string(cache_iter->second.cache_controller->getLastModificationTimestamp()),
                std::to_string(last_modification_timestamp));
            cache_iter->second.cache_controller->markInvalid();
        }
        else
        {
            // move the key to the list end
            keys.splice(keys.end(), keys, cache_iter->second.key_iterator);
            return {
                std::make_shared<LocalCachedFileReader>(cache_iter->second.cache_controller.get(), file_size),
                RemoteReadBufferCacheError::OK};
        }
    }

    auto clear_ret = clearLocalCache();
    cache_iter = caches.find(local_path);
    if (cache_iter != caches.end())
    {
        if (cache_iter->second.cache_controller->isValid())
        {
            // move the key to the list end, this case should not happen?
            keys.splice(keys.end(), keys, cache_iter->second.key_iterator);
            return {
                std::make_shared<LocalCachedFileReader>(cache_iter->second.cache_controller.get(), file_size),
                RemoteReadBufferCacheError::OK};
        }
        else
        {
            // maybe someone is holding this file
            return {nullptr, RemoteReadBufferCacheError::FILE_INVALID};
        }
    }

    // reach the disk capacity limit
    if (!clear_ret)
    {
        LOG_INFO(log, "Reached local cache capacity limit size ({})", limit_size);
        return {nullptr, RemoteReadBufferCacheError::DISK_FULL};
    }

    fs::create_directories(local_path);

    auto callback = [this](RemoteCacheController * cntrl) { total_size += cntrl->size(); };
    auto cache_controller
        = std::make_shared<RemoteCacheController>(remote_file_meta, local_path, local_cache_bytes_read_before_flush, read_buffer, callback);
    CacheCell cache_cell;
    cache_cell.cache_controller = cache_controller;
    cache_cell.key_iterator = keys.insert(keys.end(), local_path);
    caches[local_path] = cache_cell;

    return {std::make_shared<LocalCachedFileReader>(cache_controller.get(), file_size), RemoteReadBufferCacheError::OK};
}

bool RemoteReadBufferCache::clearLocalCache()
{
    for (auto it = keys.begin(); it != keys.end();)
    {
        // TODO keys is not thread-safe
        auto cache_it = caches.find(*it);
        auto cache_controller = cache_it->second.cache_controller;
        if (!cache_controller->isValid() && cache_controller->closable())
        {
            LOG_TRACE(log, "Clear invalid cache entry with key {} from local cache", *it);
            total_size
                = total_size > cache_it->second.cache_controller->size() ? total_size - cache_it->second.cache_controller->size() : 0;
            cache_controller->close();
            it = keys.erase(it);
            caches.erase(cache_it);
        }
        else
            it++;
    }
    // clear closable cache from the list head
    for (auto it = keys.begin(); it != keys.end();)
    {
        if (total_size < limit_size)
            break;
        auto cache_it = caches.find(*it);
        if (cache_it == caches.end())
            throw Exception(ErrorCodes::LOGICAL_ERROR, "Found no entry in local cache with key: {}", *it);

        if (cache_it->second.cache_controller->closable())
        {
            total_size
                = total_size > cache_it->second.cache_controller->size() ? total_size - cache_it->second.cache_controller->size() : 0;
            cache_it->second.cache_controller->close();
            caches.erase(cache_it);
            it = keys.erase(it);
            LOG_TRACE(
                log,
                "clear local file {} for {}. key size:{}. next{}",
                cache_it->second.cache_controller->getLocalPath(),
                cache_it->second.cache_controller->getRemotePath(),
                keys.size(),
                *it);
        }
        else
            break;
    }
    LOG_TRACE(log, "After clear local cache, keys size:{}, total_size:{}, limit size:{}", keys.size(), total_size, limit_size);
    return total_size < limit_size;
}

}