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Diffstat (limited to 'src/seastar/demos/file_demo.cc')
-rw-r--r-- | src/seastar/demos/file_demo.cc | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/src/seastar/demos/file_demo.cc b/src/seastar/demos/file_demo.cc new file mode 100644 index 000000000..76974bdc4 --- /dev/null +++ b/src/seastar/demos/file_demo.cc @@ -0,0 +1,175 @@ +/* + * This file is open source software, licensed to you under the terms + * of the Apache License, Version 2.0 (the "License"). See the NOTICE file + * distributed with this work for additional information regarding copyright + * ownership. You may not use this file except in compliance with the License. + * + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + */ +/* + * Copyright 2020 ScyllaDB + */ + + +// Demonstration of seastar::with_file + +#include <cstring> +#include <limits> +#include <random> + +#include <seastar/core/app-template.hh> + +#include <seastar/core/aligned_buffer.hh> +#include <seastar/core/file.hh> +#include <seastar/core/fstream.hh> +#include <seastar/core/seastar.hh> +#include <seastar/core/sstring.hh> +#include <seastar/core/temporary_buffer.hh> +#include <seastar/core/loop.hh> +#include <seastar/util/log.hh> +#include <seastar/util/tmp_file.hh> + +using namespace seastar; + +constexpr size_t aligned_size = 4096; + +future<> verify_data_file(file& f, temporary_buffer<char>& rbuf, const temporary_buffer<char>& wbuf) { + return f.dma_read(0, rbuf.get_write(), aligned_size).then([&rbuf, &wbuf] (size_t count) { + assert(count == aligned_size); + fmt::print(" verifying {} bytes\n", count); + assert(!memcmp(rbuf.get(), wbuf.get(), aligned_size)); + }); +} + +future<file> open_data_file(sstring meta_filename, temporary_buffer<char>& rbuf) { + fmt::print(" retrieving data filename from {}\n", meta_filename); + return with_file(open_file_dma(meta_filename, open_flags::ro), [&rbuf] (file& f) { + return f.dma_read(0, rbuf.get_write(), aligned_size).then([&rbuf] (size_t count) { + assert(count == aligned_size); + auto data_filename = sstring(rbuf.get()); + fmt::print(" opening {}\n", data_filename); + return open_file_dma(data_filename, open_flags::ro); + }); + }); +} + +future<> demo_with_file() { + fmt::print("Demonstrating with_file():\n"); + return tmp_dir::do_with_thread([] (tmp_dir& t) { + auto rnd = std::mt19937(std::random_device()()); + auto dist = std::uniform_int_distribution<char>(0, std::numeric_limits<char>::max()); + auto wbuf = temporary_buffer<char>::aligned(aligned_size, aligned_size); + sstring meta_filename = (t.get_path() / "meta_file").native(); + sstring data_filename = (t.get_path() / "data_file").native(); + + // `with_file` is used to create/open `filename` just around the call to `dma_write` + auto write_to_file = [] (const sstring filename, temporary_buffer<char>& wbuf) { + auto count = with_file(open_file_dma(filename, open_flags::rw | open_flags::create), [&wbuf] (file& f) { + return f.dma_write(0, wbuf.get(), aligned_size); + }).get0(); + assert(count == aligned_size); + }; + + // print the data_filename into the write buffer + std::fill(wbuf.get_write(), wbuf.get_write() + aligned_size, 0); + std::copy(data_filename.cbegin(), data_filename.cend(), wbuf.get_write()); + + // and write it to `meta_filename` + fmt::print(" writing \"{}\" into {}\n", data_filename, meta_filename); + + write_to_file(meta_filename, wbuf); + + // now write some random data into data_filename + fmt::print(" writing random data into {}\n", data_filename); + std::generate(wbuf.get_write(), wbuf.get_write() + aligned_size, [&dist, &rnd] { return dist(rnd); }); + + write_to_file(data_filename, wbuf); + + // verify the data via meta_filename + fmt::print(" verifying data...\n"); + auto rbuf = temporary_buffer<char>::aligned(aligned_size, aligned_size); + + with_file(open_data_file(meta_filename, rbuf), [&rbuf, &wbuf] (file& f) { + return verify_data_file(f, rbuf, wbuf); + }).get(); + }); +} + +future<> demo_with_file_close_on_failure() { + fmt::print("\nDemonstrating with_file_close_on_failure():\n"); + return tmp_dir::do_with_thread([] (tmp_dir& t) { + auto rnd = std::mt19937(std::random_device()()); + auto dist = std::uniform_int_distribution<char>(0, std::numeric_limits<char>::max()); + auto wbuf = temporary_buffer<char>::aligned(aligned_size, aligned_size); + sstring meta_filename = (t.get_path() / "meta_file").native(); + sstring data_filename = (t.get_path() / "data_file").native(); + + // with_file_close_on_failure will close the opened file only if + // `make_file_output_stream` returns an error. Otherwise, in the error-free path, + // the opened file is moved to `file_output_stream` that in-turn closes it + // when the stream is closed. + auto make_output_stream = [] (const sstring filename) { + return with_file_close_on_failure(open_file_dma(std::move(filename), open_flags::rw | open_flags::create), [] (file f) { + return make_file_output_stream(std::move(f), aligned_size); + }); + }; + + // writes the buffer one byte at a time, to demonstrate output stream + auto write_to_stream = [] (output_stream<char>& o, const temporary_buffer<char>& wbuf) { + return seastar::do_for_each(wbuf, [&o] (char c) { + return o.write(&c, 1); + }).finally([&o] { + return o.close(); + }); + }; + + // print the data_filename into the write buffer + std::fill(wbuf.get_write(), wbuf.get_write() + aligned_size, 0); + std::copy(data_filename.cbegin(), data_filename.cend(), wbuf.get_write()); + + // and write it to `meta_filename` + fmt::print(" writing \"{}\" into {}\n", data_filename, meta_filename); + + // with_file_close_on_failure will close the opened file only if + // `make_file_output_stream` returns an error. Otherwise, in the error-free path, + // the opened file is moved to `file_output_stream` that in-turn closes it + // when the stream is closed. + output_stream<char> o = make_output_stream(meta_filename).get0(); + + write_to_stream(o, wbuf).get(); + + // now write some random data into data_filename + fmt::print(" writing random data into {}\n", data_filename); + std::generate(wbuf.get_write(), wbuf.get_write() + aligned_size, [&dist, &rnd] { return dist(rnd); }); + + o = make_output_stream(data_filename).get0(); + + write_to_stream(o, wbuf).get(); + + // verify the data via meta_filename + fmt::print(" verifying data...\n"); + auto rbuf = temporary_buffer<char>::aligned(aligned_size, aligned_size); + + with_file(open_data_file(meta_filename, rbuf), [&rbuf, &wbuf] (file& f) { + return verify_data_file(f, rbuf, wbuf); + }).get(); + }); +} + +int main(int ac, char** av) { + app_template app; + return app.run(ac, av, [] { + return demo_with_file().then([] { + return demo_with_file_close_on_failure(); + }); + }); +} |