238 lines
9.8 KiB
C++
238 lines
9.8 KiB
C++
/*
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* This file is open source software, licensed to you under the terms
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* of the Apache License, Version 2.0 (the "License"). See the NOTICE file
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* distributed with this work for additional information regarding copyright
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* ownership. You may not use this file except in compliance with the License.
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*
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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/*
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* Copyright 2020 ScyllaDB
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*/
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// Demonstration of seastar::with_file
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#include <cstring>
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#include <limits>
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#include <random>
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#include <seastar/core/app-template.hh>
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#include <seastar/core/aligned_buffer.hh>
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#include <seastar/core/file.hh>
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#include <seastar/core/fstream.hh>
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#include <seastar/core/seastar.hh>
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#include <seastar/core/sstring.hh>
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#include <seastar/core/temporary_buffer.hh>
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#include <seastar/core/loop.hh>
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#include <seastar/core/io_intent.hh>
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#include <seastar/util/log.hh>
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#include <seastar/util/tmp_file.hh>
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using namespace seastar;
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constexpr size_t aligned_size = 4096;
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future<> verify_data_file(file& f, temporary_buffer<char>& rbuf, const temporary_buffer<char>& wbuf) {
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return f.dma_read(0, rbuf.get_write(), aligned_size).then([&rbuf, &wbuf] (size_t count) {
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assert(count == aligned_size);
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fmt::print(" verifying {} bytes\n", count);
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assert(!memcmp(rbuf.get(), wbuf.get(), aligned_size));
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});
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}
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future<file> open_data_file(sstring meta_filename, temporary_buffer<char>& rbuf) {
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fmt::print(" retrieving data filename from {}\n", meta_filename);
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return with_file(open_file_dma(meta_filename, open_flags::ro), [&rbuf] (file& f) {
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return f.dma_read(0, rbuf.get_write(), aligned_size).then([&rbuf] (size_t count) {
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assert(count == aligned_size);
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auto data_filename = sstring(rbuf.get());
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fmt::print(" opening {}\n", data_filename);
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return open_file_dma(data_filename, open_flags::ro);
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});
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});
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}
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future<> demo_with_file() {
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fmt::print("Demonstrating with_file():\n");
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return tmp_dir::do_with_thread([] (tmp_dir& t) {
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auto rnd = std::mt19937(std::random_device()());
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auto dist = std::uniform_int_distribution<int>(0, std::numeric_limits<char>::max());
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auto wbuf = temporary_buffer<char>::aligned(aligned_size, aligned_size);
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sstring meta_filename = (t.get_path() / "meta_file").native();
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sstring data_filename = (t.get_path() / "data_file").native();
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// `with_file` is used to create/open `filename` just around the call to `dma_write`
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auto write_to_file = [] (const sstring filename, temporary_buffer<char>& wbuf) {
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auto count = with_file(open_file_dma(filename, open_flags::rw | open_flags::create), [&wbuf] (file& f) {
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return f.dma_write(0, wbuf.get(), aligned_size);
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}).get();
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assert(count == aligned_size);
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};
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// print the data_filename into the write buffer
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std::fill(wbuf.get_write(), wbuf.get_write() + aligned_size, 0);
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std::copy(data_filename.cbegin(), data_filename.cend(), wbuf.get_write());
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// and write it to `meta_filename`
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fmt::print(" writing \"{}\" into {}\n", data_filename, meta_filename);
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write_to_file(meta_filename, wbuf);
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// now write some random data into data_filename
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fmt::print(" writing random data into {}\n", data_filename);
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std::generate(wbuf.get_write(), wbuf.get_write() + aligned_size, [&dist, &rnd] { return dist(rnd); });
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write_to_file(data_filename, wbuf);
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// verify the data via meta_filename
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fmt::print(" verifying data...\n");
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auto rbuf = temporary_buffer<char>::aligned(aligned_size, aligned_size);
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with_file(open_data_file(meta_filename, rbuf), [&rbuf, &wbuf] (file& f) {
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return verify_data_file(f, rbuf, wbuf);
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}).get();
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});
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}
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future<> demo_with_file_close_on_failure() {
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fmt::print("\nDemonstrating with_file_close_on_failure():\n");
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return tmp_dir::do_with_thread([] (tmp_dir& t) {
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auto rnd = std::mt19937(std::random_device()());
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auto dist = std::uniform_int_distribution<int>(0, std::numeric_limits<char>::max());
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auto wbuf = temporary_buffer<char>::aligned(aligned_size, aligned_size);
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sstring meta_filename = (t.get_path() / "meta_file").native();
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sstring data_filename = (t.get_path() / "data_file").native();
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// with_file_close_on_failure will close the opened file only if
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// `make_file_output_stream` returns an error. Otherwise, in the error-free path,
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// the opened file is moved to `file_output_stream` that in-turn closes it
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// when the stream is closed.
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auto make_output_stream = [] (std::string_view filename) {
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return with_file_close_on_failure(open_file_dma(filename, open_flags::rw | open_flags::create), [] (file f) {
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return make_file_output_stream(std::move(f), aligned_size);
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});
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};
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// writes the buffer one byte at a time, to demonstrate output stream
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auto write_to_stream = [] (output_stream<char>& o, const temporary_buffer<char>& wbuf) {
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return seastar::do_for_each(wbuf, [&o] (char c) {
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return o.write(&c, 1);
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}).finally([&o] {
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return o.close();
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});
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};
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// print the data_filename into the write buffer
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std::fill(wbuf.get_write(), wbuf.get_write() + aligned_size, 0);
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std::copy(data_filename.cbegin(), data_filename.cend(), wbuf.get_write());
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// and write it to `meta_filename`
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fmt::print(" writing \"{}\" into {}\n", data_filename, meta_filename);
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// with_file_close_on_failure will close the opened file only if
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// `make_file_output_stream` returns an error. Otherwise, in the error-free path,
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// the opened file is moved to `file_output_stream` that in-turn closes it
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// when the stream is closed.
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output_stream<char> o = make_output_stream(meta_filename).get();
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write_to_stream(o, wbuf).get();
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// now write some random data into data_filename
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fmt::print(" writing random data into {}\n", data_filename);
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std::generate(wbuf.get_write(), wbuf.get_write() + aligned_size, [&dist, &rnd] { return dist(rnd); });
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o = make_output_stream(data_filename).get();
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write_to_stream(o, wbuf).get();
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// verify the data via meta_filename
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fmt::print(" verifying data...\n");
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auto rbuf = temporary_buffer<char>::aligned(aligned_size, aligned_size);
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with_file(open_data_file(meta_filename, rbuf), [&rbuf, &wbuf] (file& f) {
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return verify_data_file(f, rbuf, wbuf);
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}).get();
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});
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}
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static constexpr size_t half_aligned_size = aligned_size / 2;
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future<> demo_with_io_intent() {
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fmt::print("\nDemonstrating demo_with_io_intent():\n");
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return tmp_dir::do_with_thread([] (tmp_dir& t) {
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sstring filename = (t.get_path() / "testfile.tmp").native();
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auto f = open_file_dma(filename, open_flags::rw | open_flags::create).get();
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auto rnd = std::mt19937(std::random_device()());
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auto dist = std::uniform_int_distribution<int>(0, std::numeric_limits<char>::max());
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auto wbuf = temporary_buffer<char>::aligned(aligned_size, aligned_size);
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fmt::print(" writing random data into {}\n", filename);
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std::generate(wbuf.get_write(), wbuf.get_write() + aligned_size, [&dist, &rnd] { return dist(rnd); });
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f.dma_write(0, wbuf.get(), aligned_size).get();
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auto wbuf_n = temporary_buffer<char>::aligned(aligned_size, aligned_size);
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fmt::print(" starting to overwrite {} with other random data in two steps\n", filename);
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std::generate(wbuf_n.get_write(), wbuf_n.get_write() + aligned_size, [&dist, &rnd] { return dist(rnd); });
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io_intent intent;
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auto f1 = f.dma_write(0, wbuf_n.get(), half_aligned_size);
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auto f2 = f.dma_write(half_aligned_size, wbuf_n.get() + half_aligned_size, half_aligned_size, &intent);
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fmt::print(" cancel the 2nd overwriting\n");
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intent.cancel();
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fmt::print(" wait for overwriting IOs to complete\n");
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f1.get();
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bool cancelled = false;
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try {
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f2.get();
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// The file::dma_write doesn't preemt, but if it
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// suddenly will, the 2nd write will pass before
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// the intent would be cancelled
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fmt::print(" 2nd write won the race with cancellation\n");
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} catch (cancelled_error& ex) {
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cancelled = true;
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}
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fmt::print(" verifying data...\n");
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auto rbuf = allocate_aligned_buffer<unsigned char>(aligned_size, aligned_size);
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f.dma_read(0, rbuf.get(), aligned_size).get();
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// First part of the buffer must coincide with the overwritten data
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assert(!memcmp(rbuf.get(), wbuf_n.get(), half_aligned_size));
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if (cancelled) {
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// Second part -- with the old data ...
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assert(!memcmp(rbuf.get() + half_aligned_size, wbuf.get() + half_aligned_size, half_aligned_size));
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} else {
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// ... or with new if the cancellation didn't happen
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assert(!memcmp(rbuf.get() + half_aligned_size, wbuf.get() + half_aligned_size, half_aligned_size));
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}
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});
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}
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int main(int ac, char** av) {
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app_template app;
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return app.run(ac, av, [] {
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return demo_with_file().then([] {
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return demo_with_file_close_on_failure().then([] {
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return demo_with_io_intent();
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});
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});
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});
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}
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