mirror of https://github.com/ceph/ceph
299 lines
9.1 KiB
C++
299 lines
9.1 KiB
C++
// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
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// vim: ts=8 sw=2 smarttab
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/*
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* Ceph - scalable distributed file system
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*
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* This is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License version 2.1, as published by the Free Software
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* Foundation. See file COPYING.
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* Copyright 2013 Inktank
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*/
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// install the librados-dev package to get this
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#include <rados/librados.hpp>
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#include <iostream>
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#include <string>
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int main(int argc, const char **argv)
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{
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int ret = 0;
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// we will use all of these below
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const char *pool_name = "hello_world_pool";
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std::string hello("hello world!");
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std::string object_name("hello_object");
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librados::IoCtx io_ctx;
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// first, we create a Rados object and initialize it
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librados::Rados rados;
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{
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ret = rados.init("admin"); // just use the client.admin keyring
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if (ret < 0) { // let's handle any error that might have come back
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std::cerr << "couldn't initialize rados! error " << ret << std::endl;
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ret = EXIT_FAILURE;
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goto out;
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} else {
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std::cout << "we just set up a rados cluster object" << std::endl;
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}
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}
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/*
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* Now we need to get the rados object its config info. It can
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* parse argv for us to find the id, monitors, etc, so let's just
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* use that.
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*/
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{
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ret = rados.conf_parse_argv(argc, argv);
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if (ret < 0) {
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// This really can't happen, but we need to check to be a good citizen.
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std::cerr << "failed to parse config options! error " << ret << std::endl;
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ret = EXIT_FAILURE;
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goto out;
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} else {
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std::cout << "we just parsed our config options" << std::endl;
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// We also want to apply the config file if the user specified
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// one, and conf_parse_argv won't do that for us.
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for (int i = 0; i < argc; ++i) {
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if ((strcmp(argv[i], "-c") == 0) || (strcmp(argv[i], "--conf") == 0)) {
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ret = rados.conf_read_file(argv[i+1]);
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if (ret < 0) {
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// This could fail if the config file is malformed, but it'd be hard.
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std::cerr << "failed to parse config file " << argv[i+1]
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<< "! error" << ret << std::endl;
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ret = EXIT_FAILURE;
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goto out;
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}
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break;
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}
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}
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}
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}
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/*
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* next, we actually connect to the cluster
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*/
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{
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ret = rados.connect();
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if (ret < 0) {
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std::cerr << "couldn't connect to cluster! error " << ret << std::endl;
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ret = EXIT_FAILURE;
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goto out;
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} else {
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std::cout << "we just connected to the rados cluster" << std::endl;
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}
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}
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/*
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* let's create our own pool instead of scribbling over real data.
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* Note that this command creates pools with default PG counts specified
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* by the monitors, which may not be appropriate for real use -- it's fine
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* for testing, though.
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*/
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{
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ret = rados.pool_create(pool_name);
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if (ret < 0) {
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std::cerr << "couldn't create pool! error " << ret << std::endl;
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return EXIT_FAILURE;
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} else {
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std::cout << "we just created a new pool named " << pool_name << std::endl;
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}
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}
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/*
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* create an "IoCtx" which is used to do IO to a pool
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*/
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{
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ret = rados.ioctx_create(pool_name, io_ctx);
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if (ret < 0) {
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std::cerr << "couldn't set up ioctx! error " << ret << std::endl;
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ret = EXIT_FAILURE;
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goto out;
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} else {
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std::cout << "we just created an ioctx for our pool" << std::endl;
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}
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}
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/*
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* now let's do some IO to the pool! We'll write "hello world!" to a
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* new object.
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*/
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{
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/*
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* "bufferlist"s are Ceph's native transfer type, and are carefully
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* designed to be efficient about copying. You can fill them
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* up from a lot of different data types, but strings or c strings
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* are often convenient. Just make sure not to deallocate the memory
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* until the bufferlist goes out of scope and any requests using it
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* have been finished!
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*/
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librados::bufferlist bl;
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bl.append(hello);
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/*
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* now that we have the data to write, let's send it to an object.
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* We'll use the synchronous interface for simplicity.
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*/
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ret = io_ctx.write_full(object_name, bl);
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if (ret < 0) {
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std::cerr << "couldn't write object! error " << ret << std::endl;
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ret = EXIT_FAILURE;
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goto out;
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} else {
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std::cout << "we just wrote new object " << object_name
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<< ", with contents\n" << hello << std::endl;
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}
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}
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/*
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* now let's read that object back! Just for fun, we'll do it using
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* async IO instead of synchronous. (This would be more useful if we
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* wanted to send off multiple reads at once; see
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* http://docs.ceph.com/docs/master/rados/api/librados/#asychronous-io )
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*/
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{
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librados::bufferlist read_buf;
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int read_len = 4194304; // this is way more than we need
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// allocate the completion from librados
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librados::AioCompletion *read_completion = librados::Rados::aio_create_completion();
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// send off the request.
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ret = io_ctx.aio_read(object_name, read_completion, &read_buf, read_len, 0);
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if (ret < 0) {
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std::cerr << "couldn't start read object! error " << ret << std::endl;
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ret = EXIT_FAILURE;
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goto out;
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}
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// wait for the request to complete, and check that it succeeded.
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read_completion->wait_for_complete();
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ret = read_completion->get_return_value();
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if (ret < 0) {
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std::cerr << "couldn't read object! error " << ret << std::endl;
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ret = EXIT_FAILURE;
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goto out;
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} else {
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std::cout << "we read our object " << object_name
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<< ", and got back " << ret << " bytes with contents\n";
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std::string read_string;
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read_buf.copy(0, ret, read_string);
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std::cout << read_string << std::endl;
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}
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}
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/*
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* We can also use xattrs that go alongside the object.
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*/
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{
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librados::bufferlist version_bl;
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version_bl.append('1');
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ret = io_ctx.setxattr(object_name, "version", version_bl);
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if (ret < 0) {
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std::cerr << "failed to set xattr version entry! error "
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<< ret << std::endl;
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ret = EXIT_FAILURE;
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goto out;
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} else {
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std::cout << "we set the xattr 'version' on our object!" << std::endl;
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}
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}
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/*
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* And if we want to be really cool, we can do multiple things in a single
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* atomic operation. For instance, we can update the contents of our object
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* and set the version at the same time.
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*/
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{
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librados::bufferlist bl;
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bl.append(hello);
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bl.append("v2");
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librados::ObjectWriteOperation write_op;
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write_op.write_full(bl);
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librados::bufferlist version_bl;
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version_bl.append('2');
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write_op.setxattr("version", version_bl);
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ret = io_ctx.operate(object_name, &write_op);
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if (ret < 0) {
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std::cerr << "failed to do compound write! error " << ret << std::endl;
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ret = EXIT_FAILURE;
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goto out;
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} else {
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std::cout << "we overwrote our object " << object_name
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<< " with contents\n" << bl.c_str() << std::endl;
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}
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}
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/*
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* And to be even cooler, we can make sure that the object looks the
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* way we expect before doing the write! Notice how this attempt fails
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* because the xattr differs.
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*/
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{
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librados::ObjectWriteOperation failed_write_op;
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librados::bufferlist bl;
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bl.append(hello);
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bl.append("v2");
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librados::ObjectWriteOperation write_op;
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write_op.write_full(bl);
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librados::bufferlist version_bl;
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version_bl.append('2');
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librados::bufferlist old_version_bl;
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old_version_bl.append('1');
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failed_write_op.cmpxattr("version", LIBRADOS_CMPXATTR_OP_EQ, old_version_bl);
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failed_write_op.write_full(bl);
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failed_write_op.setxattr("version", version_bl);
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ret = io_ctx.operate(object_name, &failed_write_op);
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if (ret < 0) {
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std::cout << "we just failed a write because the xattr wasn't as specified"
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<< std::endl;
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} else {
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std::cerr << "we succeeded on writing despite an xattr comparison mismatch!"
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<< std::endl;
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ret = EXIT_FAILURE;
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goto out;
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}
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/*
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* Now let's do the update with the correct xattr values so it
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* actually goes through
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*/
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bl.clear();
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bl.append(hello);
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bl.append("v3");
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old_version_bl.clear();
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old_version_bl.append('2');
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version_bl.clear();
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version_bl.append('3');
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librados::ObjectWriteOperation update_op;
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update_op.cmpxattr("version", LIBRADOS_CMPXATTR_OP_EQ, old_version_bl);
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update_op.write_full(bl);
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update_op.setxattr("version", version_bl);
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ret = io_ctx.operate(object_name, &update_op);
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if (ret < 0) {
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std::cerr << "failed to do a compound write update! error " << ret
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<< std::endl;
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ret = EXIT_FAILURE;
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goto out;
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} else {
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std::cout << "we overwrote our object " << object_name
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<< " following an xattr test with contents\n" << bl.c_str()
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<< std::endl;
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}
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}
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ret = EXIT_SUCCESS;
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out:
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/*
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* And now we're done, so let's remove our pool and then
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* shut down the connection gracefully.
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*/
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int delete_ret = rados.pool_delete(pool_name);
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if (delete_ret < 0) {
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// be careful not to
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std::cerr << "We failed to delete our test pool!" << std::endl;
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ret = EXIT_FAILURE;
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}
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rados.shutdown();
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return ret;
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}
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