--- /dev/null
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+/*
+ * Ceph - scalable distributed file system
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software
+ * Foundation. See file COPYING.
+ * Copyright 2013 Inktank
+ */
+
+// install the librados-dev package to get this
+#include <rados/librados.hpp>
+#include <iostream>
+#include <string>
+
+int main(int argc, const char **argv)
+{
+ int ret = 0;
+
+ // we will use all of these below
+ const char *pool_name = "hello_world_pool";
+ std::string hello("hello world!");
+ std::string object_name("hello_object");
+ librados::IoCtx io_ctx;
+
+ // first, we create a Rados object and initialize it
+ librados::Rados rados;
+ {
+ ret = rados.init("admin"); // just use the client.admin keyring
+ if (ret < 0) { // let's handle any error that might have come back
+ std::cerr << "couldn't initialize rados! error " << ret << std::endl;
+ ret = EXIT_FAILURE;
+ goto out;
+ } else {
+ std::cout << "we just set up a rados cluster object" << std::endl;
+ }
+ }
+
+ /*
+ * Now we need to get the rados object its config info. It can
+ * parse argv for us to find the id, monitors, etc, so let's just
+ * use that.
+ */
+ {
+ ret = rados.conf_parse_argv(argc, argv);
+ if (ret < 0) {
+ // This really can't happen, but we need to check to be a good citizen.
+ std::cerr << "failed to parse config options! error " << ret << std::endl;
+ ret = EXIT_FAILURE;
+ goto out;
+ } else {
+ std::cout << "we just parsed our config options" << std::endl;
+ // We also want to apply the config file if the user specified
+ // one, and conf_parse_argv won't do that for us.
+ for (int i = 0; i < argc; ++i) {
+ if ((strcmp(argv[i], "-c") == 0) || (strcmp(argv[i], "--conf") == 0)) {
+ ret = rados.conf_read_file(argv[i+1]);
+ if (ret < 0) {
+ // This could fail if the config file is malformed, but it'd be hard.
+ std::cerr << "failed to parse config file " << argv[i+1]
+ << "! error" << ret << std::endl;
+ ret = EXIT_FAILURE;
+ goto out;
+ }
+ break;
+ }
+ }
+ }
+ }
+
+ /*
+ * next, we actually connect to the cluster
+ */
+ {
+ ret = rados.connect();
+ if (ret < 0) {
+ std::cerr << "couldn't connect to cluster! error " << ret << std::endl;
+ ret = EXIT_FAILURE;
+ goto out;
+ } else {
+ std::cout << "we just connected to the rados cluster" << std::endl;
+ }
+ }
+
+ /*
+ * let's create our own pool instead of scribbling over real data.
+ * Note that this command creates pools with default PG counts specified
+ * by the monitors, which may not be appropriate for real use -- it's fine
+ * for testing, though.
+ */
+ {
+ ret = rados.pool_create(pool_name);
+ if (ret < 0) {
+ std::cerr << "couldn't create pool! error " << ret << std::endl;
+ return EXIT_FAILURE;
+ } else {
+ std::cout << "we just created a new pool named " << pool_name << std::endl;
+ }
+ }
+
+ /*
+ * create an "IoCtx" which is used to do IO to a pool
+ */
+ {
+ ret = rados.ioctx_create(pool_name, io_ctx);
+ if (ret < 0) {
+ std::cerr << "couldn't set up ioctx! error " << ret << std::endl;
+ ret = EXIT_FAILURE;
+ goto out;
+ } else {
+ std::cout << "we just created an ioctx for our pool" << std::endl;
+ }
+ }
+
+ /*
+ * now let's do some IO to the pool! We'll write "hello world!" to a
+ * new object.
+ */
+ {
+ /*
+ * "bufferlist"s are Ceph's native transfer type, and are carefully
+ * designed to be efficient about copying. You can fill them
+ * up from a lot of different data types, but strings or c strings
+ * are often convenient. Just make sure not to deallocate the memory
+ * until the bufferlist goes out of scope and any requests using it
+ * have been finished!
+ */
+ librados::bufferlist bl;
+ bl.append(hello);
+
+ /*
+ * now that we have the data to write, let's send it to an object.
+ * We'll use the synchronous interface for simplicity.
+ */
+ ret = io_ctx.write_full(object_name, bl);
+ if (ret < 0) {
+ std::cerr << "couldn't write object! error " << ret << std::endl;
+ ret = EXIT_FAILURE;
+ goto out;
+ } else {
+ std::cout << "we just wrote new object " << object_name
+ << ", with contents\n" << hello << std::endl;
+ }
+ }
+
+ /*
+ * now let's read that object back! Just for fun, we'll do it using
+ * async IO instead of synchronous. (This would be more useful if we
+ * wanted to send off multiple reads at once; see
+ * http://docs.ceph.com/docs/master/rados/api/librados/#asychronous-io )
+ */
+ {
+ librados::bufferlist read_buf;
+ int read_len = 4194304; // this is way more than we need
+ // allocate the completion from librados
+ librados::AioCompletion *read_completion = librados::Rados::aio_create_completion();
+ // send off the request.
+ ret = io_ctx.aio_read(object_name, read_completion, &read_buf, read_len, 0);
+ if (ret < 0) {
+ std::cerr << "couldn't start read object! error " << ret << std::endl;
+ ret = EXIT_FAILURE;
+ goto out;
+ }
+ // wait for the request to complete, and check that it succeeded.
+ read_completion->wait_for_complete();
+ ret = read_completion->get_return_value();
+ if (ret < 0) {
+ std::cerr << "couldn't read object! error " << ret << std::endl;
+ ret = EXIT_FAILURE;
+ goto out;
+ } else {
+ std::cout << "we read our object " << object_name
+ << ", and got back " << ret << " bytes with contents\n";
+ std::string read_string;
+ read_buf.copy(0, ret, read_string);
+ std::cout << read_string << std::endl;
+ }
+ }
+
+ /*
+ * We can also use xattrs that go alongside the object.
+ */
+ {
+ librados::bufferlist version_bl;
+ version_bl.append('1');
+ ret = io_ctx.setxattr(object_name, "version", version_bl);
+ if (ret < 0) {
+ std::cerr << "failed to set xattr version entry! error "
+ << ret << std::endl;
+ ret = EXIT_FAILURE;
+ goto out;
+ } else {
+ std::cout << "we set the xattr 'version' on our object!" << std::endl;
+ }
+ }
+
+ /*
+ * And if we want to be really cool, we can do multiple things in a single
+ * atomic operation. For instance, we can update the contents of our object
+ * and set the version at the same time.
+ */
+ {
+ librados::bufferlist bl;
+ bl.append(hello);
+ bl.append("v2");
+ librados::ObjectWriteOperation write_op;
+ write_op.write_full(bl);
+ librados::bufferlist version_bl;
+ version_bl.append('2');
+ write_op.setxattr("version", version_bl);
+ ret = io_ctx.operate(object_name, &write_op);
+ if (ret < 0) {
+ std::cerr << "failed to do compound write! error " << ret << std::endl;
+ ret = EXIT_FAILURE;
+ goto out;
+ } else {
+ std::cout << "we overwrote our object " << object_name
+ << " with contents\n" << bl.c_str() << std::endl;
+ }
+ }
+
+ /*
+ * And to be even cooler, we can make sure that the object looks the
+ * way we expect before doing the write! Notice how this attempt fails
+ * because the xattr differs.
+ */
+ {
+ librados::ObjectWriteOperation failed_write_op;
+ librados::bufferlist bl;
+ bl.append(hello);
+ bl.append("v2");
+ librados::ObjectWriteOperation write_op;
+ write_op.write_full(bl);
+ librados::bufferlist version_bl;
+ version_bl.append('2');
+ librados::bufferlist old_version_bl;
+ old_version_bl.append('1');
+ failed_write_op.cmpxattr("version", LIBRADOS_CMPXATTR_OP_EQ, old_version_bl);
+ failed_write_op.write_full(bl);
+ failed_write_op.setxattr("version", version_bl);
+ ret = io_ctx.operate(object_name, &failed_write_op);
+ if (ret < 0) {
+ std::cout << "we just failed a write because the xattr wasn't as specified"
+ << std::endl;
+ } else {
+ std::cerr << "we succeeded on writing despite an xattr comparison mismatch!"
+ << std::endl;
+ ret = EXIT_FAILURE;
+ goto out;
+ }
+
+ /*
+ * Now let's do the update with the correct xattr values so it
+ * actually goes through
+ */
+ bl.clear();
+ bl.append(hello);
+ bl.append("v3");
+ old_version_bl.clear();
+ old_version_bl.append('2');
+ version_bl.clear();
+ version_bl.append('3');
+ librados::ObjectWriteOperation update_op;
+ update_op.cmpxattr("version", LIBRADOS_CMPXATTR_OP_EQ, old_version_bl);
+ update_op.write_full(bl);
+ update_op.setxattr("version", version_bl);
+ ret = io_ctx.operate(object_name, &update_op);
+ if (ret < 0) {
+ std::cerr << "failed to do a compound write update! error " << ret
+ << std::endl;
+ ret = EXIT_FAILURE;
+ goto out;
+ } else {
+ std::cout << "we overwrote our object " << object_name
+ << " following an xattr test with contents\n" << bl.c_str()
+ << std::endl;
+ }
+ }
+
+ ret = EXIT_SUCCESS;
+ out:
+ /*
+ * And now we're done, so let's remove our pool and then
+ * shut down the connection gracefully.
+ */
+ int delete_ret = rados.pool_delete(pool_name);
+ if (delete_ret < 0) {
+ // be careful not to
+ std::cerr << "We failed to delete our test pool!" << std::endl;
+ ret = EXIT_FAILURE;
+ }
+
+ rados.shutdown();
+
+ return ret;
+}
Code Review / stor4nfv.git / blobdiff