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Diffstat (limited to 'examples/librados/hello_world_c.c')
| -rw-r--r-- | examples/librados/hello_world_c.c | 304 |
1 files changed, 304 insertions, 0 deletions
diff --git a/examples/librados/hello_world_c.c b/examples/librados/hello_world_c.c new file mode 100644 index 00000000..88a45485 --- /dev/null +++ b/examples/librados/hello_world_c.c @@ -0,0 +1,304 @@ +// -*- 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.h> +#include <stdio.h> +#include <stdlib.h> + +int main(int argc, const char **argv) +{ + int ret = 0; + + // we will use all of these below + const char *pool_name = "hello_world_pool"; + const char* hello = "hello world!"; + const char* object_name = "hello_object"; + rados_ioctx_t io_ctx = NULL; + int pool_created = 0; + + // first, we create a Rados object and initialize it + rados_t rados = NULL; + { + ret = rados_create(&rados, "admin"); // just use the client.admin keyring + if (ret < 0) { // let's handle any error that might have come back + printf("couldn't initialize rados! error %d\n", ret); + ret = EXIT_FAILURE; + goto out; + } + printf("we just set up a rados cluster object\n"); + } + + /* + * 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(rados, argc, argv); + if (ret < 0) { + // This really can't happen, but we need to check to be a good citizen. + printf("failed to parse config options! error %d\n", ret); + ret = EXIT_FAILURE; + goto out; + } + + printf("we just parsed our config options\n"); + // We also want to apply the config file if the user specified + // one, and conf_parse_argv won't do that for us. + int i; + for (i = 0; i < argc; ++i) { + if ((strcmp(argv[i], "-c") == 0) || (strcmp(argv[i], "--conf") == 0)) { + ret = rados_conf_read_file(rados, argv[i+1]); + if (ret < 0) { + // This could fail if the config file is malformed, but it'd be hard. + printf("failed to parse config file %s! error %d\n", argv[i+1], ret); + ret = EXIT_FAILURE; + goto out; + } + break; + } + } + } + + /* + * next, we actually connect to the cluster + */ + { + ret = rados_connect(rados); + if (ret < 0) { + printf("couldn't connect to cluster! error %d\n", ret); + ret = EXIT_FAILURE; + goto out; + } + printf("we just connected to the rados cluster\n"); + } + + /* + * 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(rados, pool_name); + if (ret < 0) { + printf("couldn't create pool! error %d\n", ret); + return EXIT_FAILURE; + } + printf("we just created a new pool named %s\n", pool_name); + pool_created = 1; + } + + /* + * create an "IoCtx" which is used to do IO to a pool + */ + { + ret = rados_ioctx_create(rados, pool_name, &io_ctx); + if (ret < 0) { + printf("couldn't set up ioctx! error %d\n", ret); + ret = EXIT_FAILURE; + goto out; + } + printf("we just created an ioctx for our pool\n"); + } + + /* + * now let's do some IO to the pool! We'll write "hello world!" to a + * new object. + */ + { + /* + * now that we have the data to write, let's send it to an object. + * We'll use the synchronous interface for simplicity. + */ + ret = rados_write_full(io_ctx, object_name, hello, strlen(hello)); + if (ret < 0) { + printf("couldn't write object! error %d\n", ret); + ret = EXIT_FAILURE; + goto out; + } + printf("we just wrote new object %s, with contents '%s'\n", object_name, hello); + } + + /* + * 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 ) + */ + { + int read_len = 4194304; // this is way more than we need + char* read_buf = malloc(read_len + 1); // add one for the terminating 0 we'll add later + if (!read_buf) { + printf("couldn't allocate read buffer\n"); + ret = EXIT_FAILURE; + goto out; + } + // allocate the completion from librados + rados_completion_t read_completion; + ret = rados_aio_create_completion(NULL, NULL, NULL, &read_completion); + if (ret < 0) { + printf("couldn't create completion! error %d\n", ret); + ret = EXIT_FAILURE; + free(read_buf); + goto out; + } + printf("we just created a new completion\n"); + + // send off the request. + ret = rados_aio_read(io_ctx, object_name, read_completion, read_buf, read_len, 0); + if (ret < 0) { + printf("couldn't start read object! error %d\n", ret); + ret = EXIT_FAILURE; + free(read_buf); + rados_aio_release(read_completion); + goto out; + } + // wait for the request to complete, and check that it succeeded. + rados_aio_wait_for_complete(read_completion); + ret = rados_aio_get_return_value(read_completion); + if (ret < 0) { + printf("couldn't read object! error %d\n", ret); + ret = EXIT_FAILURE; + free(read_buf); + rados_aio_release(read_completion); + goto out; + } + read_buf[ret] = 0; // null-terminate the string + printf("we read our object %s, and got back %d bytes with contents\n%s\n", object_name, ret, read_buf); + + free(read_buf); + rados_aio_release(read_completion); + } + + /* + * We can also use xattrs that go alongside the object. + */ + { + const char* version = "1"; + ret = rados_setxattr(io_ctx, object_name, "version", version, strlen(version)); + if (ret < 0) { + printf("failed to set xattr version entry! error %d\n", ret); + ret = EXIT_FAILURE; + goto out; + } + printf("we set the xattr 'version' on our object!\n"); + } + + /* + * 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. + */ + { + const char* content = "v2"; + rados_write_op_t write_op = rados_create_write_op(); + if (!write_op) { + printf("failed to allocate write op\n"); + ret = EXIT_FAILURE; + goto out; + } + rados_write_op_write_full(write_op, content, strlen(content)); + const char* version = "2"; + rados_write_op_setxattr(write_op, "version", version, strlen(version)); + ret = rados_write_op_operate(write_op, io_ctx, object_name, NULL, 0); + if (ret < 0) { + printf("failed to do compound write! error %d\n", ret); + ret = EXIT_FAILURE; + rados_release_write_op(write_op); + goto out; + } + printf("we overwrote our object %s with contents\n%s\n", object_name, content); + rados_release_write_op(write_op); + } + + /* + * 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. + */ + { + rados_write_op_t failed_write_op = rados_create_write_op(); + if (!failed_write_op) { + printf("failed to allocate write op\n"); + ret = EXIT_FAILURE; + goto out; + } + const char* content = "v2"; + const char* version = "2"; + const char* old_version = "1"; + rados_write_op_cmpxattr(failed_write_op, "version", LIBRADOS_CMPXATTR_OP_EQ, old_version, strlen(old_version)); + rados_write_op_write_full(failed_write_op, content, strlen(content)); + rados_write_op_setxattr(failed_write_op, "version", version, strlen(version)); + ret = rados_write_op_operate(failed_write_op, io_ctx, object_name, NULL, 0); + if (ret < 0) { + printf("we just failed a write because the xattr wasn't as specified\n"); + } else { + printf("we succeeded on writing despite an xattr comparison mismatch!\n"); + ret = EXIT_FAILURE; + rados_release_write_op(failed_write_op); + goto out; + } + rados_release_write_op(failed_write_op); + + /* + * Now let's do the update with the correct xattr values so it + * actually goes through + */ + content = "v3"; + old_version = "2"; + version = "3"; + rados_write_op_t update_op = rados_create_write_op(); + if (!failed_write_op) { + printf("failed to allocate write op\n"); + ret = EXIT_FAILURE; + goto out; + } + rados_write_op_cmpxattr(update_op, "version", LIBRADOS_CMPXATTR_OP_EQ, old_version, strlen(old_version)); + rados_write_op_write_full(update_op, content, strlen(content)); + rados_write_op_setxattr(update_op, "version", version, strlen(version)); + ret = rados_write_op_operate(update_op, io_ctx, object_name, NULL, 0); + if (ret < 0) { + printf("failed to do a compound write update! error %d\n", ret); + ret = EXIT_FAILURE; + rados_release_write_op(update_op); + goto out; + } + printf("we overwrote our object %s following an xattr test with contents\n%s\n", object_name, content); + rados_release_write_op(update_op); + } + + ret = EXIT_SUCCESS; + + out: + if (io_ctx) { + rados_ioctx_destroy(io_ctx); + } + + if (pool_created) { + /* + * And now we're done, so let's remove our pool and then + * shut down the connection gracefully. + */ + int delete_ret = rados_pool_delete(rados, pool_name); + if (delete_ret < 0) { + // be careful not to + printf("We failed to delete our test pool!\n"); + ret = EXIT_FAILURE; + } + } + + rados_shutdown(rados); + + return ret; +} |