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Diffstat (limited to 'src/cls/hello')
| -rw-r--r-- | src/cls/hello/cls_hello.cc | 344 |
1 files changed, 344 insertions, 0 deletions
diff --git a/src/cls/hello/cls_hello.cc b/src/cls/hello/cls_hello.cc new file mode 100644 index 00000000..accca898 --- /dev/null +++ b/src/cls/hello/cls_hello.cc @@ -0,0 +1,344 @@ +// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*- +// vim: ts=8 sw=2 smarttab + +/* + * This is a simple example RADOS class, designed to be usable as a + * template for implementing new methods. + * + * Our goal here is to illustrate the interface between the OSD and + * the class and demonstrate what kinds of things a class can do. + * + * Note that any *real* class will probably have a much more + * sophisticated protocol dealing with the in and out data buffers. + * For an example of the model that we've settled on for handling that + * in a clean way, please refer to cls_lock or cls_version for + * relatively simple examples of how the parameter encoding can be + * encoded in a way that allows for forward and backward compatibility + * between client vs class revisions. + */ + +/* + * A quick note about bufferlists: + * + * The bufferlist class allows memory buffers to be concatenated, + * truncated, spliced, "copied," encoded/embedded, and decoded. For + * most operations no actual data is ever copied, making bufferlists + * very convenient for efficiently passing data around. + * + * bufferlist is actually a typedef of buffer::list, and is defined in + * include/buffer.h (and implemented in common/buffer.cc). + */ + +#include <algorithm> +#include <string> +#include <sstream> +#include <errno.h> + +#include "objclass/objclass.h" + +CLS_VER(1,0) +CLS_NAME(hello) + +/** + * say hello - a "read" method that does not depend on the object + * + * This is an example of a method that does some computation and + * returns data to the caller, without depending on the local object + * content. + */ +static int say_hello(cls_method_context_t hctx, bufferlist *in, bufferlist *out) +{ + // see if the input data from the client matches what this method + // expects to receive. your class can fill this buffer with what it + // wants. + if (in->length() > 100) + return -EINVAL; + + // we generate our reply + out->append("Hello, "); + if (in->length() == 0) + out->append("world"); + else + out->append(*in); + out->append("!"); + + // this return value will be returned back to the librados caller + return 0; +} + +/** + * record hello - a "write" method that creates an object + * + * This method modifies a local object (in this case, by creating it + * if it doesn't exist). We make multiple write calls (write, + * setxattr) which are accumulated and applied as an atomic + * transaction. + */ +static int record_hello(cls_method_context_t hctx, bufferlist *in, bufferlist *out) +{ + // we can write arbitrary stuff to the ceph-osd debug log. each log + // message is accompanied by an integer log level. smaller is + // "louder". how much of this makes it into the log is controlled + // by the debug_cls option on the ceph-osd, similar to how other log + // levels are controlled. this message, at level 20, will generally + // not be seen by anyone unless debug_cls is set at 20 or higher. + CLS_LOG(20, "in record_hello"); + + // see if the input data from the client matches what this method + // expects to receive. your class can fill this buffer with what it + // wants. + if (in->length() > 100) + return -EINVAL; + + // only say hello to non-existent objects + if (cls_cxx_stat(hctx, NULL, NULL) == 0) + return -EEXIST; + + bufferlist content; + content.append("Hello, "); + if (in->length() == 0) + content.append("world"); + else + content.append(*in); + content.append("!"); + + // create/write the object + int r = cls_cxx_write_full(hctx, &content); + if (r < 0) + return r; + + // also make note of who said it + entity_inst_t origin; + cls_get_request_origin(hctx, &origin); + ostringstream ss; + ss << origin; + bufferlist attrbl; + attrbl.append(ss.str()); + r = cls_cxx_setxattr(hctx, "said_by", &attrbl); + if (r < 0) + return r; + + // For write operations, there are two possible outcomes: + // + // * For a failure, we return a negative error code. The out + // buffer can contain any data that we want, and that data will + // be returned to the caller. No change is made to the object. + // + // * For a success, we must return 0 and *no* data in the out + // buffer. This is becaues the OSD does not log write result + // codes or output buffers and we need a replayed/resent + // operation (e.g., after a TCP disconnect) to be idempotent. + // + // If a class returns a positive value or puts data in the out + // buffer, the OSD code will ignore it and return 0 to the + // client. + return 0; +} + +static int writes_dont_return_data(cls_method_context_t hctx, bufferlist *in, bufferlist *out) +{ + // make some change to the object + bufferlist attrbl; + attrbl.append("bar"); + int r = cls_cxx_setxattr(hctx, "foo", &attrbl); + if (r < 0) + return r; + + if (in->length() > 0) { + // note that if we return anything < 0 (an error), this + // operation/transaction will abort, and the setattr above will + // never happen. however, we *can* return data on error. + out->append("too much input data!"); + return -EINVAL; + } + + // try to return some data. note that this *won't* reach the + // client! see the matching test case in test_cls_hello.cc. + out->append("you will never see this"); + + // if we try to return anything > 0 here the client will see 0. + return 42; +} + + +/** + * replay - a "read" method to get a previously recorded hello + * + * This is a read method that will retrieve a previously recorded + * hello statement. + */ +static int replay(cls_method_context_t hctx, bufferlist *in, bufferlist *out) +{ + // read contents out of the on-disk object. our behavior can be a + // function of either the request alone, or the request and the + // on-disk state, depending on whether the RD flag is specified when + // registering the method (see the __cls__init function below). + int r = cls_cxx_read(hctx, 0, 1100, out); + if (r < 0) + return r; + + // note that our return value need not be the length of the returned + // data; it can be whatever value we want: positive, zero or + // negative (this is a read). + return 0; +} + +/** + * turn_it_to_11 - a "write" method that mutates existing object data + * + * A write method can depend on previous object content (i.e., perform + * a read/modify/write operation). This atomically transitions the + * object state from the old content to the new content. + */ +static int turn_it_to_11(cls_method_context_t hctx, bufferlist *in, bufferlist *out) +{ + // see if the input data from the client matches what this method + // expects to receive. your class can fill this buffer with what it + // wants. + if (in->length() != 0) + return -EINVAL; + + bufferlist previous; + int r = cls_cxx_read(hctx, 0, 1100, &previous); + if (r < 0) + return r; + + std::string str(previous.c_str(), previous.length()); + std::transform(str.begin(), str.end(), str.begin(), ::toupper); + previous.clear(); + previous.append(str); + + // replace previous byte data content (write_full == truncate(0) + write) + r = cls_cxx_write_full(hctx, &previous); + if (r < 0) + return r; + + // record who did it + entity_inst_t origin; + cls_get_request_origin(hctx, &origin); + ostringstream ss; + ss << origin; + bufferlist attrbl; + attrbl.append(ss.str()); + r = cls_cxx_setxattr(hctx, "amplified_by", &attrbl); + if (r < 0) + return r; + + // return value is 0 for success; out buffer is empty. + return 0; +} + +/** + * example method that does not behave + * + * This method is registered as WR but tries to read + */ +static int bad_reader(cls_method_context_t hctx, bufferlist *in, bufferlist *out) +{ + return cls_cxx_read(hctx, 0, 100, out); +} + +/** + * example method that does not behave + * + * This method is registered as RD but tries to write + */ +static int bad_writer(cls_method_context_t hctx, bufferlist *in, bufferlist *out) +{ + return cls_cxx_write_full(hctx, in); +} + + +class PGLSHelloFilter : public PGLSFilter { + string val; +public: + int init(bufferlist::const_iterator& params) override { + try { + decode(xattr, params); + decode(val, params); + } catch (buffer::error &e) { + return -EINVAL; + } + return 0; + } + + ~PGLSHelloFilter() override {} + bool filter(const hobject_t &obj, bufferlist& xattr_data, + bufferlist& outdata) override + { + if (val.size() != xattr_data.length()) + return false; + + if (memcmp(val.c_str(), xattr_data.c_str(), val.size())) + return false; + + return true; + } +}; + + +PGLSFilter *hello_filter() +{ + return new PGLSHelloFilter(); +} + + +/** + * initialize class + * + * We do two things here: we register the new class, and then register + * all of the class's methods. + */ +CLS_INIT(hello) +{ + // this log message, at level 0, will always appear in the ceph-osd + // log file. + CLS_LOG(0, "loading cls_hello"); + + cls_handle_t h_class; + cls_method_handle_t h_say_hello; + cls_method_handle_t h_record_hello; + cls_method_handle_t h_replay; + cls_method_handle_t h_writes_dont_return_data; + cls_method_handle_t h_turn_it_to_11; + cls_method_handle_t h_bad_reader; + cls_method_handle_t h_bad_writer; + + cls_register("hello", &h_class); + + // There are two flags we specify for methods: + // + // RD : whether this method (may) read prior object state + // WR : whether this method (may) write or update the object + // + // A method can be RD, WR, neither, or both. If a method does + // neither, the data it returns to the caller is a function of the + // request and not the object contents. + + cls_register_cxx_method(h_class, "say_hello", + CLS_METHOD_RD, + say_hello, &h_say_hello); + cls_register_cxx_method(h_class, "record_hello", + CLS_METHOD_WR | CLS_METHOD_PROMOTE, + record_hello, &h_record_hello); + cls_register_cxx_method(h_class, "writes_dont_return_data", + CLS_METHOD_WR, + writes_dont_return_data, &h_writes_dont_return_data); + cls_register_cxx_method(h_class, "replay", + CLS_METHOD_RD, + replay, &h_replay); + + // RD | WR is a read-modify-write method. + cls_register_cxx_method(h_class, "turn_it_to_11", + CLS_METHOD_RD | CLS_METHOD_WR | CLS_METHOD_PROMOTE, + turn_it_to_11, &h_turn_it_to_11); + + // counter-examples + cls_register_cxx_method(h_class, "bad_reader", CLS_METHOD_WR, + bad_reader, &h_bad_reader); + cls_register_cxx_method(h_class, "bad_writer", CLS_METHOD_RD, + bad_writer, &h_bad_writer); + + // A PGLS filter + cls_register_cxx_filter(h_class, "hello", hello_filter); +} |