创建image时服务端产生的对象

创建一个volume：
如何命名服务端的volume的名字（以format==2为例）：
rbd.cc
模块 主要函数 主要数据结构

RBD     do_create(librbd::RBD &rbd, librados::IoCtx& io_ctx,                         imgname （char *）   由用户指定        const char *imgname, uint64_t size, int *order,        int format, uint64_t features,        uint64_t stripe_unit, uint64_t stripe_count)        {        。。。        }librbd/internal.h        create(IoCtx& io_ctx, const char *imgname, uint64_t size,        bool old_format, uint64_t features, int *order,        uint64_t stripe_unit, uint64_t stripe_count)        {        ...        Rados rados(io_ctx);        uint64_t bid = rados.get_instance_id();        ...        return create_v2(io_ctx, imgname, bid, size, *order, features,                         stripe_unit, stripe_count);        ...        }        create_v2(IoCtx& io_ctx, const char *imgname, uint64_t bid, uint64_t size,           bid （uint64_t）        int order, uint64_t features, uint64_t stripe_unit,                                  imgname(char *)        uint64_t stripe_count)                                                                       {        ...        id_obj = id_obj_name(imgname)    //RBD_ID_PREFIX + name  #define RBD_ID_PREFIX  "rbd_id."        r = io_ctx.create(id_obj, true); // 创建objetct name实例        ...        extra = rand() % 0xFFFFFFFF;    //生产一个随机数        bid_ss << std::hex << bid << std::hex << extra; //将bid和产生的随机数转换成16进制并拼接        id = bid_ss.str(); //转换成字符串        r = cls_client::set_id(&io_ctx, id_obj, id); //为之前创建的object name对象设置id。        ...        cls_client::dir_add_image(&io_ctx, RBD_DIRECTORY, imgname, id);//将该image的name和id注册到RBD_DIRECTORY对象中                                                                       //#define RBD_DIRECTORY           "rbd_directory"        ...        oss << RBD_DATA_PREFIX << id; //#define RBD_DATA_PREFIX        "rbd_data."        header_oid = header_name(id); //RBD_HEADER_PREFIX + id  #define RBD_HEADER_PREFIX      "rbd_header."        cls_client::create_image(&io_ctx, header_oid, size, order,features, oss.str()) //创建object header对象        ...        }cls/rbd/cls_rbd_client.cc        create_image(librados::IoCtx *ioctx, const std::string &oid,                          object_prefix(string) //RBD_DATA_PREFIX + image_id        uint64_t size, uint8_t order, uint64_t features,                                      oid(string) //object header        const std::string &object_prefix)        {        bufferlist bl, bl2;                                                                                                                                                                      ::encode(size, bl);                                                                                                                                                                      ::encode(order, bl);                                                                                                                                                                     ::encode(features, bl);                                                                                                                                                                  ::encode(object_prefix, (bl));        //image 的prefix为  RBD_DATA_PREFIX + image_id                                                                                                                                                                             return ioctx->exec(oid, "rbd", "create", bl, bl2);        }librados/librados.cc        librados::IoCtx::exec(const std::string& oid, const char *cls, const char *method,               oid（string） //object header        bufferlist& inbl, bufferlist& outbl)        {        object_t obj(oid);                                                                                                                                                                                                      return io_ctx_impl->exec(obj, cls, method, inbl, outbl);        }

//bid是怎么来的，

uint64_t librados::Rados::get_instance_id(){                                                                                                                                                                                                                   return client->get_instance_id();}uint64_t librados::RadosClient::get_instance_id()                                                                                                                                                                 {  return instance_id;}int librados::RadosClient::connect(){       ...  instance_id = monclient.get_global_id();      ...}   uint64_t get_global_id() const {                                                                                                                                                                                ¦ return global_id;}uint64_t AuthMonitor::assign_global_id(MAuth *m, bool should_increase_max)                                                                                                             {                                                                                                                                                                                        int total_mon = mon->monmap->size();                                                                                                                                                   dout(10) << "AuthMonitor::assign_global_id m=" << *m << " mon=" << mon->rank << "/" << total_mon                                                                                             ¦ ¦<< " last_allocated=" << last_allocated_id << " max_global_id=" <<  max_global_id << dendl;                                                                                   uint64_t next_global_id = last_allocated_id + 1;                                                                                                                                       int remainder = next_global_id % total_mon;                                                                                                                                            if (remainder)                                                                                                                                                                         ¦ remainder = total_mon - remainder;                                                                                                                                                   next_global_id += remainder + mon->rank;                                                                                                                                               dout(10) << "next_global_id should be " << next_global_id << dendl;                                                                                                                    // if we can't bump the max, bail out now on an out-of-bounds gid                                                                                                                      if (next_global_id > max_global_id &&                                                                                                                                                  ¦ ¦ (!mon->is_leader() || !should_increase_max)) {                                                                                                                                     ¦ return 0;                                                                                                                                                                            }                                                                                                                                                                                      // can we return a gid?                                                                                                                                                                bool return_next = (next_global_id <= max_global_id);                                                                                                                                  // bump the max?                                                                                                                                                                       while (mon->is_leader() &&                                                                                                                                                                   ¦(max_global_id < g_conf->mon_globalid_prealloc ||                                                                                                                                     ¦ next_global_id >= max_global_id - g_conf->mon_globalid_prealloc / 2)) {                                                                                                        ¦ increase_max_global_id();                                                                                                                                                            }                                                                                                                                                                                      if (return_next) {                                                                                                                                                                     ¦ last_allocated_id = next_global_id;                                                                                                                                                  ¦ return next_global_id;                                                                                                                                                               } else {                                                                                                                                                                               ¦ return 0;                                                                                                                                                                            }                                                                                                                                                                                    }

bid来源于monclient，monclient是从monitor服务中申请的ID。

总结：在创建image的时候会在服务端创建两个对象：1.object name对象（rbd_id.{image_name}）2.object header对象（rbd_header.{image_id}）;
image_id是由一个随机数和bid转换成16进制之后拼接生成的。 bid是由MonClient从monitor服务中申请而来的（标识一个MonClient）。