【ceph学习】ceph如何进行数据的读写（3）

本章摘要

上文说到，osdc中封装请求，使用message中的相关机制将请求发送出去。
本文详细介绍osd服务端如何进行请求的接收。

osd初始化

osd启动时，定义了message变量ms_public，该变量绑定public网络，负责接收客户端的请求。ms_public会启动对应的线程进行接收，并指定接收函数。

  //ceph_osd.cc
  Messenger *ms_public = Messenger::create(g_ceph_context, public_msg_type,
                       entity_name_t::OSD(whoami), "client", nonce);
  Messenger *ms_cluster = Messenger::create(g_ceph_context, cluster_msg_type,
                        entity_name_t::OSD(whoami), "cluster", nonce);
  ms_public->set_default_policy(Messenger::Policy::stateless_registered_server(0));
  ms_public->set_policy_throttlers(entity_name_t::TYPE_CLIENT,
                   client_byte_throttler.get(),
                   client_msg_throttler.get());
  ms_public->set_policy(entity_name_t::TYPE_MON,
                        Messenger::Policy::lossy_client(osd_required));
  ms_public->set_policy(entity_name_t::TYPE_MGR,
                        Messenger::Policy::lossy_client(osd_required));

  ms_cluster->set_default_policy(Messenger::Policy::stateless_server(0));
  ms_cluster->set_policy(entity_name_t::TYPE_MON, Messenger::Policy::lossy_client(0));
  ms_cluster->set_policy(entity_name_t::TYPE_OSD,
             Messenger::Policy::lossless_peer(osd_required));
  ms_cluster->set_policy(entity_name_t::TYPE_CLIENT,
             Messenger::Policy::stateless_server(0));

在create中，初始化一个AsyncMessenger的对象

Messenger *Messenger::create(CephContext *cct, const std::string &type,
                 entity_name_t name, std::string lname,
                 uint64_t nonce)
{
  if (type == "random" || type.find("async") != std::string::npos)
    return new AsyncMessenger(cct, name, type, std::move(lname), nonce);
  lderr(cct) << "unrecognized ms_type '" << type << "'" << dendl;
  return nullptr;
}
AsyncMessenger::AsyncMessenger(CephContext *cct, entity_name_t name,
                               const std::string &type, std::string mname, uint64_t _nonce)
  : SimplePolicyMessenger(cct, name),
    dispatch_queue(cct, this, mname),
    nonce(_nonce)
{
  std::string transport_type = "posix";
  if (type.find("rdma") != std::string::npos)
    transport_type = "rdma";
  else if (type.find("dpdk") != std::string::npos)
    transport_type = "dpdk";

  auto single = &cct->lookup_or_create_singleton_object(
    "AsyncMessenger::NetworkStack::" + transport_type, true, cct);
  single->ready(transport_type);
  stack = single->stack.get();
  stack->start();
  local_worker = stack->get_worker();
  local_connection = ceph::make_ref(cct, this, &dispatch_queue,
                     local_worker, true, true);
  init_local_connection();
  reap_handler = new C_handle_reap(this);
  unsigned processor_num = 1;
  if (stack->support_local_listen_table())
    processor_num = stack->get_num_worker();
  for (unsigned i = 0; i < processor_num; ++i)
    processors.push_back(new Processor(this, stack->get_worker(i), cct));
}

绑定IP，初始化osd对象的时候，ms_public作为参数传入。osd在调用init的时候，进行设置。

  if (ms_public->bindv(public_addrs) < 0)
    forker.exit(1);
  if (ms_cluster->bindv(cluster_addrs) < 0)
    forker.exit(1);
  osdptr = new OSD(g_ceph_context,
           std::move(store),
           whoami,
           ms_cluster,
           ms_public,
           ms_hb_front_client,
           ms_hb_back_client,
           ms_hb_front_server,
           ms_hb_back_server,
           ms_objecter,
           &mc,
           data_path,
           journal_path,
           poolctx);

  int err = osdptr->pre_init();
  if (err < 0) {
    derr << TEXT_RED << " ** ERROR: osd pre_init failed: " << cpp_strerror(-err)
     << TEXT_NORMAL << dendl;
    forker.exit(1);
  }

  ms_public->start();
  ms_hb_front_client->start();
  ms_hb_back_client->start();
  ms_hb_front_server->start();
  ms_hb_back_server->start();
  ms_cluster->start();
  ms_objecter->start();

bindv的具体流程

int Messenger::bindv(const entity_addrvec_t& addrs)
{
  return bind(addrs.legacy_addr());
}
int AsyncMessenger::bind(const entity_addr_t &bind_addr)
{
  ldout(cct,10) << __func__ << " " << bind_addr << dendl;
  // old bind() can take entity_addr_t(). new bindv() can take a
  // 0.0.0.0-like address but needs type and family to be set.
  auto a = bind_addr;
  if (a == entity_addr_t()) {
    a.set_type(entity_addr_t::TYPE_LEGACY);
    if (cct->_conf->ms_bind_ipv6) {
      a.set_family(AF_INET6);
    } else {
      a.set_family(AF_INET);
    }
  }
  return bindv(entity_addrvec_t(a));
}
int AsyncMessenger::bindv(const entity_addrvec_t &bind_addrs)
{
  lock.lock();

  if (!pending_bind && started) {
    ldout(cct,10) << __func__ << " already started" << dendl;
    lock.unlock();
    return -1;
  }

  ldout(cct,10) << __func__ << " " << bind_addrs << dendl;

  if (!stack->is_ready()) {
    ldout(cct, 10) << __func__ << " Network Stack is not ready for bind yet - postponed" << dendl;
    pending_bind_addrs = bind_addrs;
    pending_bind = true;
    lock.unlock();
    return 0;
  }

  lock.unlock();

  // bind to a socket
  std::set avoid_ports;
  entity_addrvec_t bound_addrs;
  unsigned i = 0;
  for (auto &&p : processors) {
    int r = p->bind(bind_addrs, avoid_ports, &bound_addrs);
    if (r) {
      // Note: this is related to local tcp listen table problem.
      // Posix(default kernel implementation) backend shares listen table
      // in the kernel, so all threads can use the same listen table naturally
      // and only one thread need to bind. But other backends(like dpdk) uses local
      // listen table, we need to bind/listen tcp port for each worker. So if the
      // first worker failed to bind, it could be think the normal error then handle
      // it, like port is used case. But if the first worker successfully to bind
      // but the second worker failed, it's not expected and we need to assert
      // here
      ceph_assert(i == 0);
      return r;
    }
    ++i;
  }
  _finish_bind(bind_addrs, bound_addrs);
  return 0;
}

osdptr进行init的时候会江client_messenger（ms_cluster）add进去。

  //ceph_osd.cc
  // start osd
  err = osdptr->init();
//OSD.cc
int OSD::init(){
  // i'm ready!
  client_messenger->add_dispatcher_tail(&mgrc);
  client_messenger->add_dispatcher_tail(this);
  cluster_messenger->add_dispatcher_head(this);
}

//Message.h
void add_dispatcher_tail(Dispatcher *d) {
bool first = dispatchers.empty();
dispatchers.push_back(d);
if (d->ms_can_fast_dispatch_any())
    fast_dispatchers.push_back(d);
if (first)
    ready();
}
//AsyncMessenger.cc
void AsyncMessenger::ready()
{
  ldout(cct,10) << __func__ << " " << get_myaddrs() << dendl;

  stack->ready();
  if (pending_bind) {
    int err = bindv(pending_bind_addrs);
    if (err) {
      lderr(cct) << __func__ << " postponed bind failed" << dendl;
      ceph_abort();
    }
  }

  std::lock_guard l{lock};
  for (auto &&p : processors)
    p->start();
  dispatch_queue.start();
}
//启动信息接收线程
void DispatchQueue::start()
{
  ceph_assert(!stop);
  ceph_assert(!dispatch_thread.is_started());
  dispatch_thread.create("ms_dispatch");
  local_delivery_thread.create("ms_local");
}
//DispatchQueue.h
  class DispatchThread : public Thread {
    DispatchQueue *dq;
  public:
    explicit DispatchThread(DispatchQueue *dq) : dq(dq) {}
    void *entry() override {
      dq->entry();
      return 0;
    }
  } dispatch_thread;

  ceph::mutex local_delivery_lock;
  ceph::condition_variable local_delivery_cond;
  bool stop_local_delivery;
  std::queue, int>> local_messages;
  class LocalDeliveryThread : public Thread {
    DispatchQueue *dq;
  public:
    explicit LocalDeliveryThread(DispatchQueue *dq) : dq(dq) {}
    void *entry() override {
      dq->run_local_delivery();
      return 0;
    }
  } local_delivery_thread;

/*
 * This function delivers incoming messages to the Messenger.
 * Connections with messages are kept in queues; when beginning a message
 * delivery the highest-priority queue is selected, the connection from the
 * front of the queue is removed, and its message read. If the connection
 * has remaining messages at that priority level, it is re-placed on to the
 * end of the queue. If the queue is empty; it's removed.
 * The message is then delivered and the process starts again.
 */
void DispatchQueue::entry()
{
  std::unique_lock l{lock};
  while (true) {
    while (!mqueue.empty()) {
      QueueItem qitem = mqueue.dequeue();
      if (!qitem.is_code())
    remove_arrival(qitem.get_message());
      l.unlock();

      if (qitem.is_code()) {
    if (cct->_conf->ms_inject_internal_delays &&
        cct->_conf->ms_inject_delay_probability &&
        (rand() % 10000)/10000.0 < cct->_conf->ms_inject_delay_probability) {
      utime_t t;
      t.set_from_double(cct->_conf->ms_inject_internal_delays);
      ldout(cct, 1) << "DispatchQueue::entry  inject delay of " << t
            << dendl;
      t.sleep();
    }
    switch (qitem.get_code()) {
    case D_BAD_REMOTE_RESET:
      msgr->ms_deliver_handle_remote_reset(qitem.get_connection());
      break;
    case D_CONNECT:
      msgr->ms_deliver_handle_connect(qitem.get_connection());
      break;
    case D_ACCEPT:
      msgr->ms_deliver_handle_accept(qitem.get_connection());
      break;
    case D_BAD_RESET:
      msgr->ms_deliver_handle_reset(qitem.get_connection());
      break;
    case D_CONN_REFUSED:
      msgr->ms_deliver_handle_refused(qitem.get_connection());
      break;
    default:
      ceph_abort();
    }
      } else {
    const ref_t& m = qitem.get_message();
    if (stop) {
      ldout(cct,10) << " stop flag set, discarding " << m << " " << *m << dendl;
    } else {
      uint64_t msize = pre_dispatch(m);
      msgr->ms_deliver_dispatch(m);
      post_dispatch(m, msize);
    }
      }

      l.lock();
    }
    if (stop)
      break;

    // wait for something to be put on queue
    cond.wait(l);
  }
}

//DispatchQueue.cc
void DispatchQueue::run_local_delivery()
{
  std::unique_lock l{local_delivery_lock};
  while (true) {
    if (stop_local_delivery)
      break;
    if (local_messages.empty()) {
      local_delivery_cond.wait(l);
      continue;
    }
    auto p = std::move(local_messages.front());
    local_messages.pop();
    l.unlock();
    const ref_t& m = p.first;
    int priority = p.second;
    fast_preprocess(m);
    if (can_fast_dispatch(m)) {
      fast_dispatch(m);
    } else {
      enqueue(m, priority, 0);
    }
    l.lock();
  }
}

void fast_dispatch(Message* m) {
    return fast_dispatch(ceph::ref_t(m, false)); /* consume ref */
}
void DispatchQueue::fast_dispatch(const ref_t& m)
{
  uint64_t msize = pre_dispatch(m);
  msgr->ms_fast_dispatch(m);
  post_dispatch(m, msize);
}
//Dispather.h
  /**
   * Perform a "fast dispatch" on a given message. See
   * ms_can_fast_dispatch() for the requirements.
   *
   * @param m The Message to fast dispatch.
   */
  virtual void ms_fast_dispatch(Message *m) { ceph_abort(); }

  /* ms_fast_dispatch2 because otherwise the child must define both */
  virtual void ms_fast_dispatch2(const MessageRef &m) {
    /* allow old style dispatch handling that expects a Message * with a floating ref */
    return ms_fast_dispatch(MessageRef(m).detach()); /* XXX N.B. always consumes ref */
  }
//OSD.cc
void OSD::ms_fast_dispatch(Message *m)
{
  auto dispatch_span = tracing::osd::tracer.start_trace(__func__);
  FUNCTRACE(cct);
  if (service.is_stopping()) {
    m->put();
    return;
  }
  // peering event?
  switch (m->get_type()) {
  case CEPH_MSG_PING:
    dout(10) << "ping from " << m->get_source() << dendl;
    m->put();
    return;
  case MSG_OSD_FORCE_RECOVERY:
    handle_fast_force_recovery(static_cast(m));
    return;
  case MSG_OSD_SCRUB2:
    handle_fast_scrub(static_cast(m));
    return;
  case MSG_OSD_PG_CREATE2:
    return handle_fast_pg_create(static_cast(m));
  case MSG_OSD_PG_NOTIFY:
    return handle_fast_pg_notify(static_cast(m));
  case MSG_OSD_PG_INFO:
    return handle_fast_pg_info(static_cast(m));
  case MSG_OSD_PG_REMOVE:
    return handle_fast_pg_remove(static_cast(m));
    // these are single-pg messages that handle themselves
  case MSG_OSD_PG_LOG:
  case MSG_OSD_PG_TRIM:
  case MSG_OSD_PG_NOTIFY2:
  case MSG_OSD_PG_QUERY2:
  case MSG_OSD_PG_INFO2:
  case MSG_OSD_BACKFILL_RESERVE:
  case MSG_OSD_RECOVERY_RESERVE:
  case MSG_OSD_PG_LEASE:
  case MSG_OSD_PG_LEASE_ACK:
    {
      MOSDPeeringOp *pm = static_cast(m);
      if (require_osd_peer(pm)) {
    enqueue_peering_evt(
      pm->get_spg(),
      PGPeeringEventRef(pm->get_event()));
      }
      pm->put();
      return;
    }
  }

  OpRequestRef op = op_tracker.create_request(m);
  {
#ifdef WITH_LTTNG
    osd_reqid_t reqid = op->get_reqid();
#endif
    tracepoint(osd, ms_fast_dispatch, reqid.name._type,
        reqid.name._num, reqid.tid, reqid.inc);
  }
  op->osd_parent_span = tracing::osd::tracer.add_span("op-request-created", dispatch_span);

  if (m->trace)
    op->osd_trace.init("osd op", &trace_endpoint, &m->trace);

  // note sender epoch, min req's epoch
  op->sent_epoch = static_cast(m)->get_map_epoch();
  op->min_epoch = static_cast(m)->get_min_epoch();
  ceph_assert(op->min_epoch <= op->sent_epoch); // sanity check!

  service.maybe_inject_dispatch_delay();

  if (m->get_connection()->has_features(CEPH_FEATUREMASK_RESEND_ON_SPLIT) ||
      m->get_type() != CEPH_MSG_OSD_OP) {
    // queue it directly
    enqueue_op(
      static_cast(m)->get_spg(),
      std::move(op),
      static_cast(m)->get_map_epoch());
  } else {
    // legacy client, and this is an MOSDOp (the *only* fast dispatch
    // message that didn't have an explicit spg_t); we need to map
    // them to an spg_t while preserving delivery order.
    auto priv = m->get_connection()->get_priv();
    if (auto session = static_cast(priv.get()); session) {
      std::lock_guard l{session->session_dispatch_lock};
      op->get();
      session->waiting_on_map.push_back(*op);
      OSDMapRef nextmap = service.get_nextmap_reserved();
      dispatch_session_waiting(session, nextmap);
      service.release_map(nextmap);
    }
  }
  OID_EVENT_TRACE_WITH_MSG(m, "MS_FAST_DISPATCH_END", false);
}

void OSD::dispatch_session_waiting(const ceph::ref_t& session, OSDMapRef osdmap)
{
  ceph_assert(ceph_mutex_is_locked(session->session_dispatch_lock));

  auto i = session->waiting_on_map.begin();
  while (i != session->waiting_on_map.end()) {
    OpRequestRef op = &(*i);
    ceph_assert(ms_can_fast_dispatch(op->get_req()));
    auto m = op->get_req();
    if (m->get_min_epoch() > osdmap->get_epoch()) {
      break;
    }
    session->waiting_on_map.erase(i++);
    op->put();

    spg_t pgid;
    if (m->get_type() == CEPH_MSG_OSD_OP) {
      pg_t actual_pgid = osdmap->raw_pg_to_pg(
    static_cast(m)->get_pg());
      if (!osdmap->get_primary_shard(actual_pgid, &pgid)) {
    continue;
      }
    } else {
      pgid = m->get_spg();
    }
    enqueue_op(pgid, std::move(op), m->get_map_epoch());
  }

  if (session->waiting_on_map.empty()) {
    clear_session_waiting_on_map(session);
  } else {
    register_session_waiting_on_map(session);
  }
}