stream_session::stream_session(inet_address peer_, inet_address connecting_,
int index_, bool keep_ss_table_level_)
: peer(peer_)
, connecting(connecting_)
, conn_handler(shared_from_this())
Calling shared_from_this() inside stream_session's constructor is
problematic. I got
Exiting on unhandled exception of type 'std::bad_weak_ptr': bad_weak_ptr
exceptions, with
auto session = std::make_shared<stream_session>(peer, connecting, size, _keep_ss_table_level)
Also, the logic in connection_handler is not very useful for us. The
sending and receiving of messages are handled using messaging_service.
There is no need to add another layer.
I tried our lw_shared_ptr, the compiler complained endless usage of
incomplete type stream_session. I can not include stream_session.hh
everywhere due to circular dependency.
For now, I'm using std::shared_ptr which works fine.
In streaming code, we need core to core connection(the second connection
from B to A). That is when node A initiates a stream to node B, it is
possible that node A will transfer data to node B and vice verse, so we
need two connections. When node A creates a tcp connection (within the
messaging_service) to node B, we have a connection ip_a:core_a to
ip_b:core_b. When node B creates a connection to node B, we can not
guarantee it is ip_b:core_b to ip_a:core_a.
Current messaging_service does not support core to core connection yet,
although we use shard_id{ip, cpu_id} as the destination of the message.
We can solve the issue in upper layer. We can pass extra cpu_id as a
user msg.
Node A sends stream_init_message with my_cpu_id = current_cpu_id
Node B receives stream_init_message, it runs on whatever cpu this
connection goes to, then it sends response back with Node B's
current_cpu_id.
After this, each node knows which cpu_id to send to each other.
TODO: we need to handle the case when peer node reboots with different
number of cpus.
This is a bit different from Origin. We always send back a
prepare_message even if the initializer requested no data from the
follower, to unify the handling.
It is used to register the streaming message handler once. We don't need
it in every stream_session instance. The side effect is making
stream_session copyable, which is needed in get_all_stream_sessions.
