- Main process should be connected to all other processes.
- Controller should be connected to Router.
- Router should be connected to Controller and all Workers.
- Workers should be connected to Router worker thread ports only.
This filtering helps to avoid unnecessary communication and various errors
during massive application workers stop / restart.
- Each sendmsg() transmits no more than port->max_size payload data.
- Longer buffers are fragmented and send using multiple sendmsg() calls.
- On receive side, buffers are connected in chain.
- Number of handler calls is the same as number of nxt_port_socket_write()
calls.
- nxt_buf_make_plain() function introduced to make single plain buffer from
the chain.
Remove pid proxying to worker engines implementation was originally
overcomplicated. Memory pool and 2 engine posts (there and back again) are
optimized out and replaced with band new nxt_port_post() call.
Use counter helps to simplify logic around port and application free.
Port 'post' function introduced to simplify post execution of particular
function to original port engine's thread.
Write message queue is protected by mutex which makes port write operation
thread safe.
To allow use port from different threads, the first step is to avoid using
port's memory pool for temporary allocations required to send data through
the port. Including but not limited by:
- buffers for data;
- send message structures;
- new mmap fd notifications;
It is still safe to use port memory pool for incoming buffers allocations
because recieve operation bound to single thread.
Usage:
1. Register handlers in incoming port with nxt_port_rpc_register_handler().
2. Use return value as a stream identifier for next nxt_port_socket_write().
nxt_req_conn_link_t still used for lookup connection by request id.
New nxt_req_app_link_t (ra) allocated from conn->mem_pool using mp_retain().
ra stored in app->requests if there is no free worker to process request.
New port message type introduced NXT_PORT_MSG_REMOVE_PID. Default handler
removes process description from nxt_runtime_t with all ports, incoming and
outgoing mmaps etc.
There is a case in router where we use port in router connection thread.
Buffers are allocated within connection memory pool which can be used only in
this router thread. sendmsg() can be postponed into main router thread and
completion handler will compare current engine and post itself to correct
engine.
- request to connection mapping in engine;
- requests queue in connection;
- engine port creation;
- connected ports hash for each process;
- engine port data messages processing (app responses);
