Module sage_broker::service [−][src]
Expand description
All functions related to service control. The broker service is made of a set of background async tasks.
The sage broker service is ran by calling service::run which is responsible
for spawning all asynchronous tasks and waiting for their safe shut down
at the end.
Loops
Command Loop
The higher level task is command_loop.
Command loop is the first executed task and the last terminated.
It holds the command channel receiver. As long as at least one command
channel sender is open, the loop stays.
The job of the command loop is to process and dispatch any packet received
from any peer.
When all CommandSender instances are closed, the command loop ends.
Listen TCP
The Listen TCP loop runs as long as the Broker is not set to a closing state. It holds an instance of the command channel sender. Each time a valid TCP connection is made, the loop creates a new Peer instance which invokes the creations of:
- A new packet channel used to send packets to the peer stream
- A send_peer task which receives from the packet channel
- A listen_peer task which receives from the stream
- A Peer object which is held by the listen_peer task
When the broker is marked as shut down, the listen tcp loop ends. This operation will drop:
- A command channel sender
Listen peer
One listen peer exist per active connexion. This loop is created by the listen tcp loop. The listen peer holds an instance of command sender. It parses any incoming data from the stream and send to the command loop. It also holds an owning reference to the Peer instance, sending a copy to the command channel from time to time.
When the peer is marked as closed, the listen peer loop ends. This action will drop:
- A command channel sender
- The associated Peer The loop has a timeout that will ask for closing the peer if it does not receive incoming data from the stream in a given amount of time.
The associated Peer is generaly the only instance. But the list peer loop is able to clone it and send it to the command channel at any time. It means that if the listen peer loop ends and there is still pending operations for that peer, the associated peer won’t be closed until those operations are complete.
Send peer
The Send peer task is the writing half of a peer stream. It waits for any
incoming packets from the packet channel and serializes it before sending it through TCP. There is one instance of the send peer loop per active peer.
When all PacketSender instances have been closed, the sender peer loop ends.
Safe Close
The safe close is initiated by calling shutdown on the Broker object.
At that moment, the following performs:
- The Listen TCP loop ends, releasing a Command Sender
- The Command Loop ends.
Functions
The command loop is reponsible from receiving and treating any command
packet. It thus represents the actual instance of a running broker.
The loop holds and manages the list of sessions, dispatching messages from
client to client.
The loop automatically ends when all command sender channels are dropped.
These are held by listen_loop (one per peer) and the listen_tcp
tasks. Meaning when all peers are dropped and port listenning is stopped
The command loop ends.
Eventually, this task may become a spawner for other tasks
Creates a channel for control packets and starts the command loop and the
listen Tcp loop.
listener can be any instance of async_std::net::TcpListener but you can
use bind to obtain one.
Task ends when the shutdown object is triggered.
It owns all peer listen/send in order to wait for them once the server is stopping.