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use crate::core::{ElectionCore, State};
use crate::msg::Message;
use crate::{ElectionType, Event};
use crossbeam_channel::RecvTimeoutError;
/// Observer is similar like follower, but can not to be candidate.
pub struct Observer<'a, T: ElectionType> {
core: &'a mut ElectionCore<T>,
}
impl<'a, T: ElectionType> Observer<'a, T> {
#[inline]
pub fn new(core: &'a mut ElectionCore<T>) -> Self {
Self { core }
}
pub fn run(mut self) {
self.core.increase_state_id();
self.core.step_up_or_down = false;
// Use set_prev_state to ensure prev_state can be set at most once.
let mut set_prev_state = Some(true);
assert!(self.core.is_state(State::Observer));
self.core.next_election_timeout = None;
let _result = self.core.spawn_event_handling_task(Event::TransitToObserver {
term: self.core.current_term(),
prev_state: self.core.prev_state(),
});
self.core.report_metrics();
info!(
"[{}][Term({})] start the observer loop",
self.core.node_id(),
self.core.current_term()
);
loop {
if !self.core.is_state(State::Observer) {
return;
}
let election_timeout = self.core.next_election_timeout();
match self.core.msg_rx.recv_deadline(election_timeout) {
Ok(msg) => match msg {
Message::HeartbeatRequest { req, tx } => {
trace!(
"[{}][Term({})] receive heartbeat: {:?}",
self.core.node_id(),
self.core.current_term(),
req
);
let result = self.core.handle_heartbeat(req, set_prev_state.as_mut());
if let Err(ref e) = result {
debug!(
"[{}][Term({})] failed to handle heartbeat request: {}",
self.core.node_id(),
self.core.current_term(),
e
);
}
let _ = tx.send(result);
}
Message::HeartbeatResponse(_) => {
// ignore heartbeat response
}
Message::VoteRequest { req, tx } => {
let result = self.core.handle_vote_request(req, set_prev_state.as_mut());
if let Err(ref e) = result {
debug!(
"[{}][Term({})] failed to handle vote request: {}",
self.core.node_id(),
self.core.current_term(),
e
);
}
let _ = tx.send(result);
}
Message::VoteResponse { .. } => {
// ignore vote response
}
Message::Initialize { tx, .. } => {
self.core.reject_init_with_members(tx);
}
Message::UpdateOptions { options, tx } => {
info!(
"[{}][Term({})] election update options: {:?}",
self.core.node_id(),
self.core.current_term(),
options
);
self.core.update_options(options);
let _ = tx.send(Ok(()));
}
Message::Shutdown => {
info!(
"[{}][Term({})] election received shutdown message",
self.core.node_id(),
self.core.current_term()
);
self.core.set_state(State::Shutdown, set_prev_state.as_mut());
}
Message::EventHandlingResult {
event,
error,
term,
state_id: _,
} => {
if let Some(e) = error {
error!(
"[{}][Term({})] failed to handle event ({:?}) in term {}: {} ",
self.core.node_id(),
self.core.current_term(),
event,
term,
e
);
} else {
debug!(
"[{}][Term({})] event ({:?}) in term {} is handled",
self.core.node_id(),
self.core.current_term(),
event,
term,
);
}
}
Message::MoveLeader { tx, .. } => {
self.core.reject_move_leader(tx);
}
Message::MoveLeaderRequest { tx, .. } => {
self.core.reject_move_leader(tx);
}
Message::StepUpToLeader { tx, .. } => {
self.core.reject_step_up_to_leader(tx);
}
Message::StepDownToFollower { tx } => {
self.core.reject_step_down_to_follower(tx);
}
},
Err(e) => match e {
RecvTimeoutError::Timeout => {
self.core.next_election_timeout = None;
}
RecvTimeoutError::Disconnected => {
info!(
"[{}][Term({})] the election message channel is disconnected",
self.core.node_id(),
self.core.current_term()
);
self.core.set_state(State::Shutdown, set_prev_state.as_mut());
}
},
}
}
}
}