Struct Waiters 

pub struct Waiters { /* private fields */ }

Every parked client, oldest first.

The order is the order they blocked in and it is the order they are served in, which is what makes a queue with several workers on it fair: two clients blocked on the same key take the two elements a RPUSH q first second adds in the order they arrived. A Vec is the right structure for that while the list is short, and it is short, because a waiter is a client doing nothing.

Implementations

impl Waiters

pub fn is_empty(&self) -> bool

Whether anybody is waiting.

pub fn len(&self) -> usize

How many clients are parked, which is what INFO clients calls blocked_clients.

pub fn at(&self, at: usize) -> Parked

Where the waiter at at has to be answered.

Panics

If at is past the end, which only a caller that ignored Waiters::len can manage.

pub fn db_of(&self, at: usize) -> usize

The database the waiter at at blocked on.

Panics

As Waiters::at.

pub fn drop_at(&mut self, at: usize)

Take a waiter off the list.

Panics

As Waiters::at.

pub fn forget(&mut self, client: u64)

Take off every waiter belonging to a client that has gone.

Called when a connection closes rather than left for the deadline sweep to find, because a BLPOP key 0 on a connection nobody will ever write to again has no deadline to be found by.

pub fn bind(&mut self, client: u64, conn: u32)

Say which slot the waiter this client just registered is answered on.

The command layer knows which client blocked and the engine knows which slot that client is on, so the slot is filled in afterwards by the half that has it. A client can only be parked once, since it is not reading commands while it waits, so the search finds the one that was just added.

Trait Implementations

impl Default for Waiters

fn default() -> Waiters

Returns the “default value” for a type.