Struct scylla::transport::locator::TokenRing

pub struct TokenRing<ElemT> { /* private fields */ }

A token ring is a continuous hash ring. It defines association by hashing a key onto the ring and then walking the ring in one direction. Cassandra and Scylla use it for determining data ownership which allows for efficient load balancing. The token ring is used by the driver to find the replicas for a given token. Each ring member has a token (i64 number) which defines the member’s position on the ring. The ring is circular and can be traversed in the order of increasing tokens. TokenRing makes it easy and efficient to traverse the ring starting at a given token.

Implementations

impl<ElemT> TokenRing<ElemT>

pub fn iter(&self) -> impl Iterator<Item = &(Token, ElemT)>

Iterates over all members of the ring starting at the lowest token.

pub fn ring_range_full( &self, token: Token, ) -> impl Iterator<Item = &(Token, ElemT)>

Provides an iterator over the ring members starting at the given token. The iterator traverses the whole ring in the direction of increasing tokens. After reaching the maximum token it wraps around and continues from the lowest one. The iterator visits each member once, it doesn’t have infinite length.

pub fn ring_range(&self, token: Token) -> impl Iterator<Item = &ElemT>

Provides an iterator over the ring’s elements starting at the given token. The iterator traverses the whole ring in the direction of increasing tokens. After reaching the maximum token it wraps around and continues from the lowest one. The iterator visits each member once, it doesn’t have an infinite length. To access the token along with the element you can use ring_range_full.

pub fn get_elem_for_token(&self, token: Token) -> Option<&ElemT>

Traverses the ring starting at the given token and returns the first ring member encountered.

pub fn len(&self) -> usize

Get the total number of members in the ring.

pub fn is_empty(&self) -> bool

Returns true if the token ring contains no elements.

Trait Implementations

impl<ElemT: Clone> Clone for TokenRing<ElemT>

fn clone(&self) -> TokenRing<ElemT>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<ElemT: Debug> Debug for TokenRing<ElemT>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.