Struct QuorumSystem 

pub struct QuorumSystem<T: Element> { /* private fields */ }

A read-write quorum system.

Implementations

impl<T: Element> QuorumSystem<T>

pub fn from_reads(reads: Expr<T>) -> Self

Build a quorum system from reads only; writes are the dual.

pub fn from_writes(writes: Expr<T>) -> Self

Build a quorum system from writes only; reads are the dual.

pub fn new(reads: Expr<T>, writes: Expr<T>) -> Result<Self>

Build a quorum system from both read and write expressions.

Errors

Returns Error::NonOverlappingQuorums unless every read quorum intersects every write quorum.

pub fn reads(&self) -> &Expr<T>

The read expression.

pub fn writes(&self) -> &Expr<T>

The write expression.

pub fn read_quorums(&self) -> Box<dyn Iterator<Item = HashSet<T>> + '_>

Iterate over all read quorums.

pub fn write_quorums(&self) -> Box<dyn Iterator<Item = HashSet<T>> + '_>

Iterate over all write quorums.

pub fn is_read_quorum(&self, xs: &HashSet<T>) -> bool

Whether xs contains a read quorum.

pub fn is_write_quorum(&self, xs: &HashSet<T>) -> bool

Whether xs contains a write quorum.

pub fn node(&self, x: &T) -> Result<&Node<T>>

Look up a node by its identifier.

Errors

Returns Error::InvalidQuorumSystem if x is not in the system.

pub fn nodes(&self) -> HashSet<Node<T>>

All nodes in the system.

pub fn elements(&self) -> HashSet<T>

All node identifiers in the system.

pub fn resilience(&self) -> usize

The resilience of the system: the minimum of read and write resilience.

pub fn read_resilience(&self) -> usize

The resilience of the read expression.

pub fn write_resilience(&self) -> usize

The resilience of the write expression.

pub fn dup_free(&self) -> bool

Whether both read and write expressions are duplicate-free.

pub fn uniform_strategy(&self, f: usize) -> Result<Strategy<T>>

A strategy that picks uniformly among the minimal f-resilient quorums.

Errors

Returns Error::NoStrategyFound if there are no f-resilient read or write quorums.

pub fn make_strategy( &self, sigma_r: BTreeMap<Quorum<T>, f64>, sigma_w: BTreeMap<Quorum<T>, f64>, ) -> Result<Strategy<T>>

Build a strategy from explicit quorum weights.

Each key is a list of node identifiers (order and duplicates do not matter); weights for the same set are added together, and weights are normalized to sum to 1. Zero-weight quorums are dropped.

Errors

Returns Error::InvalidQuorumSystem if a key is not a read (or write) quorum, a weight is negative or not finite, or all weights are zero.

pub fn strategy( &self, objective: Objective, read_fraction: Option<&Distribution>, write_fraction: Option<&Distribution>, limits: &StrategyLimits, f: usize, ) -> Result<Strategy<T>>

Compute the optimal strategy by linear programming.

Minimizes objective subject to limits, considering only f-resilient quorums (quorums that still contain a quorum after any f of their nodes fail). Exactly one of read_fraction and write_fraction must be Some.

Errors

• Error::InvalidQuorumSystem if the limit matching objective is set.
• Error::InvalidDistribution for a bad read/write fraction.
• Error::NoStrategyFound if the limits cannot be met or there are no f-resilient quorums.
• Error::LpError if the solver fails for another reason.

Trait Implementations

impl<T: Clone + Element> Clone for QuorumSystem<T>

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T: Debug + Element> Debug for QuorumSystem<T>

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

Formats the value using the given formatter.

impl<T: Element> Display for QuorumSystem<T>

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

Formats the value using the given formatter.