Struct Querier 

pub struct Querier<'a> { /* private fields */ }

A querier that allows sending queries to a Queryable.

The querier is a preconfigured object that can be used to send multiple queries to a given key expression. It is declared using Session::declare_querier.

Examples

let session = zenoh::open(zenoh::Config::default()).await.unwrap();
let querier = session.declare_querier("key/expression").await.unwrap();
let replies = querier.get().await.unwrap();

Implementations

impl<'a> Querier<'a>

pub fn id(&self) -> EntityGlobalId

Available on crate feature unstable only.

Returns the EntityGlobalId of this Querier.

This API has been marked as unstable: it works as advertised, but it may be changed in a future release.

Examples

let session = zenoh::open(zenoh::Config::default()).await.unwrap();
let querier = session.declare_querier("key/expression")
    .await
    .unwrap();
let querier_id = querier.id();

pub fn key_expr(&self) -> &KeyExpr<'a>

Returns the KeyExpr this querier sends queries on.

pub fn congestion_control(&self) -> CongestionControl

Get the CongestionControl applied when routing the data.

pub fn priority(&self) -> Priority

Get the Priority of the querier requests.

pub fn accept_replies(&self) -> ReplyKeyExpr

See details in the ReplyKeyExpr documentation.

Queries may or may not accept replies on key expressions that do not intersect with their own key expression. This getter allows you to check whether this querier accepts such disjoint replies. Currently, this information is passed in the Selector parameters as the _anyke parameter.

pub fn get(&self) -> QuerierGetBuilder<'_, '_, DefaultHandler>

Send a query. Returns a builder to customize the query. The builder resolves to a handler generating a series of Reply values for each response received.

Examples

let session = zenoh::open(zenoh::Config::default()).await.unwrap();
let querier = session.declare_querier("key/expression").await.unwrap();
let replies = querier.get();

pub fn undeclare(self) -> QuerierUndeclaration<'a>

Undeclare the Querier, informing the network that it needn’t optimize queries for its key expression anymore.

Examples

let session = zenoh::open(zenoh::Config::default()).await.unwrap();
let querier = session.declare_querier("key/expression").await.unwrap();
querier.undeclare().await.unwrap();

pub fn matching_status(&self) -> impl Resolve<ZResult<MatchingStatus>> + '_

Return the MatchingStatus of the querier.

MatchingStatus::matching will return true if there are Queryables matching the Querier’s key expression and target, and false otherwise.

Examples

let session = zenoh::open(zenoh::Config::default()).await.unwrap();
let querier = session.declare_querier("key/expression").await.unwrap();
let matching_queriers: bool = querier
    .matching_status()
    .await
    .unwrap()
    .matching();

pub fn matching_listener(&self) -> MatchingListenerBuilder<'_, DefaultHandler>

Return a MatchingListener for this Querier.

The MatchingListener will send a notification each time the MatchingStatus of the Querier changes.

Examples

let session = zenoh::open(zenoh::Config::default()).await.unwrap();
let querier = session.declare_querier("key/expression").await.unwrap();
let matching_listener = querier.matching_listener().await.unwrap();
while let Ok(matching_status) = matching_listener.recv_async().await {
    if matching_status.matching() {
        println!("Querier has matching queryables.");
    } else {
        println!("Querier has NO MORE matching queryables.");
    }
}

Trait Implementations

impl<'a> Debug for Querier<'a>

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

Formats the value using the given formatter.

impl Drop for Querier<'_>

fn drop(&mut self)

Executes the destructor for this type.