Add express support (#829)

* Improve docs

* Add express to examples

* Fix doc in sample.rs

examples/examples/z_ping.rs

@@ -22,7 +22,7 @@ fn main() {
     // initiate logging
     env_logger::init();
 
-    let (config, warmup, size, n) = parse_args();
+    let (config, warmup, size, n, express) = parse_args();
     let session = zenoh::open(config).res().unwrap();
 
     // The key expression to publish data on
@@ -35,6 +35,7 @@ fn main() {
     let publisher = session
         .declare_publisher(key_expr_ping)
         .congestion_control(CongestionControl::Block)
+        .express(express)
         .res()
         .unwrap();
 
@@ -78,6 +79,9 @@ fn main() {
 
 #[derive(Parser)]
 struct Args {
+    /// express for sending data
+    #[arg(long, default_value = "false")]
+    no_express: bool,
     #[arg(short, long, default_value = "1")]
     /// The number of seconds to warm up (float)
     warmup: f64,
@@ -90,12 +94,13 @@ struct Args {
     common: CommonArgs,
 }
 
-fn parse_args() -> (Config, Duration, usize, usize) {
+fn parse_args() -> (Config, Duration, usize, usize, bool) {
     let args = Args::parse();
     (
         args.common.into(),
         Duration::from_secs_f64(args.warmup),
         args.payload_size,
         args.samples,
+        !args.no_express,
     )
 }

examples/examples/z_pong.rs

@@ -21,7 +21,7 @@ fn main() {
     // initiate logging
     env_logger::init();
 
-    let config = parse_args();
+    let (config, express) = parse_args();
 
     let session = zenoh::open(config).res().unwrap().into_arc();
 
@@ -34,6 +34,7 @@ fn main() {
     let publisher = session
         .declare_publisher(key_expr_pong)
         .congestion_control(CongestionControl::Block)
+        .express(express)
         .res()
         .unwrap();
 
@@ -47,11 +48,14 @@ fn main() {
 
 #[derive(clap::Parser, Clone, PartialEq, Eq, Hash, Debug)]
 struct Args {
+    /// express for sending data
+    #[arg(long, default_value = "false")]
+    no_express: bool,
     #[command(flatten)]
     common: CommonArgs,
 }
 
-fn parse_args() -> Config {
+fn parse_args() -> (Config, bool) {
     let args = Args::parse();
-    args.common.into()
+    (args.common.into(), !args.no_express)
 }

examples/examples/z_pub_thr.rs

@@ -41,6 +41,7 @@ fn main() {
         .declare_publisher("test/thr")
         .congestion_control(CongestionControl::Block)
         .priority(prio)
+        .express(args.express)
         .res()
         .unwrap();
 
@@ -65,6 +66,9 @@ fn main() {
 
 #[derive(Parser, Clone, PartialEq, Eq, Hash, Debug)]
 struct Args {
+    /// express for sending data
+    #[arg(long, default_value = "false")]
+    express: bool,
     /// Priority for sending data
     #[arg(short, long)]
     priority: Option<u8>,

zenoh/src/publication.rs

@@ -102,7 +102,9 @@ impl PutBuilder<'_, '_> {
         self
     }
 
-    /// Change the `congestion_control` to apply when routing the data.
+    /// Change the `express` policy to apply when routing the data.
+    /// When express is set to `true`, then the message will not be batched.
+    /// This usually has a positive impact on latency but negative impact on throughput.
     #[inline]
     pub fn express(mut self, is_express: bool) -> Self {
         self.publisher = self.publisher.express(is_express);
@@ -783,7 +785,9 @@ impl<'a, 'b> PublisherBuilder<'a, 'b> {
         self
     }
 
-    /// Change the `congestion_control` to apply when routing the data.
+    /// Change the `express` policy to apply when routing the data.
+    /// When express is set to `true`, then the message will not be batched.
+    /// This usually has a positive impact on latency but negative impact on throughput.
     #[inline]
     pub fn express(mut self, is_express: bool) -> Self {
         self.is_express = is_express;

zenoh/src/sample.rs

@@ -556,7 +556,7 @@ impl QoS {
         self.inner.get_congestion_control()
     }
 
-    /// Gets express flag value. If true, the message is not batched during transmission, in order to reduce latency.
+    /// Gets express flag value. If `true`, the message is not batched during transmission, in order to reduce latency.
     pub fn express(&self) -> bool {
         self.inner.is_express()
     }