Concurrency Coordination Reports

Sync Channel Capacity Coordination Report

A capacity report records how a bounded channel handles offered messages. This program uses sync_channel with try_send and reports buffered versus rejected sends for the selected capacity.

Program

Play the program to choose the channel capacity and watch how many sends are buffered or rejected.

capacity
sync_channel_capacity_coordination_report.rs
Replay: real traced execution (multi-file project)
use std::sync::mpsc::sync_channel;

fn main() {
    let capacity = 2;
    let messages = 3;
    let (tx, _rx) = sync_channel(capacity);
    let mut sent = 0;
    let mut rejected = 0;
    for value in 0..messages {
        match tx.try_send(value) {
            Ok(()) => sent += 1,
            Err(_) => rejected += 1,
        }
    }
    let status = if rejected == 0 {
        "buffered"
    } else if sent == 0 {
        "saturated"
    } else {
        "partial"
    };
    println!("capacity={capacity} sent={sent} rejected={rejected} {status}");
}

use std::sync::mpsc::sync_channel;

fn main() {
    let capacity = 0;
    let messages = 3;
    let (tx, _rx) = sync_channel(capacity);
    let mut sent = 0;
    let mut rejected = 0;
    for value in 0..messages {
        match tx.try_send(value) {
            Ok(()) => sent += 1,
            Err(_) => rejected += 1,
        }
    }
    let status = if rejected == 0 {
        "buffered"
    } else if sent == 0 {
        "saturated"
    } else {
        "partial"
    };
    println!("capacity={capacity} sent={sent} rejected={rejected} {status}");
}

use std::sync::mpsc::sync_channel;

fn main() {
    let capacity = 4;
    let messages = 3;
    let (tx, _rx) = sync_channel(capacity);
    let mut sent = 0;
    let mut rejected = 0;
    for value in 0..messages {
        match tx.try_send(value) {
            Ok(()) => sent += 1,
            Err(_) => rejected += 1,
        }
    }
    let status = if rejected == 0 {
        "buffered"
    } else if sent == 0 {
        "saturated"
    } else {
        "partial"
    };
    println!("capacity={capacity} sent={sent} rejected={rejected} {status}");
}

  1. capacity ← 2, messages ← 3, sent ← 0, rejected ← 0

    3fn main() {4    let capacit→ 2y = 2; //@capacity=2, 4, 05    let message→ 3s = 3;6    let (tx, _rx) = sync_channel(capacit2y);7    let mut sen→ 0t = 0;8    let mut rejecte→ 0d = 0;9    for value in 0..messages {

  2. for value in 0..messages

    pass 1 of 3
    8let mut rejected = 0;9for valu0e in 0..message3s {10    match tx.try_send(value) {
    All 3 passes — pass 1 is the card above
    passvalue
    10
    21
    32

  3. status ← "partial"

    14    }15    let statu→ "partial"s = if rejecte1d == 0 {16        "buffered"17    } else if sen2t == 0 {18        "saturated"19    } else {20        "partial"21    };22    println!("capacity={capacity} sent={sent} rejected={rejected} {status}");23}
    outputcapacity=2 sent=2 rejected=1 partial

  1. capacity ← 0, messages ← 3, sent ← 0, rejected ← 0

    3fn main() {4    let capacit→ 0y = 0;5    let message→ 3s = 3;6    let (tx, _rx) = sync_channel(capacit0y);7    let mut sen→ 0t = 0;8    let mut rejecte→ 0d = 0;9    for value in 0..messages {

  2. for value in 0..messages

    pass 1 of 3
    8let mut rejected = 0;9for valu0e in 0..message3s {10    match tx.try_send(value) {
    All 3 passes — pass 1 is the card above
    passvalue
    10
    21
    32

  3. status ← "saturated"

    14    }15    let statu→ "saturated"s = if rejecte3d == 0 {16        "buffered"17    } else if sen0t == 0 {18        "saturated"19    } else {20        "partial"21    };22    println!("capacity={capacity} sent={sent} rejected={rejected} {status}");23}
    outputcapacity=0 sent=0 rejected=3 saturated

  1. capacity ← 4, messages ← 3, sent ← 0, rejected ← 0

    3fn main() {4    let capacit→ 4y = 4;5    let message→ 3s = 3;6    let (tx, _rx) = sync_channel(capacit4y);7    let mut sen→ 0t = 0;8    let mut rejecte→ 0d = 0;9    for value in 0..messages {

  2. for value in 0..messages

    pass 1 of 3
    8let mut rejected = 0;9for valu0e in 0..message3s {10    match tx.try_send(value) {
    All 3 passes — pass 1 is the card above
    passvalue
    10
    21
    32

  3. status ← "buffered"

    14    }15    let statu→ "buffered"s = if rejecte0d == 0 {16        "buffered"17    } else if sen3t == 0 {18        "saturated"19    } else {20        "partial"21    };22    println!("capacity={capacity} sent={sent} rejected={rejected} {status}");23}
    outputcapacity=4 sent=3 rejected=0 buffered
bounded buffer `sync_channel` creates a bounded queue, so `try_send` reports `Ok` only while buffer space remains.
capacity report The selected capacity controls how many messages are buffered before `try_send` is rejected.
rendezvous A zero-capacity channel has no buffer, so every `try_send` without a waiting receiver is rejected and the report saturates.