Real-time monitoring and metrics for Rust channels

Console TUI Example

This crate provides an easy-to-configure way to monitor std::sync, Tokio and futures-rs channels (more flavors soon!). Track per-channel metrics such as queue depth, send/receive rates, and memory usage, directly from your terminal.

Features

Zero-cost when disabled — fully gated by a feature flag
Minimal configuration - just one instrument! macro to start collecting metrics
Detailed stats - per channel status, sent/received messages, queue capacity, and memory usage
Background processing - minimal profiling impact
Live monitoring - view metrics in a clear, real-time TUI dashboard (built with ratatui.rs)

Getting started

Cargo.toml

channels-console = { version = "0.1", optional = true, features=['tokio', 'futures'] }

[features]
channels-console = ["dep:channels-console"]

This config ensures that the lib has zero overhead unless explicitly enabled via a channels-console feature.

std::sync channels can be instrumented by default. Enable tokio and futures features for Tokio and futures-rs channels, respectively.

Next use instrument! macro to monitor selected channels:

let (tx1, rx1) = tokio::sync::mpsc::channel::<i32>(10);
#[cfg(feature = "channels-console")]
let (tx1, rx1) = channels_console::instrument!((tx1, rx1));

let (mut txb, mut rxb) = futures_channel::mpsc::channel::<i32>(10);
#[cfg(feature = "channels-console")]
let (mut txb, mut rxb) = channels_console::instrument!((txb, rxb), capacity = 10);

Futures and std::sync bounded channels don't provide an API exposing their size, so you have to provide capacity to the instrument! macro.

This is the only change you have to do in your codebase. instrument! macro returns exactly the same channel types so it remains 100% compatible.

Now, install channels-console TUI:

cargo install channels-console --features=tui

Execute your program with --features=channels-console:

cargo run --features=channels-console

In a different terminal run channels-console CLI to start the TUI and see live usage metrics:

channels-console

Console Dashboard

Quickstart demo guide

Install CLI:

cargo install channels-console --features=tui

Clone this repo:

git clone git@github.com:pawurb/channels-console.git

Run console_feed example:

cd channels-console
cargo run --example console_feed_tokio --features=channels-console

Run TUI (in a different terminal):

channels-console

How it works?

instrument! wraps Tokio channels with lightweight proxies that transparently forward all messages while collecting real-time statistics. Each send and recv operation passes through a monitored proxy channel that emits updates to a background metrics system.

In the background a HTTP server process exposes gathered metrics in a JSON format, allowing TUI process to display them in the interface.

There be bugs 🐛

This library has just been released. I've tested it with several apps, and it consistently produced reliable metrics. However, please note that enabling monitoring can subtly affect channel behavior in some cases. For example, using try_send may not return an error as expected, since the proxy layers effectively increase total capacity. I'm actively improving the library, so any feedback, issues, bug reports are welcome.

API

Supported Channel Types

`std::sync` Channels

Tokio Channels

Futures Channels

I'm planning to support more channel types. PRs are welcome!

`instrument!` Macro

The instrument! macro is the primary way to monitor channels. It wraps channel creation expressions and returns instrumented versions that collect metrics.

Basic Usage:

use tokio::sync::mpsc;

#[tokio::main]
async fn main() {
    // Create channels normally
    let (tx, rx) = mpsc::channel::<String>(100);

    // Instrument them only when the feature is enabled
    #[cfg(feature = "channels-console")]
    let (tx, rx) = channels_console::instrument!((tx, rx));

    // The channel works exactly the same way
    tx.send("Hello".to_string()).await.unwrap();
}

Zero-Cost Abstraction: When the channels-console feature is disabled, the #[cfg] attribute ensures the instrumentation code is completely removed at compile time - there's absolutely zero runtime overhead.

Note: The first invocation of instrument! automatically starts:

A background thread for metrics collection
An HTTP server on http://127.0.0.1:6770 (default port) exposing metrics in JSON format

This initialization happens only once and is shared across all instrumented channels.

Channel Labels:

By default, channels are labeled with their file location and line number (e.g., src/worker.rs:25). You can provide custom labels for easier identification:

let (tx, rx) = mpsc::channel::<Task>(10);
#[cfg(feature = "channels-console")]
let (tx, rx) = channels_console::instrument!((tx, rx), label = "task-queue");

Capacity Parameter Requirement:

⚠️ Important: For std::sync::mpsc and futures::channel::mpsc bounded channels, you must specify the capacity parameter because their APIs don't expose the capacity after creation:

use std::sync::mpsc;

// std::sync::mpsc::sync_channel - MUST specify capacity
let (tx, rx) = mpsc::sync_channel::<String>(10);
#[cfg(feature = "channels-console")]
let (tx, rx) = channels_console::instrument!((tx, rx), capacity = 10);

// With label
let (tx, rx) = mpsc::sync_channel::<i32>(10);
#[cfg(feature = "channels-console")]
let (tx, rx) = channels_console::instrument!((tx, rx), label = "worker-queue", capacity = 10);

use futures_channel::mpsc;

// futures bounded channel - MUST specify capacity
let (tx, rx) = mpsc::channel::<String>(10);
#[cfg(feature = "channels-console")]
let (tx, rx) = channels_console::instrument!((tx, rx), capacity = 10);

Tokio channels don't require the capacity parameter because their capacity is accessible from the channel handles.

`ChannelsGuard` - Printing Statistics on Drop

Similar to the hotpath API the ChannelsGuard is a RAII guard that automatically prints channel statistics when dropped (typically at program end). This is useful for debugging and getting a summary of channel usage.

Basic Usage:

use tokio::sync::mpsc;

#[tokio::main]
async fn main() {
    // Create guard at the start of your program (only when feature is enabled)
    #[cfg(feature = "channels-console")]
    let _guard = channels_console::ChannelsGuard::new();

    // Your code with instrumented channels...
    let (tx, rx) = mpsc::channel::<i32>(10);
    #[cfg(feature = "channels-console")]
    let (tx, rx) = channels_console::instrument!((tx, rx));

    // ... use your channels ...

    // Statistics will be printed when _guard is dropped (at program end)
}

Output Formats:

You can customize the output format using ChannelsGuardBuilder:

#[tokio::main]
async fn main() {
    #[cfg(feature = "channels-console")]
    let _guard = channels_console::ChannelsGuardBuilder::new()
        .format(channels_console::Format::Json)
        .build();
}

Output Example (Table Format):

=== Channel Statistics (runtime: 5.23s) ===

+------------------+-------------+--------+------+-------+----------+--------+-------+
| Channel          | Type        | State  | Sent | Mem   | Received | Queued | Mem   |
+------------------+-------------+--------+------+-------+----------+--------+-------+
| task-queue       | bounded[10] | active | 1543 | 12 KB | 1543     | 0      | 0 B   |
| http-responses   | unbounded   | active | 892  | 89 KB | 890      | 2      | 200 B |
| shutdown-signal  | oneshot     | closed | 1    | 8 B   | 1        | 0      | 0 B   |
+------------------+-------------+--------+------+-------+----------+--------+-------+

Configuration

Metrics Server Port

The HTTP metrics server runs on port 6770 by default. You can customize this using the channels_console_METRICS_PORT environment variable:

CHANNELS_CONSOLE_METRICS_PORT=8080 cargo run --features channels-console

When using the TUI console, specify the matching port with the --metrics-port flag:

channels-console --metrics-port 8080

channels-console 0.2.0