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tokio-console

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what's all this, then?

this repository contains an implementation of TurboWish/tokio-console, a diagnostics and debugging tool for asynchronous Rust programs. the diagnostic toolkit consists of multiple components:

a wire protocol for streaming diagnostic data from instrumented applications to diagnostic tools. the wire format is defined using gRPC and protocol buffers, for efficient transport on the wire and interoperability between different implementations of data producers and consumers.

the console-api crate contains generated code for this wire format for projects using the tonic gRPC implementation. additionally, projects using other gRPC code generators (including those in other languages!) can depend on the protobuf definitions themselves.
instrumentation for collecting diagnostic data from a process and exposing it over the wire format. the console-subscriber crate in this repository contains an implementation of the instrumentation-side API as a tracing-subscriber Layer, for projects using Tokio and tracing.
tools for displaying and exploring diagnostic data, implemented as gRPC clients using the console wire protocol. the tokio-console crate implements an an interactive command-line tool that consumes this data, but other implementations, such as graphical or web-based tools, are also possible.

extremely cool and amazing screenshots

wow! whoa! it's like top(1) for tasks!

task list view

viewing details for a single task:

task details view

on the shoulders of giants

the console is part of a much larger effort to improve debugging tooling for async Rust. a 2019 Google Summer of Code project by Matthias Prechtl (@matprec) implemented an initial prototype, with a focus on interactive log viewing. more recently, both the Tokio team and the async foundations working group have made diagnostics and debugging tools a priority for async Rust in 2021 and beyond. in particular, a series of blog posts by @pnkfelix lay out much of the vision that this project seeks to eventually implement.

furthermore, we're indebted to our antecedents in other programming languages and environments for inspiration. this includes tools and systems such as pprof, Unix top(1) and htop(1), XCode's Instruments, and many others.

using it

instrumenting your program

to instrument an application using Tokio, add a dependency on the console-subscriber crate, and add this one-liner to the top of your main function:

console_subscriber::init();

notes:

in order to collect task data from Tokio, the tokio_unstable cfg must be enabled. for example, you could build your project with
```
RUSTFLAGS="--cfg tokio_unstable" cargo build
```
or add the following to your .cargo/config.toml file:
```
[build]
rustflags = ["--cfg", "tokio_unstable"]
```
For more information on the appropriate location of your .cargo/config.toml file, especially when using workspaces, see the console-subscriber readme.
the tokio and runtime tracing targets must be enabled at the TRACE level.
- if you're using the console_subscriber::init() or console_subscriber::Builder APIs, these targets are enabled automatically.
- if you are manually configuring the tracing subscriber using the EnvFilter or Targets filters from tracing-subscriber, add "tokio=trace,runtime=trace" to your filter configuration.
- also, ensure you have not enabled any of the compile time filter features in your Cargo.toml.

running the console

to run the console command-line tool, install tokio-console from crates.io

cargo install --locked tokio-console

and run locally

tokio-console

alternative method: run the tool from a local checkout of this repository
$ cargo run

by default, this will attempt to connect to an instrumented application running on localhost on port 6669. if the application is running somewhere else, or is serving the console endpoint on a different port, a target address can be passed as an argument to the console (either as an <IP>:<PORT> or <DNS_NAME>:<PORT>). for example:

cargo run -- http://my.great.console.app.local:5555

The console command-line tool supports a number of additional flags to configure its behavior. The help command will print a list of supported command-line flags and arguments:

$ tokio-console --help
The Tokio console: a debugger for async Rust.

Usage: tokio-console[EXE] [OPTIONS] [TARGET_ADDR] [COMMAND]

Commands:
  gen-config      Generate a `console.toml` config file with the default
                  configuration values, overridden by any provided
                  command-line arguments
  gen-completion  Generate shell completions
  help            Print this message or the help of the given
                  subcommand(s)

Arguments:
  [TARGET_ADDR]
          The address of a console-enabled process to connect to.
          
          This may be an IP address and port, or a DNS name.
          
          On Unix platforms, this may also be a URI with the `file`
          scheme that specifies the path to a Unix domain socket, as in
          `file://localhost/path/to/socket`.
          
          [default: http://127.0.0.1:6669]

Options:
      --log <LOG_FILTER>
          Log level filter for the console's internal diagnostics.
          
          Logs are written to a new file at the path given by the
          `--log-dir` argument (or its default value), or to the system
          journal if `systemd-journald` support is enabled.
          
          If this is set to 'off' or is not set, no logs will be
          written.
          
          [default: off]
          
          [env: RUST_LOG=]

  -W, --warn <WARNINGS>...
          Enable lint warnings.
          
          This is a comma-separated list of warnings to enable.
          
          Each warning is specified by its name, which is one of:
          
          * `self-wakes` -- Warns when a task wakes itself more than a
          certain percentage of its total wakeups. Default percentage is
          50%.
          
          * `lost-waker` -- Warns when a task is dropped without being
          woken.
          
          * `never-yielded` -- Warns when a task has never yielded.
          
          * `auto-boxed-future` -- Warnings when the future driving a
          task was automatically boxed by the runtime because it was
          large.
          
          * `large-future` -- Warnings when the future driving a task
          occupies a large amount of stack space.
          
          [default: self-wakes lost-waker never-yielded
          auto-boxed-future large-future]
          [possible values: self-wakes, lost-waker, never-yielded,
          auto-boxed-future, large-future]

  -A, --allow <ALLOW_WARNINGS>...
          Allow lint warnings.
          
          This is a comma-separated list of warnings to allow.
          
          Each warning is specified by its name, which is one of:
          
          * `self-wakes` -- Warns when a task wakes itself more than a
          certain percentage of its total wakeups. Default percentage is
          50%.
          
          * `lost-waker` -- Warns when a task is dropped without being
          woken.
          
          * `never-yielded` -- Warns when a task has never yielded.
          
          * `auto-boxed-future` -- Warnings when the future driving a
          task was automatically boxed by the runtime because it was
          large.
          
          * `large-future` -- Warnings when the future driving a task
          occupies a large amount of stack space.
          
          If this is set to `all`, all warnings are allowed.
          
          [possible values: all, self-wakes, lost-waker, never-yielded,
          large-future, auto-boxed-future]

      --log-dir <LOG_DIRECTORY>
          Path to a directory to write the console's internal logs to.
          
          [default: /tmp/tokio-console/logs]

      --lang <LANG>
          Overrides the terminal's default language
          
          [env: LANG=en_US.UTF-8]

      --ascii-only <ASCII_ONLY>
          Explicitly use only ASCII characters
          
          [possible values: true, false]

      --no-colors
          Disable ANSI colors entirely

      --colorterm <truecolor>
          Overrides the value of the `COLORTERM` environment variable.
          
          If this is set to `24bit` or `truecolor`, 24-bit RGB color
          support will be enabled.
          
          [env: COLORTERM=truecolor]
          [possible values: 24bit, truecolor]

      --palette <PALETTE>
          Explicitly set which color palette to use
          
          [possible values: 8, 16, 256, all, off]

      --no-duration-colors <COLOR_DURATIONS>
          Disable color-coding for duration units
          
          [possible values: true, false]

      --no-terminated-colors <COLOR_TERMINATED>
          Disable color-coding for terminated tasks
          
          [possible values: true, false]

      --retain-for <RETAIN_FOR>
          How long to continue displaying completed tasks and dropped
          resources after they have been closed.
          
          This accepts either a duration, parsed as a combination of
          time spans (such as `5days 2min 2s`), or `none` to disable
          removing completed tasks and dropped resources.
          
          Each time span is an integer number followed by a suffix.
          Supported suffixes are:
          
          * `nsec`, `ns` -- nanoseconds
          
          * `usec`, `us` -- microseconds
          
          * `msec`, `ms` -- milliseconds
          
          * `seconds`, `second`, `sec`, `s`
          
          * `minutes`, `minute`, `min`, `m`
          
          * `hours`, `hour`, `hr`, `h`
          
          * `days`, `day`, `d`
          
          * `weeks`, `week`, `w`
          
          * `months`, `month`, `M` -- defined as 30.44 days
          
          * `years`, `year`, `y` -- defined as 365.25 days
          
          [default: 6s]

  -h, --help
          Print help (see a summary with '-h')

  -V, --version
          Print version

running the console on windows

The console uses the UTF-8 character set to display graphs and other visual features in the terminal. In order to display this rich terminal UI on Windows, it's necessary to use a UTF-8-enabled terminal emulator, such as the new Windows Terminal.

If you're using a terminal that supports UTF-8, make sure to explicitly call tokio-console with the UTF-8 language flag set:

tokio-console --lang en_US.UTF-8

for development

the console-subscriber/examples directory contains some potentially useful tools:

app.rs: a very simple example program that spawns a bunch of tasks in a loop forever
dump.rs: a simple CLI program that dumps the data stream from a Tasks server

Examples can be executed with:

cargo run --example $name