Struct tokio::runtime::Builder

pub struct Builder { /* private fields */ }

Builds Tokio Runtime with custom configuration values.

Methods can be chained in order to set the configuration values. The Runtime is constructed by calling build.

New instances of Builder are obtained via Builder::new.

See function level documentation for details on the various configuration settings.

Examples

extern crate tokio;
extern crate tokio_timer;

use std::time::Duration;

use tokio::runtime::Builder;
use tokio_timer::clock::Clock;

fn main() {
    // build Runtime
    let mut runtime = Builder::new()
        .blocking_threads(4)
        .clock(Clock::system())
        .core_threads(4)
        .keep_alive(Some(Duration::from_secs(60)))
        .name_prefix("my-custom-name-")
        .stack_size(3 * 1024 * 1024)
        .build()
        .unwrap();

    // use runtime ...
}

Implementations

impl Builder

pub fn new() -> Builder

Returns a new runtime builder initialized with default configuration values.

Configuration methods can be chained on the return value.

pub fn clock(&mut self, clock: Clock) -> &mut Self

Set the Clock instance that will be used by the runtime.

pub fn panic_handler<F>(&mut self, f: F) -> &mut Self where
    F: Fn(Box<dyn Any + Send>) + Send + Sync + 'static, 

Sets a callback to handle panics in futures.

The callback is triggered when a panic during a future bubbles up to Tokio. By default Tokio catches these panics, and they will be ignored. The parameter passed to this callback is the same error value returned from std::panic::catch_unwind(). To abort the process on panics, use std::panic::resume_unwind() in this callback as shown below.

Examples

let mut rt = runtime::Builder::new()
    .panic_handler(|err| std::panic::resume_unwind(err))
    .build()
    .unwrap();

pub fn core_threads(&mut self, val: usize) -> &mut Self

Set the maximum number of worker threads for the Runtime’s thread pool.

This must be a number between 1 and 32,768 though it is advised to keep this value on the smaller side.

The default value is the number of cores available to the system.

Examples

let mut rt = runtime::Builder::new()
    .core_threads(4)
    .build()
    .unwrap();

pub fn blocking_threads(&mut self, val: usize) -> &mut Self

Set the maximum number of concurrent blocking sections in the Runtime’s thread pool.

When the maximum concurrent blocking calls is reached, any further calls to blocking will return NotReady and the task is notified once previously in-flight calls to blocking return.

This must be a number between 1 and 32,768 though it is advised to keep this value on the smaller side.

The default value is 100.

Examples

let mut rt = runtime::Builder::new()
    .blocking_threads(200)
    .build();

pub fn keep_alive(&mut self, val: Option<Duration>) -> &mut Self

Set the worker thread keep alive duration for threads in the Runtime’s thread pool.

If set, a worker thread will wait for up to the specified duration for work, at which point the thread will shutdown. When work becomes available, a new thread will eventually be spawned to replace the one that shut down.

When the value is None, the thread will wait for work forever.

The default value is None.

Examples

use std::time::Duration;

let mut rt = runtime::Builder::new()
    .keep_alive(Some(Duration::from_secs(30)))
    .build();

pub fn name_prefix<S: Into<String>>(&mut self, val: S) -> &mut Self

Set name prefix of threads spawned by the Runtime’s thread pool.

Thread name prefix is used for generating thread names. For example, if prefix is my-pool-, then threads in the pool will get names like my-pool-1 etc.

The default prefix is “tokio-runtime-worker-”.

Examples

let mut rt = runtime::Builder::new()
    .name_prefix("my-pool-")
    .build();

pub fn stack_size(&mut self, val: usize) -> &mut Self

Set the stack size (in bytes) for worker threads.

The actual stack size may be greater than this value if the platform specifies minimal stack size.

The default stack size for spawned threads is 2 MiB, though this particular stack size is subject to change in the future.

Examples

let mut rt = runtime::Builder::new()
    .stack_size(32 * 1024)
    .build();

pub fn after_start<F>(&mut self, f: F) -> &mut Self where
    F: Fn() + Send + Sync + 'static, 

Execute function f after each thread is started but before it starts doing work.

This is intended for bookkeeping and monitoring use cases.

Examples

let thread_pool = runtime::Builder::new()
    .after_start(|| {
        println!("thread started");
    })
    .build();

pub fn before_stop<F>(&mut self, f: F) -> &mut Self where
    F: Fn() + Send + Sync + 'static, 

Execute function f before each thread stops.

This is intended for bookkeeping and monitoring use cases.

Examples

let thread_pool = runtime::Builder::new()
    .before_stop(|| {
        println!("thread stopping");
    })
    .build();

pub fn build(&mut self) -> Result<Runtime>

Create the configured Runtime.

The returned ThreadPool instance is ready to spawn tasks.

Examples

let runtime = Builder::new().build().unwrap();
// ... call runtime.run(...)

Trait Implementations

impl Debug for Builder

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

Formats the value using the given formatter.