Struct tokio::runtime::Builder [−][src]
pub struct Builder { /* fields omitted */ }Expand description
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_multi_thread
or Builder::new_current_thread.
See function level documentation for details on the various configuration settings.
Examples
use tokio::runtime::Builder;
fn main() {
// build runtime
let runtime = Builder::new_multi_thread()
.worker_threads(4)
.thread_name("my-custom-name")
.thread_stack_size(3 * 1024 * 1024)
.build()
.unwrap();
// use runtime ...
}Implementations
Returns a new builder with the current thread scheduler selected.
Configuration methods can be chained on the return value.
To spawn non-Send tasks on the resulting runtime, combine it with a
LocalSet.
Returns a new builder with the multi thread scheduler selected.
Configuration methods can be chained on the return value.
Enables both I/O and time drivers.
Doing this is a shorthand for calling enable_io and enable_time
individually. If additional components are added to Tokio in the future,
enable_all will include these future components.
Examples
use tokio::runtime;
let rt = runtime::Builder::new_multi_thread()
.enable_all()
.build()
.unwrap();Sets the number of worker threads the Runtime will use.
This can be any number above 0 though it is advised to keep this value on the smaller side.
Default
The default value is the number of cores available to the system.
Panic
When using the current_thread runtime this method will panic, since
those variants do not allow setting worker thread counts.
Examples
Multi threaded runtime with 4 threads
use tokio::runtime;
// This will spawn a work-stealing runtime with 4 worker threads.
let rt = runtime::Builder::new_multi_thread()
.worker_threads(4)
.build()
.unwrap();
rt.spawn(async move {});Current thread runtime (will only run on the current thread via Runtime::block_on)
use tokio::runtime;
// Create a runtime that _must_ be driven from a call
// to `Runtime::block_on`.
let rt = runtime::Builder::new_current_thread()
.build()
.unwrap();
// This will run the runtime and future on the current thread
rt.block_on(async move {});Panic
This will panic if val is not larger than 0.
Specifies the limit for additional threads spawned by the Runtime.
These threads are used for blocking operations like tasks spawned
through spawn_blocking. Unlike the worker_threads, they are not
always active and will exit if left idle for too long. You can change
this timeout duration with thread_keep_alive.
The default value is 512.
Panic
This will panic if val is not larger than 0.
Upgrading from 0.x
In old versions max_threads limited both blocking and worker threads, but the
current max_blocking_threads does not include async worker threads in the count.
Sets name of threads spawned by the Runtime’s thread pool.
The default name is “tokio-runtime-worker”.
Examples
let rt = runtime::Builder::new_multi_thread()
.thread_name("my-pool")
.build();Sets a function used to generate the name of threads spawned by the Runtime’s thread pool.
The default name fn is || "tokio-runtime-worker".into().
Examples
let rt = runtime::Builder::new_multi_thread()
.thread_name_fn(|| {
static ATOMIC_ID: AtomicUsize = AtomicUsize::new(0);
let id = ATOMIC_ID.fetch_add(1, Ordering::SeqCst);
format!("my-pool-{}", id)
})
.build();Sets 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 rt = runtime::Builder::new_multi_thread()
.thread_stack_size(32 * 1024)
.build();Executes function f after each thread is started but before it starts
doing work.
This is intended for bookkeeping and monitoring use cases.
Examples
let runtime = runtime::Builder::new_multi_thread()
.on_thread_start(|| {
println!("thread started");
})
.build();Executes function f before each thread stops.
This is intended for bookkeeping and monitoring use cases.
Examples
let runtime = runtime::Builder::new_multi_thread()
.on_thread_stop(|| {
println!("thread stopping");
})
.build();Executes function f just before a thread is parked (goes idle).
f is called within the Tokio context, so functions like tokio::spawn
can be called, and may result in this thread being unparked immediately.
This can be used to start work only when the executor is idle, or for bookkeeping and monitoring purposes.
Note: There can only be one park callback for a runtime; calling this function more than once replaces the last callback defined, rather than adding to it.
Examples
Multithreaded executor
let once = AtomicBool::new(true);
let barrier = Arc::new(Barrier::new(2));
let runtime = runtime::Builder::new_multi_thread()
.worker_threads(1)
.on_thread_park({
let barrier = barrier.clone();
move || {
let barrier = barrier.clone();
if once.swap(false, Ordering::Relaxed) {
tokio::spawn(async move { barrier.wait().await; });
}
}
})
.build()
.unwrap();
runtime.block_on(async {
barrier.wait().await;
})Current thread executor
let once = AtomicBool::new(true);
let barrier = Arc::new(Barrier::new(2));
let runtime = runtime::Builder::new_current_thread()
.on_thread_park({
let barrier = barrier.clone();
move || {
let barrier = barrier.clone();
if once.swap(false, Ordering::Relaxed) {
tokio::spawn(async move { barrier.wait().await; });
}
}
})
.build()
.unwrap();
runtime.block_on(async {
barrier.wait().await;
})Executes function f just after a thread unparks (starts executing tasks).
This is intended for bookkeeping and monitoring use cases; note that work in this callback will increase latencies when the application has allowed one or more runtime threads to go idle.
Note: There can only be one unpark callback for a runtime; calling this function more than once replaces the last callback defined, rather than adding to it.
Examples
let runtime = runtime::Builder::new_multi_thread()
.on_thread_unpark(|| {
println!("thread unparking");
})
.build();
runtime.unwrap().block_on(async {
tokio::task::yield_now().await;
println!("Hello from Tokio!");
})Creates the configured Runtime.
The returned Runtime instance is ready to spawn tasks.
Examples
use tokio::runtime::Builder;
let rt = Builder::new_multi_thread().build().unwrap();
rt.block_on(async {
println!("Hello from the Tokio runtime");
});Sets a custom timeout for a thread in the blocking pool.
By default, the timeout for a thread is set to 10 seconds. This can be overridden using .thread_keep_alive().
Example
let rt = runtime::Builder::new_multi_thread()
.thread_keep_alive(Duration::from_millis(100))
.build();Enables the time driver.
Doing this enables using tokio::time on the runtime.
Examples
use tokio::runtime;
let rt = runtime::Builder::new_multi_thread()
.enable_time()
.build()
.unwrap();