nautilus_common/
runtime.rs

1// -------------------------------------------------------------------------------------------------
2//  Copyright (C) 2015-2025 Nautech Systems Pty Ltd. All rights reserved.
3//  https://nautechsystems.io
4//
5//  Licensed under the GNU Lesser General Public License Version 3.0 (the "License");
6//  You may not use this file except in compliance with the License.
7//  You may obtain a copy of the License at https://www.gnu.org/licenses/lgpl-3.0.en.html
8//
9//  Unless required by applicable law or agreed to in writing, software
10//  distributed under the License is distributed on an "AS IS" BASIS,
11//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12//  See the License for the specific language governing permissions and
13//  limitations under the License.
14// -------------------------------------------------------------------------------------------------
15
16//! The centralized Tokio runtime for a running Nautilus system.
17
18use std::sync::OnceLock;
19
20use tokio::runtime::Builder;
21
22static RUNTIME: OnceLock<tokio::runtime::Runtime> = OnceLock::new();
23
24/// Environment variable name to configure the number of OS threads for the common runtime.
25/// If not set or if the value cannot be parsed as a positive integer, the default value is used.
26const NAUTILUS_WORKER_THREADS: &str = "NAUTILUS_WORKER_THREADS";
27
28/// The default number of OS threads to use if the environment variable is not set.
29///
30/// 0 means Tokio will use the default (number of logical CPUs).
31const DEFAULT_OS_THREADS: usize = 0;
32
33/// Retrieves a reference to a globally shared Tokio runtime.
34/// The runtime is lazily initialized on the first call and reused thereafter.
35///
36/// This global runtime is intended for use cases where passing a runtime
37/// around is impractical. The number of OS threads is configured using the
38/// `NAUTILUS_WORKER_THREADS` environment variable. If not set, all available
39/// logical CPUs will be used.
40///
41/// # Panics
42///
43/// Panics if the runtime could not be created, which typically indicates
44/// an inability to spawn threads or allocate necessary resources.
45pub fn get_runtime() -> &'static tokio::runtime::Runtime {
46    let worker_threads = std::env::var(NAUTILUS_WORKER_THREADS)
47        .ok()
48        .and_then(|val| val.parse::<usize>().ok())
49        .unwrap_or(DEFAULT_OS_THREADS);
50
51    RUNTIME.get_or_init(|| {
52        let mut builder = Builder::new_multi_thread();
53
54        let builder = if worker_threads > 0 {
55            builder.worker_threads(worker_threads)
56        } else {
57            &mut builder
58        };
59
60        builder
61            .enable_all()
62            .build()
63            .expect("Failed to create tokio runtime")
64    })
65}
nautilus_common/runtime.rs

nautilus_common/
runtime.rs
