use anyhow::Result;
use bytes::Bytes;
use fn0::cache::BundleCache;
use fn0::{CodeExecutor, ExecutionContext, panic_payload_string};
use futures::FutureExt;
use http_body_util::combinators::UnsyncBoxBody;
use std::hash::Hasher;
use std::panic::AssertUnwindSafe;
use std::rc::Rc;
use std::sync::Arc;
use std::thread;
use tokio::sync::{mpsc, oneshot};
pub type Body = UnsyncBoxBody<Bytes, anyhow::Error>;
pub type Request = hyper::Request<Body>;
pub type Response = hyper::Response<Body>;
pub struct RequestEnvelope {
pub code_id: String,
pub req: Request,
pub resp_tx: oneshot::Sender<Result<Response>>,
}
pub enum DispatchError {
Full,
Closed,
}
const QUEUE_CAPACITY: usize = 256;
pub fn spawn_workers<C>(
ctx: Arc<ExecutionContext<C>>,
num_threads: usize,
) -> Vec<mpsc::Sender<RequestEnvelope>>
where
C: BundleCache,
{
assert!(num_threads > 0, "worker pool must have at least one thread");
let mut senders = Vec::with_capacity(num_threads);
for idx in 0..num_threads {
let (tx, rx) = mpsc::channel::<RequestEnvelope>(QUEUE_CAPACITY);
senders.push(tx);
let ctx = ctx.clone();
thread::Builder::new()
.name(format!("fn0-worker-{idx}"))
.spawn(move || run_worker(idx, ctx, rx))
.expect("failed to spawn worker thread");
}
senders
}
pub fn dispatch(
senders: &[mpsc::Sender<RequestEnvelope>],
env: RequestEnvelope,
) -> Result<(), DispatchError> {
let idx = pick_worker(&env.code_id, senders.len());
match senders[idx].try_send(env) {
Ok(()) => Ok(()),
Err(mpsc::error::TrySendError::Full(_)) => Err(DispatchError::Full),
Err(mpsc::error::TrySendError::Closed(_)) => Err(DispatchError::Closed),
}
}
fn pick_worker(code_id: &str, n: usize) -> usize {
let mut hasher = std::collections::hash_map::DefaultHasher::new();
hasher.write(code_id.as_bytes());
(hasher.finish() as usize) % n
}
fn run_worker<C>(idx: usize, ctx: Arc<ExecutionContext<C>>, mut rx: mpsc::Receiver<RequestEnvelope>)
where
C: BundleCache,
{
let rt = tokio::runtime::Builder::new_current_thread()
.enable_all()
.thread_name(format!("fn0-worker-{idx}"))
.build()
.expect("failed to build current_thread runtime");
let local = tokio::task::LocalSet::new();
rt.block_on(local.run_until(async move {
let executor = Rc::new(CodeExecutor::new(ctx));
while let Some(env) = rx.recv().await {
let executor = executor.clone();
tokio::task::spawn_local(async move {
let RequestEnvelope {
code_id,
req,
resp_tx,
} = env;
let outcome =
AssertUnwindSafe(executor.run(&code_id, "/", req, None))
.catch_unwind()
.await;
match outcome {
Ok(result) => {
let _ = resp_tx.send(result);
}
Err(panic) => {
let panic_msg = panic_payload_string(&panic);
tracing::error!(
%code_id,
panic = %panic_msg,
"executor panicked; response channel dropped"
);
}
}
});
}
}));
tracing::info!(worker = idx, "worker thread exiting");
}
pub fn default_num_threads() -> usize {
if let Ok(s) = std::env::var("FN0_WORKER_THREADS")
&& let Ok(n) = s.parse::<usize>()
&& n > 0
{
return n;
}
std::thread::available_parallelism()
.map(|n| n.get())
.unwrap_or(1)
}