Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Reduce SSR Buffers in VList #2826

Merged
merged 1 commit into from Aug 14, 2022
Merged

Reduce SSR Buffers in VList #2826

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Jump to
Jump to file
Failed to load files.
Diff view
Diff view
2 changes: 1 addition & 1 deletion packages/yew/Cargo.toml
View file
Open in desktop
Expand Up @@ -25,7 +25,7 @@ slab = "0.4"
wasm-bindgen = "0.2"
yew-macro = { version = "^0.19.0", path = "../yew-macro" }
thiserror = "1.0"
futures = { version = "0.3", default-features = false, features = ["std"] }
futures = { version = "0.3", default-features = false, features = ["std", "async-await"] }
html-escape = { version = "0.2.9", optional = true }
implicit-clone = { version = "0.3", features = ["map"] }
base64ct = { version = "1.5.0", features = ["std"], optional = true }
Expand Down
108 changes: 63 additions & 45 deletions packages/yew/src/virtual_dom/vlist.rs
View file
Open in desktop
Expand Up @@ -156,8 +156,10 @@ mod test {

#[cfg(feature = "ssr")]
mod feat_ssr {
use futures::stream::{FuturesUnordered, StreamExt};
use futures::{future, FutureExt};
use std::task::Poll;

use futures::stream::StreamExt;
use futures::{join, pin_mut, poll, FutureExt};

use super::*;
use crate::html::AnyScope;
Expand All @@ -175,52 +177,68 @@ mod feat_ssr {
[child] => {
child.render_into_stream(w, parent_scope, hydratable).await;
}
[first_child, rest_children @ ..] => {
let buf_capacity = w.capacity();
let mut child_streams = Vec::with_capacity(self.children.len() - 1);

// Concurrently render rest children into a separate buffer.
let rest_child_furs = rest_children.iter().map(|child| {
let (mut w, r) = io::buffer(buf_capacity);

child_streams.push(r);

async move {
child
.render_into_stream(&mut w, parent_scope, hydratable)
.await;
}
});

// Concurrently resolve all child futures.
let resolve_fur = if rest_children.len() <= 30 {
// 30 is selected by join_all to be deemed small.
let rest_child_furs = future::join_all(rest_child_furs);
async move {
rest_child_furs.await;
}
.left_future()
} else {
let mut rest_child_furs: FuturesUnordered<_> = rest_child_furs.collect();
async move { while rest_child_furs.next().await.is_some() {} }
.right_future()
};

let transfer_fur = async move {
// Render first child to parent buffer directly.
first_child
.render_into_stream(w, parent_scope, hydratable)
.await;

// Transfer results to parent writer.
for mut r in child_streams {
while let Some(next_chunk) = r.next().await {
w.write(next_chunk.into());
_ => {
async fn render_child_iter<'a, I>(
mut children: I,
w: &mut BufWriter,
parent_scope: &AnyScope,
hydratable: bool,
) where
I: Iterator<Item = &'a VNode>,
{
let buf_capacity = w.capacity();
let mut w = w;
while let Some(m) = children.next() {
let child_fur = async move {
// Rust's Compiler does not release the mutable reference to
// BufWriter until the end of the loop, regardless of whether an
// await statement has dropped the child_fur.
//
// We capture and return the mutable reference to avoid this.

m.render_into_stream(w, parent_scope, hydratable).await;
w
};
pin_mut!(child_fur);

match poll!(child_fur.as_mut()) {
Poll::Pending => {
let (mut next_w, next_r) = io::buffer(buf_capacity);
// Move buf writer into an async block for it to be dropped at
// the end of the future.
let rest_render_fur = async move {
render_child_iter(
children,
&mut next_w,
parent_scope,
hydratable,
)
.await;
}
// boxing to avoid recursion
.boxed_local();
Comment on lines +218 to +219
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Out of curiosity, what happens this isn't boxed? If the issue is stack overflow, is this something tail recursion can fix?

Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

With Rust’s async/await design, it’s not possible to recursively call async functions without boxing.

https://rust-lang.github.io/async-book/07_workarounds/04_recursion.html


let transfer_fur = async move {
let w = child_fur.await;

pin_mut!(next_r);
while let Some(m) = next_r.next().await {
w.write(m.into());
}
};

join!(rest_render_fur, transfer_fur);
break;
}
Poll::Ready(w_) => {
w = w_;
}
}
}
};
}

future::join(resolve_fur, transfer_fur).await;
let children = self.children.iter();
render_child_iter(children, w, parent_scope, hydratable).await;
}
}
}
Expand Down