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Refactor ChangeProcessor to be easier to follow

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This commit is contained in:
Lucien Greathouse
2019-12-19 17:41:35 -08:00
parent 46d7bba87d
commit 26e2e81188
1 changed files with 193 additions and 143 deletions
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336
src/change_processor.rs
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@@ -1,11 +1,6 @@
//! Defines the process by which changes are pulled from the Vfs, filtered, and
//! used to mutate Rojo's tree during a live session.
//!
//! This object is owned by a ServeSession.
use std::sync::{Arc, Mutex};
use crossbeam_channel::{select, Receiver, Sender};
use crossbeam_channel::{select, Sender};
use jod_thread::JoinHandle;
use rbx_dom_weak::RbxId;
@@ -18,186 +13,241 @@ use crate::{
vfs::{FsResultExt, Vfs, VfsEvent, VfsFetcher},
};
/// Owns the connection between Rojo's VFS and its DOM by holding onto another
/// thread that processes messages.
///
/// Consumers of ChangeProcessor, like ServeSession, are intended to communicate
/// with this object via channels.
///
/// ChangeProcessor expects to be the only writer to the RojoTree and Vfs
/// objects passed to it.
pub struct ChangeProcessor {
/// Controls the runtime of the processor thread. When signaled, the job
/// thread will finish its current work and terminate.
///
/// This channel should be signaled before dropping ChangeProcessor or we'll
/// hang forever waiting for the message processing loop to terminate.
shutdown_sender: Sender<()>,
_thread_handle: JoinHandle<()>,
/// A handle to the message processing thread. When dropped, we'll block
/// until it's done.
///
/// Allowed to be unused because dropping this value has side effects.
#[allow(unused)]
job_thread: JoinHandle<()>,
}
impl ChangeProcessor {
/// Spin up the ChangeProcessor, connecting it to the given tree, VFS, and
/// outbound message queue.
pub fn start<F: VfsFetcher + Send + Sync + 'static>(
tree: Arc<Mutex<RojoTree>>,
message_queue: Arc<MessageQueue<AppliedPatchSet>>,
vfs: Arc<Vfs<F>>,
) -> Self {
let (shutdown_sender, shutdown_receiver) = crossbeam_channel::bounded(1);
let vfs_receiver = vfs.change_receiver();
let task = JobThreadContext {
tree,
vfs,
message_queue,
};
let thread_handle = jod_thread::Builder::new()
let job_thread = jod_thread::Builder::new()
.name("ChangeProcessor thread".to_owned())
.spawn(move || {
log::trace!("ChangeProcessor thread started");
Self::main_task(shutdown_receiver, tree, message_queue, vfs);
#[allow(
// Crossbeam's select macro generates code that Clippy doesn't like,
// and Clippy blames us for it.
clippy::drop_copy,
// Crossbeam uses 0 as *const _ and Clippy doesn't like that either,
// but this isn't our fault.
clippy::zero_ptr,
)]
loop {
select! {
recv(vfs_receiver) -> event => {
task.handle_vfs_event(event.unwrap());
},
recv(shutdown_receiver) -> _ => {
log::trace!("ChangeProcessor shutdown signal received...");
break;
},
}
}
log::trace!("ChangeProcessor thread stopped");
})
.expect("Could not start ChangeProcessor thread");
Self {
shutdown_sender,
_thread_handle: thread_handle,
}
}
fn main_task<F: VfsFetcher>(
shutdown_receiver: Receiver<()>,
tree: Arc<Mutex<RojoTree>>,
message_queue: Arc<MessageQueue<AppliedPatchSet>>,
vfs: Arc<Vfs<F>>,
) {
let vfs_receiver = vfs.change_receiver();
#[allow(
// Crossbeam's select macro generates code that Clippy doesn't like,
// and Clippy blames us for it.
clippy::drop_copy,
// Crossbeam uses 0 as *const _ and Clippy doesn't like that either,
// but this isn't our fault.
clippy::zero_ptr,
)]
loop {
select! {
recv(vfs_receiver) -> event => {
let event = event.unwrap();
log::trace!("Vfs event: {:?}", event);
let applied_patches = {
vfs.commit_change(&event).expect("Error applying VFS change");
let mut tree = tree.lock().unwrap();
let mut applied_patches = Vec::new();
match event {
VfsEvent::Created(path) | VfsEvent::Modified(path) | VfsEvent::Removed(path) => {
let mut current_path = path.as_path();
let affected_ids = loop {
let ids = tree.get_ids_at_path(&current_path);
log::trace!("Path {} affects IDs {:?}", current_path.display(), ids);
if !ids.is_empty() {
break ids.to_vec();
}
log::trace!("Trying parent path...");
match current_path.parent() {
Some(parent) => current_path = parent,
None => break Vec::new(),
}
};
update_affected_instances(&mut tree, &vfs, &mut applied_patches, &affected_ids)
}
}
applied_patches
};
{
message_queue.push_messages(&applied_patches);
}
},
recv(shutdown_receiver) -> _ => {
log::trace!("ChangeProcessor shutdown signal received...");
break;
},
}
job_thread,
}
}
}
impl Drop for ChangeProcessor {
fn drop(&mut self) {
// Signal the job thread to start spinning down. Without this we'll hang
// forever waiting for the thread to finish its infinite loop.
let _ = self.shutdown_sender.send(());
// After this function ends, the job thread will be joined. It might
// block for a small period of time while it processes its last work.
}
}
fn update_affected_instances<F: VfsFetcher>(
tree: &mut RojoTree,
vfs: &Vfs<F>,
applied_patches: &mut Vec<AppliedPatchSet>,
affected_ids: &[RbxId],
) {
for &id in affected_ids {
let metadata = tree
.get_metadata(id)
.expect("metadata missing for instance present in tree");
/// Contains all of the state needed to synchronize the DOM and VFS.
struct JobThreadContext<F> {
/// A handle to the DOM we're managing.
tree: Arc<Mutex<RojoTree>>,
let instigating_source = match &metadata.instigating_source {
Some(path) => path,
None => {
log::warn!("Instance {} did not have an instigating source, but was considered for an update.", id);
log::warn!("This is a Rojo bug. Please file an issue!");
continue;
}
};
/// A handle to the VFS we're managing.
vfs: Arc<Vfs<F>>,
// How we process a file change event depends on what created this
// file/folder in the first place.
let applied_patch_set = match instigating_source {
InstigatingSource::Path(path) => {
let maybe_entry = vfs
.get(path)
.with_not_found()
.expect("unexpected VFS error");
/// Whenever changes are applied to the DOM, we should push those changes
/// into this message queue to inform any connected clients.
message_queue: Arc<MessageQueue<AppliedPatchSet>>,
}
match maybe_entry {
Some(entry) => {
// Our instance was previously created from a path and
// that path still exists. We can generate a snapshot
// starting at that path and use it as the source for
// our patch.
impl<F: VfsFetcher> JobThreadContext<F> {
fn handle_vfs_event(&self, event: VfsEvent) {
log::trace!("Vfs event: {:?}", event);
let snapshot = snapshot_from_vfs(&metadata.context, &vfs, &entry)
.expect("snapshot failed")
.expect("snapshot did not return an instance");
// Update the VFS immediately with the event.
self.vfs
.commit_change(&event)
.expect("Error applying VFS change");
let patch_set = compute_patch_set(&snapshot, &tree, id);
apply_patch_set(tree, patch_set)
}
None => {
// Our instance was previously created from a path, but
// that path no longer exists.
//
// We associate deleting the instigating file for an
// instance with deleting that instance.
// For a given VFS event, we might have many changes to different parts
// of the tree. Calculate and apply all of these changes.
let applied_patches = {
let mut tree = self.tree.lock().unwrap();
let mut applied_patches = Vec::new();
let mut patch_set = PatchSet::new();
patch_set.removed_instances.push(id);
match event {
VfsEvent::Created(path) | VfsEvent::Modified(path) | VfsEvent::Removed(path) => {
// Find the nearest ancestor to this path that has
// associated instances in the tree. This helps make sure
// that we handle additions correctly, especially if we
// receive events for descendants of a large tree being
// created all at once.
let mut current_path = path.as_path();
let affected_ids = loop {
let ids = tree.get_ids_at_path(&current_path);
apply_patch_set(tree, patch_set)
log::trace!("Path {} affects IDs {:?}", current_path.display(), ids);
if !ids.is_empty() {
break ids.to_vec();
}
log::trace!("Trying parent path...");
match current_path.parent() {
Some(parent) => current_path = parent,
None => break Vec::new(),
}
};
for id in affected_ids {
if let Some(patch) = compute_and_apply_changes(&mut tree, &self.vfs, id) {
applied_patches.push(patch);
}
}
}
}
InstigatingSource::ProjectNode(project_path, instance_name, project_node) => {
// This instance is the direct subject of a project node. Since
// there might be information associated with our instance from
// the project file, we snapshot the entire project node again.
let snapshot = snapshot_project_node(
&metadata.context,
&project_path,
instance_name,
project_node,
&vfs,
)
.expect("snapshot failed")
.expect("snapshot did not return an instance");
let patch_set = compute_patch_set(&snapshot, &tree, id);
apply_patch_set(tree, patch_set)
}
applied_patches
};
applied_patches.push(applied_patch_set);
// Notify anyone listening to the message queue about the changes we
// just made.
self.message_queue.push_messages(&applied_patches);
}
}
fn compute_and_apply_changes<F: VfsFetcher>(
tree: &mut RojoTree,
vfs: &Vfs<F>,
id: RbxId,
) -> Option<AppliedPatchSet> {
let metadata = tree
.get_metadata(id)
.expect("metadata missing for instance present in tree");
let instigating_source = match &metadata.instigating_source {
Some(path) => path,
None => {
log::warn!(
"Instance {} did not have an instigating source, but was considered for an update.",
id
);
log::warn!("This is a Rojo bug. Please file an issue!");
return None;
}
};
// How we process a file change event depends on what created this
// file/folder in the first place.
let applied_patch_set = match instigating_source {
InstigatingSource::Path(path) => {
let maybe_entry = vfs
.get(path)
.with_not_found()
.expect("unexpected VFS error");
match maybe_entry {
Some(entry) => {
// Our instance was previously created from a path and
// that path still exists. We can generate a snapshot
// starting at that path and use it as the source for
// our patch.
let snapshot = snapshot_from_vfs(&metadata.context, &vfs, &entry)
.expect("snapshot failed")
.expect("snapshot did not return an instance");
let patch_set = compute_patch_set(&snapshot, &tree, id);
apply_patch_set(tree, patch_set)
}
None => {
// Our instance was previously created from a path, but
// that path no longer exists.
//
// We associate deleting the instigating file for an
// instance with deleting that instance.
let mut patch_set = PatchSet::new();
patch_set.removed_instances.push(id);
apply_patch_set(tree, patch_set)
}
}
}
InstigatingSource::ProjectNode(project_path, instance_name, project_node) => {
// This instance is the direct subject of a project node. Since
// there might be information associated with our instance from
// the project file, we snapshot the entire project node again.
let snapshot = snapshot_project_node(
&metadata.context,
&project_path,
instance_name,
project_node,
&vfs,
)
.expect("snapshot failed")
.expect("snapshot did not return an instance");
let patch_set = compute_patch_set(&snapshot, &tree, id);
apply_patch_set(tree, patch_set)
}
};
Some(applied_patch_set)
}