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publication_cache.rs
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publication_cache.rs
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//
// Copyright (c) 2023 ZettaScale Technology
//
// This program and the accompanying materials are made available under the
// terms of the Eclipse Public License 2.0 which is available at
// http://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
// which is available at https://www.apache.org/licenses/LICENSE-2.0.
//
// SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
//
// Contributors:
// ZettaScale Zenoh Team, <zenoh@zettascale.tech>
//
use std::collections::{HashMap, VecDeque};
use std::convert::TryInto;
use std::future::Ready;
use std::time::Duration;
use zenoh::prelude::r#async::*;
use zenoh::queryable::{Query, Queryable};
use zenoh::subscriber::FlumeSubscriber;
use zenoh::SessionRef;
use zenoh_core::{AsyncResolve, Resolvable, SyncResolve};
use zenoh_result::{bail, ZResult};
use zenoh_task::TerminatableTask;
use zenoh_util::core::ResolveFuture;
/// The builder of PublicationCache, allowing to configure it.
#[must_use = "Resolvables do nothing unless you resolve them using the `res` method from either `SyncResolve` or `AsyncResolve`"]
pub struct PublicationCacheBuilder<'a, 'b, 'c> {
session: SessionRef<'a>,
pub_key_expr: ZResult<KeyExpr<'b>>,
queryable_prefix: Option<ZResult<KeyExpr<'c>>>,
queryable_origin: Option<Locality>,
complete: Option<bool>,
history: usize,
resources_limit: Option<usize>,
}
impl<'a, 'b, 'c> PublicationCacheBuilder<'a, 'b, 'c> {
pub(crate) fn new(
session: SessionRef<'a>,
pub_key_expr: ZResult<KeyExpr<'b>>,
) -> PublicationCacheBuilder<'a, 'b, 'c> {
PublicationCacheBuilder {
session,
pub_key_expr,
queryable_prefix: None,
queryable_origin: None,
complete: None,
history: 1,
resources_limit: None,
}
}
/// Change the prefix used for queryable.
pub fn queryable_prefix<TryIntoKeyExpr>(mut self, queryable_prefix: TryIntoKeyExpr) -> Self
where
TryIntoKeyExpr: TryInto<KeyExpr<'c>>,
<TryIntoKeyExpr as TryInto<KeyExpr<'c>>>::Error: Into<zenoh_result::Error>,
{
self.queryable_prefix = Some(queryable_prefix.try_into().map_err(Into::into));
self
}
/// Restrict the matching queries that will be receive by this [`PublicationCache`]'s queryable
/// to the ones that have the given [`Locality`](zenoh::prelude::Locality).
#[zenoh_macros::unstable]
#[inline]
pub fn queryable_allowed_origin(mut self, origin: Locality) -> Self {
self.queryable_origin = Some(origin);
self
}
/// Set completeness option for the queryable.
pub fn queryable_complete(mut self, complete: bool) -> Self {
self.complete = Some(complete);
self
}
/// Change the history size for each resource.
pub fn history(mut self, history: usize) -> Self {
self.history = history;
self
}
/// Change the limit number of cached resources.
pub fn resources_limit(mut self, limit: usize) -> Self {
self.resources_limit = Some(limit);
self
}
}
impl<'a> Resolvable for PublicationCacheBuilder<'a, '_, '_> {
type To = ZResult<PublicationCache<'a>>;
}
impl SyncResolve for PublicationCacheBuilder<'_, '_, '_> {
fn res_sync(self) -> <Self as Resolvable>::To {
PublicationCache::new(self)
}
}
impl<'a> AsyncResolve for PublicationCacheBuilder<'a, '_, '_> {
type Future = Ready<Self::To>;
fn res_async(self) -> Self::Future {
std::future::ready(self.res_sync())
}
}
pub struct PublicationCache<'a> {
local_sub: FlumeSubscriber<'a>,
_queryable: Queryable<'a, flume::Receiver<Query>>,
task: TerminatableTask,
}
impl<'a> PublicationCache<'a> {
fn new(conf: PublicationCacheBuilder<'a, '_, '_>) -> ZResult<PublicationCache<'a>> {
let key_expr = conf.pub_key_expr?;
// the queryable_prefix (optional), and the key_expr for PublicationCache's queryable ("[<queryable_prefix>]/<pub_key_expr>")
let (queryable_prefix, queryable_key_expr): (Option<OwnedKeyExpr>, KeyExpr) =
match conf.queryable_prefix {
None => (None, key_expr.clone()),
Some(Ok(ke)) => {
let queryable_key_expr = (&ke) / &key_expr;
(Some(ke.into()), queryable_key_expr)
}
Some(Err(e)) => bail!("Invalid key expression for queryable_prefix: {}", e),
};
tracing::debug!(
"Create PublicationCache on {} with history={} resource_limit={:?}",
&key_expr,
conf.history,
conf.resources_limit
);
if conf.session.hlc().is_none() {
bail!(
"Failed requirement for PublicationCache on {}: \
the Session is not configured with 'add_timestamp=true'",
key_expr
)
}
// declare the local subscriber that will store the local publications
let local_sub = conf
.session
.declare_subscriber(&key_expr)
.allowed_origin(Locality::SessionLocal)
.res_sync()?;
// declare the queryable which returns the cached publications
let mut queryable = conf.session.declare_queryable(&queryable_key_expr);
if let Some(origin) = conf.queryable_origin {
queryable = queryable.allowed_origin(origin);
}
if let Some(complete) = conf.complete {
queryable = queryable.complete(complete);
}
let queryable = queryable.res_sync()?;
// take local ownership of stuff to be moved into task
let sub_recv = local_sub.receiver.clone();
let quer_recv = queryable.receiver.clone();
let pub_key_expr = key_expr.into_owned();
let resources_limit = conf.resources_limit;
let history = conf.history;
// TODO(yuyuan): use CancellationToken to manage it
let token = TerminatableTask::create_cancellation_token();
let token2 = token.clone();
let task = TerminatableTask::spawn(
zenoh_runtime::ZRuntime::Application,
async move {
let mut cache: HashMap<OwnedKeyExpr, VecDeque<Sample>> =
HashMap::with_capacity(resources_limit.unwrap_or(32));
let limit = resources_limit.unwrap_or(usize::MAX);
loop {
tokio::select! {
// on publication received by the local subscriber, store it
sample = sub_recv.recv_async() => {
if let Ok(sample) = sample {
let queryable_key_expr: KeyExpr<'_> = if let Some(prefix) = &queryable_prefix {
prefix.join(&sample.key_expr).unwrap().into()
} else {
sample.key_expr.clone()
};
if let Some(queue) = cache.get_mut(queryable_key_expr.as_keyexpr()) {
if queue.len() >= history {
queue.pop_front();
}
queue.push_back(sample);
} else if cache.len() >= limit {
tracing::error!("PublicationCache on {}: resource_limit exceeded - can't cache publication for a new resource",
pub_key_expr);
} else {
let mut queue: VecDeque<Sample> = VecDeque::new();
queue.push_back(sample);
cache.insert(queryable_key_expr.into(), queue);
}
}
},
// on query, reply with cached content
query = quer_recv.recv_async() => {
if let Ok(query) = query {
if !query.selector().key_expr.as_str().contains('*') {
if let Some(queue) = cache.get(query.selector().key_expr.as_keyexpr()) {
for sample in queue {
if let (Ok(Some(time_range)), Some(timestamp)) = (query.selector().time_range(), sample.timestamp) {
if !time_range.contains(timestamp.get_time().to_system_time()){
continue;
}
}
if let Err(e) = query.reply(Ok(sample.clone())).res_async().await {
tracing::warn!("Error replying to query: {}", e);
}
}
}
} else {
for (key_expr, queue) in cache.iter() {
if query.selector().key_expr.intersects(unsafe{ keyexpr::from_str_unchecked(key_expr) }) {
for sample in queue {
if let (Ok(Some(time_range)), Some(timestamp)) = (query.selector().time_range(), sample.timestamp) {
if !time_range.contains(timestamp.get_time().to_system_time()){
continue;
}
}
if let Err(e) = query.reply(Ok(sample.clone())).res_async().await {
tracing::warn!("Error replying to query: {}", e);
}
}
}
}
}
}
},
_ = token2.cancelled() => return
}
}
},
token,
);
Ok(PublicationCache {
local_sub,
_queryable: queryable,
task,
})
}
/// Close this PublicationCache
#[inline]
pub fn close(self) -> impl Resolve<ZResult<()>> + 'a {
ResolveFuture::new(async move {
let PublicationCache {
_queryable,
local_sub,
task,
} = self;
_queryable.undeclare().res_async().await?;
local_sub.undeclare().res_async().await?;
task.terminate(Duration::from_secs(10));
Ok(())
})
}
pub fn key_expr(&self) -> &KeyExpr<'static> {
self.local_sub.key_expr()
}
}