| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/tower-0.4.13/src/ready_cache/cache.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>cache.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../../normalize.css"><link rel="stylesheet" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../../ayu.css" disabled><link rel="stylesheet" href="../../../dark.css" disabled><link rel="stylesheet" href="../../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../../storage.js"></script><script defer src="../../../source-script.js"></script><script defer src="../../../source-files.js"></script><script defer src="../../../main.js"></script><noscript><link rel="stylesheet" href="../../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../../tower/index.html"><div class="logo-container"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../tower/index.html"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="doccomment">//! A cache of services. |
| |
| </span><span class="kw">use </span><span class="kw">super</span>::error; |
| <span class="kw">use </span>futures_core::Stream; |
| <span class="kw">use </span>futures_util::{stream::FuturesUnordered, task::AtomicWaker}; |
| <span class="kw">pub use </span>indexmap::Equivalent; |
| <span class="kw">use </span>indexmap::IndexMap; |
| <span class="kw">use </span>std::fmt; |
| <span class="kw">use </span>std::future::Future; |
| <span class="kw">use </span>std::hash::Hash; |
| <span class="kw">use </span>std::pin::Pin; |
| <span class="kw">use </span>std::sync::atomic::{AtomicBool, Ordering}; |
| <span class="kw">use </span>std::sync::Arc; |
| <span class="kw">use </span>std::task::{Context, Poll}; |
| <span class="kw">use </span>tower_service::Service; |
| <span class="kw">use </span>tracing::{debug, trace}; |
| |
| <span class="doccomment">/// Drives readiness over a set of services. |
| /// |
| /// The cache maintains two internal data structures: |
| /// |
| /// * a set of _pending_ services that have not yet become ready; and |
| /// * a set of _ready_ services that have previously polled ready. |
| /// |
| /// As each `S` typed [`Service`] is added to the cache via [`ReadyCache::push`], it |
| /// is added to the _pending set_. As [`ReadyCache::poll_pending`] is invoked, |
| /// pending services are polled and added to the _ready set_. |
| /// |
| /// [`ReadyCache::call_ready`] (or [`ReadyCache::call_ready_index`]) dispatches a |
| /// request to the specified service, but panics if the specified service is not |
| /// in the ready set. The `ReadyCache::check_*` functions can be used to ensure |
| /// that a service is ready before dispatching a request. |
| /// |
| /// The ready set can hold services for an abitrarily long time. During this |
| /// time, the runtime may process events that invalidate that ready state (for |
| /// instance, if a keepalive detects a lost connection). In such cases, callers |
| /// should use [`ReadyCache::check_ready`] (or [`ReadyCache::check_ready_index`]) |
| /// immediately before dispatching a request to ensure that the service has not |
| /// become unavailable. |
| /// |
| /// Once `ReadyCache::call_ready*` is invoked, the service is placed back into |
| /// the _pending_ set to be driven to readiness again. |
| /// |
| /// When `ReadyCache::check_ready*` returns `false`, it indicates that the |
| /// specified service is _not_ ready. If an error is returned, this indicats that |
| /// the server failed and has been removed from the cache entirely. |
| /// |
| /// [`ReadyCache::evict`] can be used to remove a service from the cache (by key), |
| /// though the service may not be dropped (if it is currently pending) until |
| /// [`ReadyCache::poll_pending`] is invoked. |
| /// |
| /// Note that the by-index accessors are provided to support use cases (like |
| /// power-of-two-choices load balancing) where the caller does not care to keep |
| /// track of each service's key. Instead, it needs only to access _some_ ready |
| /// service. In such a case, it should be noted that calls to |
| /// [`ReadyCache::poll_pending`] and [`ReadyCache::evict`] may perturb the order of |
| /// the ready set, so any cached indexes should be discarded after such a call. |
| </span><span class="kw">pub struct </span>ReadyCache<K, S, Req> |
| <span class="kw">where |
| </span>K: Eq + Hash, |
| { |
| <span class="doccomment">/// A stream of services that are not yet ready. |
| </span>pending: FuturesUnordered<Pending<K, S, Req>>, |
| <span class="doccomment">/// An index of cancelation handles for pending streams. |
| </span>pending_cancel_txs: IndexMap<K, CancelTx>, |
| |
| <span class="doccomment">/// Services that have previously become ready. Readiness can become stale, |
| /// so a given service should be polled immediately before use. |
| /// |
| /// The cancelation oneshot is preserved (though unused) while the service is |
| /// ready so that it need not be reallocated each time a request is |
| /// dispatched. |
| </span>ready: IndexMap<K, (S, CancelPair)>, |
| } |
| |
| <span class="comment">// Safety: This is safe because we do not use `Pin::new_unchecked`. |
| </span><span class="kw">impl</span><S, K: Eq + Hash, Req> Unpin <span class="kw">for </span>ReadyCache<K, S, Req> {} |
| |
| <span class="attribute">#[derive(Debug)] |
| </span><span class="kw">struct </span>Cancel { |
| waker: AtomicWaker, |
| canceled: AtomicBool, |
| } |
| |
| <span class="attribute">#[derive(Debug)] |
| </span><span class="kw">struct </span>CancelRx(Arc<Cancel>); |
| |
| <span class="attribute">#[derive(Debug)] |
| </span><span class="kw">struct </span>CancelTx(Arc<Cancel>); |
| |
| <span class="kw">type </span>CancelPair = (CancelTx, CancelRx); |
| |
| <span class="attribute">#[derive(Debug)] |
| </span><span class="kw">enum </span>PendingError<K, E> { |
| Canceled(K), |
| Inner(K, E), |
| } |
| |
| <span class="macro">pin_project_lite::pin_project! </span>{ |
| <span class="doccomment">/// A [`Future`] that becomes satisfied when an `S`-typed service is ready. |
| /// |
| /// May fail due to cancelation, i.e. if the service is evicted from the balancer. |
| </span><span class="kw">struct </span>Pending<K, S, Req> { |
| key: <span class="prelude-ty">Option</span><K>, |
| cancel: <span class="prelude-ty">Option</span><CancelRx>, |
| ready: <span class="prelude-ty">Option</span><S>, |
| _pd: std::marker::PhantomData<Req>, |
| } |
| } |
| |
| <span class="comment">// === ReadyCache === |
| |
| </span><span class="kw">impl</span><K, S, Req> Default <span class="kw">for </span>ReadyCache<K, S, Req> |
| <span class="kw">where |
| </span>K: Eq + Hash, |
| S: Service<Req>, |
| { |
| <span class="kw">fn </span>default() -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ |
| ready: IndexMap::default(), |
| pending: FuturesUnordered::new(), |
| pending_cancel_txs: IndexMap::default(), |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><K, S, Req> fmt::Debug <span class="kw">for </span>ReadyCache<K, S, Req> |
| <span class="kw">where |
| </span>K: fmt::Debug + Eq + Hash, |
| S: fmt::Debug, |
| { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter) -> fmt::Result { |
| <span class="kw">let </span><span class="self">Self </span>{ |
| pending, |
| pending_cancel_txs, |
| ready, |
| } = <span class="self">self</span>; |
| f.debug_struct(<span class="string">"ReadyCache"</span>) |
| .field(<span class="string">"pending"</span>, pending) |
| .field(<span class="string">"pending_cancel_txs"</span>, pending_cancel_txs) |
| .field(<span class="string">"ready"</span>, ready) |
| .finish() |
| } |
| } |
| |
| <span class="kw">impl</span><K, S, Req> ReadyCache<K, S, Req> |
| <span class="kw">where |
| </span>K: Eq + Hash, |
| { |
| <span class="doccomment">/// Returns the total number of services in the cache. |
| </span><span class="kw">pub fn </span>len(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="self">self</span>.ready_len() + <span class="self">self</span>.pending_len() |
| } |
| |
| <span class="doccomment">/// Returns whether or not there are any services in the cache. |
| </span><span class="kw">pub fn </span>is_empty(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.ready.is_empty() && <span class="self">self</span>.pending.is_empty() |
| } |
| |
| <span class="doccomment">/// Returns the number of services in the ready set. |
| </span><span class="kw">pub fn </span>ready_len(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="self">self</span>.ready.len() |
| } |
| |
| <span class="doccomment">/// Returns the number of services in the unready set. |
| </span><span class="kw">pub fn </span>pending_len(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="self">self</span>.pending.len() |
| } |
| |
| <span class="doccomment">/// Returns true iff the given key is in the unready set. |
| </span><span class="kw">pub fn </span>pending_contains<Q: Hash + Equivalent<K>>(<span class="kw-2">&</span><span class="self">self</span>, key: <span class="kw-2">&</span>Q) -> bool { |
| <span class="self">self</span>.pending_cancel_txs.contains_key(key) |
| } |
| |
| <span class="doccomment">/// Obtains a reference to a service in the ready set by key. |
| </span><span class="kw">pub fn </span>get_ready<Q: Hash + Equivalent<K>>(<span class="kw-2">&</span><span class="self">self</span>, key: <span class="kw-2">&</span>Q) -> <span class="prelude-ty">Option</span><(usize, <span class="kw-2">&</span>K, <span class="kw-2">&</span>S)> { |
| <span class="self">self</span>.ready.get_full(key).map(|(i, k, v)| (i, k, <span class="kw-2">&</span>v.<span class="number">0</span>)) |
| } |
| |
| <span class="doccomment">/// Obtains a mutable reference to a service in the ready set by key. |
| </span><span class="kw">pub fn </span>get_ready_mut<Q: Hash + Equivalent<K>>( |
| <span class="kw-2">&mut </span><span class="self">self</span>, |
| key: <span class="kw-2">&</span>Q, |
| ) -> <span class="prelude-ty">Option</span><(usize, <span class="kw-2">&</span>K, <span class="kw-2">&mut </span>S)> { |
| <span class="self">self</span>.ready |
| .get_full_mut(key) |
| .map(|(i, k, v)| (i, k, <span class="kw-2">&mut </span>v.<span class="number">0</span>)) |
| } |
| |
| <span class="doccomment">/// Obtains a reference to a service in the ready set by index. |
| </span><span class="kw">pub fn </span>get_ready_index(<span class="kw-2">&</span><span class="self">self</span>, idx: usize) -> <span class="prelude-ty">Option</span><(<span class="kw-2">&</span>K, <span class="kw-2">&</span>S)> { |
| <span class="self">self</span>.ready.get_index(idx).map(|(k, v)| (k, <span class="kw-2">&</span>v.<span class="number">0</span>)) |
| } |
| |
| <span class="doccomment">/// Obtains a mutable reference to a service in the ready set by index. |
| </span><span class="kw">pub fn </span>get_ready_index_mut(<span class="kw-2">&mut </span><span class="self">self</span>, idx: usize) -> <span class="prelude-ty">Option</span><(<span class="kw-2">&mut </span>K, <span class="kw-2">&mut </span>S)> { |
| <span class="self">self</span>.ready.get_index_mut(idx).map(|(k, v)| (k, <span class="kw-2">&mut </span>v.<span class="number">0</span>)) |
| } |
| |
| <span class="doccomment">/// Evicts an item from the cache. |
| /// |
| /// Returns true if a service was marked for eviction. |
| /// |
| /// Services are dropped from the ready set immediately. Services in the |
| /// pending set are marked for cancellation, but [`ReadyCache::poll_pending`] |
| /// must be called to cause the service to be dropped. |
| </span><span class="kw">pub fn </span>evict<Q: Hash + Equivalent<K>>(<span class="kw-2">&mut </span><span class="self">self</span>, key: <span class="kw-2">&</span>Q) -> bool { |
| <span class="kw">let </span>canceled = <span class="kw">if let </span><span class="prelude-val">Some</span>(c) = <span class="self">self</span>.pending_cancel_txs.swap_remove(key) { |
| c.cancel(); |
| <span class="bool-val">true |
| </span>} <span class="kw">else </span>{ |
| <span class="bool-val">false |
| </span>}; |
| |
| <span class="self">self</span>.ready |
| .swap_remove_full(key) |
| .map(|<span class="kw">_</span>| <span class="bool-val">true</span>) |
| .unwrap_or(canceled) |
| } |
| } |
| |
| <span class="kw">impl</span><K, S, Req> ReadyCache<K, S, Req> |
| <span class="kw">where |
| </span>K: Clone + Eq + Hash, |
| S: Service<Req>, |
| <S <span class="kw">as </span>Service<Req>>::Error: Into<<span class="kw">crate</span>::BoxError>, |
| S::Error: Into<<span class="kw">crate</span>::BoxError>, |
| { |
| <span class="doccomment">/// Pushes a new service onto the pending set. |
| /// |
| /// The service will be promoted to the ready set as [`poll_pending`] is invoked. |
| /// |
| /// Note that this does **not** remove services from the ready set. Once the |
| /// old service is used, it will be dropped instead of being added back to |
| /// the pending set; OR, when the new service becomes ready, it will replace |
| /// the prior service in the ready set. |
| /// |
| /// [`poll_pending`]: crate::ready_cache::cache::ReadyCache::poll_pending |
| </span><span class="kw">pub fn </span>push(<span class="kw-2">&mut </span><span class="self">self</span>, key: K, svc: S) { |
| <span class="kw">let </span>cancel = cancelable(); |
| <span class="self">self</span>.push_pending(key, svc, cancel); |
| } |
| |
| <span class="kw">fn </span>push_pending(<span class="kw-2">&mut </span><span class="self">self</span>, key: K, svc: S, (cancel_tx, cancel_rx): CancelPair) { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(c) = <span class="self">self</span>.pending_cancel_txs.insert(key.clone(), cancel_tx) { |
| <span class="comment">// If there is already a service for this key, cancel it. |
| </span>c.cancel(); |
| } |
| <span class="self">self</span>.pending.push(Pending { |
| key: <span class="prelude-val">Some</span>(key), |
| cancel: <span class="prelude-val">Some</span>(cancel_rx), |
| ready: <span class="prelude-val">Some</span>(svc), |
| _pd: std::marker::PhantomData, |
| }); |
| } |
| |
| <span class="doccomment">/// Polls services pending readiness, adding ready services to the ready set. |
| /// |
| /// Returns [`Poll::Ready`] when there are no remaining unready services. |
| /// [`poll_pending`] should be called again after [`push`] or |
| /// [`call_ready_index`] are invoked. |
| /// |
| /// Failures indicate that an individual pending service failed to become |
| /// ready (and has been removed from the cache). In such a case, |
| /// [`poll_pending`] should typically be called again to continue driving |
| /// pending services to readiness. |
| /// |
| /// [`poll_pending`]: crate::ready_cache::cache::ReadyCache::poll_pending |
| /// [`push`]: crate::ready_cache::cache::ReadyCache::push |
| /// [`call_ready_index`]: crate::ready_cache::cache::ReadyCache::call_ready_index |
| </span><span class="kw">pub fn </span>poll_pending(<span class="kw-2">&mut </span><span class="self">self</span>, cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<<span class="prelude-ty">Result</span><(), error::Failed<K>>> { |
| <span class="kw">loop </span>{ |
| <span class="kw">match </span>Pin::new(<span class="kw-2">&mut </span><span class="self">self</span>.pending).poll_next(cx) { |
| Poll::Pending => <span class="kw">return </span>Poll::Pending, |
| Poll::Ready(<span class="prelude-val">None</span>) => <span class="kw">return </span>Poll::Ready(<span class="prelude-val">Ok</span>(())), |
| Poll::Ready(<span class="prelude-val">Some</span>(<span class="prelude-val">Ok</span>((key, svc, cancel_rx)))) => { |
| <span class="macro">trace!</span>(<span class="string">"endpoint ready"</span>); |
| <span class="kw">let </span>cancel_tx = <span class="self">self</span>.pending_cancel_txs.swap_remove(<span class="kw-2">&</span>key); |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(cancel_tx) = cancel_tx { |
| <span class="comment">// Keep track of the cancelation so that it need not be |
| // recreated after the service is used. |
| </span><span class="self">self</span>.ready.insert(key, (svc, (cancel_tx, cancel_rx))); |
| } <span class="kw">else </span>{ |
| <span class="macro">assert!</span>( |
| cancel_tx.is_some(), |
| <span class="string">"services that become ready must have a pending cancelation" |
| </span>); |
| } |
| } |
| Poll::Ready(<span class="prelude-val">Some</span>(<span class="prelude-val">Err</span>(PendingError::Canceled(<span class="kw">_</span>)))) => { |
| <span class="macro">debug!</span>(<span class="string">"endpoint canceled"</span>); |
| <span class="comment">// The cancellation for this service was removed in order to |
| // cause this cancellation. |
| </span>} |
| Poll::Ready(<span class="prelude-val">Some</span>(<span class="prelude-val">Err</span>(PendingError::Inner(key, e)))) => { |
| <span class="kw">let </span>cancel_tx = <span class="self">self</span>.pending_cancel_txs.swap_remove(<span class="kw-2">&</span>key); |
| <span class="macro">assert!</span>( |
| cancel_tx.is_some(), |
| <span class="string">"services that return an error must have a pending cancelation" |
| </span>); |
| <span class="kw">return </span><span class="prelude-val">Err</span>(error::Failed(key, e.into())).into(); |
| } |
| } |
| } |
| } |
| |
| <span class="doccomment">/// Checks whether the referenced endpoint is ready. |
| /// |
| /// Returns true if the endpoint is ready and false if it is not. An error is |
| /// returned if the endpoint fails. |
| </span><span class="kw">pub fn </span>check_ready<Q: Hash + Equivalent<K>>( |
| <span class="kw-2">&mut </span><span class="self">self</span>, |
| cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>, |
| key: <span class="kw-2">&</span>Q, |
| ) -> <span class="prelude-ty">Result</span><bool, error::Failed<K>> { |
| <span class="kw">match </span><span class="self">self</span>.ready.get_full_mut(key) { |
| <span class="prelude-val">Some</span>((index, <span class="kw">_</span>, <span class="kw">_</span>)) => <span class="self">self</span>.check_ready_index(cx, index), |
| <span class="prelude-val">None </span>=> <span class="prelude-val">Ok</span>(<span class="bool-val">false</span>), |
| } |
| } |
| |
| <span class="doccomment">/// Checks whether the referenced endpoint is ready. |
| /// |
| /// If the service is no longer ready, it is moved back into the pending set |
| /// and `false` is returned. |
| /// |
| /// If the service errors, it is removed and dropped and the error is returned. |
| </span><span class="kw">pub fn </span>check_ready_index( |
| <span class="kw-2">&mut </span><span class="self">self</span>, |
| cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>, |
| index: usize, |
| ) -> <span class="prelude-ty">Result</span><bool, error::Failed<K>> { |
| <span class="kw">let </span>svc = <span class="kw">match </span><span class="self">self</span>.ready.get_index_mut(index) { |
| <span class="prelude-val">None </span>=> <span class="kw">return </span><span class="prelude-val">Ok</span>(<span class="bool-val">false</span>), |
| <span class="prelude-val">Some</span>((<span class="kw">_</span>, (svc, <span class="kw">_</span>))) => svc, |
| }; |
| <span class="kw">match </span>svc.poll_ready(cx) { |
| Poll::Ready(<span class="prelude-val">Ok</span>(())) => <span class="prelude-val">Ok</span>(<span class="bool-val">true</span>), |
| Poll::Pending => { |
| <span class="comment">// became unready; so move it back there. |
| </span><span class="kw">let </span>(key, (svc, cancel)) = <span class="self">self |
| </span>.ready |
| .swap_remove_index(index) |
| .expect(<span class="string">"invalid ready index"</span>); |
| |
| <span class="comment">// If a new version of this service has been added to the |
| // unready set, don't overwrite it. |
| </span><span class="kw">if </span>!<span class="self">self</span>.pending_contains(<span class="kw-2">&</span>key) { |
| <span class="self">self</span>.push_pending(key, svc, cancel); |
| } |
| |
| <span class="prelude-val">Ok</span>(<span class="bool-val">false</span>) |
| } |
| Poll::Ready(<span class="prelude-val">Err</span>(e)) => { |
| <span class="comment">// failed, so drop it. |
| </span><span class="kw">let </span>(key, <span class="kw">_</span>) = <span class="self">self |
| </span>.ready |
| .swap_remove_index(index) |
| .expect(<span class="string">"invalid ready index"</span>); |
| <span class="prelude-val">Err</span>(error::Failed(key, e.into())) |
| } |
| } |
| } |
| |
| <span class="doccomment">/// Calls a ready service by key. |
| /// |
| /// # Panics |
| /// |
| /// If the specified key does not exist in the ready |
| </span><span class="kw">pub fn </span>call_ready<Q: Hash + Equivalent<K>>(<span class="kw-2">&mut </span><span class="self">self</span>, key: <span class="kw-2">&</span>Q, req: Req) -> S::Future { |
| <span class="kw">let </span>(index, <span class="kw">_</span>, <span class="kw">_</span>) = <span class="self">self |
| </span>.ready |
| .get_full_mut(key) |
| .expect(<span class="string">"check_ready was not called"</span>); |
| <span class="self">self</span>.call_ready_index(index, req) |
| } |
| |
| <span class="doccomment">/// Calls a ready service by index. |
| /// |
| /// # Panics |
| /// |
| /// If the specified index is out of range. |
| </span><span class="kw">pub fn </span>call_ready_index(<span class="kw-2">&mut </span><span class="self">self</span>, index: usize, req: Req) -> S::Future { |
| <span class="kw">let </span>(key, (<span class="kw-2">mut </span>svc, cancel)) = <span class="self">self |
| </span>.ready |
| .swap_remove_index(index) |
| .expect(<span class="string">"check_ready_index was not called"</span>); |
| |
| <span class="kw">let </span>fut = svc.call(req); |
| |
| <span class="comment">// If a new version of this service has been added to the |
| // unready set, don't overwrite it. |
| </span><span class="kw">if </span>!<span class="self">self</span>.pending_contains(<span class="kw-2">&</span>key) { |
| <span class="self">self</span>.push_pending(key, svc, cancel); |
| } |
| |
| fut |
| } |
| } |
| |
| <span class="comment">// === impl Cancel === |
| |
| </span><span class="doccomment">/// Creates a cancelation sender and receiver. |
| /// |
| /// A `tokio::sync::oneshot` is NOT used, as a `Receiver` is not guaranteed to |
| /// observe results as soon as a `Sender` fires. Using an `AtomicBool` allows |
| /// the state to be observed as soon as the cancelation is triggered. |
| </span><span class="kw">fn </span>cancelable() -> CancelPair { |
| <span class="kw">let </span>cx = Arc::new(Cancel { |
| waker: AtomicWaker::new(), |
| canceled: AtomicBool::new(<span class="bool-val">false</span>), |
| }); |
| (CancelTx(cx.clone()), CancelRx(cx)) |
| } |
| |
| <span class="kw">impl </span>CancelTx { |
| <span class="kw">fn </span>cancel(<span class="self">self</span>) { |
| <span class="self">self</span>.<span class="number">0</span>.canceled.store(<span class="bool-val">true</span>, Ordering::SeqCst); |
| <span class="self">self</span>.<span class="number">0</span>.waker.wake(); |
| } |
| } |
| |
| <span class="comment">// === Pending === |
| |
| </span><span class="kw">impl</span><K, S, Req> Future <span class="kw">for </span>Pending<K, S, Req> |
| <span class="kw">where |
| </span>S: Service<Req>, |
| { |
| <span class="kw">type </span>Output = <span class="prelude-ty">Result</span><(K, S, CancelRx), PendingError<K, S::Error>>; |
| |
| <span class="kw">fn </span>poll(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<<span class="self">Self</span>::Output> { |
| <span class="kw">let </span>this = <span class="self">self</span>.project(); |
| <span class="comment">// Before checking whether the service is ready, check to see whether |
| // readiness has been canceled. |
| </span><span class="kw">let </span>CancelRx(cancel) = this.cancel.as_mut().expect(<span class="string">"polled after complete"</span>); |
| <span class="kw">if </span>cancel.canceled.load(Ordering::SeqCst) { |
| <span class="kw">let </span>key = this.key.take().expect(<span class="string">"polled after complete"</span>); |
| <span class="kw">return </span><span class="prelude-val">Err</span>(PendingError::Canceled(key)).into(); |
| } |
| |
| <span class="kw">match </span>this |
| .ready |
| .as_mut() |
| .expect(<span class="string">"polled after ready"</span>) |
| .poll_ready(cx) |
| { |
| Poll::Pending => { |
| <span class="comment">// Before returning Pending, register interest in cancelation so |
| // that this future is polled again if the state changes. |
| </span><span class="kw">let </span>CancelRx(cancel) = this.cancel.as_mut().expect(<span class="string">"polled after complete"</span>); |
| cancel.waker.register(cx.waker()); |
| <span class="comment">// Because both the cancel receiver and cancel sender are held |
| // by the `ReadyCache` (i.e., on a single task), then it must |
| // not be possible for the cancelation state to change while |
| // polling a `Pending` service. |
| </span><span class="macro">assert!</span>( |
| !cancel.canceled.load(Ordering::SeqCst), |
| <span class="string">"cancelation cannot be notified while polling a pending service" |
| </span>); |
| Poll::Pending |
| } |
| Poll::Ready(<span class="prelude-val">Ok</span>(())) => { |
| <span class="kw">let </span>key = this.key.take().expect(<span class="string">"polled after complete"</span>); |
| <span class="kw">let </span>cancel = this.cancel.take().expect(<span class="string">"polled after complete"</span>); |
| <span class="prelude-val">Ok</span>((key, this.ready.take().expect(<span class="string">"polled after ready"</span>), cancel)).into() |
| } |
| Poll::Ready(<span class="prelude-val">Err</span>(e)) => { |
| <span class="kw">let </span>key = this.key.take().expect(<span class="string">"polled after compete"</span>); |
| <span class="prelude-val">Err</span>(PendingError::Inner(key, e)).into() |
| } |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><K, S, Req> fmt::Debug <span class="kw">for </span>Pending<K, S, Req> |
| <span class="kw">where |
| </span>K: fmt::Debug, |
| S: fmt::Debug, |
| { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter) -> fmt::Result { |
| <span class="kw">let </span><span class="self">Self </span>{ |
| key, |
| cancel, |
| ready, |
| _pd, |
| } = <span class="self">self</span>; |
| f.debug_struct(<span class="string">"Pending"</span>) |
| .field(<span class="string">"key"</span>, key) |
| .field(<span class="string">"cancel"</span>, cancel) |
| .field(<span class="string">"ready"</span>, ready) |
| .finish() |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="tower" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
