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<!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 `/home/newkirk/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tower-service-0.3.3/src/lib.rs`."><title>lib.rs - source</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-6b053e98.ttf.woff2,FiraSans-Italic-81dc35de.woff2,FiraSans-Regular-0fe48ade.woff2,FiraSans-MediumItalic-ccf7e434.woff2,FiraSans-Medium-e1aa3f0a.woff2,SourceCodePro-Regular-8badfe75.ttf.woff2,SourceCodePro-Semibold-aa29a496.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2"href="../../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../../static.files/normalize-9960930a.css"><link rel="stylesheet" href="../../static.files/rustdoc-ca0dd0c4.css"><meta name="rustdoc-vars" data-root-path="../../" data-static-root-path="../../static.files/" data-current-crate="tower_service" data-themes="" data-resource-suffix="" data-rustdoc-version="1.93.1 (01f6ddf75 2026-02-11) (Arch Linux rust 1:1.93.1-1)" data-channel="1.93.1" data-search-js="search-9e2438ea.js" data-stringdex-js="stringdex-a3946164.js" data-settings-js="settings-c38705f0.js" ><script src="../../static.files/storage-e2aeef58.js"></script><script defer src="../../static.files/src-script-813739b1.js"></script><script defer src="../../src-files.js"></script><script defer src="../../static.files/main-a410ff4d.js"></script><noscript><link rel="stylesheet" href="../../static.files/noscript-263c88ec.css"></noscript><link rel="alternate icon" type="image/png" href="../../static.files/favicon-32x32-eab170b8.png"><link rel="icon" type="image/svg+xml" href="../../static.files/favicon-044be391.svg"></head><body class="rustdoc src"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="src-sidebar-title"><h2>Files</h2></div></nav><div class="sidebar-resizer" title="Drag to resize sidebar"></div><main><section id="main-content" class="content"><div class="main-heading"><h1><div class="sub-heading">tower_service/</div>lib.rs</h1><rustdoc-toolbar></rustdoc-toolbar></div><div class="example-wrap digits-3"><pre class="rust"><code><a href=#1 id=1 data-nosnippet>1</a><span class="attr">#![warn(
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<a href=#2 id=2 data-nosnippet>2</a> missing_debug_implementations,
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<a href=#3 id=3 data-nosnippet>3</a> missing_docs,
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<a href=#4 id=4 data-nosnippet>4</a> rust_2018_idioms,
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<a href=#5 id=5 data-nosnippet>5</a> unreachable_pub
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<a href=#6 id=6 data-nosnippet>6</a>)]
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<a href=#7 id=7 data-nosnippet>7</a>#![forbid(unsafe_code)]
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<a href=#8 id=8 data-nosnippet>8</a></span><span class="comment">// `rustdoc::broken_intra_doc_links` is checked on CI
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<a href=#9 id=9 data-nosnippet>9</a>
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<a href=#10 id=10 data-nosnippet>10</a></span><span class="doccomment">//! Definition of the core `Service` trait to Tower
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<a href=#11 id=11 data-nosnippet>11</a>//!
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<a href=#12 id=12 data-nosnippet>12</a>//! The [`Service`] trait provides the necessary abstractions for defining
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<a href=#13 id=13 data-nosnippet>13</a>//! request / response clients and servers. It is simple but powerful and is
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<a href=#14 id=14 data-nosnippet>14</a>//! used as the foundation for the rest of Tower.
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<a href=#15 id=15 data-nosnippet>15</a>
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<a href=#16 id=16 data-nosnippet>16</a></span><span class="kw">use </span>std::future::Future;
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<a href=#17 id=17 data-nosnippet>17</a><span class="kw">use </span>std::task::{Context, Poll};
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<a href=#18 id=18 data-nosnippet>18</a>
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<a href=#19 id=19 data-nosnippet>19</a><span class="doccomment">/// An asynchronous function from a `Request` to a `Response`.
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<a href=#20 id=20 data-nosnippet>20</a>///
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<a href=#21 id=21 data-nosnippet>21</a>/// The `Service` trait is a simplified interface making it easy to write
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<a href=#22 id=22 data-nosnippet>22</a>/// network applications in a modular and reusable way, decoupled from the
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<a href=#23 id=23 data-nosnippet>23</a>/// underlying protocol. It is one of Tower's fundamental abstractions.
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<a href=#24 id=24 data-nosnippet>24</a>///
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<a href=#25 id=25 data-nosnippet>25</a>/// # Functional
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<a href=#26 id=26 data-nosnippet>26</a>///
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<a href=#27 id=27 data-nosnippet>27</a>/// A `Service` is a function of a `Request`. It immediately returns a
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<a href=#28 id=28 data-nosnippet>28</a>/// `Future` representing the eventual completion of processing the
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<a href=#29 id=29 data-nosnippet>29</a>/// request. The actual request processing may happen at any time in the
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<a href=#30 id=30 data-nosnippet>30</a>/// future, on any thread or executor. The processing may depend on calling
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<a href=#31 id=31 data-nosnippet>31</a>/// other services. At some point in the future, the processing will complete,
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<a href=#32 id=32 data-nosnippet>32</a>/// and the `Future` will resolve to a response or error.
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<a href=#33 id=33 data-nosnippet>33</a>///
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<a href=#34 id=34 data-nosnippet>34</a>/// At a high level, the `Service::call` function represents an RPC request. The
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<a href=#35 id=35 data-nosnippet>35</a>/// `Service` value can be a server or a client.
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<a href=#36 id=36 data-nosnippet>36</a>///
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<a href=#37 id=37 data-nosnippet>37</a>/// # Server
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<a href=#38 id=38 data-nosnippet>38</a>///
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<a href=#39 id=39 data-nosnippet>39</a>/// An RPC server *implements* the `Service` trait. Requests received by the
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<a href=#40 id=40 data-nosnippet>40</a>/// server over the network are deserialized and then passed as an argument to the
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<a href=#41 id=41 data-nosnippet>41</a>/// server value. The returned response is sent back over the network.
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<a href=#42 id=42 data-nosnippet>42</a>///
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<a href=#43 id=43 data-nosnippet>43</a>/// As an example, here is how an HTTP request is processed by a server:
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<a href=#44 id=44 data-nosnippet>44</a>///
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<a href=#45 id=45 data-nosnippet>45</a>/// ```rust
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<a href=#46 id=46 data-nosnippet>46</a>/// # use std::pin::Pin;
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<a href=#47 id=47 data-nosnippet>47</a>/// # use std::task::{Poll, Context};
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<a href=#48 id=48 data-nosnippet>48</a>/// # use std::future::Future;
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<a href=#49 id=49 data-nosnippet>49</a>/// # use tower_service::Service;
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<a href=#50 id=50 data-nosnippet>50</a>/// use http::{Request, Response, StatusCode};
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<a href=#51 id=51 data-nosnippet>51</a>///
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<a href=#52 id=52 data-nosnippet>52</a>/// struct HelloWorld;
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<a href=#53 id=53 data-nosnippet>53</a>///
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<a href=#54 id=54 data-nosnippet>54</a>/// impl Service<Request<Vec<u8>>> for HelloWorld {
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<a href=#55 id=55 data-nosnippet>55</a>/// type Response = Response<Vec<u8>>;
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<a href=#56 id=56 data-nosnippet>56</a>/// type Error = http::Error;
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<a href=#57 id=57 data-nosnippet>57</a>/// type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>>>>;
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<a href=#58 id=58 data-nosnippet>58</a>///
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<a href=#59 id=59 data-nosnippet>59</a>/// fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
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<a href=#60 id=60 data-nosnippet>60</a>/// Poll::Ready(Ok(()))
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<a href=#61 id=61 data-nosnippet>61</a>/// }
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<a href=#62 id=62 data-nosnippet>62</a>///
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<a href=#63 id=63 data-nosnippet>63</a>/// fn call(&mut self, req: Request<Vec<u8>>) -> Self::Future {
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<a href=#64 id=64 data-nosnippet>64</a>/// // create the body
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<a href=#65 id=65 data-nosnippet>65</a>/// let body: Vec<u8> = "hello, world!\n"
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<a href=#66 id=66 data-nosnippet>66</a>/// .as_bytes()
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<a href=#67 id=67 data-nosnippet>67</a>/// .to_owned();
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<a href=#68 id=68 data-nosnippet>68</a>/// // Create the HTTP response
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<a href=#69 id=69 data-nosnippet>69</a>/// let resp = Response::builder()
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<a href=#70 id=70 data-nosnippet>70</a>/// .status(StatusCode::OK)
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<a href=#71 id=71 data-nosnippet>71</a>/// .body(body)
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<a href=#72 id=72 data-nosnippet>72</a>/// .expect("Unable to create `http::Response`");
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<a href=#73 id=73 data-nosnippet>73</a>///
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<a href=#74 id=74 data-nosnippet>74</a>/// // create a response in a future.
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<a href=#75 id=75 data-nosnippet>75</a>/// let fut = async {
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<a href=#76 id=76 data-nosnippet>76</a>/// Ok(resp)
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<a href=#77 id=77 data-nosnippet>77</a>/// };
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<a href=#78 id=78 data-nosnippet>78</a>///
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<a href=#79 id=79 data-nosnippet>79</a>/// // Return the response as an immediate future
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<a href=#80 id=80 data-nosnippet>80</a>/// Box::pin(fut)
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<a href=#81 id=81 data-nosnippet>81</a>/// }
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<a href=#82 id=82 data-nosnippet>82</a>/// }
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<a href=#83 id=83 data-nosnippet>83</a>/// ```
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<a href=#84 id=84 data-nosnippet>84</a>///
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<a href=#85 id=85 data-nosnippet>85</a>/// # Client
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<a href=#86 id=86 data-nosnippet>86</a>///
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<a href=#87 id=87 data-nosnippet>87</a>/// A client consumes a service by using a `Service` value. The client may
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<a href=#88 id=88 data-nosnippet>88</a>/// issue requests by invoking `call` and passing the request as an argument.
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<a href=#89 id=89 data-nosnippet>89</a>/// It then receives the response by waiting for the returned future.
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<a href=#90 id=90 data-nosnippet>90</a>///
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<a href=#91 id=91 data-nosnippet>91</a>/// As an example, here is how a Redis request would be issued:
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<a href=#92 id=92 data-nosnippet>92</a>///
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<a href=#93 id=93 data-nosnippet>93</a>/// ```rust,ignore
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<a href=#94 id=94 data-nosnippet>94</a>/// let client = redis::Client::new()
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<a href=#95 id=95 data-nosnippet>95</a>/// .connect("127.0.0.1:6379".parse().unwrap())
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<a href=#96 id=96 data-nosnippet>96</a>/// .unwrap();
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<a href=#97 id=97 data-nosnippet>97</a>///
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<a href=#98 id=98 data-nosnippet>98</a>/// let resp = client.call(Cmd::set("foo", "this is the value of foo")).await?;
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<a href=#99 id=99 data-nosnippet>99</a>///
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<a href=#100 id=100 data-nosnippet>100</a>/// // Wait for the future to resolve
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<a href=#101 id=101 data-nosnippet>101</a>/// println!("Redis response: {:?}", resp);
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<a href=#102 id=102 data-nosnippet>102</a>/// ```
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<a href=#103 id=103 data-nosnippet>103</a>///
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<a href=#104 id=104 data-nosnippet>104</a>/// # Middleware / Layer
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<a href=#105 id=105 data-nosnippet>105</a>///
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<a href=#106 id=106 data-nosnippet>106</a>/// More often than not, all the pieces needed for writing robust, scalable
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<a href=#107 id=107 data-nosnippet>107</a>/// network applications are the same no matter the underlying protocol. By
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<a href=#108 id=108 data-nosnippet>108</a>/// unifying the API for both clients and servers in a protocol agnostic way,
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<a href=#109 id=109 data-nosnippet>109</a>/// it is possible to write middleware that provide these pieces in a
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<a href=#110 id=110 data-nosnippet>110</a>/// reusable way.
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<a href=#111 id=111 data-nosnippet>111</a>///
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<a href=#112 id=112 data-nosnippet>112</a>/// Take timeouts as an example:
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<a href=#113 id=113 data-nosnippet>113</a>///
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<a href=#114 id=114 data-nosnippet>114</a>/// ```rust
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<a href=#115 id=115 data-nosnippet>115</a>/// use tower_service::Service;
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<a href=#116 id=116 data-nosnippet>116</a>/// use tower_layer::Layer;
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<a href=#117 id=117 data-nosnippet>117</a>/// use futures::FutureExt;
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<a href=#118 id=118 data-nosnippet>118</a>/// use std::future::Future;
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<a href=#119 id=119 data-nosnippet>119</a>/// use std::task::{Context, Poll};
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<a href=#120 id=120 data-nosnippet>120</a>/// use std::time::Duration;
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<a href=#121 id=121 data-nosnippet>121</a>/// use std::pin::Pin;
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<a href=#122 id=122 data-nosnippet>122</a>/// use std::fmt;
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<a href=#123 id=123 data-nosnippet>123</a>/// use std::error::Error;
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<a href=#124 id=124 data-nosnippet>124</a>///
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<a href=#125 id=125 data-nosnippet>125</a>/// // Our timeout service, which wraps another service and
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<a href=#126 id=126 data-nosnippet>126</a>/// // adds a timeout to its response future.
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<a href=#127 id=127 data-nosnippet>127</a>/// pub struct Timeout<T> {
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<a href=#128 id=128 data-nosnippet>128</a>/// inner: T,
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<a href=#129 id=129 data-nosnippet>129</a>/// timeout: Duration,
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<a href=#130 id=130 data-nosnippet>130</a>/// }
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<a href=#131 id=131 data-nosnippet>131</a>///
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<a href=#132 id=132 data-nosnippet>132</a>/// impl<T> Timeout<T> {
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<a href=#133 id=133 data-nosnippet>133</a>/// pub const fn new(inner: T, timeout: Duration) -> Timeout<T> {
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<a href=#134 id=134 data-nosnippet>134</a>/// Timeout {
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<a href=#135 id=135 data-nosnippet>135</a>/// inner,
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<a href=#136 id=136 data-nosnippet>136</a>/// timeout
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<a href=#137 id=137 data-nosnippet>137</a>/// }
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<a href=#138 id=138 data-nosnippet>138</a>/// }
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<a href=#139 id=139 data-nosnippet>139</a>/// }
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<a href=#140 id=140 data-nosnippet>140</a>///
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<a href=#141 id=141 data-nosnippet>141</a>/// // The error returned if processing a request timed out
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<a href=#142 id=142 data-nosnippet>142</a>/// #[derive(Debug)]
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<a href=#143 id=143 data-nosnippet>143</a>/// pub struct Expired;
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<a href=#144 id=144 data-nosnippet>144</a>///
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<a href=#145 id=145 data-nosnippet>145</a>/// impl fmt::Display for Expired {
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<a href=#146 id=146 data-nosnippet>146</a>/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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<a href=#147 id=147 data-nosnippet>147</a>/// write!(f, "expired")
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<a href=#148 id=148 data-nosnippet>148</a>/// }
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<a href=#149 id=149 data-nosnippet>149</a>/// }
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<a href=#150 id=150 data-nosnippet>150</a>///
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<a href=#151 id=151 data-nosnippet>151</a>/// impl Error for Expired {}
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<a href=#152 id=152 data-nosnippet>152</a>///
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<a href=#153 id=153 data-nosnippet>153</a>/// // We can implement `Service` for `Timeout<T>` if `T` is a `Service`
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<a href=#154 id=154 data-nosnippet>154</a>/// impl<T, Request> Service<Request> for Timeout<T>
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<a href=#155 id=155 data-nosnippet>155</a>/// where
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<a href=#156 id=156 data-nosnippet>156</a>/// T: Service<Request>,
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<a href=#157 id=157 data-nosnippet>157</a>/// T::Future: 'static,
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<a href=#158 id=158 data-nosnippet>158</a>/// T::Error: Into<Box<dyn Error + Send + Sync>> + 'static,
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<a href=#159 id=159 data-nosnippet>159</a>/// T::Response: 'static,
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<a href=#160 id=160 data-nosnippet>160</a>/// {
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<a href=#161 id=161 data-nosnippet>161</a>/// // `Timeout` doesn't modify the response type, so we use `T`'s response type
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<a href=#162 id=162 data-nosnippet>162</a>/// type Response = T::Response;
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<a href=#163 id=163 data-nosnippet>163</a>/// // Errors may be either `Expired` if the timeout expired, or the inner service's
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<a href=#164 id=164 data-nosnippet>164</a>/// // `Error` type. Therefore, we return a boxed `dyn Error + Send + Sync` trait object to erase
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<a href=#165 id=165 data-nosnippet>165</a>/// // the error's type.
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<a href=#166 id=166 data-nosnippet>166</a>/// type Error = Box<dyn Error + Send + Sync>;
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<a href=#167 id=167 data-nosnippet>167</a>/// type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>>>>;
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<a href=#168 id=168 data-nosnippet>168</a>///
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<a href=#169 id=169 data-nosnippet>169</a>/// fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
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<a href=#170 id=170 data-nosnippet>170</a>/// // Our timeout service is ready if the inner service is ready.
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<a href=#171 id=171 data-nosnippet>171</a>/// // This is how backpressure can be propagated through a tree of nested services.
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<a href=#172 id=172 data-nosnippet>172</a>/// self.inner.poll_ready(cx).map_err(Into::into)
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<a href=#173 id=173 data-nosnippet>173</a>/// }
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<a href=#174 id=174 data-nosnippet>174</a>///
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<a href=#175 id=175 data-nosnippet>175</a>/// fn call(&mut self, req: Request) -> Self::Future {
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<a href=#176 id=176 data-nosnippet>176</a>/// // Create a future that completes after `self.timeout`
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<a href=#177 id=177 data-nosnippet>177</a>/// let timeout = tokio::time::sleep(self.timeout);
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<a href=#178 id=178 data-nosnippet>178</a>///
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<a href=#179 id=179 data-nosnippet>179</a>/// // Call the inner service and get a future that resolves to the response
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<a href=#180 id=180 data-nosnippet>180</a>/// let fut = self.inner.call(req);
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<a href=#181 id=181 data-nosnippet>181</a>///
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<a href=#182 id=182 data-nosnippet>182</a>/// // Wrap those two futures in another future that completes when either one completes
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<a href=#183 id=183 data-nosnippet>183</a>/// //
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<a href=#184 id=184 data-nosnippet>184</a>/// // If the inner service is too slow the `sleep` future will complete first
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<a href=#185 id=185 data-nosnippet>185</a>/// // And an error will be returned and `fut` will be dropped and not polled again
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<a href=#186 id=186 data-nosnippet>186</a>/// //
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<a href=#187 id=187 data-nosnippet>187</a>/// // We have to box the errors so the types match
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<a href=#188 id=188 data-nosnippet>188</a>/// let f = async move {
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<a href=#189 id=189 data-nosnippet>189</a>/// tokio::select! {
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<a href=#190 id=190 data-nosnippet>190</a>/// res = fut => {
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<a href=#191 id=191 data-nosnippet>191</a>/// res.map_err(|err| err.into())
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<a href=#192 id=192 data-nosnippet>192</a>/// },
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<a href=#193 id=193 data-nosnippet>193</a>/// _ = timeout => {
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<a href=#194 id=194 data-nosnippet>194</a>/// Err(Box::new(Expired) as Box<dyn Error + Send + Sync>)
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<a href=#195 id=195 data-nosnippet>195</a>/// },
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<a href=#196 id=196 data-nosnippet>196</a>/// }
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<a href=#197 id=197 data-nosnippet>197</a>/// };
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<a href=#198 id=198 data-nosnippet>198</a>///
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<a href=#199 id=199 data-nosnippet>199</a>/// Box::pin(f)
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<a href=#200 id=200 data-nosnippet>200</a>/// }
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<a href=#201 id=201 data-nosnippet>201</a>/// }
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<a href=#202 id=202 data-nosnippet>202</a>///
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<a href=#203 id=203 data-nosnippet>203</a>/// // A layer for wrapping services in `Timeout`
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<a href=#204 id=204 data-nosnippet>204</a>/// pub struct TimeoutLayer(Duration);
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<a href=#205 id=205 data-nosnippet>205</a>///
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<a href=#206 id=206 data-nosnippet>206</a>/// impl TimeoutLayer {
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<a href=#207 id=207 data-nosnippet>207</a>/// pub const fn new(delay: Duration) -> Self {
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<a href=#208 id=208 data-nosnippet>208</a>/// TimeoutLayer(delay)
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<a href=#209 id=209 data-nosnippet>209</a>/// }
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<a href=#210 id=210 data-nosnippet>210</a>/// }
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<a href=#211 id=211 data-nosnippet>211</a>///
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<a href=#212 id=212 data-nosnippet>212</a>/// impl<S> Layer<S> for TimeoutLayer {
|
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<a href=#213 id=213 data-nosnippet>213</a>/// type Service = Timeout<S>;
|
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<a href=#214 id=214 data-nosnippet>214</a>///
|
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<a href=#215 id=215 data-nosnippet>215</a>/// fn layer(&self, service: S) -> Timeout<S> {
|
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<a href=#216 id=216 data-nosnippet>216</a>/// Timeout::new(service, self.0)
|
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<a href=#217 id=217 data-nosnippet>217</a>/// }
|
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<a href=#218 id=218 data-nosnippet>218</a>/// }
|
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<a href=#219 id=219 data-nosnippet>219</a>/// ```
|
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<a href=#220 id=220 data-nosnippet>220</a>///
|
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<a href=#221 id=221 data-nosnippet>221</a>/// The above timeout implementation is decoupled from the underlying protocol
|
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<a href=#222 id=222 data-nosnippet>222</a>/// and is also decoupled from client or server concerns. In other words, the
|
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<a href=#223 id=223 data-nosnippet>223</a>/// same timeout middleware could be used in either a client or a server.
|
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<a href=#224 id=224 data-nosnippet>224</a>///
|
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<a href=#225 id=225 data-nosnippet>225</a>/// # Backpressure
|
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<a href=#226 id=226 data-nosnippet>226</a>///
|
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<a href=#227 id=227 data-nosnippet>227</a>/// Calling a `Service` which is at capacity (i.e., it is temporarily unable to process a
|
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<a href=#228 id=228 data-nosnippet>228</a>/// request) should result in an error. The caller is responsible for ensuring
|
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<a href=#229 id=229 data-nosnippet>229</a>/// that the service is ready to receive the request before calling it.
|
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<a href=#230 id=230 data-nosnippet>230</a>///
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<a href=#231 id=231 data-nosnippet>231</a>/// `Service` provides a mechanism by which the caller is able to coordinate
|
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<a href=#232 id=232 data-nosnippet>232</a>/// readiness. `Service::poll_ready` returns `Ready` if the service expects that
|
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<a href=#233 id=233 data-nosnippet>233</a>/// it is able to process a request.
|
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<a href=#234 id=234 data-nosnippet>234</a>///
|
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<a href=#235 id=235 data-nosnippet>235</a>/// # Be careful when cloning inner services
|
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<a href=#236 id=236 data-nosnippet>236</a>///
|
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<a href=#237 id=237 data-nosnippet>237</a>/// Services are permitted to panic if `call` is invoked without obtaining `Poll::Ready(Ok(()))`
|
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<a href=#238 id=238 data-nosnippet>238</a>/// from `poll_ready`. You should therefore be careful when cloning services for example to move
|
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<a href=#239 id=239 data-nosnippet>239</a>/// them into boxed futures. Even though the original service is ready, the clone might not be.
|
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<a href=#240 id=240 data-nosnippet>240</a>///
|
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<a href=#241 id=241 data-nosnippet>241</a>/// Therefore this kind of code is wrong and might panic:
|
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<a href=#242 id=242 data-nosnippet>242</a>///
|
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<a href=#243 id=243 data-nosnippet>243</a>/// ```rust
|
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<a href=#244 id=244 data-nosnippet>244</a>/// # use std::pin::Pin;
|
|
<a href=#245 id=245 data-nosnippet>245</a>/// # use std::task::{Poll, Context};
|
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<a href=#246 id=246 data-nosnippet>246</a>/// # use std::future::Future;
|
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<a href=#247 id=247 data-nosnippet>247</a>/// # use tower_service::Service;
|
|
<a href=#248 id=248 data-nosnippet>248</a>/// #
|
|
<a href=#249 id=249 data-nosnippet>249</a>/// struct Wrapper<S> {
|
|
<a href=#250 id=250 data-nosnippet>250</a>/// inner: S,
|
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<a href=#251 id=251 data-nosnippet>251</a>/// }
|
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<a href=#252 id=252 data-nosnippet>252</a>///
|
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<a href=#253 id=253 data-nosnippet>253</a>/// impl<R, S> Service<R> for Wrapper<S>
|
|
<a href=#254 id=254 data-nosnippet>254</a>/// where
|
|
<a href=#255 id=255 data-nosnippet>255</a>/// S: Service<R> + Clone + 'static,
|
|
<a href=#256 id=256 data-nosnippet>256</a>/// R: 'static,
|
|
<a href=#257 id=257 data-nosnippet>257</a>/// {
|
|
<a href=#258 id=258 data-nosnippet>258</a>/// type Response = S::Response;
|
|
<a href=#259 id=259 data-nosnippet>259</a>/// type Error = S::Error;
|
|
<a href=#260 id=260 data-nosnippet>260</a>/// type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>>>>;
|
|
<a href=#261 id=261 data-nosnippet>261</a>///
|
|
<a href=#262 id=262 data-nosnippet>262</a>/// fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
|
|
<a href=#263 id=263 data-nosnippet>263</a>/// self.inner.poll_ready(cx)
|
|
<a href=#264 id=264 data-nosnippet>264</a>/// }
|
|
<a href=#265 id=265 data-nosnippet>265</a>///
|
|
<a href=#266 id=266 data-nosnippet>266</a>/// fn call(&mut self, req: R) -> Self::Future {
|
|
<a href=#267 id=267 data-nosnippet>267</a>/// let mut inner = self.inner.clone();
|
|
<a href=#268 id=268 data-nosnippet>268</a>/// Box::pin(async move {
|
|
<a href=#269 id=269 data-nosnippet>269</a>/// // `inner` might not be ready since its a clone
|
|
<a href=#270 id=270 data-nosnippet>270</a>/// inner.call(req).await
|
|
<a href=#271 id=271 data-nosnippet>271</a>/// })
|
|
<a href=#272 id=272 data-nosnippet>272</a>/// }
|
|
<a href=#273 id=273 data-nosnippet>273</a>/// }
|
|
<a href=#274 id=274 data-nosnippet>274</a>/// ```
|
|
<a href=#275 id=275 data-nosnippet>275</a>///
|
|
<a href=#276 id=276 data-nosnippet>276</a>/// You should instead use [`std::mem::replace`] to take the service that was ready:
|
|
<a href=#277 id=277 data-nosnippet>277</a>///
|
|
<a href=#278 id=278 data-nosnippet>278</a>/// ```rust
|
|
<a href=#279 id=279 data-nosnippet>279</a>/// # use std::pin::Pin;
|
|
<a href=#280 id=280 data-nosnippet>280</a>/// # use std::task::{Poll, Context};
|
|
<a href=#281 id=281 data-nosnippet>281</a>/// # use std::future::Future;
|
|
<a href=#282 id=282 data-nosnippet>282</a>/// # use tower_service::Service;
|
|
<a href=#283 id=283 data-nosnippet>283</a>/// #
|
|
<a href=#284 id=284 data-nosnippet>284</a>/// struct Wrapper<S> {
|
|
<a href=#285 id=285 data-nosnippet>285</a>/// inner: S,
|
|
<a href=#286 id=286 data-nosnippet>286</a>/// }
|
|
<a href=#287 id=287 data-nosnippet>287</a>///
|
|
<a href=#288 id=288 data-nosnippet>288</a>/// impl<R, S> Service<R> for Wrapper<S>
|
|
<a href=#289 id=289 data-nosnippet>289</a>/// where
|
|
<a href=#290 id=290 data-nosnippet>290</a>/// S: Service<R> + Clone + 'static,
|
|
<a href=#291 id=291 data-nosnippet>291</a>/// R: 'static,
|
|
<a href=#292 id=292 data-nosnippet>292</a>/// {
|
|
<a href=#293 id=293 data-nosnippet>293</a>/// type Response = S::Response;
|
|
<a href=#294 id=294 data-nosnippet>294</a>/// type Error = S::Error;
|
|
<a href=#295 id=295 data-nosnippet>295</a>/// type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>>>>;
|
|
<a href=#296 id=296 data-nosnippet>296</a>///
|
|
<a href=#297 id=297 data-nosnippet>297</a>/// fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
|
|
<a href=#298 id=298 data-nosnippet>298</a>/// self.inner.poll_ready(cx)
|
|
<a href=#299 id=299 data-nosnippet>299</a>/// }
|
|
<a href=#300 id=300 data-nosnippet>300</a>///
|
|
<a href=#301 id=301 data-nosnippet>301</a>/// fn call(&mut self, req: R) -> Self::Future {
|
|
<a href=#302 id=302 data-nosnippet>302</a>/// let clone = self.inner.clone();
|
|
<a href=#303 id=303 data-nosnippet>303</a>/// // take the service that was ready
|
|
<a href=#304 id=304 data-nosnippet>304</a>/// let mut inner = std::mem::replace(&mut self.inner, clone);
|
|
<a href=#305 id=305 data-nosnippet>305</a>/// Box::pin(async move {
|
|
<a href=#306 id=306 data-nosnippet>306</a>/// inner.call(req).await
|
|
<a href=#307 id=307 data-nosnippet>307</a>/// })
|
|
<a href=#308 id=308 data-nosnippet>308</a>/// }
|
|
<a href=#309 id=309 data-nosnippet>309</a>/// }
|
|
<a href=#310 id=310 data-nosnippet>310</a>/// ```
|
|
<a href=#311 id=311 data-nosnippet>311</a></span><span class="kw">pub trait </span>Service<Request> {
|
|
<a href=#312 id=312 data-nosnippet>312</a> <span class="doccomment">/// Responses given by the service.
|
|
<a href=#313 id=313 data-nosnippet>313</a> </span><span class="kw">type </span>Response;
|
|
<a href=#314 id=314 data-nosnippet>314</a>
|
|
<a href=#315 id=315 data-nosnippet>315</a> <span class="doccomment">/// Errors produced by the service.
|
|
<a href=#316 id=316 data-nosnippet>316</a> </span><span class="kw">type </span>Error;
|
|
<a href=#317 id=317 data-nosnippet>317</a>
|
|
<a href=#318 id=318 data-nosnippet>318</a> <span class="doccomment">/// The future response value.
|
|
<a href=#319 id=319 data-nosnippet>319</a> </span><span class="kw">type </span>Future: Future<Output = <span class="prelude-ty">Result</span><<span class="self">Self</span>::Response, <span class="self">Self</span>::Error>>;
|
|
<a href=#320 id=320 data-nosnippet>320</a>
|
|
<a href=#321 id=321 data-nosnippet>321</a> <span class="doccomment">/// Returns `Poll::Ready(Ok(()))` when the service is able to process requests.
|
|
<a href=#322 id=322 data-nosnippet>322</a> ///
|
|
<a href=#323 id=323 data-nosnippet>323</a> /// If the service is at capacity, then `Poll::Pending` is returned and the task
|
|
<a href=#324 id=324 data-nosnippet>324</a> /// is notified when the service becomes ready again. This function is
|
|
<a href=#325 id=325 data-nosnippet>325</a> /// expected to be called while on a task. Generally, this can be done with
|
|
<a href=#326 id=326 data-nosnippet>326</a> /// a simple `futures::future::poll_fn` call.
|
|
<a href=#327 id=327 data-nosnippet>327</a> ///
|
|
<a href=#328 id=328 data-nosnippet>328</a> /// If `Poll::Ready(Err(_))` is returned, the service is no longer able to service requests
|
|
<a href=#329 id=329 data-nosnippet>329</a> /// and the caller should discard the service instance.
|
|
<a href=#330 id=330 data-nosnippet>330</a> ///
|
|
<a href=#331 id=331 data-nosnippet>331</a> /// Once `poll_ready` returns `Poll::Ready(Ok(()))`, a request may be dispatched to the
|
|
<a href=#332 id=332 data-nosnippet>332</a> /// service using `call`. Until a request is dispatched, repeated calls to
|
|
<a href=#333 id=333 data-nosnippet>333</a> /// `poll_ready` must return either `Poll::Ready(Ok(()))` or `Poll::Ready(Err(_))`.
|
|
<a href=#334 id=334 data-nosnippet>334</a> ///
|
|
<a href=#335 id=335 data-nosnippet>335</a> /// Note that `poll_ready` may reserve shared resources that are consumed in a subsequent
|
|
<a href=#336 id=336 data-nosnippet>336</a> /// invocation of `call`. Thus, it is critical for implementations to not assume that `call`
|
|
<a href=#337 id=337 data-nosnippet>337</a> /// will always be invoked and to ensure that such resources are released if the service is
|
|
<a href=#338 id=338 data-nosnippet>338</a> /// dropped before `call` is invoked or the future returned by `call` is dropped before it
|
|
<a href=#339 id=339 data-nosnippet>339</a> /// is polled.
|
|
<a href=#340 id=340 data-nosnippet>340</a> </span><span class="kw">fn </span>poll_ready(<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><(), <span class="self">Self</span>::Error>>;
|
|
<a href=#341 id=341 data-nosnippet>341</a>
|
|
<a href=#342 id=342 data-nosnippet>342</a> <span class="doccomment">/// Process the request and return the response asynchronously.
|
|
<a href=#343 id=343 data-nosnippet>343</a> ///
|
|
<a href=#344 id=344 data-nosnippet>344</a> /// This function is expected to be callable off task. As such,
|
|
<a href=#345 id=345 data-nosnippet>345</a> /// implementations should take care to not call `poll_ready`.
|
|
<a href=#346 id=346 data-nosnippet>346</a> ///
|
|
<a href=#347 id=347 data-nosnippet>347</a> /// Before dispatching a request, `poll_ready` must be called and return
|
|
<a href=#348 id=348 data-nosnippet>348</a> /// `Poll::Ready(Ok(()))`.
|
|
<a href=#349 id=349 data-nosnippet>349</a> ///
|
|
<a href=#350 id=350 data-nosnippet>350</a> /// # Panics
|
|
<a href=#351 id=351 data-nosnippet>351</a> ///
|
|
<a href=#352 id=352 data-nosnippet>352</a> /// Implementations are permitted to panic if `call` is invoked without
|
|
<a href=#353 id=353 data-nosnippet>353</a> /// obtaining `Poll::Ready(Ok(()))` from `poll_ready`.
|
|
<a href=#354 id=354 data-nosnippet>354</a> </span><span class="attr">#[must_use = <span class="string">"futures do nothing unless you `.await` or poll them"</span>]
|
|
<a href=#355 id=355 data-nosnippet>355</a> </span><span class="kw">fn </span>call(<span class="kw-2">&mut </span><span class="self">self</span>, req: Request) -> <span class="self">Self</span>::Future;
|
|
<a href=#356 id=356 data-nosnippet>356</a>}
|
|
<a href=#357 id=357 data-nosnippet>357</a>
|
|
<a href=#358 id=358 data-nosnippet>358</a><span class="kw">impl</span><<span class="lifetime">'a</span>, S, Request> Service<Request> <span class="kw">for </span><span class="kw-2">&</span><span class="lifetime">'a </span><span class="kw-2">mut </span>S
|
|
<a href=#359 id=359 data-nosnippet>359</a><span class="kw">where
|
|
<a href=#360 id=360 data-nosnippet>360</a> </span>S: Service<Request> + <span class="lifetime">'a</span>,
|
|
<a href=#361 id=361 data-nosnippet>361</a>{
|
|
<a href=#362 id=362 data-nosnippet>362</a> <span class="kw">type </span>Response = S::Response;
|
|
<a href=#363 id=363 data-nosnippet>363</a> <span class="kw">type </span>Error = S::Error;
|
|
<a href=#364 id=364 data-nosnippet>364</a> <span class="kw">type </span>Future = S::Future;
|
|
<a href=#365 id=365 data-nosnippet>365</a>
|
|
<a href=#366 id=366 data-nosnippet>366</a> <span class="kw">fn </span>poll_ready(<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><(), S::Error>> {
|
|
<a href=#367 id=367 data-nosnippet>367</a> (<span class="kw-2">**</span><span class="self">self</span>).poll_ready(cx)
|
|
<a href=#368 id=368 data-nosnippet>368</a> }
|
|
<a href=#369 id=369 data-nosnippet>369</a>
|
|
<a href=#370 id=370 data-nosnippet>370</a> <span class="kw">fn </span>call(<span class="kw-2">&mut </span><span class="self">self</span>, request: Request) -> S::Future {
|
|
<a href=#371 id=371 data-nosnippet>371</a> (<span class="kw-2">**</span><span class="self">self</span>).call(request)
|
|
<a href=#372 id=372 data-nosnippet>372</a> }
|
|
<a href=#373 id=373 data-nosnippet>373</a>}
|
|
<a href=#374 id=374 data-nosnippet>374</a>
|
|
<a href=#375 id=375 data-nosnippet>375</a><span class="kw">impl</span><S, Request> Service<Request> <span class="kw">for </span>Box<S>
|
|
<a href=#376 id=376 data-nosnippet>376</a><span class="kw">where
|
|
<a href=#377 id=377 data-nosnippet>377</a> </span>S: Service<Request> + <span class="question-mark">?</span>Sized,
|
|
<a href=#378 id=378 data-nosnippet>378</a>{
|
|
<a href=#379 id=379 data-nosnippet>379</a> <span class="kw">type </span>Response = S::Response;
|
|
<a href=#380 id=380 data-nosnippet>380</a> <span class="kw">type </span>Error = S::Error;
|
|
<a href=#381 id=381 data-nosnippet>381</a> <span class="kw">type </span>Future = S::Future;
|
|
<a href=#382 id=382 data-nosnippet>382</a>
|
|
<a href=#383 id=383 data-nosnippet>383</a> <span class="kw">fn </span>poll_ready(<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><(), S::Error>> {
|
|
<a href=#384 id=384 data-nosnippet>384</a> (<span class="kw-2">**</span><span class="self">self</span>).poll_ready(cx)
|
|
<a href=#385 id=385 data-nosnippet>385</a> }
|
|
<a href=#386 id=386 data-nosnippet>386</a>
|
|
<a href=#387 id=387 data-nosnippet>387</a> <span class="kw">fn </span>call(<span class="kw-2">&mut </span><span class="self">self</span>, request: Request) -> S::Future {
|
|
<a href=#388 id=388 data-nosnippet>388</a> (<span class="kw-2">**</span><span class="self">self</span>).call(request)
|
|
<a href=#389 id=389 data-nosnippet>389</a> }
|
|
<a href=#390 id=390 data-nosnippet>390</a>}
|
|
</code></pre></div></section></main></body></html> |