1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
//! HTTP Client
//!
//! There are two levels of APIs provided for construct HTTP clients:
//!
//! - The higher-level [`Client`](Client) type.
//! - The lower-level [`conn`](client::conn) module.
//!
//! # Client
//!
//! The [`Client`](Client) is the main way to send HTTP requests to a server.
//! The default `Client` provides these things on top of the lower-level API:
//!
//! - A default **connector**, able to resolve hostnames and connect to
//!   destinations over plain-text TCP.
//! - A **pool** of existing connections, allowing better performance when
//!   making multiple requests to the same hostname.
//! - Automatic setting of the `Host` header, based on the request `Uri`.
//! - Automatic request **retries** when a pooled connection is closed by the
//!   server before any bytes have been written.
//!
//! Many of these features can configured, by making use of
//! [`Client::builder`](Client::builder).
//!
//! ## Example
//!
//! For a small example program simply fetching a URL, take a look at the
//! [full client example](https://github.com/hyperium/hyper/blob/0.12.x/examples/client.rs).
//!
//! ```
//! extern crate hyper;
//!
//! use hyper::{Client, Uri};
//! # #[cfg(feature = "runtime")]
//! use hyper::rt::{self, Future, Stream};
//!
//! # #[cfg(feature = "runtime")]
//! # fn fetch_httpbin() {
//! let client = Client::new();
//!
//! let fut = client
//!
//!     // Make a GET /ip to 'http://httpbin.org'
//!     .get(Uri::from_static("http://httpbin.org/ip"))
//!
//!     // And then, if the request gets a response...
//!     .and_then(|res| {
//!         println!("status: {}", res.status());
//!
//!         // Concatenate the body stream into a single buffer...
//!         // This returns a new future, since we must stream body.
//!         res.into_body().concat2()
//!     })
//!
//!     // And then, if reading the full body succeeds...
//!     .and_then(|body| {
//!         // The body is just bytes, but let's print a string...
//!         let s = ::std::str::from_utf8(&body)
//!             .expect("httpbin sends utf-8 JSON");
//!
//!         println!("body: {}", s);
//!
//!         // and_then requires we return a new Future, and it turns
//!         // out that Result is a Future that is ready immediately.
//!         Ok(())
//!     })
//!
//!     // Map any errors that might have happened...
//!     .map_err(|err| {
//!         println!("error: {}", err);
//!     });
//!
//! // A runtime is needed to execute our asynchronous code. In order to
//! // spawn the future into the runtime, it should already have been
//! // started and running before calling this code.
//! rt::spawn(fut);
//! # }
//! # fn main () {}
//! ```

use std::fmt;
use std::mem;
use std::sync::Arc;
use std::time::Duration;

use futures::{Async, Future, Poll};
use futures::future::{self, Either, Executor};
use futures::sync::oneshot;
use http::{Method, Request, Response, Uri, Version};
use http::header::{HeaderValue, HOST};
use http::uri::Scheme;

use body::{Body, Payload};
use common::{lazy as hyper_lazy, Lazy};
use self::connect::{Alpn, Connect, Connected, Destination};
use self::pool::{Key as PoolKey, Pool, Poolable, Pooled, Reservation};

#[cfg(feature = "runtime")] pub use self::connect::HttpConnector;

pub mod conn;
pub mod connect;
pub(crate) mod dispatch;
mod pool;
#[cfg(test)]
mod tests;

/// A Client to make outgoing HTTP requests.
pub struct Client<C, B = Body> {
    config: Config,
    conn_builder: conn::Builder,
    connector: Arc<C>,
    pool: Pool<PoolClient<B>>,
}

#[derive(Clone, Copy, Debug)]
struct Config {
    retry_canceled_requests: bool,
    set_host: bool,
    ver: Ver,
}

#[cfg(feature = "runtime")]
impl Client<HttpConnector, Body> {
    /// Create a new Client with the default [config](Builder).
    ///
    /// # Note
    ///
    /// The default connector does **not** handle TLS. Speaking to `https`
    /// destinations will require [configuring a connector that implements
    /// TLS](https://hyper.rs/guides/client/configuration).
    #[inline]
    pub fn new() -> Client<HttpConnector, Body> {
        Builder::default().build_http()
    }
}

#[cfg(feature = "runtime")]
impl Default for Client<HttpConnector, Body> {
    fn default() -> Client<HttpConnector, Body> {
        Client::new()
    }
}

impl Client<(), Body> {
    /// Create a builder to configure a new `Client`.
    ///
    /// # Example
    ///
    /// ```
    /// # extern crate hyper;
    /// # #[cfg(feature  = "runtime")]
    /// # fn run () {
    /// use hyper::Client;
    ///
    /// let client = Client::builder()
    ///     .keep_alive(true)
    ///     .http2_only(true)
    ///     .build_http();
    /// # let infer: Client<_, hyper::Body> = client;
    /// # drop(infer);
    /// # }
    /// # fn main() {}
    /// ```
    #[inline]
    pub fn builder() -> Builder {
        Builder::default()
    }
}

impl<C, B> Client<C, B>
where C: Connect + Sync + 'static,
      C::Transport: 'static,
      C::Future: 'static,
      B: Payload + Send + 'static,
      B::Data: Send,
{
    /// Send a `GET` request to the supplied `Uri`.
    ///
    /// # Note
    ///
    /// This requires that the `Payload` type have a `Default` implementation.
    /// It *should* return an "empty" version of itself, such that
    /// `Payload::is_end_stream` is `true`.
    ///
    /// # Example
    ///
    /// ```
    /// # extern crate hyper;
    /// # #[cfg(feature  = "runtime")]
    /// # fn run () {
    /// use hyper::{Client, Uri};
    ///
    /// let client = Client::new();
    ///
    /// let future = client.get(Uri::from_static("http://httpbin.org/ip"));
    /// # }
    /// # fn main() {}
    /// ```
    pub fn get(&self, uri: Uri) -> ResponseFuture
    where
        B: Default,
    {
        let body = B::default();
        if !body.is_end_stream() {
            warn!("default Payload used for get() does not return true for is_end_stream");
        }

        let mut req = Request::new(body);
        *req.uri_mut() = uri;
        self.request(req)
    }

    /// Send a constructed `Request` using this `Client`.
    ///
    /// # Example
    ///
    /// ```
    /// # extern crate hyper;
    /// # #[cfg(feature  = "runtime")]
    /// # fn run () {
    /// use hyper::{Body, Client, Request};
    ///
    /// let client = Client::new();
    ///
    /// let req = Request::builder()
    ///     .method("POST")
    ///     .uri("http://httpin.org/post")
    ///     .body(Body::from("Hallo!"))
    ///     .expect("request builder");
    ///
    /// let future = client.request(req);
    /// # }
    /// # fn main() {}
    /// ```
    pub fn request(&self, mut req: Request<B>) -> ResponseFuture {
        let is_http_connect = req.method() == &Method::CONNECT;
        match req.version() {
            Version::HTTP_11 => (),
            Version::HTTP_10 => if is_http_connect {
                warn!("CONNECT is not allowed for HTTP/1.0");
                return ResponseFuture::new(Box::new(future::err(::Error::new_user_unsupported_request_method())));
            },
            other_h2 @ Version::HTTP_2 => if self.config.ver != Ver::Http2 {
                return ResponseFuture::error_version(other_h2);
            },
            // completely unsupported HTTP version (like HTTP/0.9)!
            other => return ResponseFuture::error_version(other),
        };

        let domain = match extract_domain(req.uri_mut(), is_http_connect) {
            Ok(s) => s,
            Err(err) => {
                return ResponseFuture::new(Box::new(future::err(err)));
            }
        };

        let pool_key = Arc::new(domain.to_string());
        ResponseFuture::new(Box::new(self.retryably_send_request(req, pool_key)))
    }

    fn retryably_send_request(&self, req: Request<B>, pool_key: PoolKey) -> impl Future<Item=Response<Body>, Error=::Error> {
        let client = self.clone();
        let uri = req.uri().clone();

        let mut send_fut = client.send_request(req, pool_key.clone());
        future::poll_fn(move || loop {
            match send_fut.poll() {
                Ok(Async::Ready(resp)) => return Ok(Async::Ready(resp)),
                Ok(Async::NotReady) => return Ok(Async::NotReady),
                Err(ClientError::Normal(err)) => return Err(err),
                Err(ClientError::Canceled {
                    connection_reused,
                    mut req,
                    reason,
                }) => {
                    if !client.config.retry_canceled_requests || !connection_reused {
                        // if client disabled, don't retry
                        // a fresh connection means we definitely can't retry
                        return Err(reason);
                    }

                    trace!("unstarted request canceled, trying again (reason={:?})", reason);
                    *req.uri_mut() = uri.clone();
                    send_fut = client.send_request(req, pool_key.clone());
                }
            }
        })
    }

    fn send_request(&self, mut req: Request<B>, pool_key: PoolKey) -> impl Future<Item=Response<Body>, Error=ClientError<B>> {
        let conn = self.connection_for(req.uri().clone(), pool_key);

        let set_host = self.config.set_host;
        let executor = self.conn_builder.exec.clone();
        conn.and_then(move |mut pooled| {
            if pooled.is_http1() {
                if set_host {
                    let uri = req.uri().clone();
                    req
                        .headers_mut()
                        .entry(HOST)
                        .expect("HOST is always valid header name")
                        .or_insert_with(|| {
                            let hostname = uri.host().expect("authority implies host");
                            if let Some(port) = uri.port_part() {
                                let s = format!("{}:{}", hostname, port);
                                HeaderValue::from_str(&s)
                            } else {
                                HeaderValue::from_str(hostname)
                            }.expect("uri host is valid header value")
                        });
                }

                // CONNECT always sends authority-form, so check it first...
                if req.method() == &Method::CONNECT {
                    authority_form(req.uri_mut());
                } else if pooled.conn_info.is_proxied {
                    absolute_form(req.uri_mut());
                } else {
                    origin_form(req.uri_mut());
                };
            } else if req.method() == &Method::CONNECT {
                debug!("client does not support CONNECT requests over HTTP2");
                return Either::A(future::err(ClientError::Normal(::Error::new_user_unsupported_request_method())));
            }

            let fut = pooled.send_request_retryable(req)
                .map_err(ClientError::map_with_reused(pooled.is_reused()));

            // If the Connector included 'extra' info, add to Response...
            let extra_info = pooled.conn_info.extra.clone();
            let fut = fut.map(move |mut res| {
                if let Some(extra) = extra_info {
                    extra.set(&mut res);
                }
                res
            });

            // As of futures@0.1.21, there is a race condition in the mpsc
            // channel, such that sending when the receiver is closing can
            // result in the message being stuck inside the queue. It won't
            // ever notify until the Sender side is dropped.
            //
            // To counteract this, we must check if our senders 'want' channel
            // has been closed after having tried to send. If so, error out...
            if pooled.is_closed() {
                return Either::B(Either::A(fut));
            }

            Either::B(Either::B(fut
                .and_then(move |mut res| {
                    // If pooled is HTTP/2, we can toss this reference immediately.
                    //
                    // when pooled is dropped, it will try to insert back into the
                    // pool. To delay that, spawn a future that completes once the
                    // sender is ready again.
                    //
                    // This *should* only be once the related `Connection` has polled
                    // for a new request to start.
                    //
                    // It won't be ready if there is a body to stream.
                    if pooled.is_http2() || !pooled.is_pool_enabled() || pooled.is_ready() {
                        drop(pooled);
                    } else if !res.body().is_end_stream() {
                        let (delayed_tx, delayed_rx) = oneshot::channel();
                        res.body_mut().delayed_eof(delayed_rx);
                        let on_idle = future::poll_fn(move || {
                            pooled.poll_ready()
                        })
                            .then(move |_| {
                                // At this point, `pooled` is dropped, and had a chance
                                // to insert into the pool (if conn was idle)
                                drop(delayed_tx);
                                Ok(())
                            });

                        if let Err(err) = executor.execute(on_idle) {
                            // This task isn't critical, so just log and ignore.
                            warn!("error spawning task to insert idle connection: {}", err);
                        }
                    } else {
                        // There's no body to delay, but the connection isn't
                        // ready yet. Only re-insert when it's ready
                        let on_idle = future::poll_fn(move || {
                            pooled.poll_ready()
                        })
                            .then(|_| Ok(()));

                        if let Err(err) = executor.execute(on_idle) {
                            // This task isn't critical, so just log and ignore.
                            warn!("error spawning task to insert idle connection: {}", err);
                        }
                    }
                    Ok(res)
                })))
        })
    }

    fn connection_for(&self, uri: Uri, pool_key: PoolKey)
        -> impl Future<Item=Pooled<PoolClient<B>>, Error=ClientError<B>>
    {
        // This actually races 2 different futures to try to get a ready
        // connection the fastest, and to reduce connection churn.
        //
        // - If the pool has an idle connection waiting, that's used
        //   immediately.
        // - Otherwise, the Connector is asked to start connecting to
        //   the destination Uri.
        // - Meanwhile, the pool Checkout is watching to see if any other
        //   request finishes and tries to insert an idle connection.
        // - If a new connection is started, but the Checkout wins after
        //   (an idle connection becamse available first), the started
        //   connection future is spawned into the runtime to complete,
        //   and then be inserted into the pool as an idle connection.
        let checkout = self.pool.checkout(pool_key.clone());
        let connect = self.connect_to(uri, pool_key);

        let executor = self.conn_builder.exec.clone();
        checkout
            // The order of the `select` is depended on below...
            .select2(connect)
            .map(move |either| match either {
                // Checkout won, connect future may have been started or not.
                //
                // If it has, let it finish and insert back into the pool,
                // so as to not waste the socket...
                Either::A((checked_out, connecting)) => {
                    // This depends on the `select` above having the correct
                    // order, such that if the checkout future were ready
                    // immediately, the connect future will never have been
                    // started.
                    //
                    // If it *wasn't* ready yet, then the connect future will
                    // have been started...
                    if connecting.started() {
                        let bg = connecting
                            .map(|_pooled| {
                                // dropping here should just place it in
                                // the Pool for us...
                            })
                            .map_err(|err| {
                                trace!("background connect error: {}", err);
                            });
                        // An execute error here isn't important, we're just trying
                        // to prevent a waste of a socket...
                        let _ = executor.execute(bg);
                    }
                    checked_out
                },
                // Connect won, checkout can just be dropped.
                Either::B((connected, _checkout)) => {
                    connected
                },
            })
            .or_else(|either| match either {
                // Either checkout or connect could get canceled:
                //
                // 1. Connect is canceled if this is HTTP/2 and there is
                //    an outstanding HTTP/2 connecting task.
                // 2. Checkout is canceled if the pool cannot deliver an
                //    idle connection reliably.
                //
                // In both cases, we should just wait for the other future.
                Either::A((err, connecting)) => {
                    if err.is_canceled() {
                        Either::A(Either::A(connecting.map_err(ClientError::Normal)))
                    } else {
                        Either::B(future::err(ClientError::Normal(err)))
                    }
                },
                Either::B((err, checkout)) => {
                    if err.is_canceled() {
                        Either::A(Either::B(checkout.map_err(ClientError::Normal)))
                    } else {
                        Either::B(future::err(ClientError::Normal(err)))
                    }
                }
            })
    }

    fn connect_to(&self, uri: Uri, pool_key: PoolKey)
        -> impl Lazy<Item=Pooled<PoolClient<B>>, Error=::Error>
    {
        let executor = self.conn_builder.exec.clone();
        let pool = self.pool.clone();
        let mut conn_builder = self.conn_builder.clone();
        let ver = self.config.ver;
        let is_ver_h2 = ver == Ver::Http2;
        let connector = self.connector.clone();
        let dst = Destination {
            uri,
        };
        hyper_lazy(move || {
            // Try to take a "connecting lock".
            //
            // If the pool_key is for HTTP/2, and there is already a
            // connection being estabalished, then this can't take a
            // second lock. The "connect_to" future is Canceled.
            let connecting = match pool.connecting(&pool_key, ver) {
                Some(lock) => lock,
                None => {
                    let canceled = ::Error::new_canceled().with("HTTP/2 connection in progress");
                    return Either::B(future::err(canceled));
                }
            };
            Either::A(connector.connect(dst)
                .map_err(::Error::new_connect)
                .and_then(move |(io, connected)| {
                    // If ALPN is h2 and we aren't http2_only already,
                    // then we need to convert our pool checkout into
                    // a single HTTP2 one.
                    let connecting = if connected.alpn == Alpn::H2 && !is_ver_h2 {
                        match connecting.alpn_h2(&pool) {
                            Some(lock) => {
                                trace!("ALPN negotiated h2, updating pool");
                                lock
                            },
                            None => {
                                // Another connection has already upgraded,
                                // the pool checkout should finish up for us.
                                let canceled = ::Error::new_canceled().with("ALPN upgraded to HTTP/2");
                                return Either::B(future::err(canceled));
                            }
                        }
                    } else {
                        connecting
                    };
                    let is_h2 = is_ver_h2 || connected.alpn == Alpn::H2;
                    Either::A(conn_builder
                        .http2_only(is_h2)
                        .handshake(io)
                        .and_then(move |(tx, conn)| {
                            trace!("handshake complete, spawning background dispatcher task");
                            let bg = executor.execute(conn.map_err(|e| {
                                debug!("client connection error: {}", e)
                            }));

                            // This task is critical, so an execute error
                            // should be returned.
                            if let Err(err) = bg {
                                warn!("error spawning critical client task: {}", err);
                                return Either::A(future::err(err));
                            }

                            // Wait for 'conn' to ready up before we
                            // declare this tx as usable
                            Either::B(tx.when_ready())
                        })
                        .map(move |tx| {
                            pool.pooled(connecting, PoolClient {
                                conn_info: connected,
                                tx: if is_h2 {
                                    PoolTx::Http2(tx.into_http2())
                                } else {
                                    PoolTx::Http1(tx)
                                },
                            })
                        }))
                }))
        })
    }
}

impl<C, B> Clone for Client<C, B> {
    fn clone(&self) -> Client<C, B> {
        Client {
            config: self.config.clone(),
            conn_builder: self.conn_builder.clone(),
            connector: self.connector.clone(),
            pool: self.pool.clone(),
        }
    }
}

impl<C, B> fmt::Debug for Client<C, B> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.debug_struct("Client")
            .finish()
    }
}

/// A `Future` that will resolve to an HTTP Response.
///
/// This is returned by `Client::request` (and `Client::get`).
#[must_use = "futures do nothing unless polled"]
pub struct ResponseFuture {
    inner: Box<dyn Future<Item=Response<Body>, Error=::Error> + Send>,
}

impl ResponseFuture {
    fn new(fut: Box<dyn Future<Item=Response<Body>, Error=::Error> + Send>) -> Self {
        Self {
            inner: fut,
        }
    }

    fn error_version(ver: Version) -> Self {
        warn!("Request has unsupported version \"{:?}\"", ver);
        ResponseFuture::new(Box::new(future::err(::Error::new_user_unsupported_version())))
    }
}

impl fmt::Debug for ResponseFuture {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.pad("Future<Response>")
    }
}

impl Future for ResponseFuture {
    type Item = Response<Body>;
    type Error = ::Error;

    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
        self.inner.poll()
    }
}

// FIXME: allow() required due to `impl Trait` leaking types to this lint
#[allow(missing_debug_implementations)]
struct PoolClient<B> {
    conn_info: Connected,
    tx: PoolTx<B>,
}

enum PoolTx<B> {
    Http1(conn::SendRequest<B>),
    Http2(conn::Http2SendRequest<B>),
}

impl<B> PoolClient<B> {
    fn poll_ready(&mut self) -> Poll<(), ::Error> {
        match self.tx {
            PoolTx::Http1(ref mut tx) => tx.poll_ready(),
            PoolTx::Http2(_) => Ok(Async::Ready(())),
        }
    }

    fn is_http1(&self) -> bool {
        !self.is_http2()
    }

    fn is_http2(&self) -> bool {
        match self.tx {
            PoolTx::Http1(_) => false,
            PoolTx::Http2(_) => true,
        }
    }

    fn is_ready(&self) -> bool {
        match self.tx {
            PoolTx::Http1(ref tx) => tx.is_ready(),
            PoolTx::Http2(ref tx) => tx.is_ready(),
        }
    }

    fn is_closed(&self) -> bool {
        match self.tx {
            PoolTx::Http1(ref tx) => tx.is_closed(),
            PoolTx::Http2(ref tx) => tx.is_closed(),
        }
    }
}

impl<B: Payload + 'static> PoolClient<B> {
    fn send_request_retryable(&mut self, req: Request<B>) -> impl Future<Item = Response<Body>, Error = (::Error, Option<Request<B>>)>
    where
        B: Send,
    {
        match self.tx {
            PoolTx::Http1(ref mut tx) => Either::A(tx.send_request_retryable(req)),
            PoolTx::Http2(ref mut tx) => Either::B(tx.send_request_retryable(req)),
        }
    }
}

impl<B> Poolable for PoolClient<B>
where
    B: Send + 'static,
{
    fn is_open(&self) -> bool {
        match self.tx {
            PoolTx::Http1(ref tx) => tx.is_ready(),
            PoolTx::Http2(ref tx) => tx.is_ready(),
        }
    }

    fn reserve(self) -> Reservation<Self> {
        match self.tx {
            PoolTx::Http1(tx) => {
                Reservation::Unique(PoolClient {
                    conn_info: self.conn_info,
                    tx: PoolTx::Http1(tx),
                })
            },
            PoolTx::Http2(tx) => {
                let b = PoolClient {
                    conn_info: self.conn_info.clone(),
                    tx: PoolTx::Http2(tx.clone()),
                };
                let a = PoolClient {
                    conn_info: self.conn_info,
                    tx: PoolTx::Http2(tx),
                };
                Reservation::Shared(a, b)
            }
        }
    }

    fn can_share(&self) -> bool {
        self.is_http2()
    }
}

// FIXME: allow() required due to `impl Trait` leaking types to this lint
#[allow(missing_debug_implementations)]
enum ClientError<B> {
    Normal(::Error),
    Canceled {
        connection_reused: bool,
        req: Request<B>,
        reason: ::Error,
    }
}

impl<B> ClientError<B> {
    fn map_with_reused(conn_reused: bool)
        -> impl Fn((::Error, Option<Request<B>>)) -> Self
    {
        move |(err, orig_req)| {
            if let Some(req) = orig_req {
                ClientError::Canceled {
                    connection_reused: conn_reused,
                    reason: err,
                    req,
                }
            } else {
                ClientError::Normal(err)
            }
        }
    }
}

/// A marker to identify what version a pooled connection is.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
enum Ver {
    Auto,
    Http2,
}

fn origin_form(uri: &mut Uri) {
    let path = match uri.path_and_query() {
        Some(path) if path.as_str() != "/" => {
            let mut parts = ::http::uri::Parts::default();
            parts.path_and_query = Some(path.clone());
            Uri::from_parts(parts).expect("path is valid uri")
        },
        _none_or_just_slash => {
            debug_assert!(Uri::default() == "/");
            Uri::default()
        }
    };
    *uri = path
}

fn absolute_form(uri: &mut Uri) {
    debug_assert!(uri.scheme_part().is_some(), "absolute_form needs a scheme");
    debug_assert!(uri.authority_part().is_some(), "absolute_form needs an authority");
    // If the URI is to HTTPS, and the connector claimed to be a proxy,
    // then it *should* have tunneled, and so we don't want to send
    // absolute-form in that case.
    if uri.scheme_part() == Some(&Scheme::HTTPS) {
        origin_form(uri);
    }
}

fn authority_form(uri: &mut Uri) {
    if log_enabled!(::log::Level::Warn) {
        if let Some(path) = uri.path_and_query() {
            // `https://hyper.rs` would parse with `/` path, don't
            // annoy people about that...
            if path != "/" {
                warn!(
                    "HTTP/1.1 CONNECT request stripping path: {:?}",
                    path
                );
            }
        }
    }
    *uri = match uri.authority_part() {
        Some(auth) => {
            let mut parts = ::http::uri::Parts::default();
            parts.authority = Some(auth.clone());
            Uri::from_parts(parts).expect("authority is valid")
        },
        None => {
            unreachable!("authority_form with relative uri");
        }
    };
}

fn extract_domain(uri: &mut Uri, is_http_connect: bool) -> ::Result<String> {
    let uri_clone = uri.clone();
    match (uri_clone.scheme_part(), uri_clone.authority_part()) {
        (Some(scheme), Some(auth)) => {
            Ok(format!("{}://{}", scheme, auth))
        }
        (None, Some(auth)) if is_http_connect => {
            let port = auth.port_part();
            let scheme = match port.as_ref().map(|p| p.as_str()) {
                Some("443") => {
                    set_scheme(uri, Scheme::HTTPS);
                    "https"
                }
                _ => {
                    set_scheme(uri, Scheme::HTTP);
                    "http"
                },
            };
            Ok(format!("{}://{}", scheme, auth))
        },
        _ => {
            debug!("Client requires absolute-form URIs, received: {:?}", uri);
            Err(::Error::new_user_absolute_uri_required())
        }
    }
}

fn set_scheme(uri: &mut Uri, scheme: Scheme) {
    debug_assert!(uri.scheme_part().is_none(), "set_scheme expects no existing scheme");
    let old = mem::replace(uri, Uri::default());
    let mut parts: ::http::uri::Parts = old.into();
    parts.scheme = Some(scheme);
    parts.path_and_query = Some("/".parse().expect("slash is a valid path"));
    *uri = Uri::from_parts(parts).expect("scheme is valid");
}

/// A builder to configure a new [`Client`](Client).
///
/// # Example
///
/// ```
/// # extern crate hyper;
/// # #[cfg(feature  = "runtime")]
/// # fn run () {
/// use hyper::Client;
///
/// let client = Client::builder()
///     .keep_alive(true)
///     .http2_only(true)
///     .build_http();
/// # let infer: Client<_, hyper::Body> = client;
/// # drop(infer);
/// # }
/// # fn main() {}
/// ```
#[derive(Clone)]
pub struct Builder {
    client_config: Config,
    conn_builder: conn::Builder,
    pool_config: pool::Config,
}

impl Default for Builder {
    fn default() -> Self {
        Self {
            client_config: Config {
                retry_canceled_requests: true,
                set_host: true,
                ver: Ver::Auto,
            },
            conn_builder: conn::Builder::new(),
            pool_config: pool::Config {
                enabled: true,
                keep_alive_timeout: Some(Duration::from_secs(90)),
                max_idle_per_host: ::std::usize::MAX,
            },
        }
    }
}

impl Builder {
    /// Enable or disable keep-alive mechanics.
    ///
    /// Default is enabled.
    #[inline]
    pub fn keep_alive(&mut self, val: bool) -> &mut Self {
        self.pool_config.enabled = val;
        self
    }

    /// Set an optional timeout for idle sockets being kept-alive.
    ///
    /// Pass `None` to disable timeout.
    ///
    /// Default is 90 seconds.
    #[inline]
    pub fn keep_alive_timeout<D>(&mut self, val: D) -> &mut Self
    where
        D: Into<Option<Duration>>,
    {
        self.pool_config.keep_alive_timeout = val.into();
        self
    }

    /// Set whether HTTP/1 connections should try to use vectored writes,
    /// or always flatten into a single buffer.
    ///
    /// Note that setting this to false may mean more copies of body data,
    /// but may also improve performance when an IO transport doesn't
    /// support vectored writes well, such as most TLS implementations.
    ///
    /// Default is `true`.
    #[inline]
    pub fn http1_writev(&mut self, val: bool) -> &mut Self {
        self.conn_builder.h1_writev(val);
        self
    }

    /// Sets the exact size of the read buffer to *always* use.
    ///
    /// Note that setting this option unsets the `http1_max_buf_size` option.
    ///
    /// Default is an adaptive read buffer.
    #[inline]
    pub fn http1_read_buf_exact_size(&mut self, sz: usize) -> &mut Self {
        self.conn_builder.h1_read_buf_exact_size(Some(sz));
        self
    }

    /// Set the maximum buffer size for the connection.
    ///
    /// Default is ~400kb.
    ///
    /// Note that setting this option unsets the `http1_read_exact_buf_size` option.
    ///
    /// # Panics
    ///
    /// The minimum value allowed is 8192. This method panics if the passed `max` is less than the minimum.
    #[inline]
    pub fn http1_max_buf_size(&mut self, max: usize) -> &mut Self {
        self.conn_builder.h1_max_buf_size(max);
        self
    }

    /// Set whether HTTP/1 connections will write header names as title case at
    /// the socket level.
    ///
    /// Note that this setting does not affect HTTP/2.
    ///
    /// Default is false.
    pub fn http1_title_case_headers(&mut self, val: bool) -> &mut Self {
        self.conn_builder.h1_title_case_headers(val);
        self
    }

    /// Set whether the connection **must** use HTTP/2.
    ///
    /// The destination must either allow HTTP2 Prior Knowledge, or the
    /// `Connect` should be configured to do use ALPN to upgrade to `h2`
    /// as part of the connection process. This will not make the `Client`
    /// utilize ALPN by itself.
    ///
    /// Note that setting this to true prevents HTTP/1 from being allowed.
    ///
    /// Default is false.
    pub fn http2_only(&mut self, val: bool) -> &mut Self {
        self.client_config.ver = if val {
            Ver::Http2
        } else {
            Ver::Auto
        };
        self
    }

    /// Sets the [`SETTINGS_INITIAL_WINDOW_SIZE`][spec] option for HTTP2
    /// stream-level flow control.
    ///
    /// Default is 65,535
    ///
    /// [spec]: https://http2.github.io/http2-spec/#SETTINGS_INITIAL_WINDOW_SIZE
    pub fn http2_initial_stream_window_size(&mut self, sz: impl Into<Option<u32>>) -> &mut Self {
        self.conn_builder.http2_initial_stream_window_size(sz.into());
        self
    }

    /// Sets the max connection-level flow control for HTTP2
    ///
    /// Default is 65,535
    pub fn http2_initial_connection_window_size(&mut self, sz: impl Into<Option<u32>>) -> &mut Self {
        self.conn_builder.http2_initial_connection_window_size(sz.into());
        self
    }

    /// Sets the maximum idle connection per host allowed in the pool.
    ///
    /// Default is `usize::MAX` (no limit).
    pub fn max_idle_per_host(&mut self, max_idle: usize) -> &mut Self {
        self.pool_config.max_idle_per_host = max_idle;
        self
    }

    /// Set whether to retry requests that get disrupted before ever starting
    /// to write.
    ///
    /// This means a request that is queued, and gets given an idle, reused
    /// connection, and then encounters an error immediately as the idle
    /// connection was found to be unusable.
    ///
    /// When this is set to `false`, the related `ResponseFuture` would instead
    /// resolve to an `Error::Cancel`.
    ///
    /// Default is `true`.
    #[inline]
    pub fn retry_canceled_requests(&mut self, val: bool) -> &mut Self {
        self.client_config.retry_canceled_requests = val;
        self
    }

    /// Set whether to automatically add the `Host` header to requests.
    ///
    /// If true, and a request does not include a `Host` header, one will be
    /// added automatically, derived from the authority of the `Uri`.
    ///
    /// Default is `true`.
    #[inline]
    pub fn set_host(&mut self, val: bool) -> &mut Self {
        self.client_config.set_host = val;
        self
    }

    /// Provide an executor to execute background `Connection` tasks.
    pub fn executor<E>(&mut self, exec: E) -> &mut Self
    where
        E: Executor<Box<dyn Future<Item=(), Error=()> + Send>> + Send + Sync + 'static,
    {
        self.conn_builder.executor(exec);
        self
    }

    /// Builder a client with this configuration and the default `HttpConnector`.
    #[cfg(feature = "runtime")]
    pub fn build_http<B>(&self) -> Client<HttpConnector, B>
    where
        B: Payload + Send,
        B::Data: Send,
    {
        let mut connector = HttpConnector::new(4);
        if self.pool_config.enabled {
            connector.set_keepalive(self.pool_config.keep_alive_timeout);
        }
        self.build(connector)
    }

    /// Combine the configuration of this builder with a connector to create a `Client`.
    pub fn build<C, B>(&self, connector: C) -> Client<C, B>
    where
        C: Connect,
        C::Transport: 'static,
        C::Future: 'static,
        B: Payload + Send,
        B::Data: Send,
    {
        Client {
            config: self.client_config,
            conn_builder: self.conn_builder.clone(),
            connector: Arc::new(connector),
            pool: Pool::new(self.pool_config, &self.conn_builder.exec),
        }
    }
}

impl fmt::Debug for Builder {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.debug_struct("Builder")
            .field("client_config", &self.client_config)
            .field("conn_builder", &self.conn_builder)
            .field("pool_config", &self.pool_config)
            .finish()
    }
}

#[cfg(test)]
mod unit_tests {
    use super::*;

    #[test]
    fn set_relative_uri_with_implicit_path() {
        let mut uri = "http://hyper.rs".parse().unwrap();
        origin_form(&mut uri);
        assert_eq!(uri.to_string(), "/");
    }

    #[test]
    fn test_origin_form() {
        let mut uri = "http://hyper.rs/guides".parse().unwrap();
        origin_form(&mut uri);
        assert_eq!(uri.to_string(), "/guides");

        let mut uri = "http://hyper.rs/guides?foo=bar".parse().unwrap();
        origin_form(&mut uri);
        assert_eq!(uri.to_string(), "/guides?foo=bar");
    }

    #[test]
    fn test_absolute_form() {
        let mut uri = "http://hyper.rs/guides".parse().unwrap();
        absolute_form(&mut uri);
        assert_eq!(uri.to_string(), "http://hyper.rs/guides");

        let mut uri = "https://hyper.rs/guides".parse().unwrap();
        absolute_form(&mut uri);
        assert_eq!(uri.to_string(), "/guides");
    }

    #[test]
    fn test_authority_form() {
        extern crate pretty_env_logger;
        let _ = pretty_env_logger::try_init();

        let mut uri = "http://hyper.rs".parse().unwrap();
        authority_form(&mut uri);
        assert_eq!(uri.to_string(), "hyper.rs");

        let mut uri = "hyper.rs".parse().unwrap();
        authority_form(&mut uri);
        assert_eq!(uri.to_string(), "hyper.rs");
    }

    #[test]
    fn test_extract_domain_connect_no_port() {
        let mut uri = "hyper.rs".parse().unwrap();
        let domain = extract_domain(&mut uri, true).expect("extract domain");
        assert_eq!(domain, "http://hyper.rs");
    }
}