Expand docs/examples for TCP `set_nonblocking` methods. #45227

frewsxcv · 2017-10-12T02:37:24Z

Part of #44050.

rust-highfive · 2017-10-12T02:37:27Z

(rust_highfive has picked a reviewer for you, use r? to override)

sfackler · 2017-10-12T06:04:57Z

src/libstd/net/tcp.rs

+    /// This will result in `read`, `write`, `recv` and `send` operations
+    /// becoming nonblocking, i.e. immediately returning from their calls.
+    /// If the IO operation is successful, `Ok` is returned and no further
+    /// action is required. If the IO operation is pending, an error with kind


Saying that the operation is pending might be a bit misleading - WouldBlock means that the request couldn't be satisfied at that moment and you need to retry later. It's not the case that the operation's been queued up and will eventually finish.

thanks for mentioning this, was a little confused how it worked behind the scenes. i addressed it in 6c20fe5 but let me know if you know a better way of wording it

kennytm · 2017-10-12T06:48:34Z

src/libstd/net/tcp.rs

+    ///     };
+    /// };
+    /// println!("number of bytes read: {}", num_bytes_read);
+    /// println!("bytes: {:?}", buf);`


tbu- · 2017-10-12T09:37:12Z

src/libstd/net/tcp.rs

+    /// [`io::ErrorKind::WouldBlock`] is returned.
+    ///
+    /// On Unix platforms, calling this method corresponds to calling `fcntl`.
+    /// On Windows calling this method corresponds to calling `ioctlsocket`.


It is somewhat import to specify which fcntl or ioctlsocket is used, both fcntl and ioctlsocket are some kind of "catch-all" syscall that can do wildly differing things. The fcntl FIONBIO is used on Unix platforms and the ioctlsocket FIONBIO is used on Windows.

addressed in c978e73

frewsxcv · 2017-10-14T02:33:32Z

all comments have been addressed, let me know if y'all see anything else

EDIT: i'll squash before review approval

tbu- · 2017-10-14T02:36:30Z

LGTM

sfackler · 2017-10-16T03:47:52Z

src/libstd/net/tcp.rs

    ///
    /// # Examples
    ///
+    /// *Note: the usage of [busy-looping] in the following example is used


I feel kind of conflicted about these examples. We don't want to get too far down the epoll/IOCP rabbit hole, but it seems pretty bad for the example here to be a thing you should never do. We could maybe have some fake wait_for_more_data() function and add something like "typically implemented via platform-specific APIs such as epoll or IOCP" into the docs?

is this sorta what you mean?

diff --git a/src/libstd/net/tcp.rs b/src/libstd/net/tcp.rs index 51269d57e6..946584bcf2 100644 --- a/src/libstd/net/tcp.rs +++ b/src/libstd/net/tcp.rs @@ -529,7 +529,10 @@ impl TcpStream { /// let num_bytes_read = loop { /// match stream.read_to_end(&mut buf) { /// Ok(b) => break b, - /// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => (), + /// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => { + /// wait_for_fd(); // typically implemented via platform-specific + /// // APIs such as epoll or IOCP + /// } /// Err(e) => panic!("encountered IO error: {}", e), /// }; /// }; @@ -839,13 +842,20 @@ impl TcpListener { /// for stream in listener.incoming() { /// let mut stream = match stream { /// Ok(s) => s, - /// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => continue, + /// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => { + /// wait_for_more_data(); // typically implemented via platform-specific + /// // APIs such as epoll or IOCP + /// continue; + /// } /// Err(e) => panic!("encountered IO error: {}", e), /// }; /// loop { /// match stream.write_all(b"foo") { /// Ok(()) => break, - /// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => (), + /// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => { + /// wait_for_fd(); // typically implemented via platform-specific + /// // APIs such as epoll or IOCP + /// } /// Err(e) => panic!("encountered IO error: {}", e), /// }; /// }

Yeah, something like that seems better than nothing.

frewsxcv · 2017-10-20T01:23:10Z

@sfackler latest commit should hopefully address your concerns.

i also removed the note about busy-looping now that i've added in wait_for_fd();, since afaik, this is no longer busy-looping

sfackler · 2017-10-20T01:49:10Z

src/libstd/net/tcp.rs

+    ///         Err(e) => panic!("encountered IO error: {}", e),
+    ///     };
+    ///     loop {
+    ///         match stream.write_all(b"foo") {


write_all isn't going to behave properly in a nonblocking world. If fo was successfully written but we hit a WouldBlock finishing the o, everything will be sent again the next round.

We'd also need to set the stream to nonblocking mode for the WouldBlock case to come up in the first place.

sfackler · 2017-10-20T01:49:25Z

src/libstd/net/tcp.rs

    /// listener.set_nonblocking(true).expect("Cannot set non-blocking");
+    ///
+    /// # fn wait_for_fd() { unimplemented!() }
+    /// for stream in listener.incoming() {


Would it be simpler to just open a socket and write to it rather than also including a listener?

this doc comment is forTcpListener::set_nonblocking, so it made sense for me to include the listener. can you expand on what you mean?

unless you're saying i shouldn't write to the stream. i could just read from it and print out the result. i'd also avoid the write_all thing from your other comment

Oh derp, sorry. I was thinking this was on write for some reason...

sfackler · 2017-10-20T23:58:51Z

src/libstd/net/tcp.rs

+    /// # fn wait_for_fd() { unimplemented!() }
+    /// let mut buf = vec![];
+    /// let num_bytes_read = loop {
+    ///     match stream.read_to_end(&mut buf) {


One last thing (sorry!) - num_bytes_read will only contain the number of bytes read on the final call, so we probably shouldn't save it here.

no reason to be sorry! i feel bad i'm dragging this on for you 😬

sfackler · 2017-10-21T00:20:05Z

src/libstd/net/tcp.rs

@@ -780,17 +808,59 @@ impl TcpListener {

    /// Moves this TCP stream into or out of nonblocking mode.
    ///
-    /// On Unix this corresponds to calling fcntl, and on Windows this
-    /// corresponds to calling ioctlsocket.
+    /// This will result in `read`, `write`, `recv` and `send` operations


accept here since it's a listener.

sfackler · 2017-10-21T00:20:36Z

src/libstd/net/tcp.rs

+    ///     stream.set_nonblocking(true);
+    ///     let mut buf = vec![];
+    ///     loop {
+    ///         match stream.read_to_end(&mut buf) {


This got added back?

before i was doing tcp writing, this is now doing tcp reading to avoid deadling with the write_all issue. i can remove reading/writing altogether and just grab the stream from the listener, which might make things simpler but not as realistic, but i'm not opposed

One option is something like Ok(s) => handle_connection(s).

sfackler · 2017-10-21T03:09:39Z

Looks good! Can you squash down to a single commit? r=me otherwise.

kennytm · 2017-10-21T05:39:54Z

src/libstd/net/tcp.rs

+    ///     match stream {
+    ///         Ok(s) => {
+    ///             // do something with the TcpStream
+    ///             handle_connection(s),


The , should be a ;.

[01:04:21] ---- net/tcp.rs - net::tcp::TcpListener::set_nonblocking (line 826) stdout ---- [01:04:21] error: expected one of `.`, `;`, `?`, `}`, or an operator, found `,` [01:04:21] --> net/tcp.rs:16:33 [01:04:21] | [01:04:21] 16 | handle_connection(s), [01:04:21] | ^ expected one of `.`, `;`, `?`, `}`, or an operator here [01:04:21] [01:04:21] thread 'rustc' panicked at 'couldn't compile the test', /checkout/src/librustdoc/test.rs:287:12 [01:04:21] note: Run with `RUST_BACKTRACE=1` for a backtrace. [01:04:21] [01:04:21] [01:04:21] failures: [01:04:21] net/tcp.rs - net::tcp::TcpListener::set_nonblocking (line 826)

Part of rust-lang#44050.

frewsxcv · 2017-10-21T12:58:49Z

thanks for your patience and insight @sfackler ❤️

@bors r=sfackler rollup

bors · 2017-10-21T12:58:50Z

📌 Commit fe3ed20 has been approved by sfackler

…r=sfackler Expand docs/examples for TCP `set_nonblocking` methods. Part of rust-lang#44050.

Rollup of 6 pull requests - Successful merges: #45227, #45356, #45407, #45411, #45418, #45419 - Failed merges: #45421

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frewsxcv force-pushed the frewsxcv-set-nonblocking branch from 9c233ee to 8f0b531 Compare October 12, 2017 02:39

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Improve documentation for TcpStream::set_nonblocking #44050

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Expand docs/examples for TCP set_nonblocking methods.

fe3ed20

Part of rust-lang#44050.

frewsxcv force-pushed the frewsxcv-set-nonblocking branch from 439391d to fe3ed20 Compare October 21, 2017 10:13

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kennytm removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Oct 21, 2017

kennytm added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Oct 21, 2017

frewsxcv added a commit to frewsxcv/rust that referenced this pull request Oct 21, 2017

Rollup merge of rust-lang#45227 - frewsxcv:frewsxcv-set-nonblocking, …

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…r=sfackler Expand docs/examples for TCP `set_nonblocking` methods. Part of rust-lang#44050.

frewsxcv mentioned this pull request Oct 21, 2017

Rollup of 6 pull requests #45430

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Auto merge of #45430 - frewsxcv:rollup, r=frewsxcv

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Rollup of 6 pull requests - Successful merges: #45227, #45356, #45407, #45411, #45418, #45419 - Failed merges: #45421

bors merged commit fe3ed20 into rust-lang:master Oct 21, 2017

frewsxcv deleted the frewsxcv-set-nonblocking branch October 21, 2017 16:41

frewsxcv mentioned this pull request Dec 11, 2017

Clarify which TcpStream methods won't work in non-blocking mode #46597

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Expand docs/examples for TCP `set_nonblocking` methods. #45227

Expand docs/examples for TCP `set_nonblocking` methods. #45227

frewsxcv commented Oct 12, 2017

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Expand docs/examples for TCP set_nonblocking methods. #45227

Expand docs/examples for TCP set_nonblocking methods. #45227

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Expand docs/examples for TCP `set_nonblocking` methods. #45227

Expand docs/examples for TCP `set_nonblocking` methods. #45227

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