Current documentation of `sync::watch::Sender::send` may be intepreted
as the method failing if at some point in past the channel has been
closed because every receiver has been dropped. This isn't true,
however, as the channel could have been reopened by using
`sync::watch::Sender::subscribe`.
This fix clarifies the behavior. Moreover, it is noted that on failure,
the value isn't made available to future subscribers (but returned as
part of the `SendError`).
Fixes#4957.
For historical reasons, the current-thread runtime's scheduler was named
BasicScheduler and the multi-thread runtime's scheduler were named
ThreadPool. This patch renames the schedulers to mirror the runtime
names to increase consistency. This patch also moves the scheduler
implementations into a new `runtime::scheduler` module.
This patch moves the I/O driver into the runtime module. The I/O driver
is a runtime concern and is only used by the runtime. Moving the driver
is the first step to cleaning up some Tokio internals. There will be
follow-up patches that integrate the I/O driver and other runtime concerns
more closely.
Because `Interest` and `Ready` are public APIs, they were moved to the
top-level `io` module instead of moving the types to `runtime`.
This is an internal refactor and should not impact any public APIs.
The multi-threaded scheduler includes a per-worker LIFO slot to
store the last scheduled task. This can improve certain usage patterns,
especially message passing between tasks. However, this LIFO slot is not
currently stealable.
Eventually, the LIFO slot **will** become stealable. However, as a
stop-gap, this unstable option lets users disable the LIFO task when
doing so improves their application's overall performance.
Refs: #4941
The command to build the documentation locally provided in the
Contribution Guide did not work for all crates in the project workspace.
Specifically, to build the docs for `tokio-stream` the flag `--cfg
docsrs` needs to be in the environment variable `RUSTFLAGS` in addition
to being in `RUSTDOCFLAGS`.
Additionally, there was text describing that the docs cannot be built
from the root of the workspace with a link to rust-lang/cargo#9274. That
issue has since been closed as complete and the listed commands do now
work from the root of the workspace. As such, that text has been
removed.
The documentation for`PollEvented` had a single remaining reference to
`Registration::clear_read_ready`, which no longer exists. This change
updates the documentation to refer to `Registration::clear_readiness`
instead.
Upgrade the nightly to a version that works with all of miri,
cargo-hack, minimal-versions, and cargo-check-external-types.
This is a prerequisite for #4902.
The broadcast channel allows multiple senders to send messages to
multiple receivers, where each receiver receives messages starting from
when it subscribes. After all senders are dropped, the receivers will
continue to receive all waiting messages in the buffer and then receive
a `Closed` error.
To mark that a channel has closed, it stores two closed flags, one on
the channel level and another in the buffer slot *after* the last used
slot (this may also be the earliest entry being kept for lagged
receivers, see #2425).
However, we don't need both closed flags, keeping the channel level
closed flag is sufficient.
Without the slot level closed flag, each receiver receives each message
until it is up to date and for that receiver the channel is empty. Then,
the actual return message is chosen depending on the channel level
closed flag; if the channel is NOT closed, then `Empty` is returned, if
the channel is closed then `Closed` is returned instead.
With the modified logic, there is no longer a need to append a closed
token to the internal buffer (by setting the slot level closed flag on
the next slot). This fixes the off by one error described in #4814,
which caused a receiver which was created after the channel was already
closed to get `Empty` from `try_recv` (or hang forever when calling
`recv`) instead of receiving `Closed`.
As a bonus, we save a single `bool` on each buffer slot.
Refs: #4814
The contribution guide describes the Tokio code of conduct and gives a
list of steps to follow when contributing in different ways. In the
guide to contributing a pull request, commands are listed to be run by
the contributor locally to help ensure that the PR will pass on CI.
The command to run clippy isn't the same as the one run on CI,
specifically the command doesn't check the tests. This commit changes
the command to match the one on CI, so that tests are checked by clippy
as well.
As the [epoll documentation points out](https://man7.org/linux/man-pages/man7/epoll.7.html), a read that only partially fills a buffer is sufficient to show that the socket buffer has been drained.
We can take advantage of this by clearing readiness in this case, which seems to significantly improve performance under certain conditions.
Co-authored-by: Carl Lerche <[email protected]>
Noah Kennedy