When instrumenting resources in Tokio, a span is created for each
resource. Previously, all resources inherited the currently active span
as their parent (tracing default). However, this would keep that parent
span alive until the resource (and its span) were dropped. This is often
not correct, as a resource may be created in a task and then sent
elsewhere, while the originating task ends.
This artificial extension of the parent span's lifetime would make it
look like that task was still alive (but idle) in any system reading the
tracing instrumentation in Tokio, for example Tokio Console as reported
in tokio-rs/console#345.
In #6107, most of the existing resource spans were updated to
make them explicit roots, so they have no contextual parent. However,
2. were missed:
- `Sleep`
- `BatchSemaphore`
This change alters the resource spans for those 2 resources to also make
them explicit roots.
To enable unstable features in Tokio, passing `--cfg tokio_unstable` to
the compiler is necessary. We document how to do this in a variety of
ways in the main Tokio (lib.rs) documentation.
One way is to add a `[build]` section to the file `.cargo/config.toml`.
Even though this filename is stated in the documentation, it is quite
common that first time users (including this author, some time ago) put
it in their `Cargo.toml` file instead.
This change adds a "warning" section to the documentation to reiterate
the point that this section doesn't go in the cargo manifest
(`Cargo.toml`).
On my machine, any test that calls `is_pidfd_available` fails as my
kernel string does not contain a '-'; the code expects there to be one.
Fix the test so that is works regardless on whether the kernel string
contains a '-'.
This impl had a bound on `StreamReader<S, E>`; this is incorrect
because:
- The second generic parameter to `StreamReader` is not an error type;
it's a buffer type.
- The `Stream` error type in `StreamReader` should not need to be the
same as the `Sink` error type.
This "passthrough" `Sink` impl was effectively unusable because it
required the `Sink` error type be the same as the `StreamReader` buffer
type.
Resolve this by allowing the `StreamReader` buffer to be anything in
this impl.
