The various background daemon tasks that `arti-client` used to spawn are
now handled inside their respective crates instead, with functions
provided to spawn them that return `TaskHandle`s.
This required introducing a new trait, `NetDirProvider`, which steals
some functionality from the `DirProvider` trait to enable `tor-circmgr`
to depend on it (`tor-circmgr` is a dependency of `tor-dirmgr`, so it
can't depend on `DirProvider` directly).
While we're at it, we also make some of the tasks wait for events from
the `NetDirProvider` instead of sleeping, slightly increasing
efficiency.
This is a revised version of !397; it implements a scheduling system for
periodic tasks that can be externally controlled, and then uses the
external control aspect to implement a basic dormant mode (#90).
More technically, the scheduling system consists of a `Stream` that
periodic tasks are expected to embed in a `while` loop or similar, a
way for tasks themselves to choose how long to wait until the stream
next yields a result, and a handle to control this outside of the task.
Currently, Arti doesn't need this. But once it does, it will be
way better to have a separate type for connected sockets, rather
than having to error-check every time somebody gives us a socket.
Part of #410
This makes using the `PreferredRuntime` the first-class option inside
`arti-client`, freeing users who don't want to think about runtimes from
having to do so.
`TorClient::create_unbootstrapped` and `builder` now automatically
use this runtime, leaving only `builder_custom` for users who wish to
manually specify a runtime.
This lets us clean up the docs a lot: mentions of using custom runtimes
are now relegated to nearer the end of the crate-level documentation,
and we mostly just link to `tor_rtcompat`'s docs to explain more there.
Instead, we take some more time to explain how you use the builder API
to create clients synchronously.
Other doc cleanups included getting rid of the explanation of `TorAddr`
in the main crate-level doc; this is already well-documented elsewhere,
and is something users should discover organically later.
fixes arti#326
`PreferredRuntime` is now an opaque wrapper struct that contains the
"actual" preferred runtime as a type alias. The `current_user_runtime`
and `create_runtime` functions become `PreferredRuntime::current` and
`PreferredRuntime::create`, respectively.
This removes the dependence on `impl Trait`, meaning we can now name the
returned runtime (yay!).
In addition, the documentation was cleaned up a bit to make it
(hopefully) flow better. Items that don't make sense to publicize, like
testing implementation details, have been marked #[doc(hidden)] and
semver warnings added.
This lint is IMO inherently ill-conceived.
I have looked for the reasons why this might be thought to be a good
idea and there were basically two (and they are sort of contradictory):
I. "Calling ‘.clone()` on an Rc, Arc, or Weak can obscure the fact
that only the pointer is being cloned, not the underlying data."
This is the wording from
https://rust-lang.github.io/rust-clippy/v0.0.212/#clone_on_ref_ptr
It is a bit terse; we are left to infer why it is a bad idea to
obscure this fact. It seems to me that if it is bad to obscure some
fact, that must be because the fact is a hazard. But why would it be
a hazard to not copy the underlying data ?
In other languages, faliing to copy the underlying data is a serious
correctness hazard. There is a whose class of bugs where things were
not copied, and then mutated and/or reused in multiple places in ways
that were not what the programmer intended. In my experience, this is
a very common bug when writing Python and Javascript. I'm told it's
common in golang too.
But in Rust this bug is much much harder to write. The data inside an
Arc is immutable. To have this bug you'd have use interior mutability
- ie mess around with Mutex or RefCell. That provides a good barrier
to these kind of accidents.
II. "The reason for writing Rc::clone and Arc::clone [is] to make it
clear that only the pointer is being cloned, as opposed to the
underlying data. The former is always fast, while the latter can
be very expensive depending on what is being cloned."
This is the reasoning found here
https://github.com/rust-lang/rust-clippy/issues/2048
This is saying that *not* using Arc::clone is hazardous.
Specifically, that a deep clone is a performance hazard.
But for this argument, the lint is precisely backwards. It's linting
the "good" case and asking for it to be written in a more explicit
way; while the supposedly bad case can be written conveniently.
Also, many objects (in our codebase, and in all the libraries we use)
that are Clone are in fact simply handles. They contain Arc(s) (or
similar) and are cheap to clone. Indeed, that is the usual case.
It does not make sense to distinguish in the syntax we use to clone
such a handle, whether the handle is a transparent Arc, or an opaque
struct containing one or more other handles.
Forcing Arc::clone to be written as such makes for code churn when a
type is changed from Arc<Something> to Something: Clone, or vice
versa.
Now all of the runtime types we provide all
impl<S> TlsProvider<S> where S: ...
rather than merely TlsProvider<Self::TcpStream>.
And we document and intent to perhaps require this in the future.
This makes our layout more similar to our other crates, and
successfully informs our grcov exclusion pattern that these tests
are indeed tests.
Doing this knocks down the reported coverage for the tor-rtcompat
crate, but that's okay: we hadn't earned it.
I hereby promise that this commit is only code-movement.
This took some refactoring, so that I wouldn't need to define 9
different versions of the function. It also required that we change
the behavior of test_with_all_runtimes slightly, so that it asserts
on _any_ failure rather than asserting on most but returning Err()
for others. That in turn required changes to a few of its callers.
There's probably a better way to do all of this macro business, but
this is the best I could find.
This commit puts the native-tls crate behind a feature. The feature
is off-by-default in the tor-rtcompat crate, but can be enabled
either from arti or arti-client.
There is an included script that I used to test that tor-rtcompat
could build and run its tests with all subsets of its features.
Closes#300
eta
Nick Mathewson
trinity-1686a
Ian Jackson
Ian Jackson