Provides a middleware that immediately fails any request if the
underlying service isn't ready yet. This is useful when used in
conjunction with `InFlightLimit` or others, so that requests are
rejected immediately, instead of keeping track of extra pending
requests.
This patch adds a new type, `Pool`, which wraps a
`tower_balance::Balance` and a `tower_service::NewService` together so
that new `Service` instances are added when load is high, and removed
again if load is low.
The pool uses an exponentially weighted moving average of successful
calls to `poll_ready` on the underlying `Balance` to estimate whether
there are enough services available. If `poll_ready` frequently returns
`NotReady`, then a new service is produced, whereas if `poll_ready`
pretty much never returns `NotReady`, the most recently added service is
removed from the pool (down to a minimum of 1).
Add the `CallAll` combinator, which provides:
```rust
Stream<Item = Request> + Service<Request> => Stream<Item = Response>
```
That is, given a `Stream` of requests and a `Service` that can accept
those requests, it produces a `Stream` of the corresponding responses.
This patch does not migrate tower-filter to use an error type of
Box<Error>. Instead, it defines a new type that optionally contains
a Box<Error>.
The filter layer can be used as part of routing. The router would
sequentially attempt to dispatch a request to an inner service. If
the request is rejected, it attempts the next one. In this case, allocating
a Box<Error> for each attempt is not great.
This strategy still fits within the greater picture. tower_filter::error::Error
implements the error trait, which means that all other layers that take
T: Into<Error> will still work with Filter. Also, only the immediate caller
of Filter should care about rejection errors. In which case, Filter will be
referenced explicitly.
Refs: #131
This change introduces the new `tower-layer` crate and the foundational `Layer` trait to go along with it. This trait allows one to easily compose a set of `Service`s that take an inner service. These services only modify the request/response. This also provides the `Layer` implementation for many of the tower crates.
This updates the `Service` contract requiring `poll_ready` to be called
before `call`. This allows `Service::call` to panic in the event the
user of the service omits `poll_ready` or does not wait until `Ready` is
observed.
This adds the inital base tower crate, as of right now it contains
nothing and is only needed to ensure that cargo workspaces can
properly compile with rust 1.32.
See also rust-lang/rust#57524. Previously, the examples were
never even compiled.
In the past, any errors thrown by a `Service` wrapped in a
`tower_buffer::Buffer` were silently swallowed, and the handles were
simply informed that the connection to the `Service` was closed.
This patch captures errors from a wrapped `Service`, and communicates
that error to all pending and future requests. It does so by wrapping up
the error in an `Arc`, which is sent to all pending `oneshot` request
channels, and is stored in a shared location so that future requests
will see the error when their send to the `Worker` fail.
Note that this patch also removes the `open` field from `State`, as it
is no longer necessary following #120, since bounded channels have a
`try_ready` method we can rely on instead.
Note that this change is not entirely backwards compatible -- the error
type for a `Service` that is wrapped in `Buffer` must now be `Send +
Sync` so that it can safely be communicated back to callers.
Furthermore, `tower_buffer::Error::Closed` now contains the error that
the failed `Service` produced, which may trip up old code.
Carl Lerche
Lucio Franco
Sean McArthur
Jon Gjengset
Stefano Probst
David Barsky
Ty Coghlan