This makes all tower subcrates have the following lints as warn (rather
than allow): `missing_docs`, `rust_2018_idioms`, `unreachable_pub`, and
`missing_debug_implementations`. In addition, it consistently applies
`deny(warning)` *only* under CI so that deprecations and macro changes in minor
version bumps in dependencies will never cause `tower` crates to stop
compiling, and so that tests can be run even if not all warnings have been
dealt with. See also https://github.com/rust-unofficial/patterns/blob/master/anti_patterns/deny-warnings.md
Note that `tower-reconnect` has the `missing_docs` lint disabled for now
since it contained _no_ documentation previously. Also note that this
patch does not add documentation to the various `new` methods, as they
are considered self-explanatory. They are instead marked as
`#[allow(missing_docs)]`.
Add tower-hedge, a layer that preemptively retries requests which have been
outstanding for longer than a given latency percentile. If either of the original
future or the retry future completes, that value is used. For more information
about hedge requests, see: [The Tail at Scale][1]
[1]: https://cseweb.ucsd.edu/~gmporter/classes/fa17/cse124/post/schedule/p74-dean.pdf
Signed-off-by: Alex Leong <alex@buoyant.io>
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 changes the Service request type to a generic instead of an associated
type. This is more appropriate as requests are inputs to the service.
This change enables a single implementation of `Service` to accept many
kinds of request types. This also enables requests to be references.
Fixes#99
