With the introduction of profile-based classification, the proxy would
not perform normal gRPC classification in some cases when it could &
should.
This change simplifies our default classifier logic and falls back to
the default grpc-aware behavior whenever another classification cannot
be performed.
Furthermore, this change moves the `proxy::http::classify` module to
`proxy::http::metrics::classify`, as these modules should only be relied
on for metrics classification. Other module (for instance, retries),
should provide their own abstractions.
Finally, this change fixes a test error-formatting issue.
As the proxy's functionality has grown, the HTTP routing functionality
has become complex. Module boundaries have become ill-defined, which
leads to tight coupling--especially around the `ctx` metadata types and
`Service` type signatures.
This change introduces a `Stack` type (and subcrate) that is used as the
base building block for proxy functionality. The `proxy` module now
exposes generic components--stack layers--that are configured and
instantiated in the `app::main` module.
This change reorganizes the repo as follows:
- Several auxiliary crates have been split out from the `src/` directory
into `lib/fs-watch`, `lib/stack` and `lib/task`.
- All logic specific to configuring and running the linkerd2 sidecar
proxy has been moved into `src/app`. The `Main` type has been moved
from `src/lib.rs` to `src/app/main.rs`.
- The `src/proxy` has reusable, generic components useful for building
proxies in terms of `Stack`s.
The logic contained in `lib/bind.rs`, pertaining to per-endpoint service
behavior, has almost entirely been moved into `app::main`.
`control::destination` has changed so that it is not responsible for
building services. (It used to take a clone of `Bind` and use it to
create per-endpoint services). Instead, the destination service
implements the new `proxy::Resolve` trait, which produces an infinite
`Resolution` stream for each lookup. This allows the `proxy::balance`
module to be generic over the servie discovery source.
Furthermore, the `router::Recognize` API has changed to only expose a
`recgonize()` method and not a `bind_service()` method. The
`bind_service` logic is now modeled as a `Stack`.
The `telemetry::http` module has been replaced by a
`proxy::http::metrics` module that is generic over its metadata types
and does not rely on the old telemetry event system. These events are
now a local implementation detail of the `tap` module.
There are no user-facing changes in the proxy's behavior.
The `timeout` module has very little to do with the proxy, specifically.
This change moves it into a dedicated subcrate. This helps to clarify
dependencies and to minimize generic logic in the main proxy crate.
In doing this, an unused implementation of AsyncRead/AsyncWrite for
Timeout was deleted.
Furthermore, the `HumanDuration` type has been copied into
tests/support/mod.rs so that this type need not be part of the timeout
module's public API.
Oliver Gould