Introduce a new net::server module
#482
Draft
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
'Service' and 'ServiceLayer' are the most important traits defined here
('{Consume,Produce,Transform}Message' are auxiliary traits providing
high-level message parsing and building, specific to DNS server code).
The vast majority of the code is complex blanket implementations which
make these traits effortless to use. As some examples:
- (ServiceLayer, Service): Service
- (Vec<ServiceLayer>, Service): Service
- (Vec<ServiceLayer>, Arc<ServiceLayer>, Service): Service
This makes it incredibly easy to compose services together, without
the restrictions of nesting that 'net::server' imposes. Each service
layer is also much simpler, since it does not have to be generic over
the next layer in the pipeline.
The provided tuple implementations make it easy to use these layers in
static contexts, and it allows the compiler to inline everything into a
single function.
The auxiliary traits are also critical to the design -- they allow
messages to be parsed and built in a single iteration, preventing the
repetitive parsing of e.g. compressed names. There are still open
questions regarding their flexibility for certain use cases.
The next step is to implement services and service layers using these
traits, and to use the traits from a transport implementation.
- 'Service' and 'ServiceLayer' have been split into "local" (i.e. single-threaded) and non-local versions, both using 'async'. A synchronous trait could be added for them in the future. - Rust was having issues with the 'req lifetime and its interactions with 'async' through an associated type. I gave up and dropped the 'ConsumeMessage' trait, now directly providing the request message to 'respond()'. - A stub 'RequestMessage' type has been defined, which will provide relatively efficient access to the message. It contains caches of indices for the initial records and EDNS options.
- Layers can now modify requests before passing them forward.
- Layers can now see the entire request, allowing them to ensure that
it is entirely consistent. Previously, they could only see one piece
at a time, in order, preventing them from modifying a record based on
the contents of a record following it.
- Layers can now truncate a message when they see fit.
- 'ParsedMessage' is used to represent requests and responses; it will
allocate on the heap, but it provides extremely fast traversal of the
entire message (as every message component is directly indexable).
- EDNS support is hardcoded in 'ParsedMessage'; this could make it
brittle to future changes in the DNS specs, but service layers rely
on EDNS and need to be able to find EDNS options quickly.
- Trait objects are better supported, in terms of performance; there
will only be two method calls to every 'dyn ServiceLayer'. The old
API would have one method call for every message component in the
request and the response.
- The 'Service' and 'ServiceLayer' traits no longer have associated
types, and are now possible to use as trait objects directly.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This is a work-in-progress PR for overhauling
net::serveron top ofnew_base. It aims to address some of the shortcomings we have encountered with the service layering design, while otherwise being a relatively faithful refactoring of the entire module.