mirror of https://github.com/grpc/grpc.git
[promises] New `Seq`, `TrySeq` implementation (#33991)
Our current implementation of `Seq`, `TrySeq` leverage some complicated template stuff to work, which makes them hard to maintain. I've been thinking about ways to simplify that for some time and had something like this in mind - using a code generator that's at least a little more understandable to code generate most of the complexity into a file that is checkable. Concurrently - I have a cool optimization in mind - but it requires that we can move promises after polling, which is a contract change. I'm going to work through the set of primitives we have in the coming weeks and change that contract to enable the optimization. --------- Co-authored-by: ctiller <ctiller@users.noreply.github.com>pull/33995/head
Craig Tiller
2 years ago
committed by
GitHub
parent
66f60aa763
commit
54651a7168
33 changed files with 2457 additions and 433 deletions
File diff suppressed because it is too large
Load Diff
@ -0,0 +1,271 @@ |
||||
#!/usr/bin/env python3 |
||||
|
||||
# Copyright 2023 gRPC authors. |
||||
# |
||||
# Licensed under the Apache License, Version 2.0 (the "License"); |
||||
# you may not use this file except in compliance with the License. |
||||
# You may obtain a copy of the License at |
||||
# |
||||
# http://www.apache.org/licenses/LICENSE-2.0 |
||||
# |
||||
# Unless required by applicable law or agreed to in writing, software |
||||
# distributed under the License is distributed on an "AS IS" BASIS, |
||||
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
||||
# See the License for the specific language governing permissions and |
||||
# limitations under the License. |
||||
|
||||
import sys |
||||
|
||||
from mako.template import Template |
||||
|
||||
seq_state = Template( |
||||
""" |
||||
<%def name="decl(promise_name, i, n)"> |
||||
using Promise${i} = ${promise_name}; |
||||
% if i < n-1: |
||||
using NextFactory${i} = OncePromiseFactory<typename Promise${i}::Result, F${i}>; |
||||
${decl(f"typename NextFactory{i}::Promise", i+1, n)} |
||||
% endif |
||||
</%def> |
||||
|
||||
<%def name="state(i, n)"> |
||||
% if i == 0: |
||||
Promise0 current_promise; |
||||
NextFactory0 next_factory; |
||||
% elif i == n-1: |
||||
union { |
||||
struct { ${state(i-1, n)} } prior; |
||||
Promise${i} current_promise; |
||||
}; |
||||
% else: |
||||
union { |
||||
struct { ${state(i-1, n)} } prior; |
||||
P${i} current_promise; |
||||
}; |
||||
NextFactory${i} next_factory; |
||||
% endif |
||||
</%def> |
||||
|
||||
template <template<typename> class Traits, typename P, ${",".join(f"typename F{i}" for i in range(0,n-1))}> |
||||
struct SeqState<Traits, P, ${",".join(f"F{i}" for i in range(0,n-1))}> { |
||||
<% name="PromiseLike<P>" %> |
||||
% for i in range(0,n-1): |
||||
using Promise${i} = ${name}; |
||||
using PromiseResult${i} = typename Promise${i}::Result; |
||||
using PromiseResultTraits${i} = Traits<PromiseResult${i}>; |
||||
using NextFactory${i} = OncePromiseFactory<typename PromiseResultTraits${i}::UnwrappedType, F${i}>; |
||||
<% name=f"typename NextFactory{i}::Promise" %>\\ |
||||
% endfor |
||||
using Promise${n-1} = ${name}; |
||||
using PromiseResult${n-1} = typename Promise${n-1}::Result; |
||||
using PromiseResultTraits${n-1} = Traits<PromiseResult${n-1}>; |
||||
using Result = typename PromiseResultTraits${n-1}::WrappedType; |
||||
% if n == 1: |
||||
Promise0 current_promise; |
||||
% else: |
||||
% for i in range(0,n-1): |
||||
struct Running${i} { |
||||
% if i != 0: |
||||
union { |
||||
GPR_NO_UNIQUE_ADDRESS Running${i-1} prior; |
||||
% endif |
||||
GPR_NO_UNIQUE_ADDRESS Promise${i} current_promise; |
||||
% if i != 0: |
||||
}; |
||||
% endif |
||||
GPR_NO_UNIQUE_ADDRESS NextFactory${i} next_factory; |
||||
}; |
||||
% endfor |
||||
union { |
||||
GPR_NO_UNIQUE_ADDRESS Running${n-2} prior; |
||||
GPR_NO_UNIQUE_ADDRESS Promise${n-1} current_promise; |
||||
}; |
||||
% endif |
||||
enum class State : uint8_t { ${",".join(f"kState{i}" for i in range(0,n))} }; |
||||
GPR_NO_UNIQUE_ADDRESS State state = State::kState0; |
||||
|
||||
SeqState(P&& p, ${",".join(f"F{i}&& f{i}" for i in range(0,n-1))}) noexcept { |
||||
Construct(&${"prior."*(n-1)}current_promise, std::forward<P>(p)); |
||||
% for i in range(0,n-1): |
||||
Construct(&${"prior."*(n-1-i)}next_factory, std::forward<F${i}>(f${i})); |
||||
% endfor |
||||
} |
||||
~SeqState() { |
||||
switch (state) { |
||||
% for i in range(0,n-1): |
||||
case State::kState${i}: |
||||
Destruct(&${"prior."*(n-1-i)}current_promise); |
||||
goto tail${i}; |
||||
% endfor |
||||
case State::kState${n-1}: |
||||
Destruct(¤t_promise); |
||||
return; |
||||
} |
||||
% for i in range(0,n-1): |
||||
tail${i}: |
||||
Destruct(&${"prior."*(n-1-i)}next_factory); |
||||
% endfor |
||||
} |
||||
SeqState(const SeqState& other) noexcept : state(other.state) { |
||||
GPR_ASSERT(state == State::kState0); |
||||
Construct(&${"prior."*(n-1-i)}current_promise, |
||||
other.${"prior."*(n-1-i)}current_promise); |
||||
% for i in range(0,n-1): |
||||
Construct(&${"prior."*(n-1-i)}next_factory, |
||||
other.${"prior."*(n-1-i)}next_factory); |
||||
% endfor |
||||
} |
||||
SeqState& operator=(const SeqState& other) = delete; |
||||
SeqState(SeqState&& other) noexcept : state(other.state) { |
||||
switch (state) { |
||||
% for i in range(0,n-1): |
||||
case State::kState${i}: |
||||
Construct(&${"prior."*(n-1-i)}current_promise, |
||||
std::move(other.${"prior."*(n-1-i)}current_promise)); |
||||
goto tail${i}; |
||||
% endfor |
||||
case State::kState${n-1}: |
||||
Construct(¤t_promise, std::move(other.current_promise)); |
||||
return; |
||||
} |
||||
% for i in range(0,n-1): |
||||
tail${i}: |
||||
Construct(&${"prior."*(n-1-i)}next_factory, |
||||
std::move(other.${"prior."*(n-1-i)}next_factory)); |
||||
% endfor |
||||
} |
||||
SeqState& operator=(SeqState&& other) = delete; |
||||
Poll<Result> PollOnce() { |
||||
switch (state) { |
||||
% for i in range(0,n-1): |
||||
case State::kState${i}: { |
||||
auto result = ${"prior."*(n-1-i)}current_promise(); |
||||
PromiseResult${i}* p = result.value_if_ready(); |
||||
if (p == nullptr) return Pending{}; |
||||
if (!PromiseResultTraits${i}::IsOk(*p)) { |
||||
return PromiseResultTraits${i}::template ReturnValue<Result>(std::move(*p)); |
||||
} |
||||
Destruct(&${"prior."*(n-1-i)}current_promise); |
||||
auto next_promise = PromiseResultTraits${i}::CallFactory(&${"prior."*(n-1-i)}next_factory, std::move(*p)); |
||||
Destruct(&${"prior."*(n-1-i)}next_factory); |
||||
Construct(&${"prior."*(n-2-i)}current_promise, std::move(next_promise)); |
||||
state = State::kState${i+1}; |
||||
} |
||||
ABSL_FALLTHROUGH_INTENDED; |
||||
% endfor |
||||
default: |
||||
case State::kState${n-1}: { |
||||
auto result = current_promise(); |
||||
auto* p = result.value_if_ready(); |
||||
if (p == nullptr) return Pending{}; |
||||
return Result(std::move(*p)); |
||||
} |
||||
} |
||||
} |
||||
};""" |
||||
) |
||||
|
||||
front_matter = """ |
||||
#ifndef GRPC_SRC_CORE_LIB_PROMISE_DETAIL_SEQ_STATE_H |
||||
#define GRPC_SRC_CORE_LIB_PROMISE_DETAIL_SEQ_STATE_H |
||||
|
||||
// This file is generated by tools/codegen/core/gen_seq.py |
||||
|
||||
#include <grpc/support/port_platform.h> |
||||
|
||||
#include <stdint.h> |
||||
|
||||
#include <utility> |
||||
|
||||
#include "absl/base/attributes.h" |
||||
|
||||
#include <grpc/support/log.h> |
||||
|
||||
#include "src/core/lib/gprpp/construct_destruct.h" |
||||
#include "src/core/lib/promise/detail/promise_factory.h" |
||||
#include "src/core/lib/promise/detail/promise_like.h" |
||||
#include "src/core/lib/promise/poll.h" |
||||
|
||||
// A sequence under some traits for some set of callables P, Fs. |
||||
// P should be a promise-like object that yields a value. |
||||
// Fs... should be promise-factory-like objects that take the value from the |
||||
// previous step and yield a promise. Note that most of the machinery in |
||||
// PromiseFactory exists to make it possible for those promise-factory-like |
||||
// objects to be anything that's convenient. |
||||
// Traits defines how we move from one step to the next. Traits sets up the |
||||
// wrapping and escape handling for the sequence. |
||||
// Promises return wrapped values that the trait can inspect and unwrap before |
||||
// passing them to the next element of the sequence. The trait can |
||||
// also interpret a wrapped value as an escape value, which terminates |
||||
// evaluation of the sequence immediately yielding a result. Traits for type T |
||||
// have the members: |
||||
// * type UnwrappedType - the type after removing wrapping from T (i.e. for |
||||
// TrySeq, T=StatusOr<U> yields UnwrappedType=U). |
||||
// * type WrappedType - the type after adding wrapping if it doesn't already |
||||
// exist (i.e. for TrySeq if T is not Status/StatusOr/void, then |
||||
// WrappedType=StatusOr<T>; if T is Status then WrappedType=Status (it's |
||||
// already wrapped!)) |
||||
// * template <typename Next> void CallFactory(Next* next_factory, T&& value) - |
||||
// call promise factory next_factory with the result of unwrapping value, and |
||||
// return the resulting promise. |
||||
// * template <typename Result, typename RunNext> Poll<Result> |
||||
// CheckResultAndRunNext(T prior, RunNext run_next) - examine the value of |
||||
// prior, and decide to escape or continue. If escaping, return the final |
||||
// sequence value of type Poll<Result>. If continuing, return the value of |
||||
// run_next(std::move(prior)). |
||||
// |
||||
// A state contains the current promise, and the promise factory to turn the |
||||
// result of the current promise into the next state's promise. We play a shell |
||||
// game such that the prior state and our current promise are kept in a union, |
||||
// and the next promise factory is kept alongside in the state struct. |
||||
// Recursively this guarantees that the next functions get initialized once, and |
||||
// destroyed once, and don't need to be moved around in between, which avoids a |
||||
// potential O(n**2) loop of next factory moves had we used a variant of states |
||||
// here. The very first state does not have a prior state, and so that state has |
||||
// a partial specialization below. The final state does not have a next state; |
||||
// that state is inlined in BasicSeq since that was simpler to type. |
||||
|
||||
namespace grpc_core { |
||||
namespace promise_detail { |
||||
template <template<typename> class Traits, typename P, typename... Fs> |
||||
struct SeqState; |
||||
""" |
||||
|
||||
end_matter = """ |
||||
} // namespace promise_detail |
||||
} // namespace grpc_core |
||||
|
||||
#endif // GRPC_SRC_CORE_LIB_PROMISE_DETAIL_SEQ_STATE_H |
||||
""" |
||||
|
||||
|
||||
# utility: print a big comment block into a set of files |
||||
def put_banner(files, banner): |
||||
for f in files: |
||||
for line in banner: |
||||
print("// %s" % line, file=f) |
||||
print("", file=f) |
||||
|
||||
|
||||
with open(sys.argv[0]) as my_source: |
||||
copyright = [] |
||||
for line in my_source: |
||||
if line[0] != "#": |
||||
break |
||||
for line in my_source: |
||||
if line[0] == "#": |
||||
copyright.append(line) |
||||
break |
||||
for line in my_source: |
||||
if line[0] != "#": |
||||
break |
||||
copyright.append(line) |
||||
|
||||
copyright = [line[2:].rstrip() for line in copyright] |
||||
|
||||
with open("src/core/lib/promise/detail/seq_state.h", "w") as f: |
||||
put_banner([f], copyright) |
||||
print(front_matter, file=f) |
||||
for n in range(2, 10): |
||||
print(seq_state.render(n=n), file=f) |
||||
print(end_matter, file=f) |
||||
Loading…
Reference in new issue