Ruben's 2025 Q1

Author: anarthal

_posts/2025-04-10-Ruben2025Q1Update.md

@@ -0,0 +1,124 @@
+---
+layout: post
+nav-class: dark
+categories: ruben
+title: "Moving Boost forward: Asio, coroutines, and maybe even modules"
+author-id: ruben
+author-name: Rubén Pérez Hidalgo
+---
+
+It's been an exciting quarter over here. Both old-but-refreshed and brand new projects
+are flourishing in the Boost ecosystem, making today a really exciting moment to contribute to it.
+
+## using std::cpp 2025: a tale of coroutines, timeouts and cancellation in Asio
+
+I had the pleasure of speaking at [using std::cpp 2025](https://eventos.uc3m.es/119554/detail/using-std-cpp-2025.html),
+the biggest C++ conference in Spain. I even had Bjarne Stroustrup himself among the audience!
+
+The talk was focused on how to write simple but effective
+asynchronous Asio code. Asio is almost two decades old, yet it keeps improving.
+Since Boost 1.86, code like this is legal:
+
+```cpp
+// Write a message over a socket, and set a timeout to the operation
+co_await asio::async_write(sock, asio::buffer(buff), asio::cancel_after(20s));
+```
+
+My talk addressed the mechanisms that power this kind of code, together with many
+tips gathered by making mistakes while working on Boost.MySQL and related projects.
+The slides and code snippets I used can be found [here](https://github.com/anarthal/usingstdcpp-2025),
+and a recording of the talk will be available soon.
+
+I've also updated the [servertech chat project](https://github.com/anarthal/servertech-chat),
+a chat application with a server powered by Boost libraries. It now uses most of the features
+that I talked about during the talk, including timeouts and C++20 coroutines.
+
+Since the project was using `asio::yield_context`, I wrote a small benchmark and found
+out that C++20 coroutines were ~10% faster. This might not be the case for all projects, though.
+
+## C++20 modules and Boost
+
+I've led an initiative to natively support C++20 modules in Boost. The ultimate goal is
+to enable the user write code like:
+
+```cpp
+import boost.mp11;
+
+using L1 = boost::mp11::mp_list<int, float, int, float>;
+```
+
+The point of the prototype is to be as complete as possible.
+I firmly believe that just writing the module units (i.e. the `boost_mp11.cppm` file)
+is far from enough. This is essentially shipping untested code to the user.
+Additionally, building modules is not trivial, specially when there are
+complex dependency chains. For this reason, the prototype also includes:
+
+- CMake files to build and install the modules, compatible with today's Boost CMake infrastructure.
+- Running the library's entire test suite with modules enabled.
+- CI scripts to automate running these tests.
+
+I've fully migrated Boost.Mp11 (as a representative of header-only libraries) and
+Boost.Charconv (representing compiled ones). I've found a myriad of problems,
+including compiler bugs, but the result is functional. Compile times wins
+are really significant - building mp11's testsuite with modules took only
+a fourth of the time it takes with headers.
+
+We haven't merged any of this yet, since it relies on CMake's experimental
+features, and there are still many compiler bugs to be fixed.
+
+I've summarized my findings in [this article](https://anarthal.github.io/cppblog/modules3).
+
+While working in Charconv, I found some problems unrelated to modules
+and helped the author fix them.
+
+## Boost.MySQL benchmarks
+
+When you use Boost.MySQL, it's logical to ask yourself
+"is this much slower than the official drivers?". Spoiler alert:
+it's as fast as libmysqlclient and libmariadb, and even faster under
+some of the benchmarks.
+
+I didn't have the data to answer this question until recently,
+since there are no standard benchmarks to measure this. I've designed
+four benchmarks that focus on the protocol implementation.
+This includes reading both small and big rows, big batches of rows
+and using statements with big parameters.
+Full information available [here](https://www.boost.org/doc/libs/develop/libs/mysql/doc/html/mysql/benchmarks.html).
+
+While I'm pretty satisfied with the results, I've also identified some
+points where performance could be improved. These will be addressed in the near future.
+
+## Boost.MySQL new features and maintenance
+
+Per user request, I've added `any_connection::connection_id()`, equivalent
+to `mysql_thread_id()` in the official API. This allows using `KILL` statements
+to cancel queries.
+
+I've also improved safety by detecting the violation of some preconditions
+and issuing errors rather than incurring in undefined behavior. For example,
+attempting to start an asynchronous operation in an `any_connection` while
+another one is outstanding is no longer UB:
+
+```cpp
+// Since Boost 1.88, this is no longer UB.
+// The second operation will fail with client_errc::operation_in_progress
+conn.async_execute("SELECT 1", r1, [](...) {});
+conn.async_execute("SELECT 1", r2, [](...) {});
+```
+
+I've fixed some other minor bugs and made some improvements to the docs.
+The most remarkable is the addition of a
+[fully-fledged HTTP server example] (https://github.com/boostorg/mysql/tree/07200f17c28293e910151abbc46d22eeff944384/example/3_advanced/http_server_cpp20)
+that uses C++20 coroutines. I'm in the process of writing the equivalent using callbacks,
+for users that prefer them.
+
+## Boost.Decimal review
+
+Another exciting submission. As usual, I contributed to it by integrating it
+into Boost.MySQL, to parse `DECIMAL` types.
+
+## Next steps
+
+I'm preparing a Postgres library that I aim to submit to Boost on the long run.
+It's still in a very early state. I intend to make it similar to Boost.MySQL,
+but exposing the protocol interface as a public API. More on this next quarter!