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Swish Concurrency Engine

The Swish Concurrency Engine is a framework used to write fault-tolerant programs with message-passing concurrency. It uses the Chez Scheme programming language and embeds concepts from the Erlang programming language. Swish also provides a web server.

Design

The latest design document can be found here.

Swish uses libuv for cross-platform asynchronous I/O.

Although Swish can be run in threaded Chez Scheme for convenience, it is not thread safe and should be used from the main thread only.

Versioning

Swish follows the semantic versioning scheme, starting with 2.0.0 to avoid confusion with internal projects.

Odd minor-version numbers are used for development. As such, we are extremely unlikely to use a patch number other than 0 during development.

Even minor-version numbers are used for official tagged releases.

The first commit after an official tagged release should increment either the minor-version or patch-version number so that the version number for an official tagged release corresponds to a unique commit hash.

Notes

install the prerequisites (see Build System Requirements)
./configure (see ./configure --help for options)
make
make test

After ./configure; you can also cd src; ./go to build and run the engine.
We disable the expression editor with --eedisable because Chez Scheme's expression editor does not use asynchronous console I/O. We would have to modify the places where s/expeditor.ss calls $ee-read-char in blocking mode to use libuv's asynchronous read function instead of the one in c/expeditor.c.
If you get a "symbol(s) not found" error, you may need to use CPPFLAGS and LDFLAGS to supply the header and library path. If the C compiler refuses unused arguments, you may need CFLAGS="-Qunused-arguments". e.g.,
```
./configure CPPFLAGS="-I/usr/local/opt/libiconv/include" \
  CFLAGS="-Qunused-arguments" LDFLAGS="-L/usr/local/opt/libiconv/lib"
```

Build System Requirements

Linux

Chez Scheme 9.6.4 or later
GCC, the GNU Compiler Collection
GNU make 4.4 or later
GNU C++ compiler for libuv
cmake for libuv
libsystemd-dev and uuid-dev packages
graphviz, texlive, texlive-latex-recommended, and texlive-latex-extra packages for building the documentation

Mac

Chez Scheme 9.6.4 or later
coreutils (install via Homebrew: brew install coreutils)
cmake for libuv (install via Homebrew: brew install cmake)
XCode Command Line Tools
dot (install via Homebrew: brew install graphviz)
pdflatex (install via Homebrew: brew cask install mactex)
Latin Modern fonts from LaTeX (can be installed with Font Book from a location like /usr/local/texlive/2020/texmf-dist/fonts/opentype/public/lm)

Windows

Chez Scheme 9.6.4 or later
Cygwin or MinGW/MSYS with bash, git, graphviz, grep, perl, texlive, GNU make, etc.
cmake for libuv (https://cmake.org/)
Microsoft Visual Studio 2022, 2019, or 2017 with Visual C++
Put scheme in PATH.

Stand-alone Swish Applications

Swish can be used to build, test, and deploy stand-alone applications. A given application might load foreign code for image processing or USB access. Code that may block should use the API described in the "Operating System Interface" chapter of the documentation to integrate with Swish's I/O loop.

Build

For details about building a Swish application, see: swish-build --help

Test

For details about testing a Swish application, see: swish-test --help

Deploying a Stand-alone Application

On Linux and macOS, you can deploy your application's executable and boot file.

On Windows, your install should include the application's executable and boot file, osi.dll, uv.dll, sqlite3.dll, Chez Scheme's csv964.dll or the csv*.dll for the version you are using, and Microsoft's C Runtime Library vcruntime140.dll.

You can define most applications entirely in Scheme, using the Swish libraries. If you need to integrate C code that relies on Swish exports, clone the Swish repository and run configure. This generates a src/swish/Mf-config that your makefile can include to define variables for system-specific paths. Swish's source repository provides swish.h to define callable exports for osi.dll.