= Unicorn Hacker's Guide
== Polyglot Infrastructure
Like Mongrel, we use Ruby where it makes sense, and Ragel with C where
it helps performance. All of the code that actually runs your Rack
application is written Ruby, Ragel or C.
As far as tests and documentation goes, we're not afraid to embrace Unix
and use traditional Unix tools where they make sense and get the job
Tests are good, but slow tests make development slow, so we make tests
faster (in parallel) with GNU make (instead of Rake) and avoiding
Users of GNU-based systems (such as GNU/Linux) usually have GNU make
installed as "make" instead of "gmake".
Running the entire test suite with 4 tests in parallel:
gmake -j4 check
Running just one unit test:
Running just one test case in a unit test:
We strive to write as little code as possible while still maintaining
readability. However, readability and flexibility may be sacrificed for
performance in hot code paths. For Ruby, less code generally means
Memory allocation should be minimized as much as practically possible.
Buffers for IO#readpartial are preallocated in the hot paths to avoid
building up garbage. Hash assignments use frozen strings to avoid the
We spend as little time as possible inside signal handlers and instead
defer handling them for predictability and robustness. Most of the
Unix-specific things are in the Unicorn::HttpServer class. Unix systems
programming experience will come in handy (or be learned) here.
Please wrap documentation at 72 characters-per-line or less (long URLs
are exempt) so it is comfortably readable from terminals.
When referencing mailing list posts, use
<tt>https://yhbt.net/unicorn-public/$MESSAGE_ID/</tt> if possible
since the Message-ID remains searchable even if a particular site
=== Ruby/C Compatibility
We target C Ruby 2.5 and later. We need the Ruby
implementation to support fork, exec, pipe, UNIX signals, access to
integer file descriptors and ability to use unlinked files.
All of our C code is OS-independent and should run on compilers
supported by the versions of Ruby we target.
=== Ragel Compatibility
We target the latest released version of Ragel and will update our code
to keep up with new releases. Packaged tarballs and gems include the
generated source code so they will remain usable if compatibility is
Contributions are welcome in the form of patches, pull requests, code
review, testing, documentation, user support or any other feedback is
welcome. The mailing list is the central coordination point for all
user and developer feedback and bug reports.
=== Submitting Patches
Follow conventions already established in the code and do not exceed 80
characters per line.
Inline patches (from "git format-patch -M") to the mailing list are
preferred because they allow code review and comments in the reply to
We will adhere to mostly the same conventions for patch submissions as
git itself. See the
distributed with git on on patch submission guidelines to follow. Just
don't email the git mailing list or maintainer with Unicorn patches :)
== Building a Gem
You can build the Unicorn gem with the following command:
== Running Development Versions
It is easy to install the contents of your git working directory: