Apache Mesos Doxygen Style Guide

This guide introduces a consistent style for documenting Mesos source code using Doxygen. There is an ongoing, incremental effort with the goal to document all public Mesos, libprocess, and stout APIs this way. For now, existing code may not follow these guidelines, but new code should.

Source Code Documentation Syntax

Doxygen documentation needs only to be applied to source code parts that constitute an interface for which we want to generate Mesos API documentation files. Implementation code that does not participate in this should still be enhanced by source code comments as appropriate, but these comments should not follow the doxygen style.

We follow the Javadoc syntax to mark comment blocks. These have the general form:

 * Brief summary.
 * Detailed description. More detail.
 * @see Some reference
 * @param <name> Parameter description.
 * @return Return value description.


 * Returns a compressed version of a string.
 * Compresses an input string using the foobar algorithm.
 * @param uncompressed The input string.
 * @return A compressed version of the input string.
 std::string compress(const std::string& uncompressed);

Doxygen Tags

This is the allowed set of doxygen tags that can be used.

  • \@param Describes function parameters.
  • \@return Describes return values.
  • \@see Describes a cross-reference to classes, functions, methods, variables, files or URL.


 * Available kinds of implementations.
 * @see process::network::PollSocketImpl
  • \@file Describes a refence to a file. It is required when documenting global functions, variables, typedefs, or enums in separate files.
  • \@link and \@endlink Describes a link to a file, class, or member.
  • \@example Describes source code examples.
  • \@image Describes an image.

  • When following these links be aware that the doxygen documentation is using another syntax in that \@param is explained as \param.


We wrap long descriptions using four spaces on the next line.

@param uncompressed The input string that requires
    a very long description and an even longer
    description on this line as well.

Constants and Variables


 * Prefix used to name Docker containers in order to distinguish
 * those created by Mesos from those created manually.
extern const std::string DOCKER_NAME_PREFIX;



 * The parent side of the pipe for stdin.
 * If the mode is not PIPE, None will be stored.
 * **NOTE**: stdin is a macro on some systems, hence this name instead.
Option<int> in;

Functions and Methods


 * Forks a subprocess and execs the specified 'path' with the
 * specified 'argv', redirecting stdin, stdout, and stderr as
 * specified by 'in', 'out', and 'err' respectively.
 * If 'setup' is not None, runs the specified function after forking
 * but before exec'ing. If the return value of 'setup' is non-zero
 * then that gets returned in 'status()' and we will not exec.
 * @param path Relative or absolute path in the filesytem to the
 *     executable.
 * @param argv Argument vector to pass to exec.
 * @param in Redirection specification for stdin.
 * @param out Redirection specification for stdout.
 * @param err Redirection specification for stderr.
 * @param flags Flags to be stringified and appended to 'argv'.
 * @param environment Environment variables to use for the new
 *     subprocess or if None (the default) then the new subprocess
 *     will inherit the environment of the current process.
 * @param setup Function to be invoked after forking but before
 *     exec'ing. NOTE: Take extra care not to invoke any
 *     async unsafe code in the body of this function.
 * @param clone Function to be invoked in order to fork/clone the
 *     subprocess.
 * @return The subprocess or an error if one occurred.
Try<Subprocess> subprocess(
    const std::string& path,
    std::vector<std::string> argv,
    const Subprocess::IO& in = Subprocess::FD(STDIN_FILENO),
    const Subprocess::IO& out = Subprocess::FD(STDOUT_FILENO),
    const Subprocess::IO& err = Subprocess::FD(STDERR_FILENO),
    const Option<flags::FlagsBase>& flags = None(),
    const Option<std::map<std::string, std::string>>& environment = None(),
    const Option<lambda::function<int()>>& setup = None(),
    const Option<lambda::function<
        pid_t(const lambda::function<int()>&)>>& clone = None());

Classes and Structs


 * Represents a fork() exec()ed subprocess. Access is provided to the
 * input / output of the process, as well as the exit status. The
 * input / output file descriptors are only closed after:
 *   1. The subprocess has terminated.
 *   2. There are no longer any references to the associated
 *      Subprocess object.
class Subprocess

Library and Component Overview Pages and Developer Guides

Substantial libraries, components, and subcomponents of the Mesos system such as stout, libprocess, master, slave, containerizer, allocator, and others should have an overview page in markdown format that explains their purpose, overall structure, and general use. This can even be a complete developer guide.

This page must be located in the top directory of the library/component and named "README.md".

The first line in such a document must be a section heading bearing the title which will appear in the generated Doxygen index. Example: "# Libprocess Developer Guide"

Example Code

C++ code examples should be enclosed by '~~~{.cpp}'.


int main(int argc, char** argv)

NOTE: Because of shortcomings of Doxygen's markdown parser we currently use indentation for wrapping all non C++ code blocks.

Building Doxygen Documentation

As of right now, the Doxygen documentation should be built from the build subdirectory using doxygen ../Doxyfile . The documentation will then be generated into the ./doxygen subdirectory.