wassail

wassail is a set of C++ building blocks to check the health of UNIX-based systems. Python bindings are also included.

The library is based on the observation that high performance computing sites tend to create their own custom local health tools. The user interfaces vary widely but the health checks themselves are universal. wassail provides highly customizable "low level" building blocks for creating bespoke user level system health tools.

Examples

Check whether the value of the environment variable FOO is equal to bar:

#include <wassail.hpp>

auto d = wassail::data::environment();
auto c = wassail::check::misc::environment("FOO", "bar");
auto r = c.check(d); /* implicitly evalutes d */

// {"action":"","brief":"Checking environment variable 'FOO'","children":[],"detail":"Value 'bar' matches 'bar'","issue":0,"priority":3,"system_id":["MacBook-Pro.local"],"timestamp":1578031355}
std::cout << static_cast<json>(r) << std::endl;

The three categories of building blocks are shown in this example.

1. Data building blocks collect information about the system. wassail provides multiple data sources in the wassail::data namespace. Data sources are not queried when the object is initialized but rather when the evaluate() method is invoked (the data is cached).

2. Check building blocks validate the collected data against a specified reference value. wassail provides multiple checks in the wassail::check namespace as well as flexible generic checks. The reference value could be hard-coded or user configurable via the user interface of the user level system health tool.

3. Checks return result objects. The user level health tool can easily customize the presentation of the result, such as choosing the terminology to appear if an issue is detected. In C++ tools the result << operator can be overloaded. The message strings can also be customized by specifying alternative templates when constructing the check.

// customize the result message templates (libfmt syntax)
auto c = wassail::check::misc::environment("FOO", "bar", false,
           "Validating environment variable {0}",
           "Observed value '{0}' does not equal the reference value '{1}'",
           "Unable to validate",
           "Observed value and reference value are the same: '{0}'");
auto r = c.check(d); /* implicitly evalutes d */

// {"action":"","brief":"Validating environment variable FOO","children":[],"detail":"Observed value and reference value are the same: 'bar'","issue":0,"priority":3,"system_id":["MacBook-Pro.local"],"timestamp":1578033076}
std::cout << static_cast<json>(r) << std::endl;

The equivalent example to check the value of the environment variable FOO using the Python binding:

import wassail

d = wassail.data.environment()
c = wassail.check.misc.environment('FOO', 'bar')
r = c.check(d) # implicitly evaluates d

# {"action":"","brief":"Checking environment variable 'FOO'","children":[],"detail":"Value 'bar' matches 'bar'","issue":0,"priority":3,"system_id":["MacBook-Pro.local"],"timestamp":1578031355}
print(r)

Several C++ and Python samples are included.

Installation

A C++14 compiler is required (C++17 preferred). See INSTALL.

License

wassail is distributed under the Mozilla Public License 2.0.

Copyright © 2018-2020 Scott McMillan

Third Party Software

wassail incorporates the following third party software.

• catch Copyright (c) 2019 Two Blue Cubes Ltd.

• fmtlib Copyright (c) 2012 - present, Victor Zverovich

• json Copyright (c) 2013-2019 Niels Lohmann <http://nlohmann.me>

• OSU Micro-Benchmarks Copyright (c) 2001-2019, The Ohio State University.

• pybind11 Copyright (c) 2016 Wenzel Jakob <[email protected]>

• pybind11_json Copyright (c) 2019, Martin Renou

• spdlog Copyright (c) 2015-present, Gabi Melman & spdlog contributors.

• STREAM Copyright 1991-2013: John D. McCalpin

Entomology

wassail originates from the Middle English "wæs hæil", or "be in good health". May your system be in good health!

Here we come a-wassailing
Among the leaves so green
Here we come a-wand'ring
So fair to be seen

Love and joy come to you,
And to you your wassail too;
And God bless you and send you a Happy New Year
And God send you a Happy New Year