Configuration manager ( confman )

Description

A library component responsible for tracking current configuration accepting configuration changes and notifing parties of configuration changes.

Features

Log configuration changes
Make configuration management available on dbus ( cockpit f.e. )
Services declare configuration fields, type, limits and defaults to configuration manager over dbus.
Configuration to be persistent between reboots
Eazy backup of configuration
Eazy restore of configureation
Configuration retention

Play confman interface

#include <chrono>
#include <cstdint>
#include <string>

#include <mp-units/systems/si/si.h>
#include <boost/asio.hpp>

#include <tfc/confman.hpp>
#include <tfc/confman/observable.hpp>
#include <tfc/progbase.hpp>
#include <tfc/stx/glaze_meta.hpp>
#include <tfc/utils/units_glaze_meta.hpp>

namespace asio = boost::asio;

struct simple_config {
  int a{};
  std::string b{};
  tfc::confman::observable<bool> c{};
  std::vector<int> d{};
  std::chrono::nanoseconds sec{};
  mp_units::quantity<mp_units::si::deci<mp_units::si::ampere>> amper{};
  struct glaze {
    using type = simple_config;
    static constexpr auto value{ glz::object(
        "a",
        &type::a,
        tfc::json::schema{ .description = "A description", .minimum = 100, .maximum = 300 },
        "b",
        &type::b,
        "c",
        &type::c,
        "C description",
        "d",
        &type::d,
        "D description",
        "sec",
        &type::sec,
        tfc::json::schema{ .description = "Sec description", .minimum = 1000, .maximum = 30000 },
        "amper",
        &type::amper,
        "Amper description") };
    static constexpr auto name{ "simple_config" };
  };
};

int main(int argc, char** argv) {
  tfc::base::init(argc, argv);

  asio::io_context ctx{};

  tfc::confman::config<simple_config> const config{ ctx, "key" };
  config->c.observe(
      [](bool new_value, bool old_value) { fmt::print("new value: {}, old value: {}\n", new_value, old_value); });

  fmt::print("Schema is: {}\n", config.schema());
  fmt::print("Config is: {}\n", config.string());

  ctx.run();
  return 0;
}

Inital implementation of storage and backup

Will utilize file level json files. Backups will be implemented by joining the relevant json files and downloading a single large file.

Log changes to configuration

In the first iteration this can be as simple as printing the current json and the json to bo applied.

==================> Configuration changed from 
JSON BLOB
==================< TO 
JSON BLOB
==================<>

Confman description of underlying communication

Confman exposes a dbus interface that can be used to change configuration and to get the current configuration.

Configuration retention policy

Confman will keep a configurable minumum number of backups of the configuration. Suggested default is 4, this can be adjusted by an environment variable. TFC_CONFMAN_MIN_RETENTION_COUNT. Confman will also keep all backups that are newer then some days. Suggested default is 30 days. This can be adjusted by an environment variable. TFC_CONFMAN_MIN_RETENTION_DAYS.

Confman shall only act upon these rules when writing new configuration and no routine checks shall be performed to remove old backups.

Configuration naming rules

Confman will name configuration files with the following naming scheme: <configuration_name>_<uuid>.json. Where uuid is specified by https://datatracker.ietf.org/doc/html/rfc4122