Configuration Documentation

 

Configuration module

The Configuration module provides a way to access Configuration data from various backends in a uniform way. Users get an interface to backends by providing a URI to the ConfigurationFactory class, which returns an implementation of ConfigurationInterface. Values can be retrieved from the interface one-by-one using simple getters, or multiple at a time using getRecursive(). The getRecursive() function returns a tree-like data structure, which models the hierarchy of directories or paths.

Installation

To install without aliBuild follow these instructions.

aliBuild installation

Follow this tutorial to install aliBuild.

Install Configuration module: ``` aliBuild build Configuration –defaults o2 alienv load Configuration/latest ```

Development

If you want to make changes to the source code initialise the development package first: ``` aliBuild init Configuration `` and then usemaketo recompile `` cd sw/BUILD/Configuration-latest/Configuration make -j install ```

Instance and backends

The configuration instance can be requested form the factory based on provided URI: ```cpp #include <Configuration/ConfigurationFactory.h> using namespace o2::configuration;

std::unique_ptr<ConfigurationInterface> = ConfigurationFactory::getConfiguration("backend://[host][:port][/path]"); ```

The URI is constructed based on the table below:

Backend name	URI backned	Host	Port	Path	Dependency
INI file	ini://	-	-	File path	-
JSON file	json://	-	-	File path	-
Consul	consul://	Server's hostname	Server's port	-	ppconsul

Getting values

Use . as path separator.

Getting a value

Simply use templated get method and provide path as parameter: ```cpp auto conf = ConfigurationFactory::getConfiguration("ini:///temp/config.ini"); int value = conf->get<int>("my_dir.my_key"); ```

Using prefix

If you need to get multiple values from a single node consider using setPrefix: ```cpp auto conf = ConfigurationFactory::getConfiguration("json:///temp/config.json"); conf->setPrefix("my_dir"); int value = conf->get<int>("my_key"); ```

Managing failures

When the value under requested path does not exist use one of the following ways to handle it.

1. Catch an exception

```cpp auto conf = ConfigurationFactory::getConfiguration("ini:///temp/config.ini"); try { conf->get<int>("my_dir.my_wrong_key"); } catch (std::runtime_error&) { ... }

```

1. Provide default value as a second parameter to get method

```cpp auto conf = ConfigurationFactory::getConfiguration("ini:///temp/config.ini"); int value = conf->get<int>("my_dir.my_wrong_key", 321); ```

Getting a subtree of values

When tree of values or flat key-value map is needed: ```cpp auto conf = ConfigurationFactory::getConfiguration("consul://localhost:8500");

// Get a tree boost::property_tree::ptree subTree = conf->getRecursive("my_dir"); subTree.get<int>("my_key");

// Get flat key-value map std::unordered_map<std::string, std::string> map = conf->getRecursiveMap("my_dir"); map["my_key"]; ```

Putting values

Putting values in currently supported only by Consul backend. ```cpp auto conf = ConfigurationFactory::getConfiguration("consul://localhost:8500"); conf->put<int>("my_dir.my_key", 123); ```

Consul server setup

See detailed instructions.