# Vert.x Config

Vert.x Config provides a way to configure your Vert.x application.

It:

- offers multiple configuration syntaxes (json, properties, yaml (extension), hocon (extension)…​

- offers multiple configuration stores (files, directories, http, git (extension), redis (extension), system properties, environment properties)…​

- lets you define the processing order and overloading

- supports runtime reconfiguration

## Concepts

The library is structured around:

- a Config Retriever instantiated and used by the Vert.x application. It configures a set of configuration store

- Configuration store defines a location from where the configuration data is read and and a syntax (json by default)

The configuration is retrieved as a JSON Object.

## Using the Config Retriever

To use the Config Retriever, add the following dependency to the dependencies section of your build descriptor:

- Maven (in your `pom.xml`):

    <dependency>
      <groupId>io.vertx</groupId>
      <artifactId>vertx-config</artifactId>
      <version>3.4.1</version>
    </dependency>

- Gradle (in your `build.gradle` file):

    compile 'io.vertx:vertx-config:3.4.1'

Once done, you first need to instantiate the `ConfigRetriever`:

    require 'vertx-config/config_retriever'
    retriever = VertxConfig::ConfigRetriever.create(vertx)

By default the Config Retriever is configured with the following stores (in this order):

- The Vert.x verticle `config()`

- The system properties

- The environment variables

You can configure your own stores:

    require 'vertx-config/config_retriever'
    httpStore = {
      'type' => "http",
      'config' => {
        'host' => "localhost",
        'port' => 8080,
        'path' => "/conf"
      }
    }

    fileStore = {
      'type' => "file",
      'config' => {
        'path' => "my-config.json"
      }
    }

    sysPropsStore = {
      'type' => "sys"
    }

    options = {
      'stores' => [
        httpStore,
        fileStore,
        sysPropsStore
      ]
    }

    retriever = VertxConfig::ConfigRetriever.create(vertx, options)

More details about the overloading rules and available stores are available below.

Once you have the instance of the Config Retriever, retrieve the configuration as follows:

    retriever.get_config() { |ar_err,ar|
      if (ar_err != nil)
        # Failed to retrieve the configuration
      else
        config = ar
      end
    }

## Overloading rules

The declaration order of the configuration store is important as it defines the overloading. For conflicting key, configuration stores arriving last overloads the value provided by the previous configuration stores. Let’s take an example. We have 2 configuration stores:

- `A` provides `{a:value, b:1}`

- `B` provides `{a:value2, c:2}`

Declared in this order (A, B), the resulting configuration would be: `{a:value2, b:1, c:2}`.

If you declare them in the reverse order (B, A), you would get: * `{a:value, b:1, c:2}`.

## Available configuration stores

The Config Retriever provides a set of configuration store and format. Some more are available as extension and you can implement your own.

### Structure of the configuration

Each declared data store must specify the `type`. It can also define the `format`. If not set JSON is used.

Some configurations tore requires additional configuration (such a path…​). This configuration is passed as a Json Object using `config`

### File

This configuration store just read the configuration from a file. It supports all supported formats.

    file = {
      'type' => "file",
      'format' => "properties",
      'config' => {
        'path' => "path-to-file.properties"
      }
    }

The `path` configuration is required.

### JSON

The JSON configuration store just serves the given JSON config as it is.

    json = {
      'type' => "json",
      'config' => {
        'key' => "value"
      }
    }

The only supported format for this configuration store is JSON.

### Environment Variables

This configuration store maps environment variables to a Json Object contributed to the global configuration.

    json = {
      'type' => "env"
    }

This configuration store does not support the `format` configuration.

### System Properties

This configuration store maps system properties to a Json Object contributed to the global configuration.

    json = {
      'type' => "sys",
      'config' => {
        'cache' => "false"
      }
    }

This configuration store does not support the `format` configuration.

You can configure the `cache` attribute (`true` by default) let you decide whether or not it caches the system properties on the first access and does not reload them.

### HTTP

This configuration stores retrieves the configuration from a HTTP location. It can use any supported format.

    http = {
      'type' => "http",
      'config' => {
        'host' => "localhost",
        'port' => 8080,
        'path' => "/A"
      }
    }

It creates a Vert.x HTTP Client with the store configuration (see next snippet). To ease the configuration, you can also configure the `host`, `port` and `path` with the `host`, `port` and `path` properties.

    http = {
      'type' => "http",
      'config' => {
        'defaultHost' => "localhost",
        'defaultPort' => 8080,
        'ssl' => true,
        'path' => "/A"
      }
    }

### Event Bus

This event bus configuration stores receives the configuration from the event bus. This stores let you distribute your configuration among your local and distributed components.

    eb = {
      'type' => "event-bus",
      'config' => {
        'address' => "address-getting-the-conf"
      }
    }

This configuration store supports any type of format.

### Directory

This configuration store is similar to the `file` configuration store, but instead of reading a single file, read several files from a directory.

This configuration store configuration requires:

- a `path` - the root directory in which files are located

- at least one `fileset` - an object to select the files

Each `fileset` contains: * a `pattern` : a Ant style pattern to select files. The pattern is applied on the relative path of the files location in the directory. * an optional `format` indicating the format of the files (each fileset can use a different format, BUT files in a fileset must share the same format).

    dir = {
      'type' => "directory",
      'config' => {
        'path' => "config",
        'filesets' => [
          {
            'pattern' => "dir/*json"
          },
          {
            'pattern' => "dir/*.properties",
            'format' => "properties"
          }
        ]
      }
    }

## Listening for configuration changes

The Configuration Retriever periodically retrieve the configuration and if the outcome is different from the current one, your application can be reconfigured. By default the configuration is reloaded every 5 seconds.

    require 'vertx/vertx'
    require 'vertx-config/config_retriever'
    options = {
      'scanPeriod' => 2000,
      'stores' => [
        store1,
        store2
      ]
    }

    retriever = VertxConfig::ConfigRetriever.create(Vertx::Vertx.vertx(), options)
    retriever.get_config() { |json_err,json|
      # Initial retrieval of the configuration
    }

    retriever.listen() { |change|
      # Previous configuration
      previous = change['previousConfiguration']
      # New configuration
      conf = change['newConfiguration']
    }

## Retrieving the last retrieved configuration

You can retrieved the last retrieved configuration without "waiting" to be retrieved using:

    last = retriever.get_cached_config()

## Reading configuration as a stream

The `ConfigRetriever` provide a way to access the stream of configuration. It’s a `ReadStream` of `JsonObject`. By registering the right set of handlers you are notified:

- when a new configuration is retrieved

- when an error occur while retrieving a configuration

- when the configuration retriever is closed (the `endHandler` is called).

    require 'vertx/vertx'
    require 'vertx-config/config_retriever'
    options = {
      'scanPeriod' => 2000,
      'stores' => [
        store1,
        store2
      ]
    }

    retriever = VertxConfig::ConfigRetriever.create(Vertx::Vertx.vertx(), options)
    retriever.config_stream().end_handler() { |v|
      # retriever closed
    }.exception_handler() { |t|
      # an error has been caught while retrieving the configuration
    }.handler() { |conf|
      # the configuration
    }

## Retrieving the configuration as a Future

The `ConfigRetriever` provide a way to retrieve the configuration as a `Future`:

    require 'vertx-config/config_retriever'
    future = VertxConfig::ConfigRetriever.get_config_as_future(retriever)
    future.set_handler() { |ar_err,ar|
      if (ar_err != nil)
        # Failed to retrieve the configuration
      else
        config = ar
      end
    }

## Extending the Config Retriever

You can extend the configuration by implementing:

- the `ConfigProcessor` SPI to add support for a format

- the `ConfigStoreFactory` SPI to add support for configuration store (place from where the configuration data is retrieved)

## Additional formats

In addition of the out of the box format supported by this library, Vert.x Config provides additional formats you can use in your application.

### Hocon Configuration Format

The Hocon Configuration Format extends the Vert.x Configuration Retriever and provides the support for the HOCON(https://github.com/typesafehub/config/blob/master/HOCON.md) format.

It supports includes, json, properties, macros…​

#### Using the Hocon Configuration Format

To use the Hocon Configuration Format, add the following dependency to the dependencies section of your build descriptor:

- Maven (in your `pom.xml`):

    <dependency>
      <groupId>io.vertx</groupId>
      <artifactId>vertx-config-hocon</artifactId>
      <version>3.4.1</version>
    </dependency>
    <dependency>
      <groupId>io.vertx</groupId>
      <artifactId>vertx-config</artifactId>
      <version>3.4.1</version>
    </dependency>

- Gradle (in your `build.gradle` file):

    compile 'io.vertx:vertx-config:3.4.1'
    compile 'io.vertx:vertx-config-hocon:3.4.1'

#### Configuring the store to use HOCON

Once added to your classpath or dependencies, you need to configure the `ConfigRetriever` to use this format:

    require 'vertx-config/config_retriever'
    store = {
      'type' => "file",
      'format' => "hocon",
      'config' => {
        'path' => "my-config.conf"
      }
    }

    retriever = VertxConfig::ConfigRetriever.create(vertx, {
      'stores' => [
        store
      ]
    })

You just need to set `format` to `hocon`.

### Yaml Configuration Format

The Yaml Configuration Format extends the Vert.x Configuration Retriever and provides the support for the Yaml Configuration Format format.

#### Using the Yaml Configuration Format

To use the Yaml Configuration Format, add the following dependency to the dependencies section of your build descriptor:

- Maven (in your `pom.xml`):

    <dependency>
      <groupId>io.vertx</groupId>
      <artifactId>vertx-config-yaml</artifactId>
      <version>3.4.1</version>
    </dependency>
    <dependency>
      <groupId>io.vertx</groupId>
      <artifactId>vertx-config</artifactId>
      <version>3.4.1</version>
    </dependency>

- Gradle (in your `build.gradle` file):

    compile 'io.vertx:vertx-config:3.4.1'
    compile 'io.vertx:vertx-config-yaml:3.4.1'

#### Configuring the store to use YAML

Once added to your classpath or dependencies, you need to configure the `ConfigRetriever` to use this format:

    require 'vertx-config/config_retriever'
    store = {
      'type' => "file",
      'format' => "yaml",
      'config' => {
        'path' => "my-config.yaml"
      }
    }

    retriever = VertxConfig::ConfigRetriever.create(vertx, {
      'stores' => [
        store
      ]
    })

You just need to set `format` to `yaml`.

## Additional stores

In addition of the out of the box stores supported by this library, Vert.x Config provides additional stores you can use in your application.

### Git Configuration Store

The Git Configuration Store is an extension to the Vert.x Configuration Retriever to retrieve configuration from a Git repository.

#### Using the Git Configuration Store

To use the Git Configuration, add the following dependency to the dependencies section of your build descriptor:

- Maven (in your `pom.xml`):

    <dependency>
      <groupId>io.vertx</groupId>
      <artifactId>vertx-config-git</artifactId>
      <version>3.4.1</version>
    </dependency>
    <dependency>
      <groupId>io.vertx</groupId>
      <artifactId>vertx-config</artifactId>
      <version>3.4.1</version>
    </dependency>

- Gradle (in your `build.gradle` file):

    compile 'io.vertx:vertx-config:3.4.1'
    compile 'io.vertx:vertx-config-git:3.4.1'

#### Configuring the store

Once added to your classpath or dependencies, you need to configure the `ConfigRetriever` to use this store:

    require 'vertx-config/config_retriever'

    git = {
      'type' => "git",
      'config' => {
        'url' => "https://github.com/cescoffier/vertx-config-test.git",
        'path' => "local",
        'filesets' => [
          {
            'pattern' => "*.json"
          }
        ]
      }
    }

    retriever = VertxConfig::ConfigRetriever.create(vertx, {
      'stores' => [
        git
      ]
    })

The configuration requires:

- the `url` of the repository

- the `path` where the repository is cloned (local directory)

- at least `fileset` indicating the set of files to read (same behavior as the directory configuration store).

You can also configure the `branch` (`master` by default) to use and the name of the `remote` repository (`origin` by default).

#### How does it works

If the local `path` does not exist, the configuration store clones the repository into this directory. Then it reads the file matching the different file sets.

It the local `path` exist, it tried to update it (it switches branch if needed)). If the update failed the configuration retrieval fails.

Periodically, the repositories is updated to check if the configuration has been updated.

### Kubernetes ConfigMap Store

The Kubernetes ConfigMap Store extends the Vert.x Configuration Retriever and provides the support Kubernetes Config Map and Secrets.

So, configuration is retrieved by reading the config map or the secrets.

#### Using the Kubernetes ConfigMap Store

To use the Kubernetes ConfigMap Store, add the following dependency to the dependencies section of your build descriptor:

- Maven (in your `pom.xml`):

    <dependency>
    <groupId>io.vertx</groupId>
    <artifactId>vertx-config-kubernetes-configmap</artifactId>
    <version>3.4.1</version>
    </dependency>
    <dependency>
    <groupId>io.vertx</groupId>
    <artifactId>vertx-config</artifactId>
    <version>3.4.1</version>
    </dependency>

- Gradle (in your `build.gradle` file):

    compile 'io.vertx:vertx-config:3.4.1'
    compile 'io.vertx:vertx-config-kubernetes-configmap:3.4.1'

#### Configuring the store

Once added to your classpath or dependencies, you need to configure the `ConfigRetriever` to use this store:

    require 'vertx-config/config_retriever'
    store = {
      'type' => "configmap",
      'config' => {
        'namespace' => "my-project-namespace",
        'name' => "configmap-name"
      }
    }

    retriever = VertxConfig::ConfigRetriever.create(vertx, {
      'stores' => [
        store
      ]
    })

You need to configure the store to find the right configmap. this is done with:

- `namespace` - the project namespace, `default` by default. If the `KUBERNETES_NAMESPACE` ENV variable is set, it uses this value.

- `name` - the name of the config map

If the config map is composed by several element, you can use the `key` parameter to tell which `key` is read

The application must have the permissions to read the config map.

To read data from a secret, just configure the `secret` property to `true`:

    require 'vertx-config/config_retriever'
    store = {
      'type' => "configmap",
      'config' => {
        'namespace' => "my-project-namespace",
        'name' => "my-secret",
        'secret' => true
      }
    }

    retriever = VertxConfig::ConfigRetriever.create(vertx, {
      'stores' => [
        store
      ]
    })

### Redis Configuration Store

The Redis Configuration Store extends the Vert.x Configuration Retriever and provides the way to retrieve configuration from a Redis server.

#### Using the Redis Configuration Store

To use the Redis Configuration Store, add the following dependency to the dependencies section of your build descriptor:

- Maven (in your `pom.xml`):

    <dependency>
      <groupId>io.vertx</groupId>
      <artifactId>vertx-config-redis</artifactId>
      <version>3.4.1</version>
    </dependency>
    <dependency>
      <groupId>io.vertx</groupId>
      <artifactId>vertx-config</artifactId>
      <version>3.4.1</version>
    </dependency>

- Gradle (in your `build.gradle` file):

    compile 'io.vertx:vertx-config:3.4.1'
    compile 'io.vertx:vertx-config-redis:3.4.1'

#### Configuring the store

Once added to your classpath or dependencies, you need to configure the `ConfigRetriever` to use this store:

    require 'vertx-config/config_retriever'
    store = {
      'type' => "redis",
      'config' => {
        'host' => "localhost",
        'port' => 6379,
        'key' => "my-configuration"
      }
    }

    retriever = VertxConfig::ConfigRetriever.create(vertx, {
      'stores' => [
        store
      ]
    })

The store configuration is used to create an instance of `RedisClient`. check the documentation of the Vert.x Redis Client for further details.

In addition, you can set the `key` instructing the store in which field the configuration is stored. `configuration` is used by default.

The created Redis client retrieves the configuration using the `HGETALL` configuration.

### Zookeeper Configuration Store

The Zookeeper Configuration Store extends the Vert.x Configuration Retriever and provides the way to retrieve configuration from a Zookeeper server.

It uses Apache Curator as client.

#### Using the Zookeeper Configuration Store

To use the Redis Configuration Store, add the following dependency to the dependencies section of your build descriptor:

- Maven (in your `pom.xml`):

    <dependency>
      <groupId>io.vertx</groupId>
      <artifactId>vertx-config-zookeeper</artifactId>
      <version>3.4.1</version>
    </dependency>
    <dependency>
      <groupId>io.vertx</groupId>
      <artifactId>vertx-config</artifactId>
      <version>3.4.1</version>
    </dependency>

- Gradle (in your `build.gradle` file):

    compile 'io.vertx:vertx-config:3.4.1'
    compile 'io.vertx:vertx-config-zookeeper:3.4.1'

#### Configuring the store

Once added to your classpath or dependencies, you need to configure the `ConfigRetriever` to use this store:

    require 'vertx-config/config_retriever'
    store = {
      'type' => "zookeeper",
      'config' => {
        'connection' => "localhost:2181",
        'path' => "/path/to/my/conf"
      }
    }

    retriever = VertxConfig::ConfigRetriever.create(vertx, {
      'stores' => [
        store
      ]
    })

The store configuration is used to configure the Apache Curator client and the path of the Zookeeper node containing the configuration. Notice that the format of the configuration can be JSON, or any supported format.

The configuration requires the `configuration` attribute indicating the connection string of the Zookeeper server, and the `path` attribute indicating the path of the node containing the configuration.

In addition you can configure:

- `maxRetries`: the number of connection attempt, 3 by default

- `baseSleepTimeBetweenRetries`: the amount of milliseconds to wait between retries (exponential backoff strategy). 1000 ms by default.

### Spring Config Server Store

The Spring Config Server Store extends the Vert.x Configuration Retriever and provides the a way to retrieve configuration from a Spring Server.

#### Using the Spring Config Server Store

To use the Spring Config Server Store, add the following dependency to the dependencies section of your build descriptor:

- Maven (in your `pom.xml`):

    <dependency>
      <groupId>io.vertx</groupId>
      <artifactId>vertx-config-spring-config-server</artifactId>
      <version>3.4.1</version>
    </dependency>
    <dependency>
      <groupId>io.vertx</groupId>
      <artifactId>vertx-config</artifactId>
      <version>3.4.1</version>
    </dependency>

- Gradle (in your `build.gradle` file):

    compile 'io.vertx:vertx-config:3.4.1'
    compile 'io.vertx:vertx-config-spring-config-server:3.4.1'

#### Configuring the store

Once added to your classpath or dependencies, you need to configure the `ConfigRetriever` to use this store:

    require 'vertx-config/config_retriever'
    store = {
      'type' => "spring-config-server",
      'config' => {
        'url' => "http://localhost:8888/foo/development"
      }
    }

    retriever = VertxConfig::ConfigRetriever.create(vertx, {
      'stores' => [
        store
      ]
    })

Configurable attributes are:

- `url` - the `url` to retrieve the configuration (mandatory)

- `timeout` - the timeout (in milliseconds) to retrieve the configuration, 3000 by default

- `user` - the `user` (no authentication by default)

- `password` - the `password`

- `httpClientConfiguration` - the configuration of the underlying HTTP client