////
This guide is maintained in the main Quarkus repository
and pull requests should be submitted there:
https://github.com/quarkusio/quarkus/tree/master/docs/src/main/asciidoc
////
= Quarkus - Reading properties from Consul

include::./attributes.adoc[]
:extension-status: preview

This guide explains how your Quarkus application can read configuration properties at runtime from https://www.consul.io[Consul].

include::./status-include.adoc[]

== Prerequisites

To complete this guide, you need:

* less than 15 minutes
* an IDE
* JDK 1.8+ installed with `JAVA_HOME` configured appropriately
* Apache Maven {maven-version}


== Solution

We recommend that you follow the instructions in the next sections and create the application step by step.

== Introduction

Consul is a versatile system which among other things, provides a distributed Key-Value store that is used in many architectures as a source of configuration for services.
This Key-Value store is what the `quarkus-consul-config` extension interacts with in order to allow Quarkus applications to read runtime configuration properties from Consul.

== Starting Consul

There are various ways to start Consul that vary in complexity, but for the purposes of this guide, we elect to start a single Consul server with no persistence via Docker, like so:

[source,bash]
----
docker run --rm --name consul -p 8500:8500 -p 8501:8501 consul:1.7 agent -dev -ui -client=0.0.0.0 -bind=0.0.0.0 --https-port=8501
----

Please consult the https://www.consul.io/docs/install[documentation] to learn more about the various Consul installation options.

== Creating the Maven project

First, we need a new project. Create a new project with the following command:

[source,bash,subs=attributes+]
----
mvn io.quarkus:quarkus-maven-plugin:{quarkus-version}:create \
    -DprojectGroupId=org.acme \
    -DprojectArtifactId=consul-config-quickstart \
    -DclassName="org.acme.consul.config.GreetingResource" \
    -Dpath="/greeting" \
    -Dextensions="consul-config"
cd consul-config-quickstart
----

This command generates a Maven project with a REST endpoint and imports the `consul-config` extension.

If you already have your Quarkus project configured, you can add the `consul-config` extension
to your project by running the following command in your project base directory:

[source,bash]
----
./mvnw quarkus:add-extension -Dextensions="consul-config"
----

This will add the following to your `pom.xml`:

[source,xml]
----
<dependency>
    <groupId>io.quarkus</groupId>
    <artifactId>quarkus-consul-config</artifactId>
</dependency>
----

== GreetingController

The Quarkus Maven plugin automatically generated a `GreetingResource` JAX-RS resource in the
`src/main/java/org/acme/consul/config/client/GreetingResource.java` file that looks like:

[source,java]
----
package org.acme.consul.config.client;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

@Path("/hello")
public class GreetingResource {

    @GET
    @Produces(MediaType.TEXT_PLAIN)
    public String hello() {
        return "hello";
    }
}
----

As we want to use configuration properties obtained from the Config Server, we will update the `GreetingResource` to inject the `message` property. The updated code will look like this:

[source,java]
----
package org.acme.consul.config.client;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

import org.eclipse.microprofile.config.inject.ConfigProperty;

@Path("/hello")
public class GreetingResource {

    @ConfigProperty(name = "message", defaultValue="Hello from default")
    String message;

    @GET
    @Produces(MediaType.TEXT_PLAIN)
    public String hello() {
        return message;
    }
}
----

== Configuring the application

Quarkus provides various configuration knobs under the `quarkus.consul-config` root. For the purposes of this guide, our Quarkus application is going to be configured in `application.properties` as follows:

[source,properties]
----
# use the same name as the application name that was configured when standing up the Config Server
quarkus.application.name=consul-test
# enable retrieval of configuration from Consul - this is off by default
quarkus.consul-config.enabled=true
# this is a key in Consul's KV store that the Quarkus application will read and try to extract properties from
quarkus.consul-config.properties-value-keys=config/${quarkus.application.name}
----

== Add Configuration to Consul

For the previous application configuration to work, we need to add a `config/consul-test` key under Consul's Key Value store. The value of this key will essentially be a properties "file" containing the application configuration.
In this case we want to add the following data to the `config/consul-test` key:

[source,properties]
----
greeting.message=Hello from Consul
----

When adding this configuration from the UI, Consul will automatically convert the data into the necessary base64 encoding. If you instead add the configuration via the Consul's https://www.consul.io/api/kv.html#create-update-key[REST API],
make sure to first encode the previous data into base64.

NOTE: In this use case we made the value of the key as a properties "file", because we used `quarkus.consul-config.properties-value-keys` in the application. The
extension also provides the ability to use the raw values of keys when `quarkus.consul-config.raw-value-keys` is used. Furthermore, these two properties can be used
simultaneously, while each one also supports setting multiple keys.

== Package and run the application

Run the application with: `./mvnw compile quarkus:dev`.
Open your browser to http://localhost:8080/greeting.

The result should be: `Hello from Consul` as it is the value obtained from the Consul Key Value store.

== Run the application as a native executable

You can of course create a native image using the instructions of the link:building-native-image[Building a native executable guide].

== Configuration Reference

include::{generated-dir}/config/quarkus-consul-config.adoc[opts=optional, leveloffset=+1]
