EtcdConfigSource adds basic etcd support to the Apache DeltaSpike configuration mechanism. In particular, it has not been tested against a cluster configuration or with TLS. Both may come at a later time.

Building

You may build this project using Maven 3.5+ and OpenJDK 8. I use binaries provided by the AdoptOpenJDK project.

First, you'll need to clone the repo:

$ git clone https://github.com/jasonhallford/EtcdConfigSource.git

Then build with Maven:

$ mvn install -DskipITs

Here, -DskipITs is used to disable integration tests. You may run them, of course, but you'll need to configure a local etcd instance first.

If you prefer an IDE, I recommend IntelliJ IDEA's Community Edition, although any IDE with Maven support should suffice.

Downloading

A pre-built binary is available from this site's packages tab. You may download the JAR directly, or integrate Maven with GitHub packages and then use the provided coordinates (hint: you want the latest version of io.miscellanea.EtcdConfigSource).

Using

To use the EtcdConfigSource, simply place the JAR and its dependencies on the classpath. Integration with DeltaSpike is achieved via the Java Service Loader Framework. With the exception of setting a few parameters (see below), no additional configuration is required!

Parameters

The configuration source makes use of parameters to control runtime behavior. They may be set in two ways

On the command line using -D (or any other means of invoking System.setProperty())
Via a property file referenced using URL syntax.

Property	Type	Description
etcd.cs.configUrl	String	The URL for a .properties file containing the other properties listed in this table. For example, to reference a file named myEtcd.properties in /var/lib/etcd/ you'd use the URL file://var/lib/etcd/myEtcd.properties.
etcd.cs.keyPrefix	String	An optional prefix to prepend to a key before performin a lookup in the key space. This permits property injection to use a stable name that may be customized via configuration on a per-execution environment basis.
etcd.cs.ordinal	Integer	The ordinal used to determine the configuration source's priority order. Defaults to 1000 if omitted. Please see the DeltaSpike configuration mechanism page for more information.
etcd.cs.watch	Boolean	If true, then the configuration source will dynamically reload previously read etcd keys should they change. If false (the default), then each key's value is only read once.
etcd.endpoint.host	String	The etcd host's DNS name or IP address.
etcd.endpoint.members	String	A comma-separated list of etcd cluter members (e.g. "http://localhost:2379,http://localhost:2389"). When present, this property causes the config source to ignore etcd.endpoint.host and etcd.endpoint.port. Specifying a single-member list may be used as an alternative to these properties.
etcd.endpoint.password	String	The etcd user's password. Must be omitted if authentication is not required.
etcd.endpoint.port	Integer	The etcd server's TCP port. Defaults to 2379 if omitted.
etcd.endpoint.user	String	The name used to authenticate with the etcd server. Must be omitted if authentication in not required.
javax.net.ssl.trustStore	String	The absolute path to a java keystore containing the etcd server's TLS certificate. This property and javax.net.ssl.trustStorePassword are required for TLS-enabled endpoints.
javax.net.ssl.trustStorePassword	String	The trust store's password. This property and javax.net.ssl.trustStore are required for TLS-enabled endpoints.

Parameters may be specified on the command line and in a properties file. In that case, command line parameters take precedence, overriding any conflicting values in the file.