ElasticSearch Settings

ElasticSearch (ES) settings start with package org.elasticsearch.common.settings.

See the following code:

    Settings t_settings = Settings.EMPTY;
    Path path = FileSystems.getDefault().getPath(args[0]);
    Settings.Builder builder = t_settings.builder();
    try {
        builder = builder.loadFromPath(path);
    } catch (IOException e) {
        e.printStackTrace();
    } 

    Settings newsettings = builder.build();
    System.out.println(newsettings.get("path.data"));

The entire node settings can be simply built using code similar to the above. Get the an empty settings object, then pass in the configuration file. According to the setting loader defined in package org.elasticsearch.common.settings.loader, the configuration file can be in any of the three formats, yml, json, or simple name value pair. the type of the file completely depends on the file extension, so you can basically have files like the following: myconf.json myconf.yml myconf.properties Use the loadFromPath to load the file, that method will return a builder object, then call the builder object build method to get a Settings object. From that point on, you can call any of the method to get the actual configuration value.

Settings is really just a SortedMap of strings, defined like this SortedMap<String, String>.

ClusterSettings:

There is also a abstract class named AbstractScopedSettings. This class represents the settings per index and per-cluster.  The scope of the class indicates if the settings are for index or node. The value of the scope can be Filtered, Dynamic, Deprecated, NodeScope and IndexScope.  AbstractScopedSettings class basically is a collection of Setting instances. Class AbstractScopedSettings gets extended by final class ClusterSettings which defines the built-in-cluster-settings by create a Collections.unmodifiableSet with many Setting instances. Here are few examples:

client.transport.nodes_sampler_interval
client.transport.ping_timeout
cluster.routing.allocation.balance.index
cluster.routing.allocation.balance.shard
cluster.routing.allocation.balance.threshold

Notes: The cluster setting configurations are also defined in the same file. There is no separate configuration files for cluster settings.