Example of a basic utility class to interact with etcd

RemoteConfigService.groovy

package com.foo.config

import com.foog.util.TomcatDatasourceUtil
import grails.plugins.rest.client.RestBuilder
import groovy.json.JsonSlurper

/**
 * Application service to get and set values from a centralized remote configuration service.
 */
class RemoteConfigService {
    def grailsApplication

    public static final String CATALOG_DB_URL_KEY = "dataSource/url"
    protected static final int INITIAL_RETRY_TIMEOUT_SECS = 5

    /**
     * Runs a process to watch for configuration changes to the plancatalog datasource URL.
     * If the URL value changes, call the datasource utility to update the connections to point at the new database.
     */
    void watchForChanges() {
        if (!grailsApplication.config.remoteConfig.enabled) {
            log.info "remoteConfigBaseUrl not configured - will not watch for config changes"
            return
        }
        log.debug("watching for changes")

        Thread.startDaemon {
            int secondsToWait = INITIAL_RETRY_TIMEOUT_SECS
            while (true) {
                try {
                    String url = get("${CATALOG_DB_URL_KEY}?wait=true")
                    if (url) {
                        grailsApplication.config.dataSource_plancatalog.url = url
                        TomcatDatasourceUtil.ensureCurrentDatasources(grailsApplication, ['dataSource_plancatalog'])
                    }
                    secondsToWait = INITIAL_RETRY_TIMEOUT_SECS
                } catch (Exception e) {
                    log.warn("Exception occurred while watching for config changes. Will wait ${secondsToWait} seconds and continue watching", e)
                    Thread.sleep(1000 * secondsToWait)
                    // double the length of the time to wait before retrying, up to a maximum of 30 minutes
                    secondsToWait = [60 * 30, 2 * secondsToWait].min()
                }
            }
        }
    }

    /**
     * Get the configured value for the given key
     * @param key
     * @return the current value
     */
    String get(String key) {
        def jsonSlurper = new JsonSlurper()
        def json = jsonSlurper.parseText(new URL("${grailsApplication.config.remoteConfig.baseUrl}/${key}").text)
        return json?.node?.value
    }

    /**
     * Set the given key to the given value in the centralized configuration service
     * @param key
     * @param valueArg
     */
    void set(String key, String valueArg) {
        RestBuilder rest = new RestBuilder()
        def resp = rest.put("${grailsApplication.config.remoteConfig.baseUrl}/${key}") {
            value = valueArg
        }
        if (resp.status != 200) {
            throw new Exception("Error setting configuration value for key=${key}. Response=${resp.body}")
        }
    }
}