ConsulConfigurationSource.java

/*
 * Copyright 2015-2016 Norbert Potocki (norbert.potocki@nort.pl)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.cfg4j.source.consul;

import static java.util.Objects.requireNonNull;

import com.google.common.net.HostAndPort;
import com.orbitz.consul.Consul;
import com.orbitz.consul.KeyValueClient;
import com.orbitz.consul.model.kv.Value;
import org.cfg4j.source.ConfigurationSource;
import org.cfg4j.source.SourceCommunicationException;
import org.cfg4j.source.context.environment.Environment;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;

/**
 * Note: use {@link ConsulConfigurationSourceBuilder} for building instances of this class.
 * <p>
 * Read configuration from the Consul K-V store.
 */
public class ConsulConfigurationSource implements ConfigurationSource {

  private static final Logger LOG = LoggerFactory.getLogger(ConsulConfigurationSource.class);

  private KeyValueClient kvClient;
  private Map<String, String> consulValues;
  private final String host;
  private final int port;
  private boolean initialized;

  /**
   * Note: use {@link ConsulConfigurationSourceBuilder} for building instances of this class.
   * <p>
   * Read configuration from the Consul K-V store located at {@code host}:{@code port}.
   *
   * @param host Consul host to connect to
   * @param port Consul port to connect to
   */
  ConsulConfigurationSource(String host, int port) {
    this.host = requireNonNull(host);
    this.port = port;

    initialized = false;
  }

  @Override
  public Properties getConfiguration(Environment environment) {
    LOG.trace("Requesting configuration for environment: " + environment.getName());

    if (!initialized) {
      throw new IllegalStateException("Configuration source has to be successfully initialized before you request configuration.");
    }

    reload();

    Properties properties = new Properties();
    String path = environment.getName();

    if (path.startsWith("/")) {
      path = path.substring(1);
    }

    if (path.length() > 0 && !path.endsWith("/")) {
      path = path + "/";
    }

    for (Map.Entry<String, String> entry : consulValues.entrySet()) {
      if (entry.getKey().startsWith(path)) {
        properties.put(entry.getKey().substring(path.length()).replace("/", "."), entry.getValue());
      }
    }

    return properties;
  }

  /**
   * @throws SourceCommunicationException when unable to connect to Consul client
   */
  @Override
  public void init() {
    try {
      LOG.info("Connecting to Consul client at " + host + ":" + port);

      Consul consul = Consul.builder().withHostAndPort(HostAndPort.fromParts(host, port)).build();

      kvClient = consul.keyValueClient();
    } catch (Exception e) {
      throw new SourceCommunicationException("Can't connect to host " + host + ":" + port, e);
    }

    initialized = true;
  }

  private void reload() {
    Map<String, String> newConsulValues = new HashMap<>();
    List<Value> valueList;

    try {
      LOG.debug("Reloading configuration from Consuls' K-V store");
      valueList = kvClient.getValues("/");
    } catch (Exception e) {
      initialized = false;
      throw new SourceCommunicationException("Can't get values from k-v store", e);
    }

    for (Value value : valueList) {
      String val = "";

      if (value.getValueAsString().isPresent()) {
        val = value.getValueAsString().get();
      }

      LOG.trace("Consul provided configuration key: " + value.getKey() + " with value: " + val);

      newConsulValues.put(value.getKey(), val);
    }

    consulValues = newConsulValues;
  }

  @Override
  public String toString() {
    return "ConsulConfigurationSource{" +
        "consulValues=" + consulValues +
        ", kvClient=" + kvClient +
        '}';
  }
}