关于flume配置加载

最近项目在用到flume，因此翻了下flume的代码，

启动脚本：

　　nohup bin/flume-ng agent -n tsdbflume -c conf -f conf/配置文件.conf -Dflume.root.logger=DEBUG,console &

翻下flume-ng的脚本,　　FLUME_AGENT_CLASS="org.apache.flume.node.Application"

从Application进入；

写了下flume-agent启动的时序图：

这是简单的启动时序图，时序图里画的都在flume-node这个项目里；

里边其实最核心的是创建配置文件里的对象，这个工作是在AbstractConfigurationProvider.getConfiguration()这个方法里做的。先上代码

  public MaterializedConfiguration getConfiguration() {
    MaterializedConfiguration conf = new SimpleMaterializedConfiguration();
　　 // getFlumeConfiguration()方法，是关键核心，负责整个配置加载，下边代码说明
    FlumeConfiguration fconfig = getFlumeConfiguration();
    AgentConfiguration agentConf = fconfig.getConfigurationFor(getAgentName());
    if (agentConf != null) {
      Map<String, ChannelComponent> channelComponentMap = Maps.newHashMap();
      Map<String, SourceRunner> sourceRunnerMap = Maps.newHashMap();
      Map<String, SinkRunner> sinkRunnerMap = Maps.newHashMap();
      try {
        loadChannels(agentConf, channelComponentMap);
        loadSources(agentConf, channelComponentMap, sourceRunnerMap);
        loadSinks(agentConf, channelComponentMap, sinkRunnerMap);
        Set<String> channelNames = new HashSet<String>(channelComponentMap.keySet());
        for (String channelName : channelNames) {
          ChannelComponent channelComponent = channelComponentMap.get(channelName);
          if (channelComponent.components.isEmpty()) {
            LOGGER.warn(String.format("Channel %s has no components connected" +
                " and has been removed.", channelName));
            channelComponentMap.remove(channelName);
            Map<String, Channel> nameChannelMap =
                channelCache.get(channelComponent.channel.getClass());
            if (nameChannelMap != null) {
              nameChannelMap.remove(channelName);
            }
          } else {
            LOGGER.info(String.format("Channel %s connected to %s",
                channelName, channelComponent.components.toString()));
            conf.addChannel(channelName, channelComponent.channel);
          }
        }
        for (Map.Entry<String, SourceRunner> entry : sourceRunnerMap.entrySet()) {
          conf.addSourceRunner(entry.getKey(), entry.getValue());
        }
        for (Map.Entry<String, SinkRunner> entry : sinkRunnerMap.entrySet()) {
          conf.addSinkRunner(entry.getKey(), entry.getValue());
        }
      } catch (InstantiationException ex) {
        LOGGER.error("Failed to instantiate component", ex);
      } finally {
        channelComponentMap.clear();
        sourceRunnerMap.clear();
        sinkRunnerMap.clear();
      }
    } else {
      LOGGER.warn("No configuration found for this host:{}", getAgentName());
    }
    return conf;
  }

下面说下这个类的具体加载过程。

PropertiesFileConfigurationProvider.getFlumeConfiguration()

  @Override
  public FlumeConfiguration getFlumeConfiguration() {
    BufferedReader reader = null;
    try {
      reader = new BufferedReader(new FileReader(file));
      Properties properties = new Properties();
      properties.load(reader);
      return new FlumeConfiguration(toMap(properties));
    } catch (IOException ex) {
      LOGGER.error("Unable to load file:" + file
          + " (I/O failure) - Exception follows.", ex);
    } finally {
      if (reader != null) {
        try {
          reader.close();
        } catch (IOException ex) {
          LOGGER.warn(
              "Unable to close file reader for file: " + file, ex);
        }
      }
    }
    return new FlumeConfiguration(new HashMap<String, String>());
  }

new FlumeConfiguration(toMap(properties))，代码在下边：

下边从代码入手写下怎么加载内容：

  /**
   * 创建一个FlumeConfiguration对象，参数为：配置文件的key-value对
   * Creates a populated Flume Configuration object.
   */
  public FlumeConfiguration(Map<String, String> properties) {
    agentConfigMap = new HashMap<String, AgentConfiguration>();
    errors = new LinkedList<FlumeConfigurationError>();
    // Construct the in-memory component hierarchy
    for (String name : properties.keySet()) {
      String value = properties.get(name);

      // addRawProperty里对agentConfigMap初始化,  
      // 1：这里插入的是agentConfiguration对象里的contextMap
      if (!addRawProperty(name, value)) {
        logger.warn("Configuration property ignored: " + name + " = " + value);
      }
    }
    // Now iterate thru the agentContext and create agent configs and add them
    // to agentConfigMap

    // validate and remove improperly configured components
    // 2：这里插入的是agentConfiguration对象里的configMap

    validateConfiguration();
  }

然后，进入FlumeConfiguration.addRawProperty(name,value)：

  private boolean addRawProperty(String name, String value) {
    // Null names and values not supported
    if (name == null || value == null) {
      errors
          .add(new FlumeConfigurationError("", "",
              FlumeConfigurationErrorType.AGENT_NAME_MISSING,
              ErrorOrWarning.ERROR));
      return false;
    }

    // Empty values are not supported
    if (value.trim().length() == 0) {
      errors
          .add(new FlumeConfigurationError(name, "",
              FlumeConfigurationErrorType.PROPERTY_VALUE_NULL,
              ErrorOrWarning.ERROR));
      return false;
    }

    // Remove leading and trailing spaces
    name = name.trim();
    value = value.trim();

    int index = name.indexOf('.');

    // All configuration keys must have a prefix defined as agent name
    if (index == -1) {
      errors
          .add(new FlumeConfigurationError(name, "",
              FlumeConfigurationErrorType.AGENT_NAME_MISSING,
              ErrorOrWarning.ERROR));
      return false;
    }

    String agentName = name.substring(0, index);

    // Agent name must be specified for all properties
    if (agentName.length() == 0) {
      errors
          .add(new FlumeConfigurationError(name, "",
              FlumeConfigurationErrorType.AGENT_NAME_MISSING,
              ErrorOrWarning.ERROR));
      return false;
    }

    String configKey = name.substring(index + 1);

    // Configuration key must be specified for every property
    if (configKey.length() == 0) {
      errors
          .add(new FlumeConfigurationError(name, "",
              FlumeConfigurationErrorType.PROPERTY_NAME_NULL,
              ErrorOrWarning.ERROR));
      return false;
    }

    AgentConfiguration aconf = agentConfigMap.get(agentName);

    // 这里创建AgentConfiguration，并插入到FlumeConfiguration的Map<String, AgentConfiguration> agentConfigMap中
    if (aconf == null) {
      aconf = new AgentConfiguration(agentName, errors);
      agentConfigMap.put(agentName, aconf);
    }

    // Each configuration key must begin with one of the three prefixes:
    // sources, sinks, or channels.
    // 最终，键值对被加载到agentConfiguration中

    return aconf.addProperty(configKey, value);
  }

最终被加载到：agentConfiguration.addProperty(String key, String value)中

      ComponentNameAndConfigKey cnck = parseConfigKey(key,
          BasicConfigurationConstants.CONFIG_SOURCES_PREFIX);

      if (cnck != null) {
        // it is a source
        String name = cnck.getComponentName();
        Context srcConf = sourceContextMap.get(name);

        if (srcConf == null) {
          srcConf = new Context();
          sourceContextMap.put(name, srcConf);
        }
        // sourceContextMap中存放new Context().put(cnck.getConifyKey(),value)
        srcConf.put(cnck.getConfigKey(), value);
        return true;
      }

所以最后是加载到AgentConfiguration中对应的*ContextMap中了；

  public static class AgentConfiguration {

    private final String agentName;
    private String sources;
    private String sinks;
    private String channels;
    private String sinkgroups;

    private final Map<String, ComponentConfiguration> sourceConfigMap;
    private final Map<String, ComponentConfiguration> sinkConfigMap;
    private final Map<String, ComponentConfiguration> channelConfigMap;
    private final Map<String, ComponentConfiguration> sinkgroupConfigMap;

    private Map<String, Context> sourceContextMap;
    private Map<String, Context> sinkContextMap;
    private Map<String, Context> channelContextMap;
    private Map<String, Context> sinkGroupContextMap;

    private Set<String> sinkSet;
    private Set<String> sourceSet;
    private Set<String> channelSet;
    private Set<String> sinkgroupSet;

    private final List<FlumeConfigurationError> errorList;

    // ** 省略其他代码
    
}

这里比较崩溃，跑来跑去的我们来梳理下：

先是FlumeConfiguration的addRawProperty方法执行put动作：

　　FlumeConfiguration.agentConfigMap.put(agentName, AgentConfiguration conf);

在这里创建AgentCponfiguration对象

　　aconf = new AgentCponfiguration(agentName, errors);

然后执行

　　aconf.addProperty(configKey, value), 将key，value插入到AgentConfiguration对象的*ContextMap中，至此完成键值对的保存工作;

最终所有的键值对都被保存在AgentConfiguration对象中；

对于AgentConfiguration的插入操作，也分为两个部分，在FlumeConifiguration构造方法中，

1：addRawProperty(name,value);将kv键值对，插入到AgentConfiguration对象的contextMap中;

2：validateConfiguration；下边跟进下validateConfiguration代码；

validateConfiguration -> aconf.isValid() -> validateChannels(channelSet)

代码注释中，其实已经写得比较详细了

    /**
     * If it is a known component it will do the full validation required for
     * that component, else it will do the validation required for that class.
     */
    private Set<String> validateChannels(Set<String> channelSet) {
      Iterator<String> iter = channelSet.iterator();
      Map<String, Context> newContextMap = new HashMap<String, Context>();
      ChannelConfiguration conf = null;
      /*
       * The logic for the following code:
       *
       * Is it a known component?
       *  -Yes: Get the ChannelType and set the string name of that to
       *        config and set configSpecified to true.
       *  -No.Look for config type for the given component:
       *      -Config Found:
       *        Set config to the type mentioned, set configSpecified to true
       *      -No Config found:
       *        Set config to OTHER, configSpecified to false,
       *        do basic validation. Leave the context in the
       *        contextMap to process later. Setting it to other returns
       *        a vanilla configuration(Source/Sink/Channel Configuration),
       *        which does basic syntactic validation. This object is not
       *        put into the map, so the context is retained which can be
       *        picked up - this is meant for older classes which don't
       *        implement ConfigurableComponent.
       */
      while (iter.hasNext()) {
        String channelName = iter.next();
        Context channelContext = channelContextMap.get(channelName);
        // Context exists in map.
        if (channelContext != null) {
          // Get the configuration object for the channel:
          ChannelType chType = getKnownChannel(channelContext.getString(
              BasicConfigurationConstants.CONFIG_TYPE));
          boolean configSpecified = false;
          String config = null;
          // Not a known channel - cannot do specific validation to this channel
          if (chType == null) {
            config = channelContext.getString(BasicConfigurationConstants.CONFIG_CONFIG);
            if (config == null || config.isEmpty()) {
              config = "OTHER";
            } else {
              configSpecified = true;
            }
          } else {
            config = chType.toString().toUpperCase(Locale.ENGLISH);
            configSpecified = true;
          }

          try {
            conf =
                (ChannelConfiguration) ComponentConfigurationFactory.create(
                    channelName, config, ComponentType.CHANNEL);
            logger.debug("Created channel " + channelName);
            if (conf != null) {
              conf.configure(channelContext);
            }
            if ((configSpecified && conf.isNotFoundConfigClass()) ||
                !configSpecified) {
              newContextMap.put(channelName, channelContext);
            } else if (configSpecified) {
              channelConfigMap.put(channelName, conf);
            }
            if (conf != null) {
              errorList.addAll(conf.getErrors());
            }
          } catch (ConfigurationException e) {
            // Could not configure channel - skip it.
            // No need to add to error list - already added before exception is
            // thrown
            if (conf != null) errorList.addAll(conf.getErrors());
            iter.remove();
            logger.warn("Could not configure channel " + channelName
                + " due to: " + e.getMessage(), e);

          }
        } else {
          iter.remove();
          errorList.add(new FlumeConfigurationError(agentName, channelName,
              FlumeConfigurationErrorType.CONFIG_ERROR, ErrorOrWarning.ERROR));
        }
      }
      channelContextMap = newContextMap;
      Set<String> tempchannelSet = new HashSet<String>();
      tempchannelSet.addAll(channelConfigMap.keySet());
      tempchannelSet.addAll(channelContextMap.keySet());
      channelSet.retainAll(tempchannelSet);
      return channelSet;
    }

在validChannels中，根据配置文件中的channel的类型，创建ChannelConfiguration对象，然后插入到AgentConfiguration的configMap中；

到这里，一个完整的FlumeConfiguration对象已经完全加载好了；下面继续；