ThreadPoolExhaustedListener 在最新版本中未发现用户配置的入口，这个功能的设计初衷我理解，是发生线程池耗尽通知给应用，目前没看到应用如何添加监听的地方。
Pattern EQUAL_SPLIT_PATTERN = Pattern.compile("\\s*[=]+\\s*");
    String DEFAULT_PROXY = "javassist";
    String DEFAULT_DIRECTORY = "dubbo";
    String PROTOCOL_KEY = "protocol";
    String DEFAULT_PROTOCOL = "dubbo";
    String DEFAULT_THREAD_NAME = "Dubbo";
    int DEFAULT_CORE_THREADS = 0;
    int DEFAULT_THREADS = 200;
    String EXECUTOR_SERVICE_COMPONENT_KEY = ExecutorService.class.getName();
    String CONSUMER_SHARED_EXECUTOR_SERVICE_COMPONENT_KEY = "CONSUMER_SHARED_SERVICE_EXECUTOR";
    String INTERNAL_EXECUTOR_SERVICE_COMPONENT_KEY = "INTERNAL_SERVICE_EXECUTOR";
    String THREADPOOL_KEY = "threadpool";
    String THREAD_NAME_KEY = "threadname";
    String CORE_THREADS_KEY = "corethreads";
    String THREADS_KEY = "threads";
    String QUEUES_KEY = "queues";
    String ALIVE_KEY = "alive";
    String DEFAULT_THREADPOOL = "limited";
    String DEFAULT_CLIENT_THREADPOOL = "cached";
    String IO_THREADS_KEY = "iothreads";
    String KEEP_ALIVE_KEY = "keep.alive";
    int DEFAULT_QUEUES = 0;
    int DEFAULT_ALIVE = 60 * 1000;
    String TIMEOUT_KEY = "timeout";
    int DEFAULT_TIMEOUT = 1000;
    String SESSION_KEY = "session";
    
    
    String TIMEOUT_ATTACHMENT_KEY = "_TO";
    String TIMEOUT_ATTACHMENT_KEY_LOWER = "_to";