system watcher

First, Prerequisites:1. Install Ruby, if I remember correctly, the Mac comes with Ruby, terminal input ruby-v, enter, if the Ruby version number is displayed, the ruby environment is already installed. If not, install ruby yourself. For example, my Mac displays:Ruby 2.0.0p648 (2015-12-16 revision 53162) [Universal.x86_64-darwin15]2. Install the sass, the process and the win system, the same, after installation, terminal input SASS-V, enter, if the Sas

Zookeeper Watcher API description, zookeeperwatcher Watcher is a core function in ZooKeeper. Watcher can monitor data changes of directory nodes and subdirectory changes. Once these statuses change, the server will notify all Watcher sets on this directory node, so that every client will soon know that the status of th

/***/Publicinterface watcher {// status is The state public void update (String status) that was observed to pass over;}Importjava.util.LinkedList;/**abstract the observed person*/ Public Abstract classwatched {/**The Observer object used to save the registration*/ protectedLinkedlistNewLinkedlist(); /**registering the Observer object*/ Public Abstract voidAdd (Watcher

The zookeeper client can set watcher for a znode so that the client can obtain the appropriate event notification when the node changes. If you do not set the Watcher, you will not receive notification. Taking zookeeper C client as an example, you can set the watcher flag at the same time when you call the following 3 functions, get the data or state of a node. Z

.registerservice (s); O3.registerservice (s); O4.registerservice (s); //Cancel SubscriptionO1.unregisterservice (s); S.setmsg ("today's News hot"); }}/** * Service class is used by observers to push messages*/classService extends observable{PrivateString msg; PublicString getmsg () {returnmsg+"(from the service person (the observed person))"; } /** * * push message*/ Public voidsetmsg (String msg) { This. msg =msg; Setchanged ();//Setting ChangesNotifyobservers ();//not

Watcher Setup is the most common development, need to understand some of the basic characteristics of watcher, for exists, GetData, getchild for the different operations of the node will receive different watcher informationstate=-112 Session Timeout StatusState=-113 Authentication failed statusState= 1 Connection SetupState= 2 (temporarily unclear how to underst

The client ClientWatchManager manages the watchers and handle events generated by ClientXncn.You can register a watcher object in the ClientWatchManager APIs such as exists, getChildren, and getData of zookeeper,Create, setData, delete, and other APIs that cause changes to the zookeeper node will trigger the execution of watcher process. The WatchManager of the server and the

Please note that this is a Libev rather than a libevent article. This article is the third, mainly about the basic concentration of watcher in Libev. This address: https://segmentfault.com/a/1190000006679929 ev_io: direct Operation FD This watcher is responsible for detecting whether the file descriptor (hereinafter referred to as FD) can write data or read the data. It is best to set FD to be non-blocking.

These days I looked at Perl's event programming framework Anyevent, focusing on a few articles: http://search.cpan.org/~mlehmann/AnyEvent-7.05/lib/AnyEvent.pm Http://search.cpan.org/~mlehmann/AnyEvent-7.05/lib/AnyEvent/Intro.pod Http://www.jb51.net/article/55278.htm 1, what is event programming? As a simple example, when you browse the Web, you click on a picture, rub a pop-up thing, you do not point, that is there, waiting for a person to point it. If you have written JS, in fact, you regi

/** * Classname:zookeeperwatcher * This class is a watcher class * date:2017 August 31 9:44:31 * @author Yanlong */ public class Zookeeperwatcher implements watcher{ Defining Atomic Variables Atomicinteger seq = new Atomicinteger (); Define session Expiration Time private static final int session_timeout = 1000; Zookeeper Server address private static final String connection_addr = "112.124.121.34:2181";

watcher implementing data structures and streaming diagrams Note: The picture is too large, right-click new tab to open the picture, enlarge view Client client receives notification message for watch event All watcher final callbacks receive messages in the CLIENTCNXN internal class Sendthread. The XID field of the message body of the notification event notification that the server sends to the client is

Observer patternIntent: define a one-to-many dependency between objects, and when the state of an object changes, all objects that depend on it are notified and automatically updated.Workaround: An object state changes to other object notification issues, and to take into account the ease of use and low coupling, to ensure a high degree of collaboration.use: the state of an object (the target object) is changed, and all dependent objects (Observer objects) are notified of the broadcast notificat