restconf/sal-rest-connector/src/main/java/org/opendaylight/netconf/sal/streams/listeners/ListenerAdapter.java

   1 /*
   2  * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
   3  *
   4  * This program and the accompanying materials are made available under the
   5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   6  * and is available at http://www.eclipse.org/legal/epl-v10.html
   7  */
   8 package org.opendaylight.netconf.sal.streams.listeners;
   9
  10 import com.google.common.base.Preconditions;
  11 import com.google.common.eventbus.AsyncEventBus;
  12 import com.google.common.eventbus.EventBus;
  13 import com.google.common.eventbus.Subscribe;
  14 import io.netty.channel.Channel;
  15 import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
  16 import io.netty.util.internal.ConcurrentSet;
  17 import java.io.ByteArrayOutputStream;
  18 import java.io.IOException;
  19 import java.io.OutputStreamWriter;
  20 import java.io.UnsupportedEncodingException;
  21 import java.nio.charset.StandardCharsets;
  22 import java.text.SimpleDateFormat;
  23 import java.util.Collection;
  24 import java.util.Date;
  25 import java.util.HashMap;
  26 import java.util.Map;
  27 import java.util.Map.Entry;
  28 import java.util.Random;
  29 import java.util.Set;
  30 import java.util.concurrent.Executors;
  31 import java.util.regex.Pattern;
  32 import javax.xml.parsers.DocumentBuilder;
  33 import javax.xml.parsers.DocumentBuilderFactory;
  34 import javax.xml.parsers.ParserConfigurationException;
  35 import javax.xml.stream.XMLOutputFactory;
  36 import javax.xml.stream.XMLStreamException;
  37 import javax.xml.stream.XMLStreamWriter;
  38 import javax.xml.transform.OutputKeys;
  39 import javax.xml.transform.Transformer;
  40 import javax.xml.transform.TransformerException;
  41 import javax.xml.transform.TransformerFactory;
  42 import javax.xml.transform.dom.DOMResult;
  43 import javax.xml.transform.dom.DOMSource;
  44 import javax.xml.transform.stream.StreamResult;
  45 import org.opendaylight.controller.md.sal.common.api.data.AsyncDataChangeEvent;
  46 import org.opendaylight.controller.md.sal.dom.api.DOMDataChangeListener;
  47 import org.opendaylight.netconf.sal.restconf.impl.ControllerContext;
  48 import org.opendaylight.yangtools.concepts.ListenerRegistration;
  49 import org.opendaylight.yangtools.yang.common.QName;
  50 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
  51 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.NodeIdentifierWithPredicates;
  52 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.NodeWithValue;
  53 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.PathArgument;
  54 import org.opendaylight.yangtools.yang.data.api.schema.MapEntryNode;
  55 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
  56 import org.opendaylight.yangtools.yang.data.api.schema.UnkeyedListEntryNode;
  57 import org.opendaylight.yangtools.yang.data.api.schema.stream.NormalizedNodeStreamWriter;
  58 import org.opendaylight.yangtools.yang.data.api.schema.stream.NormalizedNodeWriter;
  59 import org.opendaylight.yangtools.yang.data.impl.codec.xml.XMLStreamNormalizedNodeStreamWriter;
  60 import org.opendaylight.yangtools.yang.data.impl.codec.xml.XmlDocumentUtils;
  61 import org.opendaylight.yangtools.yang.data.util.DataSchemaContextTree;
  62 import org.opendaylight.yangtools.yang.model.api.SchemaContext;
  63 import org.opendaylight.yangtools.yang.model.api.SchemaPath;
  64 import org.slf4j.Logger;
  65 import org.slf4j.LoggerFactory;
  66 import org.w3c.dom.Document;
  67 import org.w3c.dom.Element;
  68 import org.w3c.dom.Node;
  69
  70 /**
  71  * {@link ListenerAdapter} is responsible to track events, which occurred by changing data in data source.
  72  */
  73 public class ListenerAdapter implements DOMDataChangeListener {
  74
  75     private static final Logger LOG = LoggerFactory.getLogger(ListenerAdapter.class);
  76     private static final DocumentBuilderFactory DBF = DocumentBuilderFactory.newInstance();
  77     private static final TransformerFactory FACTORY = TransformerFactory.newInstance();
  78     private static final Pattern RFC3339_PATTERN = Pattern.compile("(\\d\\d)(\\d\\d)$");
  79
  80     private final SimpleDateFormat rfc3339 = new SimpleDateFormat("yyyy-MM-dd'T'hh:mm:ssZ");
  81
  82     private final YangInstanceIdentifier path;
  83     private ListenerRegistration<DOMDataChangeListener> registration;
  84     private final String streamName;
  85     private Set<Channel> subscribers = new ConcurrentSet<>();
  86     private final EventBus eventBus;
  87     private final EventBusChangeRecorder eventBusChangeRecorder;
  88
  89     /**
  90      * Creates new {@link ListenerAdapter} listener specified by path and stream name.
  91      *
  92      * @param path
  93      *            Path to data in data store.
  94      * @param streamName
  95      *            The name of the stream.
  96      */
  97     ListenerAdapter(final YangInstanceIdentifier path, final String streamName) {
  98         Preconditions.checkNotNull(path);
  99         Preconditions.checkArgument(streamName != null && !streamName.isEmpty());
 100         this.path = path;
 101         this.streamName = streamName;
 102         eventBus = new AsyncEventBus(Executors.newSingleThreadExecutor());
 103         eventBusChangeRecorder = new EventBusChangeRecorder();
 104         eventBus.register(eventBusChangeRecorder);
 105     }
 106
 107     @Override
 108     public void onDataChanged(final AsyncDataChangeEvent<YangInstanceIdentifier, NormalizedNode<?, ?>> change) {
 109         if (!change.getCreatedData().isEmpty() || !change.getUpdatedData().isEmpty()
 110                 || !change.getRemovedPaths().isEmpty()) {
 111             final String xml = prepareXmlFrom(change);
 112             final Event event = new Event(EventType.NOTIFY);
 113             event.setData(xml);
 114             eventBus.post(event);
 115         }
 116     }
 117
 118     /**
 119      * Tracks events of data change by customer.
 120      */
 121     private final class EventBusChangeRecorder {
 122         @Subscribe
 123         public void recordCustomerChange(final Event event) {
 124             if (event.getType() == EventType.REGISTER) {
 125                 final Channel subscriber = event.getSubscriber();
 126                 if (!subscribers.contains(subscriber)) {
 127                     subscribers.add(subscriber);
 128                 }
 129             } else if (event.getType() == EventType.DEREGISTER) {
 130                 subscribers.remove(event.getSubscriber());
 131                 Notificator.removeListenerIfNoSubscriberExists(ListenerAdapter.this);
 132             } else if (event.getType() == EventType.NOTIFY) {
 133                 for (final Channel subscriber : subscribers) {
 134                     if (subscriber.isActive()) {
 135                         LOG.debug("Data are sent to subscriber {}:", subscriber.remoteAddress());
 136                         subscriber.writeAndFlush(new TextWebSocketFrame(event.getData()));
 137                     } else {
 138                         LOG.debug("Subscriber {} is removed - channel is not active yet.", subscriber.remoteAddress());
 139                         subscribers.remove(subscriber);
 140                     }
 141                 }
 142             }
 143         }
 144     }
 145
 146     /**
 147      * Represents event of specific {@link EventType} type, holds data and {@link Channel} subscriber.
 148      */
 149     private final class Event {
 150         private final EventType type;
 151         private Channel subscriber;
 152         private String data;
 153
 154         /**
 155          * Creates new event specified by {@link EventType} type.
 156          *
 157          * @param type
 158          *            EventType
 159          */
 160         public Event(final EventType type) {
 161             this.type = type;
 162         }
 163
 164         /**
 165          * Gets the {@link Channel} subscriber.
 166          *
 167          * @return Channel
 168          */
 169         public Channel getSubscriber() {
 170             return subscriber;
 171         }
 172
 173         /**
 174          * Sets subscriber for event.
 175          *
 176          * @param subscriber
 177          *            Channel
 178          */
 179         public void setSubscriber(final Channel subscriber) {
 180             this.subscriber = subscriber;
 181         }
 182
 183         /**
 184          * Gets event String.
 185          *
 186          * @return String representation of event data.
 187          */
 188         public String getData() {
 189             return data;
 190         }
 191
 192         /**
 193          * Sets event data.
 194          *
 195          * @param data String.
 196          */
 197         public void setData(final String data) {
 198             this.data = data;
 199         }
 200
 201         /**
 202          * Gets event type.
 203          *
 204          * @return The type of the event.
 205          */
 206         public EventType getType() {
 207             return type;
 208         }
 209     }
 210
 211     /**
 212      * Type of the event.
 213      */
 214     private enum EventType {
 215         REGISTER,
 216         DEREGISTER,
 217         NOTIFY;
 218     }
 219
 220     /**
 221      * Prepare data in printable form and transform it to String.
 222      *
 223      * @param change
 224      *            DataChangeEvent
 225      * @return Data in printable form.
 226      */
 227     private String prepareXmlFrom(final AsyncDataChangeEvent<YangInstanceIdentifier, NormalizedNode<?, ?>> change) {
 228         final SchemaContext schemaContext = ControllerContext.getInstance().getGlobalSchema();
 229         final DataSchemaContextTree dataContextTree =  DataSchemaContextTree.from(schemaContext);
 230         final Document doc = createDocument();
 231         final Element notificationElement = doc.createElementNS("urn:ietf:params:xml:ns:netconf:notification:1.0",
 232                 "notification");
 233         doc.appendChild(notificationElement);
 234
 235         final Element eventTimeElement = doc.createElement("eventTime");
 236         eventTimeElement.setTextContent(toRFC3339(new Date()));
 237         notificationElement.appendChild(eventTimeElement);
 238
 239         final Element dataChangedNotificationEventElement = doc.createElementNS(
 240                 "urn:opendaylight:params:xml:ns:yang:controller:md:sal:remote", "data-changed-notification");
 241         addValuesToDataChangedNotificationEventElement(doc, dataChangedNotificationEventElement, change,
 242                 schemaContext, dataContextTree);
 243         notificationElement.appendChild(dataChangedNotificationEventElement);
 244
 245         try {
 246             final ByteArrayOutputStream out = new ByteArrayOutputStream();
 247             final Transformer transformer = FACTORY.newTransformer();
 248             transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no");
 249             transformer.setOutputProperty(OutputKeys.METHOD, "xml");
 250             transformer.setOutputProperty(OutputKeys.INDENT, "yes");
 251             transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
 252             transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "4");
 253             transformer.transform(new DOMSource(doc), new StreamResult(new OutputStreamWriter(out, StandardCharsets.UTF_8)));
 254             final byte[] charData = out.toByteArray();
 255             return new String(charData, "UTF-8");
 256         } catch (TransformerException | UnsupportedEncodingException e) {
 257             final String msg = "Error during transformation of Document into String";
 258             LOG.error(msg, e);
 259             return msg;
 260         }
 261     }
 262
 263     /**
 264      * Formats data specified by RFC3339.
 265      *
 266      * @param d
 267      *            Date
 268      * @return Data specified by RFC3339.
 269      */
 270     private String toRFC3339(final Date d) {
 271         return RFC3339_PATTERN.matcher(rfc3339.format(d)).replaceAll("$1:$2");
 272     }
 273
 274     /**
 275      * Creates {@link Document} document.
 276      * @return {@link Document} document.
 277      */
 278     private Document createDocument() {
 279         final DocumentBuilder bob;
 280         try {
 281             bob = DBF.newDocumentBuilder();
 282         } catch (final ParserConfigurationException e) {
 283             return null;
 284         }
 285         return bob.newDocument();
 286     }
 287
 288     /**
 289      * Adds values to data changed notification event element.
 290      *
 291      * @param doc
 292      *            {@link Document}
 293      * @param dataChangedNotificationEventElement
 294      *            {@link Element}
 295      * @param change
 296      *            {@link AsyncDataChangeEvent}
 297      */
 298     private void addValuesToDataChangedNotificationEventElement(final Document doc,
 299             final Element dataChangedNotificationEventElement,
 300             final AsyncDataChangeEvent<YangInstanceIdentifier, NormalizedNode<?, ?>> change,
 301             final SchemaContext  schemaContext, final DataSchemaContextTree dataSchemaContextTree) {
 302
 303         addCreatedChangedValuesFromDataToElement(doc, change.getCreatedData().entrySet(),
 304                 dataChangedNotificationEventElement,
 305                 Operation.CREATED, schemaContext, dataSchemaContextTree);
 306
 307         addCreatedChangedValuesFromDataToElement(doc, change.getUpdatedData().entrySet(),
 308                     dataChangedNotificationEventElement,
 309                     Operation.UPDATED, schemaContext, dataSchemaContextTree);
 310
 311         addValuesFromDataToElement(doc, change.getRemovedPaths(), dataChangedNotificationEventElement,
 312                 Operation.DELETED);
 313     }
 314
 315     /**
 316      * Adds values from data to element.
 317      *
 318      * @param doc
 319      *            {@link Document}
 320      * @param data
 321      *            Set of {@link YangInstanceIdentifier}.
 322      * @param element
 323      *            {@link Element}
 324      * @param operation
 325      *            {@link Operation}
 326      */
 327     private void addValuesFromDataToElement(final Document doc, final Set<YangInstanceIdentifier> data, final Element element,
 328             final Operation operation) {
 329         if (data == null || data.isEmpty()) {
 330             return;
 331         }
 332         for (final YangInstanceIdentifier path : data) {
 333             if (!ControllerContext.getInstance().isNodeMixin(path)) {
 334                 final Node node = createDataChangeEventElement(doc, path, operation);
 335                 element.appendChild(node);
 336             }
 337         }
 338     }
 339
 340     private void addCreatedChangedValuesFromDataToElement(final Document doc, final Set<Entry<YangInstanceIdentifier,
 341                 NormalizedNode<?,?>>> data, final Element element, final Operation operation, final SchemaContext
 342             schemaContext, final DataSchemaContextTree dataSchemaContextTree) {
 343         if (data == null || data.isEmpty()) {
 344             return;
 345         }
 346         for (Entry<YangInstanceIdentifier, NormalizedNode<?, ?>> entry : data) {
 347             if (!ControllerContext.getInstance().isNodeMixin(entry.getKey())) {
 348                 final Node node = createCreatedChangedDataChangeEventElement(doc, entry, operation, schemaContext,
 349                         dataSchemaContextTree);
 350                 element.appendChild(node);
 351             }
 352         }
 353     }
 354
 355     /**
 356      * Creates changed event element from data.
 357      *
 358      * @param doc
 359      *            {@link Document}
 360      * @param path
 361      *            Path to data in data store.
 362      * @param operation
 363      *            {@link Operation}
 364      * @return {@link Node} node represented by changed event element.
 365      */
 366     private Node createDataChangeEventElement(final Document doc, final YangInstanceIdentifier path, final Operation operation) {
 367         final Element dataChangeEventElement = doc.createElement("data-change-event");
 368         final Element pathElement = doc.createElement("path");
 369         addPathAsValueToElement(path, pathElement);
 370         dataChangeEventElement.appendChild(pathElement);
 371
 372         final Element operationElement = doc.createElement("operation");
 373         operationElement.setTextContent(operation.value);
 374         dataChangeEventElement.appendChild(operationElement);
 375
 376         return dataChangeEventElement;
 377     }
 378
 379     private Node createCreatedChangedDataChangeEventElement(final Document doc, final Entry<YangInstanceIdentifier,
 380             NormalizedNode<?, ?>> entry, final Operation operation, final SchemaContext
 381             schemaContext, final DataSchemaContextTree dataSchemaContextTree) {
 382         final Element dataChangeEventElement = doc.createElement("data-change-event");
 383         final Element pathElement = doc.createElement("path");
 384         final YangInstanceIdentifier path = entry.getKey();
 385         addPathAsValueToElement(path, pathElement);
 386         dataChangeEventElement.appendChild(pathElement);
 387
 388         final Element operationElement = doc.createElement("operation");
 389         operationElement.setTextContent(operation.value);
 390         dataChangeEventElement.appendChild(operationElement);
 391
 392         try {
 393             final DOMResult domResult = writeNormalizedNode(entry.getValue(), path,
 394                     schemaContext, dataSchemaContextTree);
 395             final Node result = doc.importNode(domResult.getNode().getFirstChild(), true);
 396             final Element dataElement = doc.createElement("data");
 397             dataElement.appendChild(result);
 398             dataChangeEventElement.appendChild(dataElement);
 399         } catch (IOException e) {
 400             LOG.error("Error in writer ", e);
 401         } catch (XMLStreamException e) {
 402             LOG.error("Error processing stream", e);
 403         }
 404
 405         return dataChangeEventElement;
 406     }
 407
 408     private static DOMResult writeNormalizedNode(final NormalizedNode<?,?> normalized, final
 409         YangInstanceIdentifier path, final SchemaContext context, final DataSchemaContextTree dataSchemaContextTree) throws
 410             IOException, XMLStreamException {
 411         final XMLOutputFactory XML_FACTORY = XMLOutputFactory.newFactory();
 412         final Document doc = XmlDocumentUtils.getDocument();
 413         final DOMResult result = new DOMResult(doc);
 414         NormalizedNodeWriter normalizedNodeWriter = null;
 415         NormalizedNodeStreamWriter normalizedNodeStreamWriter = null;
 416         XMLStreamWriter writer = null;
 417         final SchemaPath nodePath;
 418
 419         if (normalized instanceof MapEntryNode || normalized instanceof UnkeyedListEntryNode) {
 420             nodePath = dataSchemaContextTree.getChild(path).getDataSchemaNode().getPath();
 421         } else {
 422             nodePath = dataSchemaContextTree.getChild(path).getDataSchemaNode().getPath().getParent();
 423         }
 424
 425         try {
 426             writer = XML_FACTORY.createXMLStreamWriter(result);
 427             normalizedNodeStreamWriter = XMLStreamNormalizedNodeStreamWriter.create(writer, context, nodePath);
 428             normalizedNodeWriter = NormalizedNodeWriter.forStreamWriter(normalizedNodeStreamWriter);
 429
 430             normalizedNodeWriter.write(normalized);
 431
 432             normalizedNodeWriter.flush();
 433         } finally {
 434             if (normalizedNodeWriter != null) {
 435                 normalizedNodeWriter.close();
 436             }
 437             if (normalizedNodeStreamWriter != null) {
 438                 normalizedNodeStreamWriter.close();
 439             }
 440             if (writer != null) {
 441                 writer.close();
 442             }
 443         }
 444
 445         return result;
 446     }
 447
 448     /**
 449      * Adds path as value to element.
 450      *
 451      * @param path
 452      *            Path to data in data store.
 453      * @param element
 454      *            {@link Element}
 455      */
 456     private void addPathAsValueToElement(final YangInstanceIdentifier path, final Element element) {
 457         // Map< key = namespace, value = prefix>
 458         final Map<String, String> prefixes = new HashMap<>();
 459         final YangInstanceIdentifier normalizedPath = ControllerContext.getInstance().toXpathRepresentation(path);
 460         final StringBuilder textContent = new StringBuilder();
 461
 462         // FIXME: BUG-1281: this is duplicated code from yangtools (BUG-1275)
 463         for (final PathArgument pathArgument : normalizedPath.getPathArguments()) {
 464             if (pathArgument instanceof YangInstanceIdentifier.AugmentationIdentifier) {
 465                 continue;
 466             }
 467             textContent.append("/");
 468             writeIdentifierWithNamespacePrefix(element, textContent, pathArgument.getNodeType(), prefixes);
 469             if (pathArgument instanceof NodeIdentifierWithPredicates) {
 470                 final Map<QName, Object> predicates = ((NodeIdentifierWithPredicates) pathArgument).getKeyValues();
 471                 for (final QName keyValue : predicates.keySet()) {
 472                     final String predicateValue = String.valueOf(predicates.get(keyValue));
 473                     textContent.append("[");
 474                     writeIdentifierWithNamespacePrefix(element, textContent, keyValue, prefixes);
 475                     textContent.append("='");
 476                     textContent.append(predicateValue);
 477                     textContent.append("'");
 478                     textContent.append("]");
 479                 }
 480             } else if (pathArgument instanceof NodeWithValue) {
 481                 textContent.append("[.='");
 482                 textContent.append(((NodeWithValue) pathArgument).getValue());
 483                 textContent.append("'");
 484                 textContent.append("]");
 485             }
 486         }
 487         element.setTextContent(textContent.toString());
 488     }
 489
 490     /**
 491      * Writes identifier that consists of prefix and QName.
 492      *
 493      * @param element
 494      *            {@link Element}
 495      * @param textContent
 496      *            StringBuilder
 497      * @param qName
 498      *            QName
 499      * @param prefixes
 500      *            Map of namespaces and prefixes.
 501      */
 502     private static void writeIdentifierWithNamespacePrefix(final Element element, final StringBuilder textContent,
 503             final QName qName, final Map<String, String> prefixes) {
 504         final String namespace = qName.getNamespace().toString();
 505         String prefix = prefixes.get(namespace);
 506         if (prefix == null) {
 507             prefix = generateNewPrefix(prefixes.values());
 508         }
 509
 510         element.setAttribute("xmlns:" + prefix, namespace);
 511         textContent.append(prefix);
 512         prefixes.put(namespace, prefix);
 513
 514         textContent.append(":");
 515         textContent.append(qName.getLocalName());
 516     }
 517
 518     /**
 519      * Generates new prefix which consists of four random characters <a-z>.
 520      *
 521      * @param prefixes
 522      *            Collection of prefixes.
 523      * @return New prefix which consists of four random characters <a-z>.
 524      */
 525     private static String generateNewPrefix(final Collection<String> prefixes) {
 526         StringBuilder result = null;
 527         final Random random = new Random();
 528         do {
 529             result = new StringBuilder();
 530             for (int i = 0; i < 4; i++) {
 531                 final int randomNumber = 0x61 + (Math.abs(random.nextInt()) % 26);
 532                 result.append(Character.toChars(randomNumber));
 533             }
 534         } while (prefixes.contains(result.toString()));
 535
 536         return result.toString();
 537     }
 538
 539     /**
 540      * Gets path pointed to data in data store.
 541      *
 542      * @return Path pointed to data in data store.
 543      */
 544     public YangInstanceIdentifier getPath() {
 545         return path;
 546     }
 547
 548     /**
 549      * Sets {@link ListenerRegistration} registration.
 550      *
 551      * @param registration DOMDataChangeListener registration
 552      */
 553     public void setRegistration(final ListenerRegistration<DOMDataChangeListener> registration) {
 554         this.registration = registration;
 555     }
 556
 557     /**
 558      * Gets the name of the stream.
 559      *
 560      * @return The name of the stream.
 561      */
 562     public String getStreamName() {
 563         return streamName;
 564     }
 565
 566     /**
 567      * Removes all subscribers and unregisters event bus change recorder form event bus.
 568      */
 569     public void close() throws Exception {
 570         subscribers = new ConcurrentSet<>();
 571         registration.close();
 572         registration = null;
 573         eventBus.unregister(eventBusChangeRecorder);
 574     }
 575
 576     /**
 577      * Checks if {@link ListenerRegistration} registration exist.
 578      *
 579      * @return True if exist, false otherwise.
 580      */
 581     public boolean isListening() {
 582         return registration == null ? false : true;
 583     }
 584
 585     /**
 586      * Creates event of type {@link EventType#REGISTER}, set {@link Channel} subscriber to the event and post event into
 587      * event bus.
 588      *
 589      * @param subscriber
 590      *            Channel
 591      */
 592     public void addSubscriber(final Channel subscriber) {
 593         if (!subscriber.isActive()) {
 594             LOG.debug("Channel is not active between websocket server and subscriber {}" + subscriber.remoteAddress());
 595         }
 596         final Event event = new Event(EventType.REGISTER);
 597         event.setSubscriber(subscriber);
 598         eventBus.post(event);
 599     }
 600
 601     /**
 602      * Creates event of type {@link EventType#DEREGISTER}, sets {@link Channel} subscriber to the event and posts event
 603      * into event bus.
 604      *
 605      * @param subscriber
 606      */
 607     public void removeSubscriber(final Channel subscriber) {
 608         LOG.debug("Subscriber {} is removed.", subscriber.remoteAddress());
 609         final Event event = new Event(EventType.DEREGISTER);
 610         event.setSubscriber(subscriber);
 611         eventBus.post(event);
 612     }
 613
 614     /**
 615      * Checks if exists at least one {@link Channel} subscriber.
 616      *
 617      * @return True if exist at least one {@link Channel} subscriber, false otherwise.
 618      */
 619     public boolean hasSubscribers() {
 620         return !subscribers.isEmpty();
 621     }
 622
 623     /**
 624      * Consists of two types {@link Store#CONFIG} and {@link Store#OPERATION}.
 625      */
 626     private static enum Store {
 627         CONFIG("config"),
 628         OPERATION("operation");
 629
 630         private final String value;
 631
 632         private Store(final String value) {
 633             this.value = value;
 634         }
 635     }
 636
 637     /**
 638      * Consists of three types {@link Operation#CREATED}, {@link Operation#UPDATED} and {@link Operation#DELETED}.
 639      */
 640     private static enum Operation {
 641         CREATED("created"),
 642         UPDATED("updated"),
 643         DELETED("deleted");
 644
 645         private final String value;
 646
 647         private Operation(final String value) {
 648             this.value = value;
 649         }
 650     }
 651
 652 }