聊聊claudb的pubsub command

序

本文主要研究一下claudb的pubsub command

PublishCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/pubsub/PublishCommand.java

@Command("publish")
@ParamLength(2)
public class PublishCommand implements DBCommand, SubscriptionSupport, PatternSubscriptionSupport {

  @Override
  public RedisToken execute(Database db, Request request) {
    String channel = request.getParam(0).toString();
    SafeString message = request.getParam(1);
    return integer(publishAll(getClauDB(request.getServerContext()), channel, message));
  }

  private int publishAll(DBServerContext server, String channel, SafeString message) {
    int count = publish(server, channel, message);
    int pcount = patternPublish(server, channel, message);
    return count + pcount;
  }
}

• PublishCommand实现了DBCommand, SubscriptionSupport, PatternSubscriptionSupport接口，其execute方法执行publishAll(getClauDB(request.getServerContext()), channel, message)

SubscribeCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/pubsub/SubscribeCommand.java

@ReadOnly
@Command("subscribe")
@ParamLength(1)
@PubSubAllowed
public class SubscribeCommand implements DBCommand, SubscriptionSupport {

  private static final String SUBSCRIBE = "subscribe";

  @Override
  public RedisToken execute(Database db, Request request) {
    Database admin = getAdminDatabase(request.getServerContext());
    String sessionId = getSessionId(request);
    Sequence<SafeString> channels = getChannels(request);
    int i = channels.size();
    List<Object> result = new LinkedList<>();
    for (SafeString channel : request.getParams()) {
      addSubscription(admin, sessionId, channel);
      getSessionState(request.getSession()).addSubscription(channel);
      result.addAll(asList(SUBSCRIBE, channel, ++i));
    }
    return convert(result);
  }

  private String getSessionId(Request request) {
    return request.getSession().getId();
  }

  private Sequence<SafeString> getChannels(Request request) {
    return getSessionState(request.getSession()).getSubscriptions();
  }
}

• SubscribeCommand实现了DBCommand, SubscriptionSupport接口，其execute方法遍历channel挨个执行addSubscription及getSessionState(request.getSession()).addSubscription(channel)

UnsubscribeCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/pubsub/UnsubscribeCommand.java

@ReadOnly
@Command("unsubscribe")
@ParamLength(1)
@PubSubAllowed
public class UnsubscribeCommand implements DBCommand, SubscriptionSupport {

  private static final String UNSUBSCRIBE = "unsubscribe";

  @Override
  public RedisToken execute(Database db, Request request) {
    Database admin = getAdminDatabase(request.getServerContext());
    String sessionId = getSessionId(request);
    Sequence<SafeString> channels = getChannels(request);
    int i = channels.size();
    List<Object> result = new LinkedList<>();
    for (SafeString channel : request.getParams()) {
      removeSubscription(admin, sessionId, channel);
      getSessionState(request.getSession()).removeSubscription(channel);
      result.addAll(asList(UNSUBSCRIBE, channel, --i));
    }
    return convert(result);
  }

  private String getSessionId(Request request) {
    return request.getSession().getId();
  }

  private Sequence<SafeString> getChannels(Request request) {
    return getSessionState(request.getSession()).getSubscriptions();
  }
}

• UnsubscribeCommand实现了DBCommand, SubscriptionSupport接口，其execute方法遍历channel挨个执行removeSubscription(admin, sessionId, channel)及getSessionState(request.getSession()).removeSubscription(channel)

PatternSubscribeCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/pubsub/PatternSubscribeCommand.java

@ReadOnly
@Command("psubscribe")
@ParamLength(1)
@PubSubAllowed
public class PatternSubscribeCommand implements DBCommand, PatternSubscriptionSupport {

  private static final String PSUBSCRIBE = "psubscribe";

  @Override
  public RedisToken execute(Database db, Request request) {
    Database admin = getAdminDatabase(request.getServerContext());
    String sessionId = getSessionId(request);
    Sequence<SafeString> channels = getChannels(request);
    int i = channels.size();
    List<Object> result = new LinkedList<>();
    for (SafeString pattern : request.getParams()) {
      addPatternSubscription(admin, sessionId, pattern);
      getSessionState(request.getSession()).addSubscription(pattern);
      result.addAll(asList(PSUBSCRIBE, pattern, ++i));
    }
    return convert(result);
  }

  private String getSessionId(Request request) {
    return request.getSession().getId();
  }

  private Sequence<SafeString> getChannels(Request request) {
    return getSessionState(request.getSession()).getSubscriptions();
  }
}

• PatternSubscribeCommand实现了DBCommand, PatternSubscriptionSupport接口，其execute方法遍历pattern挨个执行addPatternSubscription(admin, sessionId, pattern)及getSessionState(request.getSession()).addSubscription(pattern)

PatternUnsubscribeCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/pubsub/PatternUnsubscribeCommand.java

@ReadOnly
@Command("punsubscribe")
@ParamLength(1)
@PubSubAllowed
public class PatternUnsubscribeCommand implements DBCommand, PatternSubscriptionSupport {

  private static final String PUNSUBSCRIBE = "punsubscribe";

  @Override
  public RedisToken execute(Database db, Request request) {
    Database admin = getAdminDatabase(request.getServerContext());
    String sessionId = getSessionId(request);
    Sequence<SafeString> channels = getChannels(request);
    int i = channels.size();
    List<Object> result = new LinkedList<>();
    for (SafeString channel : request.getParams()) {
      removePatternSubscription(admin, sessionId, channel);
      getSessionState(request.getSession()).removeSubscription(channel);
      result.addAll(asList(PUNSUBSCRIBE, channel, --i));
    }
    return convert(result);
  }

  private String getSessionId(Request request) {
    return request.getSession().getId();
  }

  private Sequence<SafeString> getChannels(Request request) {
    return getSessionState(request.getSession()).getSubscriptions();
  }
}

• PatternUnsubscribeCommand实现了DBCommand, PatternSubscriptionSupport接口，其execute遍历channel挨个执行removePatternSubscription(admin, sessionId, channel)及getSessionState(request.getSession()).removeSubscription(channel)

小结

claudb pubsub相关的command有PublishCommand、SubscribeCommand、UnsubscribeCommand、PatternSubscribeCommand、PatternUnsubscribeCommand

doc

• command/pubsub