第 18 章： 发布与订阅
===========================

客户端订阅频道。

.. graphviz::

    digraph {

        label = "\n 图 18-1    news.it 频道和它的三个订阅者";

        rankdir = BT;

        //

        news_it [label = "news.it 频道", shape = box, width = 3.0];

        client_1 [label = "客户端 A"];
        client_2 [label = "客户端 B"];
        client_3 [label = "客户端 C"];

        //

        edge [label = "订阅"];

        client_1 -> news_it;
        client_2 -> news_it;
        client_3 -> news_it;
    }

客户端向频道发送消息，
消息被传递至各个订阅者。

.. graphviz::

    digraph {

        label = "\n 图 18-2    向 news.it 频道发送消息";

        //

        publish [label = "PUBLISH \"news.it\" \"hello\"", shape = plaintext];

        news_it [label = "news.it 频道", shape = box, width = 3.0];

        client_1 [label = "客户端 A"];
        client_2 [label = "客户端 B"];
        client_3 [label = "客户端 C"];

        //

        edge [style = dashed];

        publish -> news_it;

        edge [label = "\"hello\""];

        news_it -> client_1;
        news_it -> client_2;
        news_it -> client_3;

    }

----

客户端订阅模式。

.. graphviz::

    digraph {

        label = "\n 图 18-3     频道和模式的订阅状态";
        
        rankdir = BT;

        //

        news_et [label = "news.et 频道", shape = box, width = 3.0];

        news_it [label = "news.it 频道", shape = box, width = 3.0];

        news_iet [label = "news.[ie]t 模式", shape = hexagon, width = 3.0];

        node [shape = ellipse];

        client_1 [label = "客户端 A"];
        client_2 [label = "客户端 B"];
        client_3 [label = "客户端 C"];
        client_4 [label = "客户端 D"];

        //

        client_1 -> news_it [label = "订阅"];

        client_2 -> news_et [label = "订阅"];

        news_iet -> news_et [dir = back, label = "匹配"];
        news_iet -> news_it [dir = back, label = "匹配"];

        edge [label = "订阅"];
        client_3 -> news_iet;
        client_4 -> news_iet;
    }

客户端向频道发送消息，
消息被传递给正在订阅匹配模式的订阅者。

.. graphviz::

    digraph {

        label = "\n 图 18-4    将消息发送给频道的订阅者和匹配模式的订阅者";
        
        rankdir = BT;

        //

        news_et [label = "news.et 频道", shape = box, width = 3.0];

        news_it [label = "news.it 频道", shape = box, width = 3.0];

        news_iet [label = "news.[ie]t 模式", shape = hexagon, width = 3.0];

        publish [label = "PUBLISH \"news.it\" \"hello\"", shape = plaintext];

        node [shape = ellipse];

        client_1 [label = "客户端 A"];
        client_2 [label = "客户端 B"];
        client_3 [label = "客户端 C"];
        client_4 [label = "客户端 D"];

        //


        client_1 -> news_it [dir = back, label = "\"hello\"", style = dashed];

        client_2 -> news_et [label = "订阅"];

        news_iet -> news_et [dir = back, label = "匹配"];
        news_iet -> news_it [dir = back, label = "匹配", style = dashed];

        edge [dir = back, label = "\"hello\"", style = dashed];
        client_3 -> news_iet;
        client_4 -> news_iet;

        news_it -> publish [dir = back, style = dashed, label =""];
    }

另一个模式被匹配的例子。

.. graphviz::

    digraph {

        label = "\n 图 18-5    将消息发送给频道的订阅者和匹配模式的订阅者";
        
        rankdir = BT;

        //

        news_et [label = "news.et 频道", shape = box, width = 3.0];

        news_it [label = "news.it 频道", shape = box, width = 3.0];

        news_iet [label = "news.[ie]t 模式", shape = hexagon, width = 3.0];

        publish [label = "PUBLISH \"news.et\" \"world\"", shape = plaintext];

        node [shape = ellipse];

        client_1 [label = "客户端 A"];
        client_2 [label = "客户端 B"];
        client_3 [label = "客户端 C"];
        client_4 [label = "客户端 D"];

        //


        client_1 -> news_it [label = "订阅"];

        client_2 -> news_et [dir = back, label = "\"world\"", style = dashed];

        news_iet -> news_et [dir = back, label = "匹配", style = dashed];
        news_iet -> news_it [dir = back, label = "匹配"];

        edge [dir = back, label = "\"world\"", style = dashed];
        client_3 -> news_iet;
        client_4 -> news_iet;

        news_et -> publish [dir = back, style = dashed, label =""];
    }

----

``pubsub_channels`` 字典示例。

.. graphviz::

    digraph {

        label = "\n 图 18-6    一个 pubsub_channels 字典示例";

        rankdir = LR;

        //

        node [shape = record];

        pubsub_channels [label = " pubsub_channels | <news_it> \"news.it\" | <news_sport> \"news.sport\" | <news_business> \"news.business\" ", height = 3, width = 2.2];

        client_1 [label = "client-1"];
        client_2 [label = "client-2"];
        client_3 [label = "client-3"];
        client_4 [label = "client-4"];
        client5 [label = "client-5"];
        client6 [label = "client-6"];

        //

        pubsub_channels:news_it -> client_1; client_1 -> client_2; client_2 -> client_3;

        pubsub_channels:news_sport -> client_4;

        pubsub_channels:news_business -> client5 -> client6;

    }

----

``pubsubPattern`` 结构示例。

.. graphviz::

    digraph {

        label = "\n 图 18-10    pubsubPattern 结构示例";

        rankdir = LR;

        //

        node [shape =record];

        pubsubPattern [label = " pubsubPattern | client \n client-9 | pattern \n \"news.*\" "];
    }



``pubsub_patterns`` 链表的示例。

.. graphviz::

    digraph {

        label = "\n 图 18-11    pubsub_patterns 链表示例";

        rankdir = LR;

        //

        node [shape = record];

        redisServer [label = "redisServer | ... | <pubsub_patterns> pubsub_patterns | ...", height = 2.2, width = 2.2];

        all_music [label = " pubsubPattern | client \n client-7 | pattern \n \"music.*\" "];

        all_book [label = " pubsubPattern | client \n client-8 | pattern \n \"book.*\" "];

        all_news [label = " pubsubPattern | client \n client-9 | pattern \n \"news.*\" "];

        //

        redisServer:pubsub_patterns -> all_music;

        all_music -> all_book;

        all_book -> all_news;
    }