redis6.0.5之pubsub.c阅读笔记-发布订阅

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#include "server.h"

int clientSubscriptionsCount(client *c);

/*-----------------------------------------------------------------------------
 * Pubsub client replies API  发布订阅客户端回复API
 *----------------------------------------------------------------------------*/

/* Send a pubsub message of type "message" to the client.
 * Normally 'msg' is a Redis object containing the string to send as
 * message. However if the caller sets 'msg' as NULL, it will be able
 * to send a special message (for instance an Array type) by using the
 * addReply*() API family. */
向客户端发送类型为“message”的订阅消息。通常，“msg”是一个Redis对象，包含要作为消息发送的字符串。
但是，如果调用方将“msg”设置为NULL，它将能够使用addReply系列的API发送特殊消息（例如数组类型）
void addReplyPubsubMessage(client *c, robj *channel, robj *msg) {
    if (c->resp == 2) 协议2的版本
        addReply(c,shared.mbulkhdr[3]);
    else
        addReplyPushLen(c,3);
    addReply(c,shared.messagebulk);
    addReplyBulk(c,channel);
    if (msg) addReplyBulk(c,msg); 消息非空，回复消息
}

/* Send a pubsub message of type "pmessage" to the client. The difference
 * with the "message" type delivered by addReplyPubsubMessage() is that
 * this message format also includes the pattern that matched the message. */
发送pmessage的订阅消息给客户端。 不同于通过函数addReplyPubsubMessage发送的message类型相比，
这种消息的格式还包括匹配消息的模式
void addReplyPubsubPatMessage(client *c, robj *pat, robj *channel, robj *msg) {
    if (c->resp == 2)
        addReply(c,shared.mbulkhdr[4]);
    else
        addReplyPushLen(c,4); 
    addReply(c,shared.pmessagebulk);
    addReplyBulk(c,pat);
    addReplyBulk(c,channel);
    addReplyBulk(c,msg);
}

/* Send the pubsub subscription notification to the client. */
将pubsub订阅通知发送到客户端
void addReplyPubsubSubscribed(client *c, robj *channel) {
    if (c->resp == 2)
        addReply(c,shared.mbulkhdr[3]);
    else
        addReplyPushLen(c,3);
    addReply(c,shared.subscribebulk);
    addReplyBulk(c,channel);
    addReplyLongLong(c,clientSubscriptionsCount(c));
}

/* Send the pubsub unsubscription notification to the client.
 * Channel can be NULL: this is useful when the client sends a mass
 * unsubscribe command but there are no channels to unsubscribe from: we
 * still send a notification. */
向客户端发送pubsub取消订阅通知。通道可以为空：当客户端发送批量取消订阅命令但没有可取消订阅的通道时，
此选项非常有用：我们仍然发送通知。
void addReplyPubsubUnsubscribed(client *c, robj *channel) {
    if (c->resp == 2)
        addReply(c,shared.mbulkhdr[3]);
    else
        addReplyPushLen(c,3);
    addReply(c,shared.unsubscribebulk);
    if (channel)
        addReplyBulk(c,channel);
    else
        addReplyNull(c);
    addReplyLongLong(c,clientSubscriptionsCount(c));
}

/* Send the pubsub pattern subscription notification to the client. */
向客户端发送pubsub模式订阅通知。
void addReplyPubsubPatSubscribed(client *c, robj *pattern) {
    if (c->resp == 2)
        addReply(c,shared.mbulkhdr[3]);
    else
        addReplyPushLen(c,3);
    addReply(c,shared.psubscribebulk);
    addReplyBulk(c,pattern);
    addReplyLongLong(c,clientSubscriptionsCount(c));
}

/* Send the pubsub pattern unsubscription notification to the client.
 * Pattern can be NULL: this is useful when the client sends a mass
 * punsubscribe command but there are no pattern to unsubscribe from: we
 * still send a notification. */
向客户端发送pubsub模式取消订阅通知。模式可以为NULL：当客户端发送mass punsubscribe命令但没有模式可取消订阅时，
这非常有用：我们仍然发送通知。
void addReplyPubsubPatUnsubscribed(client *c, robj *pattern) {
    if (c->resp == 2)
        addReply(c,shared.mbulkhdr[3]);
    else
        addReplyPushLen(c,3);
    addReply(c,shared.punsubscribebulk);
    if (pattern)
        addReplyBulk(c,pattern);
    else
        addReplyNull(c);
    addReplyLongLong(c,clientSubscriptionsCount(c));
}

/*-----------------------------------------------------------------------------
 * Pubsub low level API 发布定于的底层API
 *----------------------------------------------------------------------------*/
释放发布订阅模式

typedef struct pubsubPattern {
    client *client;  客户端
    robj *pattern;  模式
} pubsubPattern;


void freePubsubPattern(void *p) {
    pubsubPattern *pat = p;

    decrRefCount(pat->pattern);
    zfree(pat);
}
列出匹配发布订阅的模式
int listMatchPubsubPattern(void *a, void *b) {
    pubsubPattern *pa = a, *pb = b;

    return (pa->client == pb->client) &&
           (equalStringObjects(pa->pattern,pb->pattern));
}

/* Return the number of channels + patterns a client is subscribed to. */
返回客户端订阅的通道数+模式数。
int clientSubscriptionsCount(client *c) {
    return dictSize(c->pubsub_channels)+
           listLength(c->pubsub_patterns);
}

/* Subscribe a client to a channel. Returns 1 if the operation succeeded, or
 * 0 if the client was already subscribed to that channel. */
绑定客户端到订阅频道。如果操作成功，则返回1；如果客户端已订阅该通道，则返回0。
int pubsubSubscribeChannel(client *c, robj *channel) {
    dictEntry *de;
    list *clients = NULL;
    int retval = 0;

    /* Add the channel to the client -> channels hash table */ 添加频道到客户端机的频道哈希表
    if (dictAdd(c->pubsub_channels,channel,NULL) == DICT_OK) {
        retval = 1;
        incrRefCount(channel);订阅通道+1
        /* Add the client to the channel -> list of clients hash table */
        添加客户端到 通道的客户端列表
        de = dictFind(server.pubsub_channels,channel);
        if (de == NULL) {
            clients = listCreate();
            dictAdd(server.pubsub_channels,channel,clients);
            incrRefCount(channel);
        } else {
            clients = dictGetVal(de);
        }
        listAddNodeTail(clients,c);
    }
    /* Notify the client */通知客户端
    addReplyPubsubSubscribed(c,channel);
    return retval;
}

/* Unsubscribe a client from a channel. Returns 1 if the operation succeeded, or
 * 0 if the client was not subscribed to the specified channel. */
从频道取消订阅客户端。如果操作成功，则返回1；如果客户端未订阅指定通道，则返回0
int pubsubUnsubscribeChannel(client *c, robj *channel, int notify) {
    dictEntry *de;
    list *clients;
    listNode *ln;
    int retval = 0;

    /* Remove the channel from the client -> channels hash table */ 从订阅频道的 客户端频道哈希表中移除
    incrRefCount(channel); /* channel may be just a pointer to the same object
                            we have in the hash tables. Protect it... */
    频道可能指向哈希表中相同对象的指针。保护它                    
    
    if (dictDelete(c->pubsub_channels,channel) == DICT_OK) {
        retval = 1;
        /* Remove the client from the channel -> clients list hash table */ 
        从频道的客户端哈希列表中移除该客户端
        de = dictFind(server.pubsub_channels,channel);
        serverAssertWithInfo(c,NULL,de != NULL);
        clients = dictGetVal(de); 获取客户端列表
        ln = listSearchKey(clients,c); 查找是否在列表中
        serverAssertWithInfo(c,NULL,ln != NULL);
        listDelNode(clients,ln); 不为空就删除
        if (listLength(clients) == 0) { 如果列表清零
            /* Free the list and associated hash entry at all if this was
             * the latest client, so that it will be possible to abuse
             * Redis PUBSUB creating millions of channels. */
如果这是最后的客户端，释放列表和相关的哈希项，这样就有避免滥用Redis PUBSUB创建数百万个无用频道
            dictDelete(server.pubsub_channels,channel); 删除频道
        }
    }
    /* Notify the client */
    if (notify) addReplyPubsubUnsubscribed(c,channel); 取消订阅
    decrRefCount(channel); /* it is finally safe to release it */ 终于可以安全地释放它了
    return retval;
}

/* Subscribe a client to a pattern. Returns 1 if the operation succeeded, 
or 0 if the client was already subscribed to that pattern. */
向客户端订阅模式。如果操作成功，则返回1；如果客户端已订阅该模式，则返回0。
int pubsubSubscribePattern(client *c, robj *pattern) {
    dictEntry *de;
    list *clients;
    int retval = 0;

    if (listSearchKey(c->pubsub_patterns,pattern) == NULL) {
        retval = 1;
        pubsubPattern *pat;
        listAddNodeTail(c->pubsub_patterns,pattern);
        incrRefCount(pattern);
        pat = zmalloc(sizeof(*pat));
        pat->pattern = getDecodedObject(pattern);
        pat->client = c;
        listAddNodeTail(server.pubsub_patterns,pat);
        /* Add the client to the pattern -> list of clients hash table */
        将客户端添加到 模式的哈希列表中
        de = dictFind(server.pubsub_patterns_dict,pattern);
        if (de == NULL) {
            clients = listCreate();
            dictAdd(server.pubsub_patterns_dict,pattern,clients); 创建新模式的哈希键和值
            incrRefCount(pattern);
        } else {
            clients = dictGetVal(de); 存在就直接获取值
        }
        listAddNodeTail(clients,c);  添加到列表的末尾
    }
    /* Notify the client */
    addReplyPubsubPatSubscribed(c,pattern);
    return retval;
}

/* Unsubscribe a client from a channel. Returns 1 if the operation succeeded, or
 * 0 if the client was not subscribed to the specified channel. */
从频道取消订阅客户端。如果操作成功，则返回1；如果客户端未订阅指定通道，则返回0。
int pubsubUnsubscribePattern(client *c, robj *pattern, int notify) {
    dictEntry *de;
    list *clients;
    listNode *ln;
    pubsubPattern pat;
    int retval = 0;

    incrRefCount(pattern); /* Protect the object. May be the same we remove */ 保护对象，万一和我们要移除的是同一对象
    if ((ln = listSearchKey(c->pubsub_patterns,pattern)) != NULL) { 是否在已有订阅模式中
        retval = 1;
        listDelNode(c->pubsub_patterns,ln); 在的话删除
        pat.client = c;
        pat.pattern = pattern;
        ln = listSearchKey(server.pubsub_patterns,&pat);
        listDelNode(server.pubsub_patterns,ln);
        /* Remove the client from the pattern -> clients list hash table */
        从模式的客户端哈希中的列表移除客户端
        de = dictFind(server.pubsub_patterns_dict,pattern);
        serverAssertWithInfo(c,NULL,de != NULL);
        clients = dictGetVal(de);
        ln = listSearchKey(clients,c);
        serverAssertWithInfo(c,NULL,ln != NULL);
        listDelNode(clients,ln);
        if (listLength(clients) == 0) {
            /* Free the list and associated hash entry at all if this was
             * the latest client. */
             如果这是最后的客户端，释放相关联的哈希实体和列表
            dictDelete(server.pubsub_patterns_dict,pattern);
        }
    }
    /* Notify the client */
    if (notify) addReplyPubsubPatUnsubscribed(c,pattern);
    decrRefCount(pattern);
    return retval;
}

/* Unsubscribe from all the channels. Return the number of channels the
 * client was subscribed to. */
取消所有频道的订阅。返回客户端订阅的频道数。
int pubsubUnsubscribeAllChannels(client *c, int notify) {
    dictIterator *di = dictGetSafeIterator(c->pubsub_channels);
    dictEntry *de;
    int count = 0;

    while((de = dictNext(di)) != NULL) {
        robj *channel = dictGetKey(de);

        count += pubsubUnsubscribeChannel(c,channel,notify);
    }
    /* We were subscribed to nothing? Still reply to the client. */
    我们虽然什么都没有订阅，但是仍然回复客户
    if (notify && count == 0) addReplyPubsubUnsubscribed(c,NULL);
    dictReleaseIterator(di);
    return count;
}

/* Unsubscribe from all the patterns. Return the number of patterns the
 * client was subscribed from. */
取消订阅所有模式。返回订阅客户端的模式数。
int pubsubUnsubscribeAllPatterns(client *c, int notify) {
    listNode *ln;
    listIter li;
    int count = 0;

    listRewind(c->pubsub_patterns,&li);
    while ((ln = listNext(&li)) != NULL) {
        robj *pattern = ln->value;

        count += pubsubUnsubscribePattern(c,pattern,notify);
    }
    if (notify && count == 0) addReplyPubsubPatUnsubscribed(c,NULL);
    return count;
}

/* Publish a message */ 发布消息
int pubsubPublishMessage(robj *channel, robj *message) {
    int receivers = 0;
    dictEntry *de;
    dictIterator *di;
    listNode *ln;
    listIter li;

    /* Send to clients listening for that channel */ 发送给监听该频道的客户端
    de = dictFind(server.pubsub_channels,channel); 找出监听该频道的客户端
    if (de) { 非空的情况下，遍历监听客户端列表
        list *list = dictGetVal(de);
        listNode *ln;
        listIter li;

        listRewind(list,&li);
        while ((ln = listNext(&li)) != NULL) { 遍历订阅的客户端列表
            client *c = ln->value;
            addReplyPubsubMessage(c,channel,message); 发出消息
            receivers++;
        }
    }
    /* Send to clients listening to matching channels */ 发送到收听匹配频道的客户端
    di = dictGetIterator(server.pubsub_patterns_dict); 查找模式匹配的客户端
    if (di) { 非空
        channel = getDecodedObject(channel);
        while((de = dictNext(di)) != NULL) {
            robj *pattern = dictGetKey(de);
            list *clients = dictGetVal(de);
            if (!stringmatchlen((char*)pattern->ptr,
                                sdslen(pattern->ptr),
                                (char*)channel->ptr,
                                sdslen(channel->ptr),0)) continue;  是否匹配，匹配就往下走，不匹配就跳到下一个

            listRewind(clients,&li);
            while ((ln = listNext(&li)) != NULL) { 遍历
                client *c = listNodeValue(ln);
                addReplyPubsubPatMessage(c,pattern,channel,message);
                receivers++;
            }
        }
        decrRefCount(channel);
        dictReleaseIterator(di);
    }
    return receivers;
}

/*-----------------------------------------------------------------------------
 * Pubsub commands implementation 发布订阅命令的实现
 *----------------------------------------------------------------------------*/

void subscribeCommand(client *c) {
    int j;

    for (j = 1; j < c->argc; j++)
        pubsubSubscribeChannel(c,c->argv[j]); 客户端订阅指定频道
    c->flags |= CLIENT_PUBSUB;
}

void unsubscribeCommand(client *c) { 客户端取消订阅频道
    if (c->argc == 1) {
        pubsubUnsubscribeAllChannels(c,1); 取消所有订阅频道
    } else {
        int j;

        for (j = 1; j < c->argc; j++)
            pubsubUnsubscribeChannel(c,c->argv[j],1); 取消指定订阅频道
    }
    if (clientSubscriptionsCount(c) == 0) c->flags &= ~CLIENT_PUBSUB;
}

根据客户端模式匹配订阅频道
void psubscribeCommand(client *c) {
    int j;

    for (j = 1; j < c->argc; j++)
        pubsubSubscribePattern(c,c->argv[j]);
    c->flags |= CLIENT_PUBSUB;
}
根据客户端模式取消匹配订阅频道
void punsubscribeCommand(client *c) {
    if (c->argc == 1) {
        pubsubUnsubscribeAllPatterns(c,1);
    } else {
        int j;

        for (j = 1; j < c->argc; j++)
            pubsubUnsubscribePattern(c,c->argv[j],1);
    }
    if (clientSubscriptionsCount(c) == 0) c->flags &= ~CLIENT_PUBSUB;
}

void publishCommand(client *c) {
    int receivers = pubsubPublishMessage(c->argv[1],c->argv[2]); 给订阅的客户端发送消息
    if (server.cluster_enabled)
        clusterPropagatePublish(c->argv[1],c->argv[2]); 集群模式下给所有群机发送消息
    else
        forceCommandPropagation(c,PROPAGATE_REPL);
    addReplyLongLong(c,receivers);
}

/* PUBSUB command for Pub/Sub introspection. */
用于发布/订阅介绍如何使用PUBSUB命令
void pubsubCommand(client *c) {
    if (c->argc == 2 && !strcasecmp(c->argv[1]->ptr,"help")) {
        const char *help[] = {
"CHANNELS [<pattern>] -- Return the currently active channels matching a pattern (default: all).",
"NUMPAT -- Return number of subscriptions to patterns.",
"NUMSUB [channel-1 .. channel-N] -- Returns the number of subscribers for the specified channels (excluding patterns, default: none).",
NULL
        };
        addReplyHelp(c, help);
    } else if (!strcasecmp(c->argv[1]->ptr,"channels") &&
        (c->argc == 2 || c->argc == 3))
    {
        /* PUBSUB CHANNELS [<pattern>] */  用于返回服务器当前被订阅的频道
        sds pat = (c->argc == 2) ? NULL : c->argv[2]->ptr;
        dictIterator *di = dictGetIterator(server.pubsub_channels);
        dictEntry *de;
        long mblen = 0;
        void *replylen;

        replylen = addReplyDeferredLen(c);
        while((de = dictNext(di)) != NULL) {
            robj *cobj = dictGetKey(de);
            sds channel = cobj->ptr;

            if (!pat || stringmatchlen(pat, sdslen(pat),
                                       channel, sdslen(channel),0)) 模式非空 匹配中
            {
                addReplyBulk(c,cobj); 返回匹配的频道
                mblen++;
            }
        }
        dictReleaseIterator(di);
        setDeferredArrayLen(c,replylen,mblen);
    } else if (!strcasecmp(c->argv[1]->ptr,"numsub") && c->argc >= 2) {
        /* PUBSUB NUMSUB [Channel_1 ... Channel_N] */ 返回对应频道订阅者（客户端）的数量
        int j;

        addReplyArrayLen(c,(c->argc-2)*2);
        for (j = 2; j < c->argc; j++) {
            list *l = dictFetchValue(server.pubsub_channels,c->argv[j]);

            addReplyBulk(c,c->argv[j]);
            addReplyLongLong(c,l ? listLength(l) : 0);
        }
    } else if (!strcasecmp(c->argv[1]->ptr,"numpat") && c->argc == 2) {
        /* PUBSUB NUMPAT */ 统计所有模式被订阅的次数
        addReplyLongLong(c,listLength(server.pubsub_patterns));
    } else {
        addReplySubcommandSyntaxError(c);
    }
}

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