Redis slowlog使用和实现

void call(client *c, int flags) {

    //如果当前在 AOF 加载上下文，不要写 slowlog / latency / INFO stats
    int update_command_stats = !isAOFLoadingContext();

    //......
    if (update_command_stats && !(c->flags & CLIENT_BLOCKED))
        slowlogPushCurrentCommand(c, real_cmd, c->duration);
    //......
    
}

void slowlogPushCurrentCommand(client *c, struct redisCommand *cmd, ustime_t duration) {
    //是否需要纪录slowlog
    if (cmd->flags & CMD_SKIP_SLOWLOG)
        return;
    robj **argv = c->original_argv ? c->original_argv : c->argv;
    int argc = c->original_argv ? c->original_argc : c->argc;
    slowlogPushEntryIfNeeded(c,argv,argc,duration);
}

void slowlogPushEntryIfNeeded(client *c, robj **argv, int argc, long long duration) {
    //判断slowlog_log_slower_than配置是否小于０，是否记录日志
    if (server.slowlog_log_slower_than < 0) return; /* Slowlog disabled */
    //如果执行时间大于slowlog_log_slower_than时间　追加到slow log list头部中
    if (duration >= server.slowlog_log_slower_than)
        listAddNodeHead(server.slowlog,
                        slowlogCreateEntry(c,argv,argc,duration));
    //判断slow log list长度是否大于slowlog_max_len,
    //如果大于slowlog_max_len　删除list尾部元素
    /* Remove old entries if needed. */
    while (listLength(server.slowlog) > server.slowlog_max_len)
        listDelNode(server.slowlog,listLast(server.slowlog));
}