IPVS调度算法之FO

FO（Weighted Fail Over）调度算法。

调度器注册

FO调度器的定义结构为ip_vs_fo_scheduler，使用函数register_ip_vs_scheduler注册到IPVS的调度器系统中。

static struct ip_vs_scheduler ip_vs_fo_scheduler = {
    .name =                 "fo",
    .refcnt =               ATOMIC_INIT(0),
    .module =               THIS_MODULE,
    .n_list =               LIST_HEAD_INIT(ip_vs_fo_scheduler.n_list),
    .schedule =             ip_vs_fo_schedule,
};

static int __init ip_vs_fo_init(void)
{
    return register_ip_vs_scheduler(&ip_vs_fo_scheduler);
}

调度处理

在此FO算法中，遍历虚拟服务所关联的真实服务器链表，找到还未过载（未设置IP_VS_DEST_F_OVERLOAD标志）的且权重最高的真实服务器，进行调度。

static struct ip_vs_dest *ip_vs_fo_schedule(struct ip_vs_service *svc, const struct sk_buff *skb, struct ip_vs_iphdr *iph)
{
    struct ip_vs_dest *dest, *hweight = NULL;
    int hw = 0; /* Track highest weight */

    /* Basic failover functionality, Find virtual server with highest weight and send it traffic
     */
    list_for_each_entry_rcu(dest, &svc->destinations, n_list) {
        if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) && atomic_read(&dest->weight) > hw) {
            hweight = dest;
            hw = atomic_read(&dest->weight);
        }
    }
    if (hweight) {
        return hweight;
    }

    ip_vs_scheduler_err(svc, "no destination available");
    return NULL;
}

内核版本 4.15