kubernetes借助系統(tǒng)的OOM KILL提升服務(wù)質(zhì)量，至于什么是OOM KILL可以去網(wǎng)上搜一下這里不再班門(mén)弄斧，下面我們就看一下Kubernetes是按照什么規(guī)則來(lái)分別設(shè)置容器的oom_score_adj。

其實(shí)規(guī)則也比較簡(jiǎn)單只有一段代碼:

//pkg/kubelet/qos/policy.go
func GetContainerOOMScoreAdjust(pod *v1.Pod, container *v1.Container, memoryCapacity int64) int {
    switch v1qos.GetPodQOS(pod) {
    case v1.PodQOSGuaranteed:
        // Guaranteed containers should be the last to get killed.
        return guaranteedOOMScoreAdj
    case v1.PodQOSBestEffort:
        return besteffortOOMScoreAdj
    }

    // Burstable containers are a middle tier, between Guaranteed and Best-Effort. Ideally,
    // we want to protect Burstable containers that consume less memory than requested.
    // The formula below is a heuristic. A container requesting for 10% of a system's
    // memory will have an OOM score adjust of 900. If a process in container Y
    // uses over 10% of memory, its OOM score will be 1000. The idea is that containers
    // which use more than their request will have an OOM score of 1000 and will be prime
    // targets for OOM kills.
    // Note that this is a heuristic, it won't work if a container has many small processes.
    memoryRequest := container.Resources.Requests.Memory().Value()
    oomScoreAdjust := 1000 - (1000*memoryRequest)/memoryCapacity
    // A guaranteed pod using 100% of memory can have an OOM score of 10. Ensure
    // that burstable pods have a higher OOM score adjustment.
    if int(oomScoreAdjust) < (1000 + guaranteedOOMScoreAdj) {
        return (1000 + guaranteedOOMScoreAdj)
    }
    // Give burstable pods a higher chance of survival over besteffort pods.
    if int(oomScoreAdjust) == besteffortOOMScoreAdj {
        return int(oomScoreAdjust - 1)
    }
    return int(oomScoreAdjust)
}

這段代碼就是講的如何計(jì)算每個(gè)容器的oom score的。
首先看這個(gè)容器所屬的Pod是屬于什么級(jí)別的，如果是Guaranteed級(jí)別的直接返回-998也是最高級(jí)最后被Kill掉的，如果是BestEffort級(jí)別則直接返回1000是最低級(jí)別的，最有可能被殺掉。如果是Burstable則是中間級(jí)別需要按照資源的申請(qǐng)量來(lái)計(jì)算oom score。

oomScoreAdjust := 1000 - (1000*memoryRequest)/memoryCapacity

就是這段公式計(jì)算出容器的score，最后得到的值會(huì)在2-999之間，從這個(gè)公式能夠看出來(lái)Burstable級(jí)別的如果越是資源申請(qǐng)的越多則給的分越低，這就意味著容器越不容易被殺掉，如果是申請(qǐng)量越少得出的分越高則越容易被殺掉。