问题描述

测试了若干天的Spark on k8s, 今天突然就无法初始化 Spark Driver Pod 了。
表现如下，

1. 客户端侧以cluster模式提交一个几秒就会结束的测试程序，一直Hang住在ContainerCreating阶段

client

2. 接着尝试查看该 Pod 的真实状态。发现 no space left on device 的错误。

 Kent@KentsMacBookPro  ~  kubectl describe pod kent-766ab96ce1498671-driver -nns1
Name:         kent-766ab96ce1498671-driver
Namespace:    ns1
Node:         10.120.237.55/10.120.237.55
Start Time:   Fri, 30 Aug 2019 14:49:57 +0800
Labels:       spark-app-selector=spark-891742f8c844486eb027aa15ae4b2849
              spark-role=driver
              syetem/tenant=tenant1
              system/namespace=ns1
              system/project-project1=true
Annotations:  <none>
Status:       Pending
IP:
Containers:
  spark-kubernetes-driver:
    Container ID:
    Image:         harbor-inner.sparkonk8s.netease.com/tenant1-project1/spark:v3-SPARK-28896
    Image ID:
    Ports:         7078/TCP, 7079/TCP, 4040/TCP
    Host Ports:    0/TCP, 0/TCP, 0/TCP
    Args:
      driver
      --properties-file
      /opt/spark/conf/spark.properties
      --class
      org.apache.spark.examples.HdfsTest
      local:///opt/spark/examples/jars/spark-examples_2.12-3.0.0-SNAPSHOT.jar
      hdfs://hz-cluster10/user/kyuubi/hive_db/kyuubi.db/hive_tbl
    State:          Waiting
      Reason:       ContainerCreating
    Ready:          False
    Restart Count:  0
    Limits:
      memory:  1408Mi
    Requests:
      cpu:     1
      memory:  1408Mi
    Environment:
      SPARK_USER:                 Kent
      SPARK_DRIVER_BIND_ADDRESS:   (v1:status.podIP)
      HADOOP_CONF_DIR:            /opt/hadoop/conf
      SPARK_LOCAL_DIRS:           /var/data/spark-e6630b91-3892-41d1-9624-a955159b176a
      SPARK_CONF_DIR:             /opt/spark/conf
    Mounts:
      /etc/krb5.conf from krb5-file (rw,path="krb5.conf")
      /mnt/secrets/kerberos-keytab from kerberos-keytab (rw)
      /opt/hadoop/conf from hadoop-properties (rw)
      /opt/spark/conf from spark-conf-volume (rw)
      /var/data/spark-e6630b91-3892-41d1-9624-a955159b176a from spark-local-dir-1 (rw)
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-nxhgg (ro)
Conditions:
  Type              Status
  Initialized       True
  Ready             False
  ContainersReady   False
  PodScheduled      True
Volumes:
  hadoop-properties:
    Type:      ConfigMap (a volume populated by a ConfigMap)
    Name:      hz10-hadoop-dir
    Optional:  false
  krb5-file:
    Type:      ConfigMap (a volume populated by a ConfigMap)
    Name:      kent-766ab96ce1498671-krb5-file
    Optional:  false
  kerberos-keytab:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  kent-766ab96ce1498671-kerberos-keytab
    Optional:    false
  spark-local-dir-1:
    Type:       EmptyDir (a temporary directory that shares a pod's lifetime)
    Medium:
    SizeLimit:  <unset>
  spark-conf-volume:
    Type:      ConfigMap (a volume populated by a ConfigMap)
    Name:      kent-766ab96ce1498671-driver-conf-map
    Optional:  false
  default-token-nxhgg:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-nxhgg
    Optional:    false
QoS Class:       Burstable
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type     Reason                    Age                   From                    Message
  ----     ------                    ----                  ----                    -------
  Normal   Scheduled                 37m                   default-scheduler       Successfully assigned ns1/kent-766ab96ce1498671-driver to 10.120.237.55
  Warning  FailedMount               37m                   kubelet, 10.120.237.55  MountVolume.SetUp failed for volume "spark-conf-volume" : configmaps "kent-766ab96ce1498671-driver-conf-map" not found
  Warning  FailedMount               37m                   kubelet, 10.120.237.55  MountVolume.SetUp failed for volume "kerberos-keytab" : secrets "kent-766ab96ce1498671-kerberos-keytab" not found
  Warning  FailedMount               37m                   kubelet, 10.120.237.55  MountVolume.SetUp failed for volume "krb5-file" : configmaps "kent-766ab96ce1498671-krb5-file" not found
  Warning  FailedCreatePodContainer  7m9s (x140 over 37m)  kubelet, 10.120.237.55  unable to ensure pod container exists: failed to create container for [kubepods burstable pod613a702e-caf2-11e9-95c4-6c92bf35a76a] : mkdir /sys/fs/cgroup/memory/kubepods/burstable/pod613a702e-caf2-11e9-95c4-6c92bf35a76a: no space left on device

3. Google一番后发现与https://github.com/rootsongjc/kubernetes-handbook/issues/313 这个同学的问题基本一致。
   存在的可能有，

• Kubelet 宿主机的 Linux 内核过低 - Linux version 3.10.0-862.el7.x86_64
• K8s集群的版本过低 - 1.11.9
• 可以通过禁用kmem解决

联系了一下我司k8s内核开发，首先发现kmem应该是禁止了

image.png

但实际上，貌似没有禁止干净

image.png

最后，因为在启动容器的时候runc的逻辑会默认打开容器的kmem accounting，导致3.10内核可能的泄漏问题

总结

从根源上看，这个问题应该是属于kubernetes 或者 操作系统内核的一个bug
但从结果上来讲，Container 因为各种原因分配失败应该是常有的事，Spark在处理这块的时候目前也没有retry的机制，这些异常的 Pod也没有自动清理的机制，需要上集群手动进行删除。