Node Fault Detection Policy¶
The node fault detection function depends on the NPD add-on. The add-on instances run on nodes and monitor nodes. This section describes how to enable node fault detection.
Prerequisites¶
The CCE Node Problem Detector add-on has been installed in the cluster.
Enabling Node Fault Detection¶
Log in to the CCE console and click the cluster name to access the cluster console.
In the navigation pane on the left, choose Nodes. Check whether the NPD add-on has been installed in the cluster or whether the add-on has been upgraded to the latest version. After the NPD add-on has been installed, you can use the fault detection function.
If the NPD add-on is running properly, click Node Fault Detection Policy to view the current fault detection items. For details about the NPD check item list, see NPD Check Items.
If the check result of the current node is abnormal, a message is displayed in the node list, indicating that the metric is abnormal.
You can click Abnormal metrics and rectify the fault as prompted.
Customized Check Items¶
Log in to the CCE console and click the cluster name to access the cluster console.
Choose Node Management on the left and click Node Fault Detection Policy.
On the displayed page, view the current check items. Click Edit in the Operation column and edit checks.
Currently, the following configurations are supported:
Enable/Disable: Enable or disable a check item.
Target Node: By default, check items run on all nodes. You can change the fault threshold based on special scenarios. For example, the spot price ECS interruption reclamation check runs only on the spot price ECS node.
Trigger Threshold: The default thresholds match common fault scenarios. You can customize and modify the fault thresholds as required. For example, change the threshold for triggering connection tracking table exhaustion from 90% to 80%.
Check Period: The default check period is 30 seconds. You can modify this parameter as required.
Troubleshooting Strategy: After a fault occurs, you can select the strategies listed in the following table.
Table 1 Troubleshooting strategies¶ Troubleshooting Strategy
Effect
Prompting Exception
Kubernetes events are reported.
Disabling scheduling
Kubernetes events are reported and the NoSchedule taint is added to the node.
Evict Node Load
Kubernetes events are reported and the NoExecute taint is added to the node. This operation will evict workloads on the node and interrupt services. Exercise caution when performing this operation.
NPD Check Items¶
Note
Check items are supported only in 1.16.0 and later versions.
Check items cover events and statuses.
Event-related
For event-related check items, when a problem occurs, NPD reports an event to the API server. The event type can be Normal (normal event) or Warning (abnormal event).
Table 2 Event-related check items¶ Check Item
Function
Description
OOMKilling
Listen to the kernel logs and check whether OOM events occur and are reported.
Typical scenario: When the memory usage of a process in a container exceeds the limit, OOM is triggered and the process is terminated.
Warning event
Listening object: /dev/kmsg
Matching rule: "Killed process \\d+ (.+) total-vm:\\d+kB, anon-rss:\\d+kB, file-rss:\\d+kB.*"
TaskHung
Listen to the kernel logs and check whether taskHung events occur and are reported.
Typical scenario: Disk I/O suspension causes process suspension.
Warning event
Listening object: /dev/kmsg
Matching rule: "task \\S+:\\w+ blocked for more than \\w+ seconds\\."
ReadonlyFilesystem
Check whether the Remount root filesystem read-only error occurs in the system kernel by listening to the kernel logs.
Typical scenario: A user detaches a data disk from a node by mistake on the ECS, and applications continuously write data to the mount point of the data disk. As a result, an I/O error occurs in the kernel and the disk is remounted as a read-only disk.
Note
If the rootfs of node pods is of the device mapper type, an error will occur in the thin pool if a data disk is detached. This will affect NPD and NPD will not be able to detect node faults.
Warning event
Listening object: /dev/kmsg
Matching rule: Remounting filesystem read-only
Status-related
For status-related check items, when a problem occurs, NPD reports an event to the API server and changes the node status synchronously. This function can be used together with Node-problem-controller fault isolation to isolate nodes.
If the check period is not specified in the following check items, the default period is 30 seconds.
Table 3 Checking system components¶ Check Item
Function
Description
Container network component error
CNIProblem
Check the status of the CNI components (container network components).
None
Container runtime component error
CRIProblem
Check the status of Docker and containerd of the CRI components (container runtime components).
Check object: Docker or containerd
Frequent restarts of Kubelet
FrequentKubeletRestart
Periodically backtrack system logs to check whether the key component Kubelet restarts frequently.
Default threshold: 10 restarts within 10 minutes
If Kubelet restarts for 10 times within 10 minutes, it indicates that the system restarts frequently and a fault alarm is generated.
Listening object: logs in the /run/log/journal directory
Frequent restarts of Docker
FrequentDockerRestart
Periodically backtrack system logs to check whether the container runtime Docker restarts frequently.
Frequent restarts of containerd
FrequentContainerdRestart
Periodically backtrack system logs to check whether the container runtime containerd restarts frequently.
kubelet error
KubeletProblem
Check the status of the key component Kubelet.
None
kube-proxy error
KubeProxyProblem
Check the status of the key component kube-proxy.
None
Table 4 Checking system metrics¶ Check Item
Function
Description
Conntrack table full
ConntrackFullProblem
Check whether the conntrack table is full.
Default threshold: 90%
Usage: nf_conntrack_count
Maximum value: nf_conntrack_max
Insufficient disk resources
DiskProblem
Check the usage of the system disk and CCE data disks (including the CRI logical disk and kubelet logical disk) on the node.
Default threshold: 90%
Source:
df -h
Currently, additional data disks are not supported.
Insufficient file handles
FDProblem
Check if the FD file handles are used up.
Default threshold: 90%
Usage: the first value in /proc/sys/fs/file-nr
Maximum value: the third value in /proc/sys/fs/file-nr
Insufficient node memory
MemoryProblem
Check whether memory is used up.
Default threshold: 80%
Usage: MemTotal-MemAvailable in /proc/meminfo
Maximum value: MemTotal in /proc/meminfo
Insufficient process resources
PIDProblem
Check whether PID process resources are exhausted.
Default threshold: 90%
Usage: nr_threads in /proc/loadavg
Maximum value: smaller value between /proc/sys/kernel/pid_max and /proc/sys/kernel/threads-max.
Table 5 Checking the storage¶ Check Item
Function
Description
Disk read-only
DiskReadonly
Periodically perform write tests on the system disk and CCE data disks (including the CRI logical disk and Kubelet logical disk) of the node to check the availability of key disks.
Detection paths:
/mnt/paas/kubernetes/kubelet/
/var/lib/docker/
/var/lib/containerd/
/var/paas/sys/log/cceaddon-npd/
The temporary file npd-disk-write-ping is generated in the detection path.
Currently, additional data disks are not supported.
emptyDir storage pool error
EmptyDirVolumeGroupStatusError
Check whether the ephemeral volume group on the node is normal.
Impact: Pods that depend on the storage pool cannot write data to the temporary volume. The temporary volume is remounted as a read-only file system by the kernel due to an I/O error.
Typical scenario: When creating a node, a user configures two data disks as a temporary volume storage pool. Some data disks are deleted by mistake. As a result, the storage pool becomes abnormal.
Detection period: 30s
Source:
vgs -o vg_name, vg_attr
Principle: Check whether the VG (storage pool) is in the P state. If yes, some PVs (data disks) are lost.
Joint scheduling: The scheduler can automatically identify a PV storage pool error and prevent pods that depend on the storage pool from being scheduled to the node.
Exceptional scenario: The NPD add-on cannot detect the loss of all PVs (data disks), resulting in the loss of VGs (storage pools). In this case, kubelet automatically isolates the node, detects the loss of VGs (storage pools), and updates the corresponding resources in nodestatus.allocatable to 0. This prevents pods that depend on the storage pool from being scheduled to the node. The damage of a single PV cannot be detected by this check item, but by the ReadonlyFilesystem check item.
PV storage pool error
LocalPvVolumeGroupStatusError
Check the PV group on the node.
Impact: Pods that depend on the storage pool cannot write data to the persistent volume. The persistent volume is remounted as a read-only file system by the kernel due to an I/O error.
Typical scenario: When creating a node, a user configures two data disks as a persistent volume storage pool. Some data disks are deleted by mistake.
Mount point error
MountPointProblem
Check the mount point on the node.
Exceptional definition: You cannot access the mount point by running the cd command.
Typical scenario: Network File System (NFS), for example, obsfs and s3fs is mounted to a node. When the connection is abnormal due to network or peer NFS server exceptions, all processes that access the mount point are suspended. For example, during a cluster upgrade, a kubelet is restarted, and all mount points are scanned. If the abnormal mount point is detected, the upgrade fails.
Alternatively, you can run the following command:
for dir in `df -h | grep -v "Mounted on" | awk "{print \\$NF}"`;do cd $dir; done && echo "ok"Suspended disk I/O
DiskHung
Check whether I/O suspension occurs on all disks on the node, that is, whether I/O read and write operations are not responded.
Definition of I/O suspension: The system does not respond to disk I/O requests, and some processes are in the D state.
Typical scenario: Disks cannot respond due to abnormal OS hard disk drivers or severe faults on the underlying network.
Check object: all data disks
Source:
/proc/diskstat
Alternatively, you can run the following command:
iostat -xmt 1
Threshold:
Average usage: ioutil >= 0.99
Average I/O queue length: avgqu-sz >= 1
Average I/O transfer volume: iops (w/s) + ioth (wMB/s) <= 1
Note
In some OSs, no data changes during I/O. In this case, calculate the CPU I/O time usage. The value of iowait should be greater than 0.8.
Slow disk I/O
DiskSlow
Check whether all disks on the node have slow I/Os, that is, whether I/Os respond slowly.
Typical scenario: EVS disks have slow I/Os due to network fluctuation.
Check object: all data disks
Source:
/proc/diskstat
Alternatively, you can run the following command:
iostat -xmt 1
Default threshold:
Average I/O latency: await >= 5000 ms
Note
If I/O requests are not responded and the await data is not updated, this check item is invalid.
Table 6 Other check items¶ Check Item
Function
Description
Abnormal NTP
NTPProblem
Check whether the node clock synchronization service ntpd or chronyd is running properly and whether a system time drift is caused.
Default clock offset threshold: 8000 ms
Process D error
ProcessD
Check whether there is a process D on the node.
Default threshold: 10 abnormal processes detected for three consecutive times
Source:
/proc/{PID}/stat
Alternately, you can run the ps aux command.
Exceptional scenario: The ProcessD check item ignores the resident D processes (heartbeat and update) on which the SDI driver on the BMS node depends.
Process Z error
ProcessZ
Check whether the node has processes in Z state.
ResolvConf error
ResolvConfFileProblem
Check whether the ResolvConf file is lost.
Check whether the ResolvConf file is normal.
Exceptional definition: No upstream domain name resolution server (nameserver) is included.
Object: /etc/resolv.conf
Existing scheduled event
ScheduledEvent
Check whether scheduled live migration events exist on the node. A live migration plan event is usually triggered by a hardware fault and is an automatic fault rectification method at the IaaS layer.
Typical scenario: The host is faulty. For example, the fan is damaged or the disk has bad sectors. As a result, live migration is triggered for VMs.
Source:
This check item is an Alpha feature and is disabled by default.
The kubelet component has the following default check items, which have bugs or defects. You can fix them by upgrading the cluster or using NPD.
Table 7 Default kubelet check items¶ Check Item
Function
Description
Insufficient PID resources
PIDPressure
Check whether PIDs are sufficient.
Interval: 10 seconds
Threshold: 90%
Defect: In community version 1.23.1 and earlier versions, this check item becomes invalid when over 65535 PIDs are used. For details, see issue 107107. In community version 1.24 and earlier versions, thread-max is not considered in this check item.
Insufficient memory
MemoryPressure
Check whether the allocable memory for the containers is sufficient.
Interval: 10 seconds
Threshold: max. 100 MiB
Allocable = Total memory of a node - Reserved memory of a node
Defect: This check item checks only the memory consumed by containers, and does not consider that consumed by other elements on the node.
Insufficient disk resources
DiskPressure
Check the disk usage and inodes usage of the kubelet and Docker disks.
Interval: 10 seconds
Threshold: 90%