What Should I Do If Container Startup Fails?

Fault Locating

On the details page of a workload, if an event is displayed indicating that the container fails to be started, perform the following steps to locate the fault:

1. Log in to the node where the abnormal workload is located.
2. Check the ID of the container where the workload pod exits abnormally.

   docker ps -a | grep $podName

3. View the logs of the corresponding container.

   docker logs $containerID

   Rectify the fault of the workload based on logs.

4. Check the error logs.

   cat /var/log/messages | grep $containerID  | grep oom

   Check whether the system OOM is triggered based on the logs.

Troubleshooting Process

Determine the cause based on the event information, as listed in Table 1.

In addition to the preceding possible causes, there are some other possible causes:

• Check Item 7: Whether the Container Startup Command Is Correctly Configured
• Check Item 8: Whether the User Service Has a Bug
• Use the correct image when you create a workload on an Arm node.

Figure 1 Troubleshooting process of the container restart failure

Check Item 1: Whether There Are Processes that Keep Running in the Container (Exit Code: 0)

1. Log in to the node where the abnormal workload is located.
2. View the container status.

   docker ps -a | grep $podName

   Example:

   

   If no running process exists in the container, the status code Exited (0) is displayed.

Check Item 2: Whether Health Check Fails to Be Performed (Exit Code: 137)

The health check configured for a workload is performed on services periodically. If an exception occurs, the pod reports an event and the pod fails to be restarted.

If the liveness-type (workload liveness probe) health check is configured for the workload and the number of health check failures exceeds the threshold, the containers in the pod will be restarted. On the workload details page, if Kubernetes events contain Liveness probe failed: Get http..., the health check fails.

Solution

Click the workload name to go to the workload details page, click the Containers tab. Then select Health Check to check whether the policy is proper or whether services are running properly.

Check Item 3: Whether the Container Disk Space Is Insufficient

The following message refers to the thin pool disk that is allocated from the Docker disk selected during node creation. You can run the lvs command as user root to view the current disk usage.

Thin Pool has 15991 free data blocks which are less than minimum required 16383 free data blocks. Create more free space in thin pool or use dm.min_free_space option to change behavior

Solution

Solution 1: Clearing images

Perform the following operations to clear unused images:

• Nodes that use containerd
  1. Obtain local images on the node.

     crictl images -v

  2. Delete the images that are not required by image ID.

     crictl rmi Image ID

• Nodes that use Docker
  1. Obtain local images on the node.

     docker images

  2. Delete the images that are not required by image ID.

     docker rmi Image ID

Do not delete system images such as the cce-pause image. Otherwise, pods may fail to be created.

Solution 2: Expanding the disk capacity

To expand a disk capacity, perform the following steps:

1. Expand the capacity of the data disk on the EVS console.
2. Log in to the CCE console and click the cluster. In the navigation pane, choose Nodes. Click More > Sync Server Data in the row containing the target node.
3. Log in to the target node.
4. Run the lsblk command to check the block device information of the node.

   A data disk is divided depending on the container storage Rootfs:

   • Overlayfs: No independent thin pool is allocated. Image data is stored in the dockersys disk.

     # lsblk
     NAME                MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
     sda                   8:0    0   50G  0 disk 
     └─sda1                8:1    0   50G  0 part /
     sdb                   8:16   0  200G  0 disk 
     ├─vgpaas-dockersys  253:0    0   90G  0 lvm  /var/lib/docker               # Space used by the container engine
     └─vgpaas-kubernetes 253:1    0   10G  0 lvm  /mnt/paas/kubernetes/kubelet  # Space used by Kubernetes

     Run the following commands on the node to add the new disk capacity to the dockersys disk:

     pvresize /dev/sdb 
     lvextend -l+100%FREE -n vgpaas/dockersys
     resize2fs /dev/vgpaas/dockersys

   • Devicemapper: A thin pool is allocated to store image data.

     # lsblk
     NAME                                MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
     sda                                   8:0    0   50G  0 disk 
     └─sda1                                8:1    0   50G  0 part /
     sdb                                   8:16   0  200G  0 disk 
     ├─vgpaas-dockersys                  253:0    0   18G  0 lvm  /var/lib/docker    
     ├─vgpaas-thinpool_tmeta             253:1    0    3G  0 lvm                   
     │ └─vgpaas-thinpool                 253:3    0   67G  0 lvm                   # Thin pool space.
     │   ...
     ├─vgpaas-thinpool_tdata             253:2    0   67G  0 lvm  
     │ └─vgpaas-thinpool                 253:3    0   67G  0 lvm  
     │   ...
     └─vgpaas-kubernetes                 253:4    0   10G  0 lvm  /mnt/paas/kubernetes/kubelet

     • Run the following commands on the node to add the new disk capacity to the thinpool disk:

       pvresize /dev/sdb 
       lvextend -l+100%FREE -n vgpaas/thinpool

     • Run the following commands on the node to add the new disk capacity to the dockersys disk:

       pvresize /dev/sdb 
       lvextend -l+100%FREE -n vgpaas/dockersys
       resize2fs /dev/vgpaas/dockersys

Check Item 4: Whether the Upper Limit of Container Resources Has Been Reached

If the upper limit of container resources has been reached, OOM will be displayed in the event details as well as in the log:

cat /var/log/messages | grep 96feb0a425d6 | grep oom

When a workload is created, if the requested resources exceed the configured upper limit, the system OOM is triggered and the container exits unexpectedly.

Check Item 5: Whether the Resource Limits Are Improperly Configured for the Container

If the resource limits set for the container during workload creation are less than required, the container fails to be restarted.

Check Item 6: Whether the Container Ports in the Same Pod Conflict with Each Other

1. Log in to the node where the abnormal workload is located.
2. Check the ID of the container where the workload pod exits abnormally.

   docker ps -a | grep $podName

3. View the logs of the corresponding container.

   docker logs $containerID

   Rectify the fault of the workload based on logs. As shown in the following figure, container ports in the same pod conflict. As a result, the container fails to be started.

   Figure 2 Container restart failure due to a container port conflict
   

Solution

Re-create the workload and set a port number that is not used by any other pod.

Check Item 7: Whether the Container Startup Command Is Correctly Configured

The error messages are as follows:

Solution

Click the workload name to go to the workload details page, click the Containers tab. Choose Lifecycle , click Startup Command, and ensure that the command is correct.

Check Item 8: Whether the User Service Has a Bug

Check whether the workload startup command is correctly executed or whether the workload has a bug.

1. Log in to the node where the abnormal workload is located.
2. Check the ID of the container where the workload pod exits abnormally.

   docker ps -a | grep $podName

3. View the logs of the corresponding container.

   docker logs $containerID

   Note: In the preceding command, containerID indicates the ID of the container that has exited.

   Figure 3 Incorrect startup command of the container
   

   As shown in the figure above, the container fails to be started due to an incorrect startup command. For other errors, rectify the bugs based on the logs.

Solution

Create a new workload and configure a correct startup command.