Container Logs

Scenario

CCE allows you to configure policies for collecting, managing, and analyzing workload logs periodically to prevent logs from being over-sized.

CCE works with AOM to collect workload logs. When a node is created, the ICAgent (the DaemonSet named icagent in the kube-system namespace of the cluster) of AOM is installed by default. After the ICAgent collects workload logs and reports them to AOM, you can view workload logs on the CCE or AOM console.

• By default, the ICAgent collects the standard outputs of containers. You do not need to perform any configuration.
• You can also configure the path for storing container logs when creating a workload so that the ICAgent collects logs from this path.
  You can select either of the following modes for container logs:

  • HostPath: The host path is mounted to the specified container path (mount path). In the node host path, you can view the container logs output into the mount path.
  • EmptyDir: The temporary path of the node is mounted to the specified path (mount path). Log data that exists in the temporary path but is not reported by the collector to AOM will disappear after the pod is deleted.

Precautions

The ICAgent only collects *.log, *.trace, and *.out text log files.

Setting the Path for Storing Container Logs

1. When creating a workload on the CCE console, add a container and expand Log Policies.
2. In the Log Policies area, click Add Log Policy. Configure parameters in the log policy. The following uses Nginx as an example.
   Figure 1 Adding a log policy
   

3. Set Storage Type to Host Path or Container Path.

   Table 1 Configuring log policies

   Parameter	Description
   Storage Type	Host Path: In HostPath mode, the host path is mounted to the specified container path (mount path). In the node host path, you can view the container logs output into the mount path. Container Path: In EmptyDir mode, the temporary path of the node is mounted to the specified path (mount path). Log data that exists in the temporary path but is not reported by the collector to AOM will disappear after the pod is deleted.
   Add Container Path
   *Host Path	Enter the host path, for example, /var/paas/sys/log/nginx.
   Container Path	Container path (for example, /tmp) to which the storage resources will be mounted. NOTICE: Do not mount storage to a system directory such as / or /var/run; this action may cause a container error to occur. You are advised to mount the container to an empty directory. If the directory is not empty, ensure that there are no files affecting container startup in the directory. Otherwise, such files will be replaced, resulting in failures to start the container and create the workload. When the container is mounted to a high-risk directory, you are advised to use an account with minimum permissions to start the container; otherwise, high-risk files on the host machine may be damaged. AOM collects only the first 20 log files that have been modified recently. It collects files from 2 levels of subdirectories by default. AOM only collects .log, .trace, and .out text log files in mounting paths. For details about how to set permissions for mount points in a container, see Configure a Security Context for a Pod or Container.
   Extended Host Path	This parameter is mandatory only if Storage Type is set to Host Path. Extended host paths contain pod IDs or container names to distinguish different containers into which the host path is mounted. A level-3 directory is added to the original volume directory/subdirectory. You can easily obtain the files output by a single Pod. None: No extended path is configured. PodUID: ID of a pod. PodName: name of a pod. PodUID/ContainerName: ID of a pod or name of a container. PodName/ContainerName: name of a pod or container.
   Log Dumping	Log dump refers to rolling log files on a local host. Enabled: AOM scans log files every minute. When a log file exceeds 50 MB, it is dumped immediately. A new .zip file is generated in the directory where the log file locates. For a log file, AOM stores only the latest 20 .zip files. When the number of .zip files exceeds 20, earlier .zip files will be deleted. After the dump is complete, the log file in AOM will be cleared. Disabled: AOM does not dump log files. NOTE: Log file rolling of AOM is implemented in the copytruncate mode. Before enabling log dumping, ensure that log files are written in the append mode. Otherwise, file holes may occur. Currently, mainstream log components such as Log4j and Logback support log file rolling. If your log files already support rolling, skip the configuration. Otherwise, conflicts may occur. You are advised to configure log file rolling for your own services to flexibly control the size and number of rolled files.
   Multi-line Log	Some program logs (for example, Java program logs) contain a log that occupies multiple lines. By default, the log collection system collects logs by line. If you want to display logs as a single log message in the log collection system, you can enable the multi-line log function and use the log time or regular pattern mode. When a line of log message matches the preset time format or regular expression, it is considered as the start of a log message and the next line starts with this line of log message is considered as the end identifier of the log message. Split Mode Log Time: Enter a time wildcard. For example, if the time in the log is 2017-01-01 23:59:59, the wildcard is YYYY-MM-DD hh:mm:ss. Regular Pattern: Enter a regular expression.

4. Click OK.

Using kubectl to Set the Container Log Storage Path

You can set the container log storage path by defining a YAML file.

As shown in the following figure, EmptyDir is mounted a temporary path to /var/log/nginx. In this way, the ICAgent collects logs in /var/log/nginx. The policy field is customized by CCE and allows the ICAgent to identify and collect logs.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: testlog
  namespace: default
spec:
  selector:
    matchLabels:
      app: testlog
  template:
    replicas: 1
    metadata:
      labels:
        app: testlog
    spec:
      containers:
        - image: 'nginx:alpine'
          name: container-0
          resources:
            requests:
              cpu: 250m
              memory: 512Mi
            limits:
              cpu: 250m
              memory: 512Mi
          volumeMounts:
            - name: vol-log
              mountPath: /var/log/nginx
              policy:
                logs:
                  rotate: ''
      volumes:
        - emptyDir: {}
          name: vol-log
      imagePullSecrets:
        - name: default-secret

The following shows how to use the HostPath mode. Compared with the EmptyDir mode, the type of volume is changed to hostPath, and the path on the host needs to be configured for this hostPath volume. In the following example, /tmp/log on the host is mounted to /var/log/nginx. In this way, the ICAgent can collects logs in /var/log/nginx, without deleting the logs from /tmp/log.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: testlog
  namespace: default
spec:
  replicas: 1
  selector:
    matchLabels:
      app: testlog
  template:
    metadata:
      labels:
        app: testlog
    spec:
      containers:
        - image: 'nginx:alpine'
          name: container-0
          resources:
            requests:
              cpu: 250m
              memory: 512Mi
            limits:
              cpu: 250m
              memory: 512Mi
          volumeMounts:
            - name: vol-log
              mountPath: /var/log/nginx
              readOnly: false
              extendPathMode: PodUID
              policy:
                logs:
                  rotate: Hourly
                  annotations:
                    
                    format: ''
      volumes:
        - hostPath:
            path: /tmp/log
          name: vol-log
      imagePullSecrets:
        - name: default-secret

{
    "multi": {
        "mode": "time",
        "value": "YYYY-MM-DD hh:mm:ss"
    }
}

Viewing Logs

After a log collection path is configured and the workload is created, the ICAgent collects log files from the configured path. The collection takes about 1 minute.

After the log collection is complete, go to the workload details page and click Logs in the upper right corner to view logs.

You can also view logs on the AOM console.

You can also run the kubectl logs command to view the standard output of a container.

# View logs of a specified pod.
kubectl logs <pod_name>
kubectl logs -f <pod_name> # Similar to tail -f

# View logs of a specified container in a specified pod.
kubectl logs <pod_name> -c <container_name>

kubectl logs pod_name -c container_name -n namespace (one-off query)
kubectl logs -f <pod_name> -n namespace (real-time query in tail -f mode)