Collecting Container Logs Using ICAgent¶
CCE works with AOM to collect workload logs. When a node is created, ICAgent (a DaemonSet named icagent in the kube-system namespace of a cluster) of AOM is installed by default. ICAgent collects workload logs and reports them to AOM. You can view workload logs on the CCE or AOM console.
Constraints¶
ICAgent only collects text logs in .log, .trace, and .out formats.
Using ICAgent to Collect Logs¶
When creating a workload, set logging for the container.
Click
to add a log policy.The following uses Nginx as an example. Log policies vary depending on workloads.
Figure 1 Adding a log policy¶
Set Volume Type to hostPath or emptyDir.
Table 1 Configuring log policies¶ Parameter
Description
Volume Type
hostPath: A 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: A 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.
hostPath
Enter a host path, for example, /var/paas/sys/log/nginx.
Mount Path
Container path (for example, /tmp) to which the storage resources will be mounted.
Important
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.
If 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 may be damaged.
AOM collects only the first 20 logs that have been modified recently. It collects logs from 2 levels of subdirectories by default.
AOM only collects .log, .trace, and .out text logs 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 Volume Type is set to HostPath.
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.
Collection Path
A collection path narrows down the scope of collection to specified logs.
If no collection path is specified, log files in .log, .trace, and .out formats will be collected from the specified path.
/Path//** indicates that all log files in .log, .trace, and .out formats will be recursively collected from the specified path and all subdirectories at 5 levels deep.
* in log file names indicates a fuzzy match.
Example: The collection path /tmp//test*.log** indicates that all .log files prefixed with test will be collected from /tmp and subdirectories at 5 levels deep.
Caution
CAUTION: Ensure that ICAgent is of v5.12.22 or later.
Log Dump
Log dump refers to rotating log files on a local host.
Enabled: AOM scans log files every minute. When a log file exceeds 50 MB, it is dumped. 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.
Disabled: AOM does not dump log files.
Note
AOM rotates log files using copytruncate. 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 rotation. If you have already set rotation for log files, skip the configuration. Otherwise, conflicts may occur.
You are advised to configure log file rotation for your own services to flexibly control the size and number of rolled files.
Click OK.
YAML Example¶
You can set the container log storage path by defining a YAML file.
As shown in the following figure, an emptyDir volume 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 a hostPath volume. Compared with emptyDir, the type of volumes 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:
pathPattern: '**'
format: ''
volumes:
- hostPath:
path: /tmp/log
name: vol-log
imagePullSecrets:
- name: default-secret
Parameter | Description | Description |
|---|---|---|
extendPathMode | Extended 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.
|
policy.logs.rotate | Log dump | Log dump refers to rotating log files on a local host.
Note
|
policy.logs.annotations.pathPattern | Collection path | A collection path narrows down the scope of collection to specified logs.
Example: The collection path /tmp//test*.log** indicates that all .log files prefixed with test will be collected from /tmp and subdirectories at 5 levels deep. Caution CAUTION: Ensure that ICAgent is of v5.12.22 or later. |
policy.logs.annotations.format | Multi-line log matching | Some programs (for example, Java program) print a log that occupies multiple lines. By default, logs are collected by line. If you want to display logs as a single log message, you can enable multi-line logging 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. The format is as follows: {
"multi": {
"mode": "time",
"value": "YYYY-MM-DD hh:mm:ss"
}
}
multi indicates the multi-line mode.
|
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 container stdout.
# 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)