Collect logs by using environment variables

Background

Simple Log Service (SLS) is an all-in-one service for log data. It allows you to collect, consume, ship, query, and analyze log data without development effort. For more information, see What is Simple Log Service?.

Prerequisites

Log Service is activated. If you have not activated Log Service, you are prompted to do so when you log on to the Log Service console. Follow the on-screen instructions to activate it.

Usage notes

• You can customize log collection by using environment variables only when you create an ECI instance. Log-related environment variables passed when you update an instance do not take effect.

• If you no longer use a custom project or Logtail configuration, delete them promptly to avoid unnecessary charges.

• If you rename a custom environment variable, the original configuration is not automatically deleted. You must manually delete the configuration to avoid unnecessary charges.

Configuration

The prefix for log-related environment variable names is aliyun_logs_{key}. The following table describes these variables.

Example

1. Connect to the cluster.

2. Create an application.

   You can pass log configurations by using environment variables for the container. The following YAML file is an example of a Deployment. After the container starts, it continuously prints to stdout and writes to a log file.

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     labels:
       app: sls
     name: eci-sls-demo
   spec:
     replicas: 1
     selector:
       matchLabels:
         app: sls
     template:
       metadata:
         labels:
           app: sls
           alibabacloud.com/eci: "true" 
       spec:
         containers:
         - image: registry-vpc.cn-beijing.aliyuncs.com/eci_open/alpine:3.5
           imagePullPolicy: Always
           args:
           - -c
           - mkdir -p /log;while true; do echo hello world; date; echo hello sls >> /log/alpine.log; sleep 1;done
           command:
           - /bin/sh
           name: alpine
           env:
           # Specify a project. You can omit this to use the default project.
           - name: aliyun_logs_test-stdout_project
             value: k8s-log-c21492
           - name: aliyun_logs_test-file_project
             value: k8s-log-c21492
           # Specify a machine group. You can omit this to use the default machine group.
           - name: aliyun_logs_test-stdout_machinegroup
             value: k8s-group-app-alpine
           - name: aliyun_logs_test-file_machinegroup
             value: k8s-group-app-alpine
           # Collect stdout logs to a Logstore named test-stdout. The log source is stdout.
           - name: aliyun_logs_test-stdout
             value: stdout
           # Collect logs from the /log/*.log path to a Logstore named test-file.
           - name: aliyun_logs_test-file
             value: /log/*.log
           # Set the log retention period. This setting applies only to the test-stdout Logstore.
           - name: aliyun_logs_test-stdout_ttl
             value: "7"
           # Set the number of shards. This setting applies only to the test-stdout Logstore.
           - name: aliyun_logs_test-stdout_shard
             value: "2"
           # Mount an emptyDir volume. This is required for collecting logs from custom directories but not for stdout.
           volumeMounts:
           - name: volume-sls
             mountPath: /log
         volumes:
         - name: volume-sls
           emptyDir: {}

   Save the preceding YAML content as test-sls-env.yaml and run the following command to create the application.

   kubectl create -f test-sls-env.yaml

3. Verify the application status.

   kubectl get pod

   Expected output:

   NAME                             READY   STATUS    RESTARTS   AGE
   eci-sls-demo-b97bbd7d6-z9twz     1/1     Running   0          2m45s

4. View the logs.

   1. Log on to the Simple Log Service console.

   2. Click the name of the target project.

   3. Find the target Logstore and click its name to view the logs.

      • Standard output

        In the Logstore list on the left, select test-stdout to view the collected stdout logs. The log records contain fields such as _container_name_: alpine, _namespace_: default, and _source_: stdout. An example of the log content is hello world.

      • File-based log

        In the Logstore list on the left, select the test-file Logstore and click the Raw button to view the raw logs. The query result shows multiple log entries, all with the content hello sls, from the ECI alpine container. The logs include tag fields such as __tag__:__container_name__ (alpine), __tag__:__namespace__ (default), __tag__:__pod_name__, and __tag__:__eci_id__. This indicates that the file-based logs are successfully collected to SLS.