Collect application logs - Container Service for Kubernetes

Log Service is an all-in-one service to manage log data. Log Service allows you to collect, consume, ship, query, and analyze log data without development work. After Log Service is enabled on Knative, you can manage and maintain serverless applications with higher efficiency.

Prerequisites

Log Service is activated. For more information, see Use Log Service to collect container logs.
A Knative Service is deployed. For more information, see Create a Knative Service.

Procedure

Collect log data of the Helloworld application.
For more information, see Use the console to collect Kubernetes stdout and stderr logs in DaemonSet mode.
1. Log on to the Log Service console.
2. In the Projects section, click Create Project to create a Log Service project named helloworld. For more information, see Manage a Logstore.
3. Click the created helloworld project.
4. Navigate to the details page of the project. In the upper-right corner of the page, click Import Data.
5. In the Import Data dialog box, find and click Docker Standard Output to navigate to the Docker Standard Output page.
6. In the Specify Logstore step, select the created Logstore and click Next.
7. Configure Create Machine Group.
  If the Logtail agent is installed, click Use Existing Machine Groups.
  You can also click Kubernetes Cluster (Recommended) to install the Logtail agent or click Standard Docker Container to deploy a Logtail container. For more information, see Use Log Service to collect container logs and Collect logs from standard Docker containers.
8. Click Complete Installation.
9. Configure Machine Group Settings.
10. Configure Specify Data Source.
  In the plug-in configuration, specify the following environment variable for log collection: "K_SERVICE": "helloworld-go". Use processors to process log data, for example, "Keys": [ "time","level", "msg" ]. The following code block is an example:
```
{
  "inputs": [
    {
      "detail": {
        "IncludeEnv": {
          "K_SERVICE": "helloworld-go"
        },
        "IncludeLabel": {},
        "ExcludeLabel": {}
      },
      "type": "service_docker_stdout"
    }
  ],
  "processors": [
    {
      "detail": {
        "KeepSource": false,
        "NoMatchError": true,
        "Keys": [
          "time",
          "level",
          "msg"
        ],
        "NoKeyError": true,
        "Regex": "(\\d+-\\d+-\\d+\\s+\\d+:\\d+:\\d+)\\s+(\\w+)\\s+(.*)",
        "SourceKey": "content"
      },
      "type": "processor_regex"
    }
  ]
}
```
11. After the data source is configured, click Next.
12. In the Configure Query and Analysis step, enable Full Text Index and set key/value index attributes.
13. Click Next to proceed to the End page.
Run the following command to access the Helloworld application.
The following log data is generated:
```
curl -H "Host: helloworld-go.default.example.com" http://112.124.XX.XX
```
Expected output:
```
Hello Knative!
```
Go to the details page of the helloworld project. On the details page, find the created Logstore, move the pointer over the icon on the right side of the Logstore, and choose > Search & Analysis. On the page that appears, you can view the log data in the Logstore.
Configure search conditions.
For more information, see Real-time log analysis.
You can modify Column Settings to specify the columns that are displayed. In the following example, three columns are displayed: level, msg, and time.

Conclusion

The preceding example demonstrates how to use Log Service to collect the log data of a serverless Knative application. You can use Log Service to collect and analyze log data of Knative applications. This helps manage and maintain serverless Knative applications in a production environment.