Logging

Spaces built using the knot base images utilize rsyslog to collect logs from services running within the space. These logs are forwarded by the knot agent to the knot server for storage and viewing.

Viewing Logs

Once a space is running, logs can be accessed directly from the Spaces page:

1. Click the Logs button next to the space whose logs you want to view.

   

2. A window will open, tailing the logs in real-time.

Sending Logs

The knot agent supports two interfaces for sending logs:

• Syslog Interface
• HTTP API (supports native JSON, msgpack, Graylog GELF, and Loki formats)

Default Ports:

• HTTP API: 12201
• Syslog Interface: 514

Sending Logs via logger

You can send messages to the syslog interface using the logger command:

logger test message

HTTP API Formats

Native JSON or Msgpack

The native JSON or msgpack format uses a simple JSON object with the following fields:

{
  "service": "my-app",
  "level": "info",
  "message": "Logging a test message"
}

• service: The name of the service sending the log message.
• level: The log level (debug, info, or error).
• message: The log message content.

Send the message using curl:

curl -X POST http://localhost:12201/logs \
  -H "Content-Type: application/json" \
  -d '{"service":"my-app", "level":"info", "message":"Logging a test message"}'

Graylog GELF

The Graylog GELF format uses the following JSON structure:

{
  "version": "1.1",
  "host": "example.org",
  "short_message": "A short message",
  "full_message": "Backtrace here\n\nmore stuff",
  "timestamp": 1291899928.412,
  "level": 3
}

Send the message using curl:

curl -X POST http://localhost:12201/gelf \
  -H "Content-Type: application/json" \
  -d '{"version":"1.1", "host":"example.org", "short_message":"A short message", "full_message":"Backtrace here\n\nmore stuff", "timestamp":1291899928.412, "level":3}'

Loki

The Loki-compatible endpoint accepts logs in the following JSON format:

{
  "streams": [
    {
      "stream": {
        "label": "my-app"
      },
      "values": [
        [ "1620000000", "Logging a test message" ]
      ]
    }
  ]
}

Send the message using curl:

curl -X POST http://localhost:12201/loki/api/v1/push \
  -H "Content-Type: application/json" \
  -d '{"streams": [{"stream": {"label": "my-app"}, "values": [[ "1620000000", "Logging a test message" ]]}]}'