Structured Logging

In Stackdriver Logging, structured logs refer to log entries that use the jsonPayload field to add structure to their payloads. If you use the Stackdriver Logging API or the command-line utility, gcloud logging, you can control the structure of your payloads. Here's an example of what a jsonPayload would look like:

{
     insertId:  "1m9mtk4g3mwilhp"
     jsonPayload: {
      [handler]:  "/"
      [method]:  "GET"
      [message]: "200 OK" 
     }
     labels: {
      compute.googleapis.com/resource_name:  "add-structured-log-resource"
     }
     logName:  "projects/my-sample-project-12345/logs/structured-log"
     receiveTimestamp:  "2018-03-21T01:53:41.118200931Z"
     resource: {
      labels: {
       instance_id:  "5351724540900470204"
       project_id:  "my-sample-project-12345"
       zone:  "us-central1-c"
      }
      type:  "gce_instance"
     }
     timestamp:  "2018-03-21T01:53:39.071920609Z"
    }

You can set your own customizable jsonPayload with the parameters and values that you would like to obtain and then write this information to Stackdriver Logs Viewer.

Setting Debug mode to True

When setting debug=True, you will be able see your app in debugging mode. You will be able to see the HTTP requests, as they will appear on your console for debugging purposes, which you could then write these requests to Stackdriver Logs Viewer. An example of a Hello world Flask app running in Debug mode.

from flask import Flask
app = Flask(__name__)

@app.route("/")
def hello():
    return "Hello World!"

if __name__ == "__main__":
    app.run(port='5000', debug=True)

Which you could add a Flask logging handler as follows:

import logging
from logging.handlers import RotatingFileHandler

from flask import Flask

app = Flask(__name__)

@app.route('/')
def foo():
    app.logger.warning('A warning occurred (%d apples)', 42)
    app.logger.error('An error occurred')
    app.logger.info('Info')
    return "foo"

if __name__ == '__main__':
    handler = RotatingFileHandler('foo.log', maxBytes=10000, backupCount=1)
    handler.setLevel(logging.INFO)
    app.logger.addHandler(handler)
    app.run()

As you can see, there are ways to achieve this, by following the proper log configuration; although, the Stackdriver Logs Viewer UI will not look the same for Kubernetes logs as in App Engine Stackdriver Logs Viewer.

Additionally, you could also take a look into Combining correlated log lines in Google Stackdriver since it will give you a better idea of how to batch your logs by categories or groups in case you need to do so.