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Logging from Python Flask application deployed on Cloud Foundry

Hi All,

I am writing this blog to describe output logs from Flask based applications on SAP cloud foundry.

Logging is very important for efficient development.  With sap_cf_logging library, it is easier to output and see logs.

Please see my GitHub repository “YoheiFukuhara/cloudfoundry-python-logging” for further detail.

If you don’t know how to deploy application to Cloud Foundry, see another article “Create simple Flask REST API using Cloud Foundry”.

 

Application

Python runtime(runtime.txt)

Since sap_cf_logging libraries supports python 2.7 and 3.5, I used python 3.5(not 3.6).

python-3.5.5

Used libraries(requirements.txt)

I only used Flask and sap_cf_logging.

Flask
sap_cf_logging

Flask application(sample-logging.py)

The application code is like this.

from flask import Flask, request
from sap.cf_logging import flask_logging
import os, logging

app = Flask(__name__)

#Iitialize logging
flask_logging.init(app, logging.INFO)

cf_port = os.getenv('PORT')

# Only get method by default
@app.route('/')
def hello():
    logger = logging.getLogger('my.logger')
    logger.info(request)
    print(request)
    return 'Hello World'

if __name__ == '__main__':
    if cf_port is None:
        app.run(host='0.0.0.0', port=5000, debug=True)
    else:
        app.run(host='0.0.0.0', port=int(cf_port), debug=True)

Deploy and Monitor Log

Deployment

There is nothing special about deployment.  Just push the application.

cf push <application name>

Monitor logs

See logs using cf CLI.

cf logs <application name>

When you want to see log history, use option “–recent”.

cf logs <application name> --recent

This is the log, after accessing the application via browser.

You can see http request information as JSON format in the red frame.  There are many helpful information as timestamp, line no and so on.

{
	"msg": "<Request 'http://sample-logging-proud-impala.cfapps.eu10.hana.ondemand.com/' [GET]>",
	"line_no": 16,
	"layer": "python",
	"written_ts": 1544603923048154000,
	"correlation_id": "74f6ee3d-433d-4797-467d-cae1f053812b",
	"component_name": "sample-logging",
	"space_name": "dev",
	"logger": "my.logger",
	"container_id": "10.0.137.233",
	"thread": "Thread-12",
	"written_at": "2018-12-12T08:38:43.048Z",
	"level": "INFO",
	"component_instance": "0",
	"type": "log",
	"space_id": "2741076c-c551-4b62-8ebc-c1328bbc08d7",
	"component_id": "1df97d1e-6386-48b7-9035-3bab082edffc",
	"component_type": "application"
}

Python “print” command can also leave log.  But it only leaves “<Request ‘http://sample-logging-proud-impala.cfapps.eu10.hana.ondemand.com/’ [GET]>” here, since “request” is object type variable.

Lastly

WIth sap_cf_logging library you will get much benefit while development.  Have fun!

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