jslog4kube (python/JSON logging for kubernetes pod/containers)

Why?

• provide a JSON-to-stdout setup for python
• provide the same JSON-to-stdout setup for gunicorn
• because creating complex log collector configs to handle whatever that other person thought was a good-idea-at-the-time is for the birds.

We want to make it easier for our clients and ourselves to start new projects that emit good logging.

making it go

Two environment variables configure this module:

• KUBE_META: specifies the mount-point for the Kubernetes downward-API volumes bits (default: /etc/meta)
• KUBE_META_ENV_PREFIX: the textual prefix for any environment variables targetted for inclusion in this pod’s log records (default: X)

---

---

These bits have been verified to be functional under python 3.9+

---

from logging.config import dictConfig
from jslog4kube import LOGGING

dictConfig(LOGGING)

From Django

project settings.py

from jslog4kube import LOGGING

gunicorn

gunicorn.conf

access_log_format = 'remote!%({X-Forwarded-For}i)s|method!%(m)s|url-path!%(U)s|query!%(q)s|username!%(u)s|protocol!%(H)s|status!%(s)s|response-length!%(b)s|referrer!%(f)s|user-agent!%(a)s|request-time!%(L)s'
accesslog = '-'
logger_class = 'jslog4kube.GunicornLogger'

gunicorn CLI

gunicorn -c /path/to/gunicorn.conf [rest of your options here]

This will produce the following kind of output:

{
  "asctime": "2017-07-12 16:07:34,624",
  "message": "Booting worker with pid: 6801",
  "name": "gunicorn.error",
  "created": 1499893654.6243172,
  "filename": "glogging.py",
  "module": "glogging",
  "funcName": "info",
  "lineno": 247,
  "msecs": 624.3171691894531,
  "pathname": "/home/gladiatr/.virtualenvs/json-logs-for-kube/lib/python3.6/site-packages/gunicorn/glogging.py",
  "process": 6801,
  "processName": "MainProcess",
  "relativeCreated": 70.62673568725586,
  "thread": 140275859264576,
  "threadName": "MainThread",
  "levelname": "INFO",
  "x_node_name": "ip-10-70-59-190.eu-central-1.compute.internal",
  "x_sa_name": "default",
  "x_pod_ip": "100.96.1.11",
  "build": "5000",
  "builder": "Stephen Spencer",
  "image": "gladiatr72/kube-demo",
  "version": "1.0.2",
  "app": "kube-demo",
  "env": "dev",
  "pod-template-hash": "2802633501",
  "something": "else"
}
{
  "asctime": "2017-07-12 21:08:16,354",
  "message": "in view: Chameleon",
  "name": "efk.views",
  "created": 1499893696.3544216,
  "filename": "views.py",
  "module": "views",
  "funcName": "Chameleon",
  "lineno": 12,
  "msecs": 354.42161560058594,
  "pathname": "/home/gladiatr/git/json-logs-for-kube/demo/efk/views.py",
  "process": 6800,
  "processName": "MainProcess",
  "relativeCreated": 41800.73118209839,
  "thread": 140275726399232,
  "threadName": "<concurrent.futures.thread.ThreadPoolExecutor object at 0x7f947f4b0828>_0",
  "levelname": "INFO",
  "x_node_name": "ip-10-70-59-190.eu-central-1.compute.internal",
  "x_sa_name": "default",
  "x_pod_ip": "100.96.1.11",
  "build": "5000",
  "builder": "Stephen Spencer",
  "image": "gladiatr72/kube-demo",
  "version": "1.0.2",
  "app": "kube-demo",
  "env": "dev",
  "pod-template-hash": "2802633501",
  "something": "else",
  "additional data": "whee"
}
{
  "asctime": "2017-07-12 21:08:16,369",
  "message": "(access record)",
  "name": "gunicorn.access",
  "created": 1499893696.3695881,
  "filename": "glogging.py",
  "module": "glogging",
  "funcName": "access",
  "lineno": 327,
  "msecs": 369.58813667297363,
  "pathname": "/home/gladiatr/.virtualenvs/json-logs-for-kube/lib/python3.6/site-packages/gunicorn/glogging.py",
  "process": 6800,
  "processName": "MainProcess",
  "relativeCreated": 41815.89770317078,
  "thread": 140275726399232,
  "threadName": "<concurrent.futures.thread.ThreadPoolExecutor object at 0x7f947f4b0828>_0",
  "levelname": "INFO",
  "x_node_name": "ip-10-70-59-190.eu-central-1.compute.internal",
  "x_sa_name": "default",
  "x_pod_ip": "100.96.1.11",
  "build": "5000",
  "builder": "Stephen Spencer",
  "image": "gladiatr72/kube-demo",
  "version": "1.0.2",
  "app": "kube-demo",
  "env": "dev",
  "pod-template-hash": "2802633501",
  "something": "else",
  "access": {
    "remote": "10.0.1.195",
    "method": "GET",
    "url-path": "/",
    "query": "",
    "username": "-",
    "protocol": "HTTP/1.0",
    "status": "200",
    "response-length": "140",
    "referrer": "-",
    "user-agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/59.0.3071.115 Safari/537.36",
    "request-time": "0.019269"
  }
}

Example Kubernetes deployment:

apiVersion: extensions/v1beta1
kind: Deployment
metadata:         <<-- This is not the metadata you are looking for
  name: kube-demo
  labels:
    project: kube-demo
    environment: dev
spec:
  replicas: 1
  selector:
    matchLabels:
      app: kube-demo
      env: dev
  template:
    metadata:
      labels:
        app: kube-demo
        env: dev
        something: else
      annotations:
        build: "5000"
        builder: "Stephen Spencer"
        image: "gladiatr72/kube-demo"
        version: "1.0.2"

Currently only metadata.(labels|annotations) are supported for exposure via volume.

(Reasons, right?)

    spec:
      volumes:
          name: podinfo
          downwardAPI:
            items:
              - path: labels
                fieldRef:
                  fieldPath: metadata.labels
              - path: annotations
                fieldRef:
                  fieldPath: metadata.annotations
      containers:
        - name: kube-demo
          image: gladiatr72/kube-demo:1.0.2
          volumeMounts:
            -
              name: run
              mountPath: /run
            -
              name: podinfo
              readOnly: true
              mountPath: /etc/meta  <<-- KUBE_META must equal this

environment variable prefixes

(or: how to avoid looking like a complete idiot when you spam your data-store password into your logging system)

You can use whatever letter or sequence for the prefix as long as it gets matched with the value of KUBE_META_ENV_PREFIX.

          env:
            - name: MEMCACHE_HOST
              value: unix:/run/memcache.sock
            - name: DJANGO_SETTINGS_MODULE
              value: "revsys.settings.dev"
            - name: DJANGO_FQDN
              value: kube-demo.dev.revsys.com
            - name: *X_NODE_NAME
              valueFrom:
                fieldRef:
                 fieldPath: spec.nodeName
            - name: *X_POD_IP
              valueFrom:
                fieldRef:
                  fieldPath: status.podIP
            - name: *X_SA_NAME
              valueFrom:
                fieldRef:
                  fieldPath: spec.serviceAccountName
            - name: REDIS_PASSWORD  (oh, nos!)
              valueFrom:
                secretKeyRef:
                  name: redis
                  key: pass
          ports:
            - containerPort: 8000

    * unmagical prefix set in KUBE_META_ENV_PREFIX

The logging configuration

It’s just a standard python dictionary. The most obvious thing to change is the handler definition.

from jslog4kube import LOGGING

LOGGING_HANDLERS = {
    'mypackage': {
        'handlers': ['json-stdout'],
        'formatters': ['json'],
        'propagate’: False,
        'level’: 'ERROR',
    }
}

LOGGING['handlers'].update(LOGGING_HANDLERS)

Setup your python/django apps to log correctly

The LOGGING dict this provides sets up the "general" things to log, but if you want to include your own Python libraries or Django apps you need to specify them. To specify a Django app named 'foo', you would simply adjust the LOGGING dict like this:

LOGGERS = {
    'foo': {
        'handlers': ['json-stdout'],
        'formatters': ['json'],
        'propagate': True,
        'level': 'INFO',
    }
}

LOGGING['loggers'].update(LOGGERS)

dictConfig(LOGGING)

Or if you want to log EVERYTHING at an DEBUG level you can set a blank (aka default) logger:

LOGGERS = {
    '': {
        'handlers': ['json-stdout'],
        'formatters': ['json'],
        'propagate': True,
        'level': 'DEBUG',
    }
}

LOGGING['loggers'].update(LOGGERS)

dictConfig(LOGGING)

Usage

This is normal Python logging so you can do something simple like our info call below or more complex like the debug call and add additional data to the log information:

import logging

logger = logging.getLogger(__name__)

logger.info("Simple log message")

foo = 12
bar = 'something else'
logger.debug("More complicated message", extra={
  "foo": foo,
  "bar": bar,
})

Need help?

REVSYS can help with your Python, Django, and infrastructure projects. If you have a question about this project, please open a GitHub issue. If you love us and want to keep track of our goings-on, here's where you can find us online: