When we've one application we need to monitor the logs in one way or another. Not only the server's logs (500 errors, response times and things like that). Sometimes the user complains about the application. Without logs we cannot do anything. We can save logs within files and let grep and tail do the magic. This's assumable with a single on-premise server, but nowadays with clouds and docker this's a nightmare. We need a central log collector to collect all the logs of the application and use this collector to create alerts, and complex searches of our application logs.
I normally work with AWS. In AWS we've CloudWatch. It's pretty straightforward to connect our application logs to CloudWatch when we're using AWS. When we aren't using AWS we can use the ELK stack. In this exaple we're going to send our Django application logs to a Elasticsearch database. Let's start:
The idea is not to send the logs directly. The idea save the logs to log files. We can use this LOGGING configuration to do that:
LOGGING = {
'version': 1,
'disable_existing_loggers': False,
'formatters': {
"json": {
'()': CustomisedJSONFormatter,
},
},
'handlers': {
'console': {
'class': 'logging.StreamHandler',
},
'app_log_file': {
'level': LOG_LEVEL,
'class': 'logging.handlers.RotatingFileHandler',
'filename': os.path.join(LOG_PATH, 'app.log.json'),
'maxBytes': 1024 * 1024 * 15, # 15MB
'backupCount': 10,
'formatter': 'json',
},
},
'root': {
'handlers': ['console', 'app_log_file'],
'level': LOG_LEVEL,
},
}Here I'm using a custom JSON formatter:
import json_log_formatter
import logging
from django.utils.timezone import now
class CustomisedJSONFormatter(json_log_formatter.JSONFormatter):
def json_record(self, message: str, extra: dict, record: logging.LogRecord):
extra['name'] = record.name
extra['filename'] = record.filename
extra['funcName'] = record.funcName
extra['msecs'] = record.msecs
if record.exc_info:
extra['exc_info'] = self.formatException(record.exc_info)
return {
'message': message,
'timestamp': now(),
'level': record.levelname,
'context': extra
}With this configuration our logs are going to be something like that:
{"message": "Hello from log", "timestamp": "2020-04-26T19:35:59.427098+00:00", "level": "INFO", "app_id": "Logs", "context": {"random": 68, "name": "app.views", "filename": "views.py", "funcName": "index", "msecs": 426.8479347229004}}Now we're going to use logstash as data shipper to send the logs to elastic search. We need to create a pipeline:
input {
file {
path => "/logs/*"
start_position => "beginning"
codec => "json"
}
}
output {
elasticsearch {
index => "app_logs"
hosts => ["elasticsearch:9200"]
}
}
We're going to use Docker to build our stack, so our logstash and our django containers will share the logs volumes.
Now we need to visualize the logs. Kibana is perfect for this task. We can set up a Kibana server connected to the Elasticsearch and visualize the logs:
Also we can monitor our server performance. Prometheus is the de facto standard for doing that. In fact it's very simple to connect our Django application to Prometheus. We only need to add django-prometheus dependency, install the application and set up two middlewares:
INSTALLED_APPS = [
...
'django_prometheus',
...
]
MIDDLEWARE = [
'django_prometheus.middleware.PrometheusBeforeMiddleware', # <-- this one
'app.middleware.RequestLogMiddleware',
'django.middleware.security.SecurityMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.common.CommonMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
'django.middleware.clickjacking.XFrameOptionsMiddleware',
'django_prometheus.middleware.PrometheusAfterMiddleware', # <-- this one
]also we need to set up some application routes
from django.contrib import admin
from django.urls import path, include
urlpatterns = [
path('admin/', admin.site.urls),
path('p/', include('django_prometheus.urls')), # <-- prometheus routes
path('', include('app.urls'))
]The easiest way to visualize the data stored in prometheus is using Grafana. In Grafana we need to create a datasource with Prometheus and build our custom dashboard. We can import pre-built dashboards. For example this one: https://grafana.com/grafana/dashboards/9528
Here the docker-compose file with all the project:
version: '3'
services:
web:
image: web:latest
restart: always
command: /bin/bash ./docker-entrypoint.sh
volumes:
- static_volume:/src/staticfiles
- logs_volume:/src/logs
environment:
DEBUG: 'False'
LOG_LEVEL: DEBUG
nginx:
image: nginx:latest
restart: always
volumes:
- static_volume:/src/staticfiles
ports:
- 80:80
depends_on:
- web
- grafana
prometheus:
image: prometheus:latest
restart: always
build:
context: .docker/prometheus
dockerfile: Dockerfile
grafana:
image: grafana:latest
restart: always
depends_on:
- prometheus
environment:
- GF_SECURITY_ADMIN_USER=${GF_SECURITY_ADMIN_USER}
- GF_SECURITY_ADMIN_PASSWORD=${GF_SECURITY_ADMIN_PASSWORD}
- GF_USERS_DEFAULT_THEME=${GF_USERS_DEFAULT_THEME}
- GF_USERS_ALLOW_SIGN_UP=${GF_USERS_ALLOW_SIGN_UP}
- GF_USERS_ALLOW_ORG_CREATE=${GF_USERS_ALLOW_ORG_CREATE}
- GF_AUTH_ANONYMOUS_ENABLED=${GF_AUTH_ANONYMOUS_ENABLED}
logstash:
image: logstash:latest
restart: always
depends_on:
- elasticsearch
volumes:
- logs_volume:/logs:ro
elasticsearch:
image: docker.elastic.co/elasticsearch/elasticsearch:7.5.2
restart: always
environment:
- discovery.type=single-node
- http.host=0.0.0.0
- xpack.security.enabled=false
- ES_JAVA_OPTS=-Xms750m -Xmx750m
volumes:
- elasticsearch_volume:/usr/share/elasticsearch/data
kibana:
image: kibana:latest
restart: always
ports:
- 5601:5601
depends_on:
- elasticsearch
volumes:
elasticsearch_volume:
static_volume:
logs_volume:
grafana_data:And that's all. Our Django application up and running fully monitored