Django/Daphne middleware and log filter to attach a unique ID to every log message generated as part of a request using context vars.
Author: Jamie Matthews, @j4mie
DEBUG [33031a43fc244539895fef70c433337e] myproject.apps.myapp.views: Doing something in a view
DEBUG [33031a43fc244539895fef70c433337e] myproject.apps.myapp.forms: The form validated successfully!
DEBUG [33031a43fc244539895fef70c433337e] myproject.apps.myapp.models: Doing some model magic
DEBUG [33031a43fc244539895fef70c433337e] myproject.apps.myapp.views: Redirecting to form success page
So you can grep (or otherwise search) a set of logs for a high-traffic application to isolate all messages associated with a single request.
The request ID is stored in a thread local. Use of thread locals is not generally considered best practice for Django applications, but seems to be the only viable approach in this case. Pull requests with better ideas are welcome.
In some cases, components further up the HTTP stack such as load balancers or proxies may generate request IDs. For example, Heroku's http-request-id feature adds a header to the request called X_REQUEST_ID. If such a header is present (and configured in your settings, see below), this ID will be used (instead of generating one). You can configure your settings to use a generated ID or return a default request_id when you expect the ID in the request header but it is not available.
The ID also gets added to the HttpRequest object that is handed to your views, in case you need to use it in your application.
If you need to pass on the ID to other services in a multi-tier architecture, the log_request_id.session module contains a wrapper for requests.Session which will include the ID in outgoing requests, using the same header as configured in your settings.
First, install the package: pip install django-log-request-id
Add the middleware to your MIDDLEWARE_CLASSES setting. It should be at the very top.
MIDDLEWARE_CLASSES = (
'log_request_id.middleware.RequestIDMiddleware',
# ... other middleware goes here
)Add the log_request_id.filters.RequestIDFilter to your LOGGING setting. You'll also need to update your formatters to include a format with the new request_id variable, add a handler to output the messages (eg to the console), and finally attach the handler to your application's logger.
If none of the above made sense, study Django's logging documentation.
An example LOGGING setting is below:
LOGGING = {
'version': 1,
'disable_existing_loggers': False,
'filters': {
'request_id': {
'()': 'log_request_id.filters.RequestIDFilter'
}
},
'formatters': {
'standard': {
'format': '%(levelname)-8s [%(asctime)s] [%(request_id)s] %(name)s: %(message)s'
},
},
'handlers': {
'console': {
'level': 'DEBUG',
'class': 'logging.StreamHandler',
'filters': ['request_id'],
'formatter': 'standard',
},
},
'loggers': {
'myapp': {
'handlers': ['console'],
'level': 'DEBUG',
'propagate': False,
},
}
}You can then output log messages as usual:
import logging
logger = logging.getLogger(__name__)
logger.debug("A wild log message appears!")If you wish to use an ID provided in a request header, add the following setting:
LOG_REQUEST_ID_HEADER = "HTTP_X_REQUEST_ID"Setting this value as above will enable requests having the header X-Request-Id to be logged with the header value supplied.
Note that this value must conform to the format for Django META keys, otherwise it will be ignored.
If you wish to fall back to a generated ID when you have the LOG_REQUEST_ID_HEADER set but it was not provided in the request, add the following setting:
GENERATE_REQUEST_ID_IF_NOT_IN_HEADER = TrueIf you wish to include the request id in the response headers, add the following setting, where RESPONSE_HEADER_NAME is the name of the custom header you are going to use:
REQUEST_ID_RESPONSE_HEADER = "RESPONSE_HEADER_NAME"If you wish to change the default request_id in the log output, the the following settings, where none (default) is the value you want to be the default value in case it's missing.
NO_REQUEST_ID = "none"The RequestIDMiddleware also has the ability to log all requests received by the application, including some useful information such as the user ID (if present). To enable this feature, add LOG_REQUESTS = True to your settings. The messages are sent to the log_request_id.middleware logger at INFO level.
If you would like to log another user attribute instead of user ID, this can be specified with the LOG_USER_ATTRIBUTE setting. Eg. to log the username, use: LOG_USER_ATTRIBUTE = "username"
from log_request_id.session import Session
session = Session()
session.get('http://myservice.myapp.com/')You can customise the header used in the outgoing request with the OUTGOING_REQUEST_ID_HEADER setting.
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