pylogctx 1.0

Using filter

This method allow to pass fields to JSON formatters, log servers, etc. or use the extra fields in format string.

LOGGING = {
    'version': 1,
    'formatters': {
        'extra': {
            'format': '%(levelname)s %(rid)s %(name)s %(message)s',
        },
    },
    'filters': {
        'context_filter': {
            '()': 'pylogctx.AddContextFilter',
            'default': {'rid': None},
        }
    },
    'handlers': {
        'console': {
            'class': 'logging.StreamHandler',
            'filters': ['context_filter'],
        },
    },
    'root': {
        'handlers': ['console'],
        'level': 'DEBUG',
    },
}

Note three things:

• %(rid) in format string is for logging rid (for request_id) from our context;

• pylogctx.AddContextFilter - filter which converts keys from context dict to attributes of LogRecord;

• 'default': {'rid': None} - some of our log events could be without context for example logs emitted on worker start. All these logs will not be recorded due to the lack of ‘rid’ attribute (in our example) on LogRecord instance. To fix this we provide default value for ‘rid’.

Using formatter

If you do not want to bother with custom log format and default context values for a filter - you can use pylogctx.AddContextFormatter.

LOGGING = {
    'version': 1,
    'formatters': {
        'append': {
            '()': 'pylogctx.AddContextFormatter'
            'format': '%(levelname)s %(name)s %(message)s'
        },
    },
    'handlers': {
        'console': {
            'class': 'logging.StreamHandler',
            'formatter': 'append',
        },
    },
    'root': {
        'handlers': ['console'],
        'level': 'DEBUG',
    },
}

As you can see in this case we doesn’t add any context related fields to a log format string. This is because pylogctx.AddContextFormatter will append all context information to every log.

Feeding the context

The context class is just a thread local dict. It is used as local registry to inject shared fields in log records. Here is a full example:

from pylogctx.log import context as log_context


log_context.push(userId=user.pk)
# code, log, etc.
for article in blog.articles:
    with log_context(articleId=article.pk):
        # code, log, ...
# code, log, etc.
log_context.pop('userId')

MIDDLEWARE_CLASSES = [
    'pylogctx.django.ExtractRequestContextMiddleware',
    # rest middlewares...
]

PYLOGCTX_REQUEST_EXTRACTOR = lambda request: {'rid': request.GET.getlist('rid')}