python-logstash-async

Python logging handler for asynchronous event processing and transport to Logstash. http://logstash.net/

About

This Python logging handler is a fork of https://github.com/eht16/python-logstash-async

It has the following features:

• Asynchronous transport of log events
• Transport of events via TCP and UDP
• TCP transport optionally SSL-encrypted
• Special formatter ready to be used in Django projects

Compared to https://github.com/eht16/python-logstash-async, this fork does not try to preserve log statements if no connection can be made to logstash.

Asynchronous processing

Unlike the original python-logstash, this handler will try to handle log events as fast as possible so that the sending program code can continue with its primary job. In other words, for web applications or web services it is important to not slow down request times due to logging delays, e.g. waiting for network timeouts to the Logstash server or similar.

So this handler will accept log events and pass them for further processing to a separate worker thread which will try to send the events to the configured Logstash server asynchronously.

The sending intervals and timeouts can be configured in the logstash_async.constants module by the corresponding module-level constants, see below for details.

Installation

Using pip:

pip install git+https://github.com/koendeschacht/python-logstash-async.git

Usage

AsynchronousLogstashHandler is a custom logging handler which sends Logstash messages using UDP and TCP. For example:

import logging
import sys
from logstash_async.handler import AsynchronousLogstashHandler

host = 'localhost'
port = 5959

test_logger = logging.getLogger('python-logstash-logger')
test_logger.setLevel(logging.INFO)
test_logger.addHandler(AsynchronousLogstashHandler(
    host, port)))
# test_logger.addHandler(AsynchronousLogstashHandler(host, port))

test_logger.error('python-logstash-async: test logstash error message.')
test_logger.info('python-logstash-async: test logstash info message.')
test_logger.warning('python-logstash-async: test logstash warning message.')

# add extra field to logstash message
extra = {
    'test_string': 'python version: ' + repr(sys.version_info),
    'test_boolean': True,
    'test_dict': {'a': 1, 'b': 'c'},
    'test_float': 1.23,
    'test_integer': 123,
    'test_list': [1, 2, '3'],
}
test_logger.info('python-logstash: test extra fields', extra=extra)

When using the extra field make sure you don't use reserved names. From Python documentation:

"The keys in the dictionary passed in extra should not clash
with the keys used by the logging system.
(See the `Formatter <https://docs.python.org/2/library/logging.html#logging.Formatter>`_ documentation
for more information on which keys are used by the logging system.)"

You can also specify an additional extra dictionary in the logging configuration with static values like the application name, environment, etc. These values will be merged with any extra dictionary items passed in the logging call into the configured extra prefix.

Usage with Django

Modify your settings.py to integrate python-logstash-async with Django's logging:

LOGGING = {
  ...
  'formatters': {
      ...
      'logstash': {
          '()': 'logstash_async.formatter.DjangoLogstashFormatter',
          'message_type': 'python-logstash',
          'fqdn': False, # Fully qualified domain name. Default value: false.
          'extra_prefix': 'dev', #
          'extra': {
              'application': PROJECT_APP,
              'project_path': PROJECT_APP_PATH,
              'environment': 'production'
          }
      },
  },
  'handlers': {
      ...
      'logstash': {
          'level': 'DEBUG',
          'class': 'logstash_async.handler.AsynchronousLogstashHandler',
          'transport': 'logstash_async.transport.TcpTransport',
          'host': 'logstash.host.tld',
          'port': 5959,
          'ssl_enable': True,
          'ssl_verify': True,
          'ca_certs': 'etc/ssl/certs/logstash_ca.crt',
          'certfile': '/etc/ssl/certs/logstash.crt',
          'keyfile': '/etc/ssl/private/logstash.key',
      },
  },
  'loggers': {
      'django.request': {
          'handlers': ['logstash'],
          'level': 'DEBUG',
          'propagate': True,
      },
  },
  ...
}

This would result in a Logstash event like the following (note: to some extend dependent of your Logstash configuration):

{
    "@timestamp": "2016-10-23T15:11:16.853Z",
    "@version": "1",
    "extra": {
        "application": "django_example",
        "django_version": "1.10.2",
        "environment": "production",
        "func_name": "get_response",
        "interpreter": "/home/enrico/example/venv/bin/python",
        "interpreter_version": "2.7.12",
        "line": 152,
        "logger_name": "django.request",
        "path": "/home/enrico/example/venv/lib/python2.7/site-packages/django/core/handlers/base.py",
        "process_name": "MainProcess",
        "project_path": "/home/enrico/example/app",
        "req_host": "localhost",
        "req_method": "GET",
        "req_referer": "",
        "req_remote_address": "127.0.0.1",
        "req_uri": "http://localhost/hosts/nonexistent/",
        "req_user": "enrico",
        "req_useragent": "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:40.0) Gecko/20100101 Firefox/40.1",
        "request": "<WSGIRequest: GET '/hosts/nonexistent/'>",
        "status_code": 404,
        "thread_name": "Thread-1"
    },
    "host": "my.host.tld",
    "level": "WARNING",
    "logsource": "endor.l8failed.net",
    "message": "Not Found: /hosts/nonexistent/",
    "pid": 23605,
    "port": 56170,
    "program": "manage.py",
    "type": "python-logstash"
}

Configuration

Options for configuring the log handler

host

The host of the Logstash server (no default)

port

The port of the Logstash server (default 5959)

transport

Callable or path to a compatible transport class (default: 'logstash_async.transport.TcpTransport').

You can specify your own transport class, e.g. to implement a transport via Redis or the Beats protocol. If you support pass a string, it should be a path to a class which can be imported. If you pass anything else, it should be an object of a class with a similar interface as logstash_async.transport.TcpTransport. Especially it should provide a close() and a send() method.

ssl_enable

Should SSL be enabled for the connection? (default: False) Only used for logstash_async.transport.TcpTransport.

ssl_verify

Should the server's SSL certificate be verified? (default: True) Only used for logstash_async.transport.TcpTransport.

keyfile

The path to client side SSL key file (default: None) Only used for logstash_async.transport.TcpTransport.

certfile

The path to client side SSL certificate file (default: None) Only used for logstash_async.transport.TcpTransport.

ca_certs

The path to the file containing recognized CA certificates (default: None) Only used for logstash_async.transport.TcpTransport.

enable

Flag to enable log processing (default is True, disabling might be handy for local testing, etc.)

Options for configuring the log formatter

The following settings are only valid for the provided formatters logstash_async.handler.LogstashFormatter and logstash_async.handler.DjangoLogstashFormatter.

You can use any other formatter by configuring Python's logging system accordingly. Any other formatter's format() method just should return valid JSON suitable to be sent to Logstash (see Example Logstash Configuration below).

Options:

message_type

The type field in the message sent to Logstash (default: 'python-logstash')

tags

Additional tags to include in the Logstash message (default: None)

fqdn

Use the system's FQDN (fully qualified domain name) in the host field of the message sent to Logstash. socket.getfqdn() is used to retrieve the FQDN, otherwise socket.gethostname() is used for the default hostname. (default: False)

extra_prefix

Name of the field in the resulting message sent to Logstash where all additional fields are grouped into. Consider it as some sort of namespace for all non-standard fields in the log event. This field will take any items passed in as extra fields via the extra configuration option (see below) as well as any extra items passed in the logging call.

To disable grouping of the extra items and have them on the top level of the log event message, simply set this option to None or the empty string. (default: 'extra')

extra

Dictionary with static items to be included in the message sent to Logstash. This dictionary will be merged with any other extra items passed in the logging call. (default: None)

Options for the asynchronous processing (in module logstash_async.constants)

SOCKET_TIMEOUT

Timeout in seconds for TCP connections (default: 5.0)

QUEUE_CHECK_INTERVAL

Interval in seconds to check the internal queue for new messages (default: 0.2)

TIMEOUT_SENDING_MESSAGES_AT_TERMINATION

When the program terminates, any remaining log messages are still send to logstash. This constant defines for how many seconds the handler can still send messages before terminating (default: 2.0)

Example Logstash Configuration

Example logstash.conf for unencrypted TCP transport:

input {
    tcp {
        host => "127.0.0.1"
        port => 5959
        mode => server
        codec => json
    }
}

Example logstash.conf for SSL-encrypted TCP transport:

input {
    tcp {
        host => "127.0.0.1"
        port => 5958
        mode => server
        codec => json

        ssl_enable => true
        ssl_verify => true
        ssl_extra_chain_certs => ["/etc/ssl/certs/logstash_ca.crt"]
        ssl_cert => "/etc/ssl/certs/logstash.crt"
        ssl_key => "/etc/ssl/private/logstash.key"
    }
}