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Date: Wed, 10 Dec 2014 13:15:14 -0500
Subject: Eliot 0.6: Logging for Complex & Distributed Systems
From: Itamar Turner-Trauring <itamar@clusterhq.com>
To: python-announce-list@python.org, twisted-python@twistedmatrix.com
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Eliot is a logging system designed not only for simple applications but for
complex applications as well, including distributed systems. Eliot supports
simple structured messages but can also record a causal chain of actions
happening within and across process boundaries: a logical trace of the
system's operation.

Structured, action-oriented logging is a great help when debugging
problems. For example, here are the combined logs of a request originating
from a client process being sent to a server. Notice how easy it is to
figure out the cause of the problem, even though it's opaque to the client:

process='client' task_uuid='40be6df2' task_level=[1] action_type='main'
    action_status='started'

process='client' task_uuid='40be6df2' task_level=[2, 1]
action_type='http_request'
    action_status='started' x=5 y=0

process='server' task_uuid='40be6df2' task_level=[2, 2, 1]
action_type='eliot:remote_task'
    action_status='started'

process='server' task_uuid='40be6df2' task_level=[2, 2, 2, 1]
action_type='divide'
    action_status='started' x=5 y=0

process='server' task_uuid='40be6df2' task_level=[2, 2, 2, 2]
action_type='divide'
    action_status='failed' exception='exceptions.ZeroDivisionError'
reason='integer division or modulo by zero'

process='server' task_uuid='40be6df2' task_level=[2, 2, 3]
action_type='eliot:remote_task'
    action_status='failed' exception='exceptions.ZeroDivisionError'
reason='integer division or modulo by zero'

process='client' task_uuid='40be6df2' task_level=[2, 3]
action_type='http_request'
   action_status='failed' exception='requests.exception.HTTPError'
reason='500 Server Error: INTERNAL SERVER ERROR'

process='client' task_uuid='40be6df2' task_level=[3] action_type='main'
   action_status='failed' exception='requests.exception.HTTPError'
reason='500 Server Error: INTERNAL SERVER ERROR'

What's New in 0.6.0

Incompatible output format change! In previous versions the ordering of
messages and actions was ambiguous and could not be deduced from
out-of-order logs, and even where it was possible sorting correctly was
difficult. To fix this the action_counter field was removed and now all
messages can be uniquely located within a specific task by the values
in an *improved
task_level field*
<http://eliot.readthedocs.org/en/0.6.0/fields.html#task-fields>.

Features:

   - Eliot tasks can now *span multiple processes and threads*
   <http://eliot.readthedocs.org/en/0.6.0/threads.html#cross-process-tasks>,
   allowing for easy tracing of actions in distributed applications.
   - *eliot.add_global_fields*
   <http://eliot.readthedocs.org/en/0.6.0/output.html#add-global-fields>
   allows adding fields with specific values to all Eliot messages logged by
   your program. This can be used to e.g. distinguish between log messages
   from different processes by including relevant identifying information.

Bug fixes:

   - On Python 3 files that accept unicode (e.g. sys.stdout) should now
   work.


Downloads are available on PyPI <https://pypi.python.org/pypi/eliot>.

Documentation can be found on Read The Docs <https://eliot.readthedocs.org/>
.

Bugs and feature requests should be filed at the project Github page
<https://github.com/ClusterHQ/eliot>.

You can ask for help on IRC at the #eliot channel on irc.freenode.net.