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Reading and Filtering Eliot Logs
================================
Eliot includes a command-line tool that makes it easier to read JSON-formatted Eliot messages:
.. code-block:: shell-session
$ python examples/stdout.py | eliot-prettyprint
af79ef5c-280c-4b9f-9652-e14deb85d52d@/1
2015-09-25T19:41:37.850208Z
another: 1
value: hello
0572701c-e791-48e8-9dd2-1fb3bf06826f@/1
2015-09-25T19:41:38.050767Z
another: 2
value: goodbye
Run ``eliot-prettyprint --help`` to see the various formatting options; you can for example use a more compact one-message-per-line format.
Additionally, the **highly recommended** third-party `eliot-tree`_ tool renders JSON-formatted Eliot messages into a tree visualizing the tasks' actions.
Filtering logs
--------------
Eliot logs are structured, and by default stored in one JSON object per line.
That means you can filter them in multiple ways:
1. Line-oriented tools like grep.
You can grep for a particular task's UUIDs, or for a particular message type (e.g. tracebacks).
2. JSON-based filtering tools.
`jq`_ allows you to filter a stream of JSON messages.
3. `eliot-tree`_ has some filtering and searching support built-in.
For example, here's how you'd extract a particular field with `jq`_:
.. code-block:: shell-session
$ python examples/stdout.py | jq '.value'
"hello"
"goodbye"
.. _eliot-tree: https://github.com/jonathanj/eliottree
.. _jq: https://stedolan.github.io/jq/
.. _parsing_logs:
Parsing Logs
------------
Eliot also includes a parser for parsing logs into Python objects:
.. code-block:: python
import json
from eliot.parse import Parser
def load_messages(logfile_path):
for line in open(logfile_path):
yield json.loads(line)
def parse(logfile_path):
for task in Parser.parse_stream(load_messages(logfile_path)):
print("Root action type is", task.root().action_type)
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