Most logging systems tell you what happened in your application, whereas eliot also tells you why it happened.
eliot is a Python logging system that outputs causal chains of actions: actions can spawn other actions, and eventually they either succeed or fail. The resulting logs tell you the story of what your software did: what happened, and what caused it.
Eliot works well within a single process, but can also be used across multiple processes to trace causality across a distributed system. Eliot is only used to generate your logs; you will still need tools like Logstash and ElasticSearch to aggregate and store logs if you are using multiple processes.
Eliot supports Python 2.7, 3.4, 3.5, 3.6 and PyPy. It is maintained by Itamar Turner-Trauring, and released under the Apache 2.0 License.