[SkyWalking] Log outlier detection

Currently Apache SkyWalking can collect logs from various sources like user agents and Envoy access logs, it also provides a log analysis language to analyze the logs and produce some metrics, with those metrics, users can configure rules to trigger alerts and react to those abnormal/exceptional logs.

But in reality, production environment exceptional logs are not known in advance and users can't enumerate all possible exceptional logs.

This task aims to add an algorithm that can identify outlier log(s) from the massive logs, and draw the users attention to see whether there is error in the system.

The algorithm should be able to learn from bot the history logs and streaming logs, and adjust itself to increase the accuracy.