Ask HN: How do you triage issues from log dumps?

Given a dump of several logs files spanning across different components of your server side stack (like proxy, application server) what is the fastest technique/tool to determine what caused an error?

I have a bunch of services running on AWS EC2 instances (with nginx and docker) managed with Elastic Beanstalk. Whenever someone reports an issue, we need to take a look at the logs for finding errors.