1. The records are stored in redis which is not migratable to another cluster for the testing purposes.
2. Some of the requests fields are not recorded.
3. People should consider using https://github.com/buger/goreplay which is an existing mature and well-tested solution for testing purposes.
Before this PR, CLI functions fatal out when encountering error
instead of returning it. Such behavior makes it hard to reuse
the functions nor writing unit tests. This PR aims to make functions
return errors instead of error out.
