Improve log/tag search

[vprithvi]

Currently, log searches are using key:value pairs, with the following characteristics:

• API
  • One needs to know the keys logs are emitted under
  • Multivalue log search can be problematic for services that emit a lot of trace data because of the Cassandra limit problem ([storage] limitations of Cassandra search on LIMIT and complex queries #166)
  • Logs may only be searched for a particular service. There is no way of combining logs from multiple services.
  • Fuzzy matching of logs is limited to wildcard search per log key
  • No notion of what amount of data was searched, and what amount was matched.
• UI
  • On search hits, the entire trace is retrieved, and it's often unclear on which log was matched, or where the match resides on the trace.
  • No easy way of identifying how to search logs
  • No easy way of narrowing time windows for search

As logs are stored as tags, all of the above apply to tags as well.

[Dieterbe]

because of the Cassandra limit problem

what is this?

related: #372