Develop a ragel-based line protocol parser for use in filtering applications

[adrian-thurston]

At the all hands it was discussed with @GeorgeMac that a ragel-based line protocol parser for use in filtering applications would be welcome, with the goal of speeding up parsing and getting a better filtering throughput.

Some context here:

#16412

[GeorgeMac]

cc @stuartcarnie as using Ragel for this was his idea first :D

[adrian-thurston]

@goller points out one exists already here:

https://github.com/influxdata/telegraf/blob/master/plugins/parsers/influx/machine.go.rl

[danielnelson]

There is currently some work on a streaming interface for this parser in the influxdb-listener-refactor branch. We plan to use this to parse request bodies without loading the full request into memory. One potential issue with the parser I should mention is that it does not do any unicode validation.

[adrian-thurston]

Closing, as this exists already in telegraf.