A real whisper-to-InfluxDB program.

The whisper-to-influxdb migration script I posted earlier is pretty bad. A shell script, without concurrency, and an undiagnosed performance issue. I hinted that one could write a Go program using the unofficial whisper-go bindings and the influxdb Go client library. That's what I did now, it's at github.com/vimeo/whisper-to-influxdb. It uses configurable amounts of workers for both whisper fetches and InfluxDB commits, but it's still a bit naive in the sense that it commits to InfluxDB one serie at a time, irrespective of how many records are in it. My series, and hence my commits have at most 60k records, and presumably InfluxDB could handle a lot more per commit, so we might leverage better batching later. Either way, this way I can consistently commit about 100k series every 2.5 hours (or 10/s), where each serie has a few thousand points on average, with peaks up to 60k points. I usually play with 1 to 30 InfluxDB workers. Even though I've hit a few InfluxDB issues, this tool has enabled me to fill in gaps after outages and to do a restore from whisper after a complete database wipe.