This commit adds a write ahead log to the shard. Entries are cached
in memory and periodically flushed back into the index. The WAL and
the cache are both partitioned into buckets so that flushing doesn't
stop the world as long.
Fixes#2869
When adding a new field to an existing measurment, Shard.validateSeriesAndFields
would also encode the fields as a side-effect. In the case of a new field
that needed to be created, the encoding would fail because the field type
had not been created for the measurement yet. The fields are re-encoded
after validateSeriesAndFields returns and after the field encoding have been
setup properly so this additional encoding during
validation isn't necessary.
This allows the new write path to be hooked up if you start the
server with `INFLUXDB_ALPHA1=1`. When set, writes will go though
the coordinator and be stubbed out to write to a single local data
node with one shards. The write will be logged and written to
disk .
The env var is used so that the current write path is not completely
broken which would break many of the tests that depend on writes.
Note that queries are not currently working w/ the this change.
Paul Dix
Ben Johnson
Philip O'Toole
Joseph Crail
Jason Wilder
Todd Persen
David Norton