The FieldIterator is used to scan over the fields of a point, providing
information, and delaying parsing/decoding the value until it is needed.
This change uses this new type to avoid the allocation of a map for the
fields which is then thrown away as soon as the points get converted
into columns within the datastore.
This allows encoders to be re-used and maintained in a pool to
avoid allocating new ones on every compactions and write of an encoded
block. The pool used is not a sync.Pool to ensure that the encoders
will not be garbage collected.
This adds a new pool type that allows byte slices
to be re-used across clients. A sync.Pool can't be used in some
cases because the the slices not in use end up getting garbage
collected due to frequent GCs.
A slower disk can can cause excessive allocations to occur when
writing to the WAL because the slower encoding and compression occurs
before taking the write lock. The encoding/compression grabs a large
byte slice from a pool and ultimately waits until it can acquire the
write lock.
This adds a throttle to limit how many inflight WAL writes can be queued
up to prevent OOMing the processess with slower disks and heavy writes.
Joe LeGasse
Jason Wilder
aviau
Ben Johnson
Jonathan A. Sternberg
Philip O'Toole
Steffen Windoffer
David Howden
Cory LaNou