This change moves tracking of next timestamp and values to simple
slices, as performance measurement showed that Peek() on TagSet cursors
was a huge performance drain. There is much more that can be done here,
but with this in place query performance has been restored to 0.9.1
levels.
This change also uses -1 to indicate that no value is available for a
given timestamp.
With this change remote mapping no longer uses HTTP, as the HTTP ports
exposed by nodes on the cluster are not known cluster wide. The TCP
ports exposed by the cluster service are, so this change uses that
functionality. Each RemoteMapper has its own dedicated connection pool
for each node, and remote mapping TCP connections are in no way coupled
with query TCP connections.
The multiple checks for Mapper and Executor type -- the lack of DRYness
in this code -- meant the same checks would need to be copied. Therefore
this change, as well as fixing the bug, improves the situation a little
bit by *asking* the Mappers what type of Executor is required. This code
is still not ideal.
Fixes#3355.
With this change, the query engine code gathers information about
shards and tagsets by working with individual shards, collating the
information, and returning that to the client. It does not assume that any
particular shard is local, and accesses all shards through abstracted
Mappers, of which there are two types -- a Mapper type for Raw queries
and a second type for Aggregate queries. There are corresponding
Executors for each type of Mapper, but both types of Executors share the
same interface.
David Norton
Philip O'Toole
Ben Johnson
Philip O'Toole