An extra sync.Pool was added during a refactor which caused some 64 bit,
atomically accessed variables to no longer be 64 bit aligned. By moving
all atomically accessed variables to the beginning of the struct they
are guaranteed to be 64 bit aligned.
Signed-off-by: Chris Marchbanks <csmarchbanks@gmail.com>
This PR gives the readonly DB the ability to create blocks from the WAL.
In order to implement this, we modify DBReadOnly.Blocks() to return an
empty slice and no error if no blocks are found.
xref: https://github.com/prometheus/tsdb/issues/346#issuecomment-520786524
Signed-off-by: Lucas Servén Marín <lserven@gmail.com>
