This ensures we close all previously opened queriers if on of the block
querier fails to open.
Also swap in new blocks before closing old ones to avoid the situation
in general. Make read locking of blocks more conservative to avoid
unnecessary retries by clients, e.g. when blocks are getting closed
before we can successfully instantiate querier against them.
The postings list index may point to series that no longer
exist during garbage collection. This clarifies that this is valid
behavior.
It would be possible, though more complex, to always keep them in sync.
However, series existance means nothing in itself as the queried time
range defines whether there's actual data. Thus our definition is sane
overall as long as drift is kept small.
This commit introduces error returns in various places and is explicit
about closing persisted blocks.
{Index,Chunk,Tombstone}Readers are more consistent about their Close()
method. Whenever a reader is retrieved, the corresponding close method
must eventually be called. We use this to track pending readers against
persisted blocks.
Querier's against the DB no longer hold a read lock for their entire
lifecycle. This avoids long running queriers to starve new ones when we
have to acquire a write lock when reloading blocks.
This change fixes the variable names holding the tsdb_head_max_time and
tsdb_head_min_time metrics. It is a cosmetic change to improve the
code readability as the metric values are taken from the correct
variables.
This allows to insert IDs to postings out of order until
a trigger function is called. This avoids the insertion sort we usually
do which can be very costly since WAL entries are more out of order than
regular adds.
This change loads the full symbol table when we open a persisted block
and allocates a string for each. This ensures that strings retrieved
through the index can be used after the block was closed.
Before we backed the strings by the mmap'd byte regions which would
segfault in this case.
Also remove an inconsistency in the disk format and move both offset
tables to the end (breaking change).
