IDs for new series are handed out before the postings are locked. Thus
series are not indexed in order of their IDs, which could result in only
partially sorted postings list.
Iterating over those silently skipped elements as the sort invariant was
violated.

Simplify series create logc in head

Add missing unlock on early return

Expose NewIndexReader() and cleanups

Signed-off-by: NGoutham Veeramachaneni <cs14btech11014@iith.ac.in>

replaced cobra with kingpin for the tsdb cli tool

Fix various races

Fixup allocation regression during compaction

Compress the series chunk details in index.

Signed-off-by: NKrasi Georgiev <krasi.root@gmail.com>

When decoding data from mmaped blocks, we would like to retrieve
a string backed by the mmaped region. As the underlying byte slice
never changes, this is safe.

We were still fsyncing while holding the write lock when we cut a new
segment. Given we cannot do anything but logging errors, we might just
as well complete segments asynchronously.

There's not realistic use case where one would fsync after every WAL
entry, thus make the default of a flush interval of 0 to never fsync
which is a much more likely use case.

Signed-off-by: NGoutham Veeramachaneni <cs14btech11014@iith.ac.in>

This adds various new locks to replace the single big lock on
the head. All parts now must be COW as they may be held by clients
after initial retrieval.
Series by ID and hashes are now held in a stripe lock to reduce
contention and total holding time during GC. This should reduce
starvation of readers.

Signed-off-by: NGoutham Veeramachaneni <cs14btech11014@iith.ac.in>

This changes the structure to a single WAL backed by a single head
block.
Parts of the head block can be compacted. This relieves us from any head
amangement and greatly simplifies any consistency and isolation concerns
by just having a single head.

Don't do blocking disk I/O under mutex blocking scrape and eval

Take the fdatasync() syscall out from under mutex lock to (mostly) avoid scrape and eval from blocking on disk I/O.