If all samples in consecutive chunks have the same timestamp, the way
we used to load chunks will fail. With this change, the persist
watermark is used to load the right amount of chunkDescs from disk.
This bug is a possible reason for the rare storage corruption we have
observed.
Fixes https://github.com/prometheus/prometheus/issues/481
While doing so, clean up and fix a few other things:
- Fix `go vet` warnings (@fabxc to blame ;).
- Fix a racey problem with unarchiving: Whenever we unarchive a
series, we essentially want to do something with it. However, until
we have done something with it, it appears like a series that is
ready to be archived or even purged. So e.g. it would be ignored
during checkpointing. With this fix, we always load the chunkDescs
upon unarchiving. This is wasteful if we only want to add a new
sample to an archived time series, but the (presumably more common)
case where we access an archived time series in a query doesn't
become more expensive.
- The change above streamlined the getOrCreateSeries ond
newMemorySeries flow. Also, the modTime is now always set correctly.
- Fix the leveldb-backed implementation of KeyValueStore.Delete. It
had the wrong behavior of still returning true, nil if a
non-existing key has been passed in.
A number of mostly minor things:
- Rename chunk type -> chunk encoding.
- After all, do not carry around the chunk encoding to all parts of
the system, but just have one place where the encoding for new
chunks is set based on the flag. The new approach has caveats as
well, but the polution of so many method signatures is worse.
- Use the default chunk encoding for new chunks of existing
series. (Previously, only new _series_ would get chunks with the
default encoding.)
- Use an enum for chunk encoding. (But keep the version number for the
flag, for reasons discussed previously.)
- Add encoding() to the chunk interface (so that a chunk knows its own
encoding - no need to have that in a different top-level function).
- Got rid of newFollowUpChunk (which would keep the existing encoding
for all chunks of a time series). Now only use newChunk(), which
will create a chunk encoding according to the flag.
- Simplified transcodeAndAdd.
- Reordered methods of deltaEncodedChunk and doubleDeltaEncoded chunk
to match the order in the chunk interface.
- Only transcode if the chunk is not yet half full. If more than half
full, add a new chunk instead.
In that commit, the 'maintainSeries' call was accidentally removed.
This commit refactors things a bit so that there is now a clean
'maintainMemorySeries' and a 'maintainArchivedSeries' call.
Straighten the nomenclature a bit (consistently use 'drop' for
chunks and 'purge' for series/metrics).
Remove the annoying 'Completed maintenance sweep through archived
fingerprints' message if there were no archived fingerprints to do
maintenance on.
- Parallelize AppendSamples as much as possible without breaking the
contract about temporal order.
- Allocate more fingerprint locker slots.
- Do not run early checkpoints if we are behind on chunk persistence.
- Increase fpMinWaitDuration to give the disk more time for more
important things.
Also, switch math.MaxInt64 and math.MinInt64 to the new constants.
- Move CONTRIBUTORS.md to the more common AUTHORS.
- Added the required NOTICE file.
- Changed "Prometheus Team" to "The Prometheus Authors".
- Reverted the erroneous changes to the Apache License.
Usually, if you unarchive a series, it is to add something to it,
which will create a new head chunk. However, if a series in
unarchived, and before anything is added to it, it is handled by the
maintenance loop, it will be archived again. In that case, we have to
load the chunkDescs to know the lastTime of the series to be
archived. Usually, this case will happen only rarely (as a race, has
never happened so far, possibly because the locking around unarchiving
and the subsequent sample append is smart enough). However, during
crash recovery, we sometimes treat series as "freshly unarchived"
without directly appending a sample. We might add more cases of that
type later, so better deal with archiving properly and load chunkDescs
if required.
- Documented checkpoint file format.
- High-level description of series sanitation.
- Replace fp.LoadFromString panic with an error.
(Change in client_golang already submitted.)
- Introduced checks for series file size where appropriate.
- Removed two Law of Demeter violations.
Change-Id: I555d97a2c8f4769820c2fc8bf5d6f4e160222abc
- Delete unneeded file view_adapter.go.
- Assessed that we still need the fingerprints in nodes
(to create iterators).
- Turned numMemChunkDescs into a metric.
Change-Id: I29be963c795a075ec00c095f76bf26405535609d
Fix the behavior if preload for non-existent series is requested.
Instead of returning an error (which triggers a panic further up),
simply count those incidents. They can happen regularly, we just want
to know if they happen too frequently because that would mean the
indexing is behind or broken.
Change-Id: I4b2d1b93c4146eeea897d188063cb9574a270f8b
The root cause was that after chunkDesc eviction, the offset between
memory representation of chunk layout (via chunkDescs in memory) was
shiftet against chunks as layed out on disk. Keeping the offset up to
date is by no means trivial, so this commit is pretty involved.
Also, found a race that for some reason didn't bite us so far:
Persisting chunks was completel unlocked, so if chunks were purged on
disk at the same time, disaster would strike. However, locking the
persisting of chunk revealed interesting dead locks. Basically, never
queue under the fp lock.
Change-Id: I1ea9e4e71024cabbc1f9601b28e74db0c5c55db8
Add gauge for chunks and chunkdescs in memory (backed by a global
variable to be used later not only for instrumentation but also for
memory management).
Refactored instrumentation code once more (instrumentation.go is back :).
Change-Id: Ife39947e22a48cac4982db7369c231947f446e17
- Staleness delta is no a proper function parameter and not replicated
from package ast.
- Named type 'chunks' replaced by explicit '[]chunk' to avoid confusion.
- For the same reason, replaced 'chunkDescs' by '[]*chunkDescs'.
- Verified that math.Modf is not a speed enhancement over conversion
(actually 5x slower).
- Renamed firstTimeField, lastTimeField into chunkFirstTime and
chunkLastTime.
- Verified unpin() is sufficiently goroutine-safe.
- Decided not to update archivedFingerprintToTimeRange upon series
truncation and added a rationale why.
Change-Id: I863b8d785e5ad9f71eb63e229845eacf1bed8534
- Head chunk persisting only happens in evictOlderThan, so do it
there. (With the previous code, it would never happen.)
- Raw accesses to chunkDesc.chunk are now done via isEvicted (with
locking).
Change-Id: I48b07b56dfea4899b50df159b4ea566954396fcd
Most important, the heads file will now persist all the chunk descs,
too. Implicitly, it will serve as the persisted form of the
fp-to-series map.
Change-Id: Ic867e78f2714d54c3b5733939cc5aef43f7bd08d
beorn7