* Add basic initial developer docs for TSDB
There's a decent amount of content already out there (blog posts,
conference talks, etc), but:
* when they get stale, they don't tend to get updated
* they still leave me with questions that I'ld like to answer
for developers (like me) who want to use, or work with, TSDB
What I propose is developer docs inside the prometheus
repository. Easy to find and harness the power of the community
to expand it and keep it up to date.
* perfect is the enemy of good. Let's have a base and incrementally improve
* Markdown docs should be broad but not too deep. Source code comments
can complement them, and are the ideal place for implementation details.
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* use example code that works out of the box
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* Apply suggestions from code review
Co-authored-by: Ganesh Vernekar <15064823+codesome@users.noreply.github.com>
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* PR feedback
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* more docs
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* PR feedback
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* Apply suggestions from code review
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
Co-authored-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Apply suggestions from code review
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
Co-authored-by: Ganesh Vernekar <15064823+codesome@users.noreply.github.com>
* feedback
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* Update tsdb/docs/usage.md
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
Co-authored-by: Ganesh Vernekar <15064823+codesome@users.noreply.github.com>
* final tweaks
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* workaround docs versioning issue
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* Move example code to real executable, testable example.
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* cleanup example test and make sure it always reproduces
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* obtain temp dir in a way that works with older Go versions
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* Fix Ganesh's comments
Signed-off-by: Ganesh Vernekar <ganeshvern@gmail.com>
Co-authored-by: Ganesh Vernekar <15064823+codesome@users.noreply.github.com>
Co-authored-by: Bartlomiej Plotka <bwplotka@gmail.com>
Co-authored-by: Ganesh Vernekar <ganeshvern@gmail.com>
* TSDB: demistify seriesRefs and ChunkRefs
The TSDB package contains many types of series and chunk references,
all shrouded in uint types. Often the same uint value may
actually mean one of different types, in non-obvious ways.
This PR aims to clarify the code and help navigating to relevant docs,
usage, etc much quicker.
Concretely:
* Use appropriately named types and document their semantics and
relations.
* Make multiplexing and demuxing of types explicit
(on the boundaries between concrete implementations and generic
interfaces).
* Casting between different types should be free. None of the changes
should have any impact on how the code runs.
TODO: Implement BlockSeriesRef where appropriate (for a future PR)
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* feedback
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* agent: demistify seriesRefs and ChunkRefs
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* Use dedicated Ref type
Throughout the code base, there are reference types masked as
regular integers. Let's use dedicated types. They are
equivalent, but clearer semantically.
This also makes it trivial to find where they are used,
and from uses, find the centralized docs.
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* postpone some work until after possible return
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* clarify
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* rename feedback
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* skip header is up to caller
Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
* Added test to reproduce panic on TSDB head chunks truncated while querying
Signed-off-by: Marco Pracucci <marco@pracucci.com>
* Added test for Querier too
Signed-off-by: Marco Pracucci <marco@pracucci.com>
* Stop the bleed on mmap-ed head chunks panic
Signed-off-by: Marco Pracucci <marco@pracucci.com>
* Lower memory pressure in tests to ensure it doesn't OOM
Signed-off-by: Marco Pracucci <marco@pracucci.com>
* Skip TestQuerier_ShouldNotPanicIfHeadChunkIsTruncatedWhileReadingQueriedChunks
Signed-off-by: Marco Pracucci <marco@pracucci.com>
* Experiment to not trigger runtime.GC() continuously
Signed-off-by: Marco Pracucci <marco@pracucci.com>
* Try to fix test in CI
Signed-off-by: Marco Pracucci <marco@pracucci.com>
* Do not call runtime.GC() at all
Signed-off-by: Marco Pracucci <marco@pracucci.com>
* I have no idea why it's failing in CI, skipping tests
Signed-off-by: Marco Pracucci <marco@pracucci.com>
* Testify: move to require
Moving testify to require to fail tests early in case of errors.
Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>
* More moves
Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>
* MultiError: Refactored MultiError for more concise and safe usage.
* Less lines
* Goland IDE was marking every usage of old MultiError "potential nil" error
* It was easy to forgot using Err() when error was returned, now it's safely assured on compile time.
NOTE: Potentially I would rename package to merrors. (: In different PR.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Addressed review comments.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Addressed comments.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Fix after rebase.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Refactor test assertions
This pull request gets rid of assert.True where possible to use
fine-grained assertions.
Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>
* tsdb: Added ChunkQueryable implementations to db; unified compactor, querier and fanout block iterating.
Chained to https://github.com/prometheus/prometheus/pull/7059
* NewMerge(Chunk)Querier now takies multiple primaries allowing tsdb DB code to use it.
* Added single SeriesEntry / ChunkEntry for all series implementations.
* Unified all vertical, and non vertical for compact and querying to single
merge series / chunk sets by reusing VerticalSeriesMergeFunc for overlapping algorithm (same logic as before)
* Added block (Base/Chunk/)Querier for block querying. We then use populateAndTomb(Base/Chunk/) to iterate over chunks or samples.
* Refactored endpoint tests and querier tests to include subtests.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Addressed comments from Brian and Beorn.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Fixed snapshot test and added chunk iterator support for DBReadOnly.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Fixed race when iterating over Ats first.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Fixed tests.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Fixed populate block tests.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Fixed endpoints test.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Fixed test.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Added test & fixed case of head open chunk.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Fixed DBReadOnly tests and bug producing 1 sample chunks.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Added cases for partial block overlap for multiple full chunks.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Added extra tests for chunk meta after compaction.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Fixed small vertical merge bug and added more tests for that.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* tsdb/chunks: Replace sync/atomic with uber-go/atomic
Signed-off-by: Javier Palomo <javier.palomo.almena@gmail.com>
* tsdb/heaad: Replace sync/atomic with uber-go/atomic
Signed-off-by: Javier Palomo <javier.palomo.almena@gmail.com>
* vendor: Make go.uber.org/atomic a direct dependency
There is no modifications to go.sum and vendor/ because
it was already vendored.
Signed-off-by: Javier Palomo <javier.palomo.almena@gmail.com>
* tsdb: Remove comments referring to the sync/atomic alignment bug
Related: https://golang.org/pkg/sync/atomic/#pkg-note-BUG
Signed-off-by: Javier Palomo <javier.palomo.almena@gmail.com>
* Moves the 64bit atomically accessed field to the top of the struct.
Signed-off-by: Bryan Varner <1652015+bvarner@users.noreply.github.com>
* Moves the 64bit atomically accessed field to the top of the struct.
Signed-off-by: Bryan Varner <1652015+bvarner@users.noreply.github.com>
* Fixing up go fmt formatting issues.
Signed-off-by: Bryan Varner <1652015+bvarner@users.noreply.github.com>
Co-authored-by: Bryan Varner <1652015+bvarner@users.noreply.github.com>
When appending to the head and a chunk is full it is flushed to the disk and m-mapped (memory mapped) to free up memory
Prom startup now happens in these stages
- Iterate the m-maped chunks from disk and keep a map of series reference to its slice of mmapped chunks.
- Iterate the WAL as usual. Whenever we create a new series, look for it's mmapped chunks in the map created before and add it to that series.
If a head chunk is corrupted the currpted one and all chunks after that are deleted and the data after the corruption is recovered from the existing WAL which means that a corruption in m-mapped files results in NO data loss.
[Mmaped chunks format](https://github.com/prometheus/prometheus/blob/master/tsdb/docs/format/head_chunks.md) - main difference is that the chunk for mmaping now also includes series reference because there is no index for mapping series to chunks.
[The block chunks](https://github.com/prometheus/prometheus/blob/master/tsdb/docs/format/chunks.md) are accessed from the index which includes the offsets for the chunks in the chunks file - example - chunks of series ID have offsets 200, 500 etc in the chunk files.
In case of mmaped chunks, the offsets are stored in memory and accessed from that. During WAL replay, these offsets are restored by iterating all m-mapped chunks as stated above by matching the series id present in the chunk header and offset of that chunk in that file.
**Prombench results**
_WAL Replay_
1h Wal reply time
30% less wal reply time - 4m31 vs 3m36
2h Wal reply time
20% less wal reply time - 8m16 vs 7m
_Memory During WAL Replay_
High Churn:
10-15% less RAM - 32gb vs 28gb
20% less RAM after compaction 34gb vs 27gb
No Churn:
20-30% less RAM - 23gb vs 18gb
40% less RAM after compaction 32.5gb vs 20gb
Screenshots are in [this comment](https://github.com/prometheus/prometheus/pull/6679#issuecomment-621678932)
Signed-off-by: Ganesh Vernekar <cs15btech11018@iith.ac.in>
* storage: Added Chunks{Queryable/Querier/SeriesSet/Series/Iteratable. Added generic Merge{SeriesSet/Querier} implementation.
## Rationales:
In many places (e.g. chunk Remote read, Thanos Receive fetching chunk from TSDB), we operate on encoded chunks not samples.
This means that we unnecessary decode/encode, wasting CPU, time and memory.
This PR adds chunk iterator interfaces and makes the merge code to be reused between both seriesSets
I will make the use of it in following PR inside tsdb itself. For now fanout implements it and mergers.
All merges now also allows passing series mergers. This opens doors for custom deduplications other than TSDB vertical ones (e.g. offline one we have in Thanos).
## Changes
* Added Chunk versions of all iterating methods. It all starts in Querier/ChunkQuerier. The plan is that
Storage will implement both chunked and samples.
* Added Seek to chunks.Iterator interface for iterating over chunks.
* NewMergeChunkQuerier was added; Both this and NewMergeQuerier are now using generigMergeQuerier to share the code. Generic code was added.
* Improved tests.
* Added some TODO for further simplifications in next PRs.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Addressed Brian's comments.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Moved s/Labeled/SeriesLabels as per Krasi suggestion.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Addressed Krasi's comments.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Second iteration of Krasi comments.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Another round of comments.
Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>
* Fix tsdb panic when querying corrupted chunks.
check that the chunk segment has enough data to read all chunk pieces.
* refactor, simplify and add tests.
* simpfiy WriteChunks implementation
Signed-off-by: Krasi Georgiev <8903888+krasi-georgiev@users.noreply.github.com>
Dieter Plaetinck