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* Write exemplars to the WAL and send them over remote write. Signed-off-by: Callum Styan <callumstyan@gmail.com> * Update example for exemplars, print data in a more obvious format. Signed-off-by: Callum Styan <callumstyan@gmail.com> * Add metrics for remote write of exemplars. Signed-off-by: Callum Styan <callumstyan@gmail.com> * Fix incorrect slices passed to send in remote write. Signed-off-by: Callum Styan <callumstyan@gmail.com> * We need to unregister the new metrics. Signed-off-by: Callum Styan <callumstyan@gmail.com> * Address review comments Signed-off-by: Callum Styan <callumstyan@gmail.com> * Order of exemplar append vs write exemplar to WAL needs to change. Signed-off-by: Callum Styan <callumstyan@gmail.com> * Several fixes to prevent sending uninitialized or incorrect samples with an exemplar. Fix dropping exemplar for missing series. Add tests for queue_manager sending exemplars Signed-off-by: Martin Disibio <mdisibio@gmail.com> * Store both samples and exemplars in the same timeseries buffer to remove the alloc when building final request, keep sub-slices in separate buffers for re-use Signed-off-by: Martin Disibio <mdisibio@gmail.com> * Condense sample/exemplar delivery tests to parameterized sub-tests Signed-off-by: Martin Disibio <mdisibio@gmail.com> * Rename test methods for clarity now that they also handle exemplars Signed-off-by: Martin Disibio <mdisibio@gmail.com> * Rename counter variable. Fix instances where metrics were not updated correctly Signed-off-by: Martin Disibio <mdisibio@gmail.com> * Add exemplars to LoadWAL benchmark Signed-off-by: Callum Styan <callumstyan@gmail.com> * last exemplars timestamp metric needs to convert value to seconds with ms precision Signed-off-by: Callum Styan <callumstyan@gmail.com> * Process exemplar records in a separate go routine when loading the WAL. Signed-off-by: Callum Styan <callumstyan@gmail.com> * Address review comments related to clarifying comments and variable names. Also refactor sample/exemplar to enqueue prompb types. Signed-off-by: Callum Styan <callumstyan@gmail.com> * Regenerate types proto with comments, update protoc version again. Signed-off-by: Callum Styan <callumstyan@gmail.com> * Put remote write of exemplars behind a feature flag. Signed-off-by: Callum Styan <callumstyan@gmail.com> * Address some of Ganesh's review comments. Signed-off-by: Callum Styan <callumstyan@gmail.com> * Move exemplar remote write feature flag to a config file field. Signed-off-by: Callum Styan <callumstyan@gmail.com> * Address Bartek's review comments. Signed-off-by: Callum Styan <callumstyan@gmail.com> * Don't allocate exemplar buffers in queue_manager if we're not going to send exemplars over remote write. Signed-off-by: Callum Styan <callumstyan@gmail.com> * Add ValidateExemplar function, validate exemplars when appending to head and log them all to WAL before adding them to exemplar storage. Signed-off-by: Callum Styan <callumstyan@gmail.com> * Address more reivew comments from Ganesh. Signed-off-by: Callum Styan <callumstyan@gmail.com> * Add exemplar total label length check. Signed-off-by: Callum Styan <callumstyan@gmail.com> * Address a few last review comments Signed-off-by: Callum Styan <callumstyan@gmail.com> Co-authored-by: Martin Disibio <mdisibio@gmail.com>
9.2 KiB
WAL Disk Format
The write ahead log operates in segments that are numbered and sequential,
e.g. 000000, 000001, 000002, etc., and are limited to 128MB by default.
A segment is written to in pages of 32KB. Only the last page of the most recent segment
may be partial. A WAL record is an opaque byte slice that gets split up into sub-records
should it exceed the remaining space of the current page. Records are never split across
segment boundaries. If a single record exceeds the default segment size, a segment with
a larger size will be created.
The encoding of pages is largely borrowed from LevelDB's/RocksDB's write ahead log.
Notable deviations are that the record fragment is encoded as:
┌───────────┬──────────┬────────────┬──────────────┐
│ type <1b> │ len <2b> │ CRC32 <4b> │ data <bytes> │
└───────────┴──────────┴────────────┴──────────────┘
The type flag has the following states:
0: rest of page will be empty1: a full record encoded in a single fragment2: first fragment of a record3: middle fragment of a record4: final fragment of a record
Record encoding
The records written to the write ahead log are encoded as follows:
Series records
Series records encode the labels that identifies a series and its unique ID.
┌────────────────────────────────────────────┐
│ type = 1 <1b> │
├────────────────────────────────────────────┤
│ ┌─────────┬──────────────────────────────┐ │
│ │ id <8b> │ n = len(labels) <uvarint> │ │
│ ├─────────┴────────────┬─────────────────┤ │
│ │ len(str_1) <uvarint> │ str_1 <bytes> │ │
│ ├──────────────────────┴─────────────────┤ │
│ │ ... │ │
│ ├───────────────────────┬────────────────┤ │
│ │ len(str_2n) <uvarint> │ str_2n <bytes> │ │
│ └───────────────────────┴────────────────┘ │
│ . . . │
└────────────────────────────────────────────┘
Sample records
Sample records encode samples as a list of triples (series_id, timestamp, value).
Series reference and timestamp are encoded as deltas w.r.t the first sample.
The first row stores the starting id and the starting timestamp.
The first sample record begins at the second row.
┌──────────────────────────────────────────────────────────────────┐
│ type = 2 <1b> │
├──────────────────────────────────────────────────────────────────┤
│ ┌────────────────────┬───────────────────────────┐ │
│ │ id <8b> │ timestamp <8b> │ │
│ └────────────────────┴───────────────────────────┘ │
│ ┌────────────────────┬───────────────────────────┬─────────────┐ │
│ │ id_delta <uvarint> │ timestamp_delta <uvarint> │ value <8b> │ │
│ └────────────────────┴───────────────────────────┴─────────────┘ │
│ . . . │
└──────────────────────────────────────────────────────────────────┘
Tombstone records
Tombstone records encode tombstones as a list of triples (series_id, min_time, max_time)
and specify an interval for which samples of a series got deleted.
┌─────────────────────────────────────────────────────┐
│ type = 3 <1b> │
├─────────────────────────────────────────────────────┤
│ ┌─────────┬───────────────────┬───────────────────┐ │
│ │ id <8b> │ min_time <varint> │ max_time <varint> │ │
│ └─────────┴───────────────────┴───────────────────┘ │
│ . . . │
└─────────────────────────────────────────────────────┘
Exemplar records
Exemplar records encode exemplars as a list of triples (series_id, timestamp, value)
plus the length of the labels list, and all the labels.
The first row stores the starting id and the starting timestamp.
Series reference and timestamp are encoded as deltas w.r.t the first exemplar.
The first exemplar record begins at the second row.
See: https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#exemplars
┌──────────────────────────────────────────────────────────────────┐
│ type = 5 <1b> │
├──────────────────────────────────────────────────────────────────┤
│ ┌────────────────────┬───────────────────────────┐ │
│ │ id <8b> │ timestamp <8b> │ │
│ └────────────────────┴───────────────────────────┘ │
│ ┌────────────────────┬───────────────────────────┬─────────────┐ │
│ │ id_delta <uvarint> │ timestamp_delta <uvarint> │ value <8b> │ │
│ ├────────────────────┴───────────────────────────┴─────────────┤ │
│ │ n = len(labels) <uvarint> │ │
│ ├──────────────────────┬───────────────────────────────────────┤ │
│ │ len(str_1) <uvarint> │ str_1 <bytes> │ │
│ ├──────────────────────┴───────────────────────────────────────┤ │
│ │ ... │ │
│ ├───────────────────────┬──────────────────────────────────────┤ │
│ │ len(str_2n) <uvarint> │ str_2n <bytes> │ │ │
│ └───────────────────────┴────────────────┴─────────────────────┘ │
│ . . . │
└──────────────────────────────────────────────────────────────────┘