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61 commits

Author SHA1 Message Date
Fabian Reinartz 8fa18d564a storage: enhance Querier interface usage
This extracts Querier as an instantiateable and closeable object
rather than just defining extending methods of the storage interface.
This improves composability and allows abstracting query transactions,
which can be useful for transaction-level caches, consistent data views,
and encapsulating teardown.
2016-10-16 10:39:29 +02:00
Julius Volz c25f0de5ae Remove local.ZeroSample{,Pair}, use model definitions 2016-09-28 23:42:45 +02:00
Julius Volz c187308366 storage: Contextify storage interfaces.
This is based on https://github.com/prometheus/prometheus/pull/1997.

This adds contexts to the relevant Storage methods and already passes
PromQL's new per-query context into the storage's query methods.
The immediate motivation supporting multi-tenancy in Frankenstein, but
this could also be used by Prometheus's normal local storage to support
cancellations and timeouts at some point.
2016-09-19 16:29:07 +02:00
Fabian Reinartz 22296dcb85 storage: clarify sample/matcher relation in docs 2016-09-12 11:19:36 +02:00
Fabian Reinartz cc6f988a5e storage: fix Querier interface documentation 2016-09-12 10:48:54 +02:00
Julius Volz 3bfec97d46 Make the storage interface higher-level.
See discussion in
https://groups.google.com/forum/#!topic/prometheus-developers/bkuGbVlvQ9g

The main idea is that the user of a storage shouldn't have to deal with
fingerprints anymore, and should not need to do an individual preload
call for each metric. The storage interface needs to be made more
high-level to not expose these details.

This also makes it easier to reuse the same storage interface for remote
storages later, as fewer roundtrips are required and the fingerprint
concept doesn't work well across the network.

NOTE: this deliberately gets rid of a small optimization in the old
query Analyzer, where we dedupe instants and ranges for the same series.
This should have a minor impact, as most queries do not have multiple
selectors loading the same series (and at the same offset).
2016-07-25 13:59:22 +02:00
beorn7 fc6737b7fb storage: improve index lookups
tl;dr: This is not a fundamental solution to the indexing problem
(like tindex is) but it at least avoids utilizing the intersection
problem to the greatest possible amount.

In more detail:

Imagine the following query:

    nicely:aggregating:rule{job="foo",env="prod"}

While it uses a nicely aggregating recording rule (which might have a
very low cardinality), Prometheus still intersects the low number of
fingerprints for `{__name__="nicely:aggregating:rule"}` with the many
thousands of fingerprints matching `{job="foo"}` and with the millions
of fingerprints matching `{env="prod"}`. This totally innocuous query
is dead slow if the Prometheus server has a lot of time series with
the `{env="prod"}` label. Ironically, if you make the query more
complicated, it becomes blazingly fast:

    nicely:aggregating:rule{job=~"foo",env=~"prod"}

Why so? Because Prometheus only intersects with non-Equal matchers if
there are no Equal matchers. That's good in this case because it
retrieves the few fingerprints for
`{__name__="nicely:aggregating:rule"}` and then starts right ahead to
retrieve the metric for those FPs and checking individually if they
match the other matchers.

This change is generalizing the idea of when to stop intersecting FPs
and go into "retrieve metrics and check them individually against
remaining matchers" mode:

- First, sort all matchers by "expected cardinality". Matchers
  matching the empty string are always worst (and never used for
  intersections). Equal matchers are in general consider best, but by
  using some crude heuristics, we declare some better than others
  (instance labels or anything that looks like a recording rule).

- Then go through the matchers until we hit a threshold of remaining
  FPs in the intersection. This threshold is higher if we are already
  in the non-Equal matcher area as intersection is even more expensive
  here.

- Once the threshold has been reached (or we have run out of matchers
  that do not match the empty string), start with "retrieve metrics
  and check them individually against remaining matchers".

A beefy server at SoundCloud was spending 67% of its CPU time in index
lookups (fingerprintsForLabelPairs), serving mostly a dashboard that
is exclusively built with recording rules. With this change, it spends
only 35% in fingerprintsForLabelPairs. The CPU usage dropped from 26
cores to 18 cores. The median latency for query_range dropped from 14s
to 50ms(!). As expected, higher percentile latency didn't improve that
much because the new approach is _occasionally_ running into the worst
case while the old one was _systematically_ doing so. The 99th
percentile latency is now about as high as the median before (14s)
while it was almost twice as high before (26s).
2016-07-20 17:35:53 +02:00
Julius Volz b7b6717438 Separate query interface out of local.Storage.
PromQL only requires a much narrower interface than local.Storage in
order to run queries. Narrower interfaces are easier to replace and
test, too.

We could also change the web interface to use local.Querier, except that
we'll probably use appending functions from there in the future.
2016-06-23 15:14:38 +02:00
beorn7 836f1db04c Improve MetricsForLabelMatchers
WIP: This needs more tests.

It now gets a from and through value, which it may opportunistically
use to optimize the retrieval. With possible future range indices,
this could be used in a very efficient way. This change merely applies
some easy checks, which should nevertheless solve the use case of
heavy rule evaluations on servers with a lot of series churn.

Idea is the following:

- Only archive series that are at least as old as the headChunkTimeout
  (which was already extremely unlikely to happen).

- Then maintain a high watermark for the last archival, i.e. no
  archived series has a sample more recent than that watermark.

- Any query that doesn't reach to a time before that watermark doesn't
  have to touch the archive index at all. (A production server at
  Soundcloud with the aforementioned series churn and heavy rule
  evaluations spends 50% of its CPU time in archive index
  lookups. Since rule evaluations usually only touch very recent
  values, most of those lookup should disappear with this change.)

- Federation with a very broad label matcher will profit from this,
  too.

As a byproduct, the un-needed MetricForFingerprint method was removed
from the Storage interface.
2016-03-09 00:25:59 +01:00
beorn7 0ea5801e47 Handle errors caused by data corruption more gracefully
This requires all the panic calls upon unexpected data to be converted
into errors returned. This pollute the function signatures quite
lot. Well, this is Go...

The ideas behind this are the following:

- panic only if it's a programming error. Data corruptions happen, and
  they are not programming errors.

- If we detect a data corruption, we "quarantine" the series,
  essentially removing it from the database and putting its data into
  a separate directory for forensics.

- Failure during writing to a series file is not considered corruption
  automatically. It will call setDirty, though, so that a
  crashrecovery upon the next restart will commence and check for
  that.

- Series quarantining and setDirty calls are logged and counted in
  metrics, but are hidden from the user of the interfaces in
  interface.go, whith the notable exception of Append(). The reasoning
  is that we treat corruption by removing the corrupted series, i.e. a
  query for it will return no results on its next call anyway, so
  return no results right now. In the case of Append(), we want to
  tell the user that no data has been appended, though.

Minor side effects:

- Now consistently using filepath.* instead of path.*.

- Introduced structured logging where I touched it. This makes things
  less consistent, but a complete change to structured logging would
  be out of scope for this PR.
2016-03-02 23:02:34 +01:00
beorn7 b6840997a7 Merge branch 'beorn7/storage2' into beorn7/storage3 2016-03-02 16:11:25 +01:00
beorn7 ce58fd357b Merge branch 'beorn7/storage' into beorn7/storage2
Conflicts:
	storage/local/chunk.go
	storage/local/interface.go
2016-03-02 16:09:32 +01:00
beorn7 2581648f70 Separate iterators by offset
Add test that exposes the problem.
2016-03-02 16:01:03 +01:00
beorn7 c740789ce3 Improve predict_linear
Fixes https://github.com/prometheus/prometheus/issues/1401

This remove the last (and in fact bogus) use of BoundaryValues.

Thus, a whole lot of unused (and arguably sub-optimal / ugly) code can
be removed here, too.
2016-02-25 12:10:55 +01:00
beorn7 454ecf3f52 Rework the way ranges and instants are handled
In a way, our instants were also ranges, just with the staleness delta
as range length. They are no treated equally, just that in one case,
the range length is set as range, in the other the staleness
delta. However, there are "real" instants where start and and time of
a query is the same. In those cases, we only want to return a single
value (the one closest before or at the equal start and end time). If
that value is the last sample in the series, odds are we have it
already in the series object. In that case, there is no need to pin or
load any chunks. A special singleSampleSeriesIterator is created for
that. This should greatly speed up instant queries as they happen
frequently for rule evaluations.
2016-02-22 01:47:18 +01:00
beorn7 1e13f89039 Return SamplePair istead of *SamplePair consistently
Formalize ZeroSamplePair as return value for non-existing samples.

Change LastSamplePairForFingerprint to return a SamplePair (and not a
pointer to it), which saves allocations in a potentially extremely
frequent call.
2016-02-19 17:00:40 +01:00
beorn7 0e202dacb4 Streamline series iterator creation
This will fix issue #1035 and will also help to make issue #1264 less
bad.

The fundamental problem in the current code:

In the preload phase, we quite accurately determine which chunks will
be used for the query being executed. However, in the subsequent step
of creating series iterators, the created iterators are referencing
_all_ in-memory chunks in their series, even the un-pinned ones. In
iterator creation, we copy a pointer to each in-memory chunk of a
series into the iterator. While this creates a certain amount of
allocation churn, the worst thing about it is that copying the chunk
pointer out of the chunkDesc requires a mutex acquisition. (Remember
that the iterator will also reference un-pinned chunks, so we need to
acquire the mutex to protect against concurrent eviction.) The worst
case happens if a series doesn't even contain any relevant samples for
the query time range. We notice that during preloading but then we
will still create a series iterator for it. But even for series that
do contain relevant samples, the overhead is quite bad for instant
queries that retrieve a single sample from each series, but still go
through all the effort of series iterator creation. All of that is
particularly bad if a series has many in-memory chunks.

This commit addresses the problem from two sides:

First, it merges preloading and iterator creation into one step,
i.e. the preload call returns an iterator for exactly the preloaded
chunks.

Second, the required mutex acquisition in chunkDesc has been greatly
reduced. That was enabled by a side effect of the first step, which is
that the iterator is only referencing pinned chunks, so there is no
risk of concurrent eviction anymore, and chunks can be accessed
without mutex acquisition.

To simplify the code changes for the above, the long-planned change of
ValueAtTime to ValueAtOrBefore time was performed at the same
time. (It should have been done first, but it kind of accidentally
happened while I was in the middle of writing the series iterator
changes. Sorry for that.) So far, we actively filtered the up to two
values that were returned by ValueAtTime, i.e. we invested work to
retrieve up to two values, and then we invested more work to throw one
of them away.

The SeriesIterator.BoundaryValues method can be removed once #1401 is
fixed. But I really didn't want to load even more changes into this
PR.

Benchmarks:

The BenchmarkFuzz.* benchmarks run 83% faster (i.e. about six times
faster) and allocate 95% fewer bytes. The reason for that is that the
benchmark reads one sample after another from the time series and
creates a new series iterator for each sample read.

To find out how much these improvements matter in practice, I have
mirrored a beefy Prometheus server at SoundCloud that suffers from
both issues #1035 and #1264. To reach steady state that would be
comparable, the server needs to run for 15d. So far, it has run for
1d. The test server currently has only half as many memory time series
and 60% of the memory chunks the main server has. The 90th percentile
rule evaluation cycle time is ~11s on the main server and only ~3s on
the test server. However, these numbers might get much closer over
time.

In addition to performance improvements, this commit removes about 150
LOC.
2016-02-19 16:24:38 +01:00
Fabian Reinartz 59f1e722df Return error on sample appending 2016-02-02 14:01:44 +01:00
beorn7 ec08c9a391 Rework the way to communicate backpressure (AKA suspended ingestion)
This gives up on the idea to communicate throuh the Append() call (by
either not returning as it is now or returning an error as
suggested/explored elsewhere). Here I have added a Throttled() call,
which has the advantage that it can be called before a whole _batch_
of Append()'s. Scrapes will happen completely or not at all. Same for
rule group evaluations. That's a highly desired behavior (as discussed
elsewhere). The code is even simpler now as the whole ingestion buffer
could be removed.

Logging of throttled mode has been streamlined and will create at most
one message per minute.
2016-02-01 14:45:44 +01:00
beorn7 3f4d22e4c7 Update doc comment
This should have gone into a previous commit, but I forgot to save
this particular file.
2016-01-12 12:38:18 +01:00
Fabian Reinartz e061595352 Move COWMetric into storage/metric package 2015-08-25 11:59:07 +02:00
Fabian Reinartz 1535ef1457 Replace metric.SamplePair with model.SamplePair 2015-08-22 14:52:35 +02:00
Fabian Reinartz 438e232c9b Fix grouping of import blocks 2015-08-22 09:42:45 +02:00
Fabian Reinartz 306e8468a0 Switch from client_golang/model to common/model 2015-08-21 13:33:38 +02:00
beorn7 8c196c1028 Minor doc fixes. 2015-06-23 17:07:18 +02:00
Fabian Reinartz 6bfb4549a6 storage: add LastSamplePairForFingerprint method 2015-06-23 13:45:15 +02:00
Fabian Reinartz 5b91ea9b36 storage: improve label matching and allow unset matching.
Matching of empty labels now also matches metrics where the label
was not explicitly set to the empty string.
2015-06-22 15:33:44 +02:00
Fabian Reinartz 5c6c0e2faa Add storage method to delete time series 2015-06-01 21:23:32 +02:00
Fabian Reinartz aff01e29c3 Limit retrievable samples to retention window.
The storage does not delete data immediately after the retention period.
We don't want to retrieve this data as it causes artifacts.
2015-05-27 13:13:59 +02:00
beorn7 3b9c421a69 Weed out all the [Gg]et* method names.
The only exception is getNumChunksToPersist to avoid naming the struct
member numChunksToPersist in a weird way.
2015-05-20 19:13:06 +02:00
beorn7 81b190bf45 Remove locking from series iterator. Cache chunk iterators. 2015-05-20 16:19:34 +02:00
Fabian Reinartz d8440d75f1 Do not start storage processing before Start() is called. 2015-05-19 13:51:45 +02:00
beorn7 be11cb2b07 Remove the sample ingestion channel.
The one central sample ingestion channel has caused a variety of
trouble. This commit removes it. Targets and rule evaluation call an
Append method directly now. To incorporate multiple storage backends
(like OpenTSDB), storage.Tee forks the Append into two different
appenders.

Note that the tsdb queue manager had its own queue anyway. It was a
queue after a queue... Much queue, so overhead...

Targets have their own little buffer (implemented as a channel) to
avoid stalling during an http scrape. But a new scrape will only be
started once the old one is fully ingested.

The contraption of three pipelined ingesters was removed. A Target is
an ingester itself now. Despite more logic in Target, things should be
less confusing now.

Also, remove lint and vet warnings in ast.go.
2015-03-15 14:08:22 +01:00
beorn7 fe518fdb28 Simplify AppendSamples by allowing it to be goroutine-unsafe. 2015-02-13 12:13:22 +01:00
beorn7 5d3cd65a5d Improve performance of ingestion.
- 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.
2015-02-12 18:12:37 +01:00
Bjoern Rabenstein 5859b74f1b Clean up license issues.
- 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.
2015-01-21 20:07:45 +01:00
Julius Volz a6bc42bc61 Minor formatting/spelling fixups. 2015-01-09 11:04:20 +01:00
Bjoern Rabenstein 622e8350cd Fix a bug handling freshly unarchived series.
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.
2015-01-08 16:25:50 +01:00
Julius Volz c9618d11e8 Introduce copy-on-write for metrics in AST.
This depends on changes in:

https://github.com/prometheus/client_golang/tree/cow-metrics.

Change-Id: I80b94833a60ddf954c7cd92fd2cfbebd8dd46142
2014-12-12 20:34:55 +01:00
Bjoern Rabenstein 14bda4180c Changes after pair code review.
Change-Id: Ib72d40f8e9027818cfbbd32a7a7201eebda07455
2014-11-25 17:12:59 +01:00
Bjoern Rabenstein f1de5b0c4e Run checkpointing of in-memory metrics and head chunks periodically.
Checkpointing interval is now a command line flag.

Along the way, several things were refactored.
- Restructure the way the storage is started and stopped..
- Number of series in checkpoint is now a uint64, not a varint.
  (Breaks old checkpoints, needs wipe!)
- More consistent naming and order of methods.

Change-Id: I883d9170c9a608ee716bb0ab3d0ded8ca03760d9
2014-11-25 17:09:04 +01:00
Bjoern Rabenstein 74c9b34a5e Improve storage instrumentation even more.
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
2014-11-25 17:09:04 +01:00
Bjoern Rabenstein 443dd33805 Improve instrumentation in storage.
Also, fix some other minor bugs.

Change-Id: If72f1c058b0f47d3e378fdf80228d7e9a8db06c7
2014-11-25 17:09:04 +01:00
Bjoern Rabenstein 096fa0f8b2 Squash a number of TODOs.
- 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
2014-11-25 17:09:04 +01:00
Bjoern Rabenstein b3ed9aa7a2 Clean up start-up and shut-down.
Change-Id: Idff4bbb0a15a9f879bfbb3da5b1025179cab5e2c
2014-11-25 17:08:45 +01:00
Bjoern Rabenstein 38fc24d0ed Fix targetpool_test.go and other tests.
Change-Id: I91a4dd1d39e01f174e1aaae653ce1ed7aecaa624
2014-11-25 17:08:26 +01:00
Bjoern Rabenstein 8fba3302bc Bold changes to concurrency.
(WIP. Probably doesn't work yet.)

Change-Id: Id1537dfcca53831a1d428078a5863ece7bdf4875
2014-11-25 17:07:45 +01:00
Bjoern Rabenstein fcdf5a8ee7 Fix bugs in chunk evict code.
Also, simplify code by re-looking up metric in metric map.

Change-Id: Ib2092f9184374e5a543e87d3a9f4a74fda64b193
2014-11-25 17:07:45 +01:00
Bjoern Rabenstein 7e6a03fbf9 Fix a few concurrency issues before starting to use the new fp locker.
Change-Id: I8615e8816e79ef0882e123163ee590c739b79d12
2014-11-25 17:07:45 +01:00
Bjoern Rabenstein e9ff29c547 Comment/code cleanup.
Change-Id: I38736e3d0fec79759a2bafa35aecf914480ff810
2014-11-25 17:07:44 +01:00