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740d448983
So far we've been using Go's native time.Time for anything related to sample timestamps. Since the range of time.Time is much bigger than what we need, this has created two problems: - there could be time.Time values which were out of the range/precision of the time type that we persist to disk, therefore causing incorrectly ordered keys. One bug caused by this was: https://github.com/prometheus/prometheus/issues/367 It would be good to use a timestamp type that's more closely aligned with what the underlying storage supports. - sizeof(time.Time) is 192, while Prometheus should be ok with a single 64-bit Unix timestamp (possibly even a 32-bit one). Since we store samples in large numbers, this seriously affects memory usage. Furthermore, copying/working with the data will be faster if it's smaller. *MEMORY USAGE RESULTS* Initial memory usage comparisons for a running Prometheus with 1 timeseries and 100,000 samples show roughly a 13% decrease in total (VIRT) memory usage. In my tests, this advantage for some reason decreased a bit the more samples the timeseries had (to 5-7% for millions of samples). This I can't fully explain, but perhaps garbage collection issues were involved. *WHEN TO USE THE NEW TIMESTAMP TYPE* The new clientmodel.Timestamp type should be used whenever time calculations are either directly or indirectly related to sample timestamps. For example: - the timestamp of a sample itself - all kinds of watermarks - anything that may become or is compared to a sample timestamp (like the timestamp passed into Target.Scrape()). When to still use time.Time: - for measuring durations/times not related to sample timestamps, like duration telemetry exporting, timers that indicate how frequently to execute some action, etc. *NOTE ON OPERATOR OPTIMIZATION TESTS* We don't use operator optimization code anymore, but it still lives in the code as dead code. It still has tests, but I couldn't get all of them to pass with the new timestamp format. I commented out the failing cases for now, but we should probably remove the dead code soon. I just didn't want to do that in the same change as this. Change-Id: I821787414b0debe85c9fffaeb57abd453727af0f
123 lines
3.3 KiB
Go
123 lines
3.3 KiB
Go
// Copyright 2013 Prometheus Team
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package metric
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import (
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"fmt"
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"code.google.com/p/goprotobuf/proto"
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clientmodel "github.com/prometheus/client_golang/model"
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"github.com/prometheus/prometheus/coding/indexable"
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dto "github.com/prometheus/prometheus/model/generated"
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)
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// SampleKey models the business logic around the data-transfer object
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// SampleKey.
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type SampleKey struct {
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Fingerprint *clientmodel.Fingerprint
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FirstTimestamp clientmodel.Timestamp
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LastTimestamp clientmodel.Timestamp
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SampleCount uint32
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}
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// Constrain merges the underlying SampleKey to fit within the keyspace of
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// the provided first and last keys and returns whether the key was modified.
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func (s *SampleKey) Constrain(first, last *SampleKey) bool {
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switch {
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case s.Before(first.Fingerprint, first.FirstTimestamp):
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*s = *first
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return true
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case last.Before(s.Fingerprint, s.FirstTimestamp):
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*s = *last
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return true
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default:
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return false
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}
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}
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func (s *SampleKey) Equal(o *SampleKey) bool {
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if s == o {
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return true
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}
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if !s.Fingerprint.Equal(o.Fingerprint) {
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return false
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}
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if !s.FirstTimestamp.Equal(o.FirstTimestamp) {
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return false
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}
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if !s.LastTimestamp.Equal(o.LastTimestamp) {
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return false
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}
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return s.SampleCount == o.SampleCount
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}
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// MayContain indicates whether the given SampleKey could potentially contain a
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// value at the provided time. Even if true is emitted, that does not mean a
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// satisfactory value, in fact, exists.
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func (s *SampleKey) MayContain(t clientmodel.Timestamp) bool {
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switch {
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case t.Before(s.FirstTimestamp):
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return false
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case t.After(s.LastTimestamp):
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return false
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default:
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return true
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}
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}
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func (s *SampleKey) Before(fp *clientmodel.Fingerprint, t clientmodel.Timestamp) bool {
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if s.Fingerprint.Less(fp) {
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return true
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}
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if !s.Fingerprint.Equal(fp) {
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return false
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}
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if s.FirstTimestamp.Before(t) {
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return true
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}
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return s.LastTimestamp.Before(t)
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}
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// ToDTO converts this SampleKey into a DTO for use in serialization purposes.
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func (s *SampleKey) Dump(d *dto.SampleKey) {
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d.Reset()
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fp := &dto.Fingerprint{}
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dumpFingerprint(fp, s.Fingerprint)
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d.Fingerprint = fp
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d.Timestamp = indexable.EncodeTime(s.FirstTimestamp)
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d.LastTimestamp = proto.Int64(s.LastTimestamp.Unix())
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d.SampleCount = proto.Uint32(s.SampleCount)
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}
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func (s *SampleKey) String() string {
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return fmt.Sprintf("SampleKey for %s at %s to %s with %d values.", s.Fingerprint, s.FirstTimestamp, s.LastTimestamp, s.SampleCount)
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}
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func (s *SampleKey) Load(d *dto.SampleKey) {
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f := &clientmodel.Fingerprint{}
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loadFingerprint(f, d.GetFingerprint())
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s.Fingerprint = f
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s.FirstTimestamp = indexable.DecodeTime(d.Timestamp)
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s.LastTimestamp = clientmodel.TimestampFromUnix(d.GetLastTimestamp())
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s.SampleCount = d.GetSampleCount()
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}
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