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Implement rollup resolution decider for incoming queries.
Signed-off-by: Harkishen-Singh <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,173 @@ | ||
| // This file and its contents are licensed under the Apache License 2.0. | ||
| // Please see the included NOTICE for copyright information and | ||
| // LICENSE for a copy of the license. | ||
|
|
||
| package rollup | ||
|
|
||
| import ( | ||
| "context" | ||
| "fmt" | ||
| "sort" | ||
| "sync" | ||
| "time" | ||
|
|
||
| "github.com/timescale/promscale/pkg/log" | ||
| "github.com/timescale/promscale/pkg/pgxconn" | ||
| ) | ||
|
|
||
| const ( | ||
| originalSchema = "prom_data" | ||
| upperLimit = 5000 // Maximum samples allowed | ||
| assumedScrapeInterval = time.Second * 30 | ||
| refreshRollupResolution = time.Minute * 30 | ||
| ) | ||
|
|
||
| type rollupInfo struct { | ||
| schemaName string | ||
| resolution time.Duration | ||
| } | ||
|
|
||
| type QueryHelper struct { | ||
| conn pgxconn.PgxConn | ||
| refreshMtx sync.RWMutex | ||
| metricType map[string]string // metric_name: metric_type | ||
| resolutionsASC []rollupInfo // {schemaName, resolution} in ascending order of resolution. | ||
| downsamplingEnabled bool | ||
| } | ||
|
|
||
| func NewQueryHelper(ctx context.Context, conn pgxconn.PgxConn) (*QueryHelper, error) { | ||
| helper := &QueryHelper{conn: conn} | ||
| if err := helper.runRefreshRoutine(ctx, refreshRollupResolution); err != nil { | ||
| return nil, fmt.Errorf("refresh: %w", err) | ||
| } | ||
| return helper, nil | ||
| } | ||
|
|
||
| // DecideSchema returns the schema name of the rollups that should be used for querying. | ||
| // The returned schema represents a downsampled resolution that should be an optimal | ||
| // resolution for querying. | ||
| // | ||
| // If no rollups exists or if downsampling is disabled, "prom_data" is returned. | ||
| func (h *QueryHelper) DecideSchema(min, max int64) string { | ||
| h.refreshMtx.RLock() | ||
| defer h.refreshMtx.RUnlock() | ||
|
|
||
| if !h.downsamplingEnabled || len(h.resolutionsASC) == 0 { | ||
| return originalSchema | ||
| } | ||
| estimateSamples := func(resolution time.Duration) int64 { | ||
| return int64(float64(max-min) / resolution.Seconds()) | ||
| } | ||
|
|
||
| numRawSamples := estimateSamples(assumedScrapeInterval) | ||
| if numRawSamples < upperLimit { | ||
| return originalSchema | ||
| } | ||
|
|
||
| for _, info := range h.resolutionsASC { | ||
| samples := estimateSamples(info.resolution) | ||
| if samples < upperLimit { | ||
| // The first highest resolution that is below upper limit is our answer, | ||
| // since it provides the highest granularity at the expected samples. | ||
| return info.schemaName | ||
| } | ||
| } | ||
| // All rollups are above upper limit. Hence, send the schema of the lowest resolution | ||
| // as this is the best we can do. | ||
| lowestRollup := h.resolutionsASC[len(h.resolutionsASC)-1] | ||
| return lowestRollup.schemaName | ||
| } | ||
|
|
||
| func (h *QueryHelper) ContainsMetricType(metricName string) bool { | ||
| _, present := h.metricType[metricName] | ||
| return present | ||
| } | ||
|
|
||
| func (h *QueryHelper) Refresh() error { | ||
| h.refreshMtx.Lock() | ||
| defer h.refreshMtx.Unlock() | ||
|
|
||
| if err := h.refreshDownsamplingState(); err != nil { | ||
| return fmt.Errorf("downsampling state: %w", err) | ||
| } | ||
| if err := h.refreshMetricTypes(); err != nil { | ||
| return fmt.Errorf("metric-type: %w", err) | ||
| } | ||
| if err := h.refreshRollupResolutions(); err != nil { | ||
| return fmt.Errorf("rollup resolutions: %w", err) | ||
| } | ||
| return nil | ||
| } | ||
|
|
||
| func (h *QueryHelper) runRefreshRoutine(ctx context.Context, refreshInterval time.Duration) error { | ||
| if err := h.Refresh(); err != nil { | ||
| return fmt.Errorf("refreshing rollup resolution: %w", err) | ||
| } | ||
| go func() { | ||
| t := time.NewTicker(refreshInterval) | ||
| defer t.Stop() | ||
| for range t.C { | ||
| if err := h.Refresh(); err != nil { | ||
| log.Error("msg", "error refreshing rollup resolution", "error", err.Error()) | ||
| } | ||
| } | ||
| }() | ||
| return nil | ||
| } | ||
|
|
||
| func (h *QueryHelper) refreshDownsamplingState() error { | ||
| var state bool | ||
| if err := h.conn.QueryRow(context.Background(), "SELECT prom_api.get_automatic_downsample()::BOOLEAN").Scan(&state); err != nil { | ||
| return fmt.Errorf("fetching automatic downsampling state: %w", err) | ||
| } | ||
| h.downsamplingEnabled = state | ||
| return nil | ||
| } | ||
|
|
||
| func (h *QueryHelper) refreshMetricTypes() error { | ||
| var metricName, metricType []string | ||
| err := h.conn.QueryRow(context.Background(), | ||
| "select array_agg(metric_family), array_agg(type) from _prom_catalog.metadata").Scan(&metricName, &metricType) | ||
| if err != nil { | ||
| return fmt.Errorf("fetching metric metadata: %w", err) | ||
| } | ||
| h.metricType = make(map[string]string) // metric_name: metric_type | ||
| for i := range metricName { | ||
| h.metricType[metricName[i]] = metricType[i] | ||
| } | ||
| return nil | ||
| } | ||
|
|
||
| func (h *QueryHelper) refreshRollupResolutions() error { | ||
| rows, err := h.conn.Query(context.Background(), "SELECT schema_name, resolution FROM _prom_catalog.rollup") | ||
| if err != nil { | ||
| return fmt.Errorf("fetching rollup resolutions: %w", err) | ||
| } | ||
| h.resolutionsASC = []rollupInfo{} | ||
| for rows.Next() { | ||
| var ( | ||
| schemaName string | ||
| resolution time.Duration | ||
| ) | ||
| if err = rows.Scan(&schemaName, &resolution); err != nil { | ||
| return fmt.Errorf("error scanning rows: %w", err) | ||
| } | ||
| h.resolutionsASC = append(h.resolutionsASC, rollupInfo{schemaName: schemaName, resolution: resolution}) | ||
| } | ||
| sort.Sort(sortRollupInfo(h.resolutionsASC)) | ||
| return nil | ||
| } | ||
|
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| type sortRollupInfo []rollupInfo | ||
|
|
||
| func (s sortRollupInfo) Len() int { | ||
| return len(s) | ||
| } | ||
|
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| func (s sortRollupInfo) Less(i, j int) bool { | ||
| return s[i].resolution.Seconds() < s[j].resolution.Seconds() | ||
| } | ||
|
|
||
| func (s sortRollupInfo) Swap(i, j int) { | ||
| s[i], s[j] = s[j], s[i] | ||
| } |
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