Basic stats support

README.md

@@ -1,6 +1,6 @@
 # ClusterCockpit Metric Store
 
-![test workflow](https://github.com/ClusterCockpit/cc-metric-store/actions/workflows/test.yml/badge.svg)
+[![Build & Test](https://github.com/ClusterCockpit/cc-metric-store/actions/workflows/test.yml/badge.svg)](https://github.com/ClusterCockpit/cc-metric-store/actions/workflows/test.yml)
 
 Barely unusable yet. Go look at the [GitHub Issues](https://github.com/ClusterCockpit/cc-metric-store/issues) for a progress overview.
 
@@ -27,7 +27,7 @@ go test -bench=. -race -v ./...
 
 Tags in InfluxDB are used to build indexes over the stored data. InfluxDB-Tags have no
 relation to each other, they do not depend on each other and have no hierarchy.
-Different tags build up different indexes.
+Different tags build up different indexes (I am no expert at all, but this is how i think they work).
 
 This project also works as a time-series database and uses the InfluxDB line protocol.
 Unlike InfluxDB, the data is indexed by one single strictly hierarchical tree structure.
@@ -83,16 +83,16 @@ The plan is later to have the structure look like this (for this, the socket of
 ### Config file
 
 - `metrics`: Map of metric-name to objects with the following properties
-    - `frequency`: Timestep/Interval/Resolution of this metric
+    - `frequency`: Timestep/Interval/Resolution of this metric (In seconds)
-    - `aggregation`: Can be `"sum"`, `"avg"` or `null`.
+    - `aggregation`: Can be `"sum"`, `"avg"` or `null`
-        - `null` means "horizontal" aggregation is disabled
+        - `null` means aggregation across nodes is forbidden for this metric
         - `"sum"` means that values from the child levels are summed up for the parent level
         - `"avg"` means that values from the child levels are averaged for the parent level
     - `scope`: Unused at the moment, should be something like `"node"`, `"socket"` or `"cpu"`
 - `nats`: Url of NATS.io server (The `updates` channel will be subscribed for metrics)
-- `archive-root`: Directory to be used as archive (__Unimplemented__)
+- `archive-root`: Directory to be used as archive
-- `restore-last-hours`: After restart, load data from the past *X* hours back to memory (__Unimplemented__)
+- `restore-last-hours`: After restart, load data from the past *X* hours back to memory
-- `checkpoint-interval-hours`: Every *X* hours, write currently held data to disk (__Unimplemented__)
+- `checkpoint-interval-hours`: Every *X* hours, write currently held data to disk
 
 ### Test the complete setup (excluding ClusterCockpit itself)
 
@@ -106,7 +106,7 @@ docker pull nats:latest
 docker run -p 4222:4222 -ti nats:latest
 ```
 
-Second, build and start start the [cc-metric-collector](https://github.com/ClusterCockpit/cc-metric-collector) using the following as `config.json`:
+Second, build and start the [cc-metric-collector](https://github.com/ClusterCockpit/cc-metric-collector) using the following as `config.json`:
 
 ```json
 {
@@ -139,13 +139,20 @@ And finally, use the API to fetch some data:
 
 ```sh
 # If the collector and store and nats-server have been running for at least 60 seconds on the same host, you may run:
-curl -D - "http://localhost:8080/api/$(expr $(date +%s) - 60)/$(date +%s)/timeseries" -d "[ { \"selector\": [\"testcluster\", \"$(hostname)\"], \"metrics\": [\"load_one\"] } ]"
+curl -D - "http://localhost:8080/api/$(expr $(date +%s) - 60)/$(date +%s)/timeseries" -d "{ \"selectors\": [[\"testcluster\", \"$(hostname)\"]], \"metrics\": [\"load_one\"] }"
 
 # Get flops_any for all CPUs:
-curl -D - "http://localhost:8080/api/$(expr $(date +%s) - 60)/$(date +%s)/timeseries" -d "[ { \"selector\": [\"testcluster\", \"$(hostname)\", \"cpu\"], \"metrics\": [\"flops_any\"] } ]"
+curl -D - "http://localhost:8080/api/$(expr $(date +%s) - 60)/$(date +%s)/timeseries" -d "{ \"selectors\": [[\"testcluster\", \"$(hostname)\", \"cpu\"]], \"metrics\": [\"flops_any\"] }"
 
 # Get flops_any for CPU 0:
-curl -D - "http://localhost:8080/api/$(expr $(date +%s) - 60)/$(date +%s)/timeseries" -d "[ { \"selector\": [\"testcluster\", \"$(hostname)\", \"cpu\", \"0\"], \"metrics\": [\"flops_any\"] } ]"
+curl -D - "http://localhost:8080/api/$(expr $(date +%s) - 60)/$(date +%s)/timeseries" -d "{ \"selectors\": [[\"testcluster\", \"$(hostname)\", \"cpu\", \"0\"]], \"metrics\": [\"flops_any\"] }"
+
+# Stats for load_one and proc_run:
+curl -D - "http://localhost:8080/api/$(expr $(date +%s) - 60)/$(date +%s)/stats" -d "{ \"selectors\": [[\"testcluster\", \"$(hostname)\"]], \"metrics\": [\"load_one\", \"proc_run\"] }"
+
+# Stats for *all* CPUs aggregated both from CPU to node and over time:
+curl -D - "http://localhost:8080/api/$(expr $(date +%s) - 60)/$(date +%s)/stats" -d "{ \"selectors\": [[\"testcluster\", \"$(hostname)\", \"cpu\"]], \"metrics\": [\"flops_sp\", \"flops_dp\"] }"
+
 
 # ...
 ```

TODO.md

@@ -10,13 +10,10 @@
     - Implement API endpoint for releasing old data
     - Make sure data is written to disk before it is released
     - Automatically free up old buffers periodically?
-- Implement basic support for aggregations over time (stats like min/max/avg)
 - Optimization: Once a buffer is full, calculate min, max and avg
     - Calculate averages buffer-wise, average weighted by length of buffer
+    - Only the head-buffer needs to be fully traversed
 - Implement basic support for query of most recent value for every metric on every host
 - Optimize horizontal aggregations
-- Optimize locking of levels in the tree structure
+- All metrics are known in advance, including the level: Use this to replace `level.metrics` hashmap by slice?
-    - In 99.9% of cases, no new level will need to be created, so all lookups into `level.children` will be read only
-    - `level.metrics` will be modified more often and will accesses will need to be serialized here
-    - Suggestion: Use a proper Mutex for `level.metrics`, but something read-optimized and possibly lock-free for `level.children`
 - ...

api.go

@@ -12,12 +12,13 @@ import (
 )
 
 // Example:
-//	[
+//	{
-//		{ "selector": ["emmy", "host123"], "metrics": ["load_one"] }
+//		"metrics": ["flops_sp", "flops_dp"]
-//	]
+//		"selectors": [["emmy", "host123", "cpu", "0"], ["emmy", "host123", "cpu", "1"]]
-type ApiRequestBody []struct {
+//	}
-	Selector []string `json:"selector"`
+type ApiRequestBody struct {
 	Metrics   []string   `json:"metrics"`
+	Selectors [][]string `json:"selectors"`
 }
 
 type ApiMetricData struct {
@@ -26,6 +27,15 @@ type ApiMetricData struct {
 	Data []Float `json:"data"`
 }
 
+type ApiStatsData struct {
+	From    int64 `json:"from"`
+	To      int64 `json:"to"`
+	Samples int   `json:"samples"`
+	Avg     Float `json:"avg"`
+	Min     Float `json:"min"`
+	Max     Float `json:"max"`
+}
+
 func handleTimeseries(rw http.ResponseWriter, r *http.Request) {
 	vars := mux.Vars(r)
 	from, err := strconv.ParseInt(vars["from"], 10, 64)
@@ -52,11 +62,11 @@ func handleTimeseries(rw http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	res := make([]map[string]ApiMetricData, 0, len(reqBody))
+	res := make([]map[string]ApiMetricData, 0, len(reqBody.Selectors))
-	for _, req := range reqBody {
+	for _, selector := range reqBody.Selectors {
 		metrics := make(map[string]ApiMetricData)
-		for _, metric := range req.Metrics {
+		for _, metric := range reqBody.Metrics {
-			data, f, t, err := memoryStore.Read(req.Selector, metric, from, to)
+			data, f, t, err := memoryStore.Read(selector, metric, from, to)
 			if err != nil {
 				http.Error(rw, err.Error(), http.StatusInternalServerError)
 				return
@@ -78,10 +88,66 @@ func handleTimeseries(rw http.ResponseWriter, r *http.Request) {
 	}
 }
 
+func handleStats(rw http.ResponseWriter, r *http.Request) {
+	vars := mux.Vars(r)
+	from, err := strconv.ParseInt(vars["from"], 10, 64)
+	if err != nil {
+		http.Error(rw, err.Error(), http.StatusBadRequest)
+		return
+	}
+	to, err := strconv.ParseInt(vars["to"], 10, 64)
+	if err != nil {
+		http.Error(rw, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	if r.Method != http.MethodPost {
+		http.Error(rw, "Method Not Allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	bodyDec := json.NewDecoder(r.Body)
+	var reqBody ApiRequestBody
+	err = bodyDec.Decode(&reqBody)
+	if err != nil {
+		http.Error(rw, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	res := make([]map[string]ApiStatsData, 0, len(reqBody.Selectors))
+	for _, selector := range reqBody.Selectors {
+		metrics := make(map[string]ApiStatsData)
+		for _, metric := range reqBody.Metrics {
+			stats, f, t, err := memoryStore.Stats(selector, metric, from, to)
+			if err != nil {
+				http.Error(rw, err.Error(), http.StatusInternalServerError)
+				return
+			}
+
+			metrics[metric] = ApiStatsData{
+				From:    f,
+				To:      t,
+				Samples: stats.Samples,
+				Avg:     stats.Avg,
+				Min:     stats.Min,
+				Max:     stats.Max,
+			}
+		}
+		res = append(res, metrics)
+	}
+
+	rw.Header().Set("Content-Type", "application/json")
+	err = json.NewEncoder(rw).Encode(res)
+	if err != nil {
+		log.Println(err.Error())
+	}
+}
+
 func StartApiServer(address string, done chan bool) error {
 	r := mux.NewRouter()
 
 	r.HandleFunc("/api/{from:[0-9]+}/{to:[0-9]+}/timeseries", handleTimeseries)
+	r.HandleFunc("/api/{from:[0-9]+}/{to:[0-9]+}/stats", handleStats)
 
 	server := &http.Server{
 		Handler:      r,

memstore_test.go

@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"math"
+	"math/rand"
 	"sync"
 	"testing"
 )
@@ -172,6 +173,75 @@ func TestMemoryStoreAggregation(t *testing.T) {
 	}
 }
 
+func TestMemoryStoreStats(t *testing.T) {
+	count := 3000
+	store := NewMemoryStore(map[string]MetricConfig{
+		"a": {Frequency: 1},
+		"b": {Frequency: 1, Aggregation: "avg"},
+	})
+
+	sel1 := []string{"cluster", "host1"}
+	sel2 := []string{"cluster", "host2", "left"}
+	sel3 := []string{"cluster", "host2", "right"}
+
+	samples := 0
+	asum, amin, amax := 0., math.MaxFloat32, -math.MaxFloat32
+	bsum, bmin, bmax := 0., math.MaxFloat32, -math.MaxFloat32
+
+	for i := 0; i < count; i++ {
+		if i%5 == 0 {
+			// Skip some writes, test if samples is calculated correctly
+			continue
+		}
+
+		samples += 1
+		a := float64(rand.Int()%100 - 50)
+		asum += a
+		amin = math.Min(amin, a)
+		amax = math.Max(amax, a)
+		b := float64(rand.Int()%100 - 50)
+		bsum += b * 2
+		bmin = math.Min(bmin, b)
+		bmax = math.Max(bmax, b)
+
+		store.Write(sel1, int64(i), []Metric{
+			{Name: "a", Value: Float(a)},
+		})
+		store.Write(sel2, int64(i), []Metric{
+			{Name: "b", Value: Float(b)},
+		})
+		store.Write(sel3, int64(i), []Metric{
+			{Name: "b", Value: Float(b)},
+		})
+	}
+
+	stats, from, to, err := store.Stats(sel1, "a", 0, int64(count))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if from != 1 || to != int64(count) || stats.Samples != samples {
+		t.Fatalf("unexpected: from=%d, to=%d, stats.Samples=%d (expected samples=%d)\n", from, to, stats.Samples, samples)
+	}
+
+	if stats.Avg != Float(asum/float64(samples)) || stats.Min != Float(amin) || stats.Max != Float(amax) {
+		t.Fatalf("wrong stats: %#v\n", stats)
+	}
+
+	stats, from, to, err = store.Stats([]string{"cluster", "host2"}, "b", 0, int64(count))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if from != 1 || to != int64(count) || stats.Samples != samples*2 {
+		t.Fatalf("unexpected: from=%d, to=%d, stats.Samples=%d (expected samples=%d)\n", from, to, stats.Samples, samples*2)
+	}
+
+	if stats.Avg != Float(bsum/float64(samples*2)) || stats.Min != Float(bmin) || stats.Max != Float(bmax) {
+		t.Fatalf("wrong stats: %#v (expected: avg=%f, min=%f, max=%f)\n", stats, bsum/float64(samples*2), bmin, bmax)
+	}
+}
+
 func TestMemoryStoreArchive(t *testing.T) {
 	store1 := NewMemoryStore(map[string]MetricConfig{
 		"a": {Frequency: 1},

stats.go

@@ -0,0 +1,139 @@
+package main
+
+import (
+	"errors"
+	"math"
+)
+
+type Stats struct {
+	Samples int
+	Avg     Float
+	Min     Float
+	Max     Float
+}
+
+// Return `Stats` by value for less allocations/GC?
+func (b *buffer) stats(from, to int64) (*Stats, int64, int64, error) {
+	if from < b.start {
+		if b.prev != nil {
+			return b.prev.stats(from, to)
+		}
+		from = b.start
+	}
+
+	samples := 0
+	sum, min, max := 0.0, math.MaxFloat32, -math.MaxFloat32
+
+	var t int64
+	for t = from; t < to; t += b.frequency {
+		idx := int((t - b.start) / b.frequency)
+		if idx >= cap(b.data) {
+			b = b.next
+			if b == nil {
+				break
+			}
+			idx = 0
+		}
+
+		if t < b.start || idx >= len(b.data) {
+			continue
+		}
+
+		xf := float64(b.data[idx])
+		if math.IsNaN(xf) {
+			continue
+		}
+
+		samples += 1
+		sum += xf
+		min = math.Min(min, xf)
+		max = math.Max(max, xf)
+	}
+
+	return &Stats{
+		Samples: samples,
+		Avg:     Float(sum) / Float(samples),
+		Min:     Float(min),
+		Max:     Float(max),
+	}, from, t, nil
+}
+
+// This function assmumes that `l.lock` is LOCKED!
+// It basically works just like level.read but calculates min/max/avg for that data level.read would return.
+// TODO: Make this DRY?
+func (l *level) stats(metric string, from, to int64, aggregation string) (*Stats, int64, int64, error) {
+	if b, ok := l.metrics[metric]; ok {
+		return b.stats(from, to)
+	}
+
+	if len(l.children) == 0 {
+		return nil, 0, 0, errors.New("no data for that metric/level")
+	}
+
+	if len(l.children) == 1 {
+		for _, child := range l.children {
+			child.lock.Lock()
+			stats, from, to, err := child.stats(metric, from, to, aggregation)
+			child.lock.Unlock()
+			return stats, from, to, err
+		}
+	}
+
+	samples := 0
+	avgSum, min, max := Float(0), Float(math.MaxFloat32), Float(-math.MaxFloat32)
+	for _, child := range l.children {
+		child.lock.Lock()
+		stats, cfrom, cto, err := child.stats(metric, from, to, aggregation)
+		child.lock.Unlock()
+
+		if err != nil {
+			return nil, 0, 0, err
+		}
+
+		if cfrom != from || cto != to {
+			// See level.read for more on this
+			if samples == 0 {
+				from = cfrom
+				to = cto
+			} else {
+				return nil, 0, 0, errors.New("data for metrics at child levels does not align")
+			}
+		}
+
+		samples += stats.Samples
+		avgSum += stats.Avg
+		min = Float(math.Min(float64(min), float64(stats.Min)))
+		max = Float(math.Max(float64(max), float64(stats.Max)))
+	}
+
+	avg := avgSum
+	if aggregation == "avg" {
+		avg /= Float(len(l.children))
+	} else if aggregation != "sum" {
+		return nil, 0, 0, errors.New("invalid aggregation strategy: " + aggregation)
+	}
+
+	return &Stats{
+		Samples: samples,
+		Avg:     avg,
+		Min:     min,
+		Max:     max,
+	}, from, to, nil
+}
+
+func (m *MemoryStore) Stats(selector []string, metric string, from, to int64) (*Stats, int64, int64, error) {
+	l := m.root.findLevelOrCreate(selector)
+	l.lock.RLock()
+	defer l.lock.RUnlock()
+
+	if from > to {
+		return nil, 0, 0, errors.New("invalid time range")
+	}
+
+	minfo, ok := m.metrics[metric]
+	if !ok {
+		return nil, 0, 0, errors.New("unkown metric: " + metric)
+	}
+
+	return l.stats(metric, from, to, minfo.Aggregation)
+}