[core] Adding http metrics endpoint

Makefile

@@ -71,7 +71,7 @@ INSTALL_WHAT:=$(patsubst %, install_%, $(WHAT))
 GENERATE_DIRS := ./apricot ./coconut/cmd ./common ./common/runtype ./common/system ./core ./core/integration/ccdb ./core/integration/dcs ./core/integration/ddsched ./core/integration/kafka ./core/integration/odc ./executor ./walnut ./core/integration/trg ./core/integration/bookkeeping
 SRC_DIRS := ./apricot ./cmd/* ./core ./coconut ./executor ./common ./configuration ./occ/peanut ./walnut
 TEST_DIRS := ./apricot/local ./common/gera ./common/utils/safeacks ./configuration/cfgbackend ./configuration/componentcfg ./configuration/template ./core/task/sm ./core/workflow ./core/integration/odc/fairmq ./core/integration ./core/environment
-GO_TEST_DIRS := ./core/repos ./core/integration/dcs
+GO_TEST_DIRS := ./core/repos ./core/integration/dcs ./common/monitoring
 
 coverage:COVERAGE_PREFIX := ./coverage_results
 coverage:GOTEST_COVERAGE_FILE := $(COVERAGE_PREFIX)/gotest.out

common/ecsmetrics/metric.go

@@ -0,0 +1,14 @@
+package ecsmetrics
+
+import (
+	"time"
+
+	"github.com/AliceO2Group/Control/common/monitoring"
+)
+
+func NewMetric(name string) monitoring.Metric {
+	timestamp := time.Now()
+	metric := monitoring.Metric{Name: name, Timestamp: timestamp.UnixMilli()}
+	metric.AddTag("subsystem", "ECS")
+	return metric
+}

common/ecsmetrics/metrics.go

@@ -0,0 +1,69 @@
+package ecsmetrics
+
+import (
+	"fmt"
+	internalmetrics "runtime/metrics"
+	"time"
+
+	"github.com/AliceO2Group/Control/common/monitoring"
+)
+
+var endRequestChannel chan struct{}
+
+func gather() monitoring.Metric {
+	samples := []internalmetrics.Sample{
+		{Name: "/gc/cycles/total:gc-cycles"},
+		{Name: "/memory/classes/other:bytes"},
+		{Name: "/memory/classes/total:bytes"},
+		{Name: "/sched/goroutines:goroutines"},
+		{Name: "/sync/mutex/wait/total:seconds"},
+		{Name: "/memory/classes/other:bytes"},
+		{Name: "/memory/classes/total:bytes"},
+		{Name: "/memory/classes/heap/free:bytes"},
+		{Name: "/memory/classes/heap/objects:bytes"},
+		{Name: "/memory/classes/heap/released:bytes"},
+		{Name: "/memory/classes/heap/stacks:bytes"},
+		{Name: "/memory/classes/heap/unused:bytes"},
+	}
+
+	// Collect metrics data
+	internalmetrics.Read(samples)
+
+	metric := NewMetric("golangruntimemetrics")
+
+	for _, sample := range samples {
+		switch sample.Value.Kind() {
+		case internalmetrics.KindUint64:
+			metric.AddValue(sample.Name, sample.Value.Uint64())
+		case internalmetrics.KindFloat64:
+			metric.AddValue(sample.Name, sample.Value.Float64())
+		case internalmetrics.KindFloat64Histogram:
+			fmt.Printf("Error: Histogram is not supported yet for metric [%s]", sample.Name)
+			continue
+		default:
+			fmt.Printf("Unsupported kind %v for metric %s\n", sample.Value.Kind(), sample.Name)
+			continue
+		}
+	}
+	return metric
+}
+
+func StartGolangMetrics(period time.Duration) {
+	go func() {
+		for {
+			select {
+			case <-endRequestChannel:
+				endRequestChannel <- struct{}{}
+				return
+			default:
+				monitoring.Send(gather())
+				time.Sleep(period)
+			}
+		}
+	}()
+}
+
+func StopGolangMetrics() {
+	endRequestChannel <- struct{}{}
+	<-endRequestChannel
+}

common/monitoring/metric.go

@@ -0,0 +1,27 @@
+package monitoring
+
+type (
+	TagsType   map[string]any
+	ValuesType map[string]any
+)
+
+type Metric struct {
+	Name      string     `json:"name"`
+	Values    ValuesType `json:"values"`
+	Tags      TagsType   `json:"tags,omitempty"`
+	Timestamp int64      `json:"timestamp"`
+}
+
+func (metric *Metric) AddTag(tagName string, value any) {
+	if metric.Tags == nil {
+		metric.Tags = make(TagsType)
+	}
+	metric.Tags[tagName] = value
+}
+
+func (metric *Metric) AddValue(valueName string, value any) {
+	if metric.Values == nil {
+		metric.Values = make(ValuesType)
+	}
+	metric.Values[valueName] = value
+}

common/monitoring/monitoring.go

@@ -0,0 +1,125 @@
+package monitoring
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/AliceO2Group/Control/common/logger"
+	"github.com/sirupsen/logrus"
+)
+
+var (
+	server       *http.Server
+	metricsLimit int = 1000000
+	metrics      []Metric
+	// channel that is used to request end of metrics server, it sends notification when server ended.
+	// It needs to be read!!!
+	endChannel chan struct{}
+
+	// channel used to send metrics into the event loop
+	metricsChannel chan Metric
+
+	// channel for sending notifications to event loop that new http Request to report metrics arrived
+	metricsRequestChannel chan struct{}
+
+	// channel used to send metrics to be reported by http request from event loop
+	metricsToRequest chan []Metric
+
+	Log = logger.New(logrus.StandardLogger(), "metrics")
+)
+
+func initChannels(messageBufferSize int) {
+	endChannel = make(chan struct{})
+	metricsRequestChannel = make(chan struct{})
+	metricsChannel = make(chan Metric, 100)
+	metricsToRequest = make(chan []Metric)
+	metricsLimit = messageBufferSize
+}
+
+func closeChannels() {
+	close(endChannel)
+	close(metricsRequestChannel)
+	close(metricsChannel)
+	close(metricsToRequest)
+}
+
+func eventLoop() {
+	for {
+		select {
+		case <-metricsRequestChannel:
+			shallowCopyMetrics := metrics
+			metrics = make([]Metric, 0)
+			metricsToRequest <- shallowCopyMetrics
+
+		case metric := <-metricsChannel:
+			if len(metrics) < metricsLimit {
+				metrics = append(metrics, metric)
+			} else {
+				Log.Warn("too many metrics waiting to be scraped. Are you sure that metrics scraping is running?")
+			}
+
+		case <-endChannel:
+			endChannel <- struct{}{}
+			return
+		}
+	}
+}
+
+func exportMetricsAndReset(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json")
+	metricsRequestChannel <- struct{}{}
+	metricsToConvert := <-metricsToRequest
+	if metricsToConvert == nil {
+		metricsToConvert = make([]Metric, 0)
+	}
+	json.NewEncoder(w).Encode(metricsToConvert)
+}
+
+func Send(metric Metric) {
+	metricsChannel <- metric
+}
+
+func handleFunc(endpointName string) {
+	// recover is here to correctly allow multiple Starts and Stops of server
+	defer func() {
+		recover()
+	}()
+
+	http.HandleFunc(endpointName, exportMetricsAndReset)
+}
+
+// \param port port where the scraping endpoint will be created
+// \param endpointName name of the endpoint, which must start with a slash eg. "/internalmetrics"
+// \param messageBufferSize size of buffer for messages where messages are kept between scraping request.
+//
+// If we attempt send more messages than the size of the buffer, these overflowing messages will be ignored and warning will be logged.
+func Start(port uint16, endpointName string, messageBufferSize int) error {
+	if server != nil {
+		return nil
+	}
+
+	initChannels(messageBufferSize)
+
+	go eventLoop()
+
+	server := &http.Server{Addr: fmt.Sprintf(":%d", port)}
+	handleFunc(endpointName)
+	return server.ListenAndServe()
+}
+
+func Stop() {
+	if server == nil {
+		return
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	server.Shutdown(ctx)
+
+	endChannel <- struct{}{}
+	<-endChannel
+	server = nil
+}