chore: sync project files

server/stats.go

@@ -0,0 +1,167 @@
+// Logic related to expvar handling: reporting live stats such as
+// session and topic counts, memory usage etc.
+// The stats updates happen in a separate go routine to avoid
+// locking on main logic routines.
+
+package main
+
+import (
+	"encoding/json"
+	"expvar"
+	"net/http"
+	"runtime"
+	"sort"
+	"time"
+
+	"github.com/tinode/chat/server/logs"
+	"github.com/tinode/chat/server/store"
+)
+
+// A simple implementation of histogram expvar.Var.
+// `Bounds` specifies the histogram buckets as follows (length = len(bounds)):
+//
+//	(-inf, Bounds[i]) for i = 0
+//	[Bounds[i-1], Bounds[i]) for 0 < i < length
+//	[Bounds[i-1], +inf) for i = length
+type histogram struct {
+	Count          int64     `json:"count"`
+	Sum            float64   `json:"sum"`
+	CountPerBucket []int64   `json:"count_per_bucket"`
+	Bounds         []float64 `json:"bounds"`
+}
+
+func (h *histogram) addSample(v float64) {
+	h.Count++
+	h.Sum += v
+	idx := sort.SearchFloat64s(h.Bounds, v)
+	h.CountPerBucket[idx]++
+}
+
+func (h *histogram) String() string {
+	if r, err := json.Marshal(h); err == nil {
+		return string(r)
+	}
+	return ""
+}
+
+type varUpdate struct {
+	// Name of the variable to update
+	varname string
+	// Value to publish (int, float, etc.)
+	value any
+	// Treat the count as an increment as opposite to the final value.
+	inc bool
+}
+
+// Initialize stats reporting through expvar.
+func statsInit(mux *http.ServeMux, path string) {
+	if path == "" || path == "-" {
+		return
+	}
+
+	mux.Handle(path, expvar.Handler())
+	globals.statsUpdate = make(chan *varUpdate, 1024)
+
+	start := time.Now()
+	expvar.Publish("Uptime", expvar.Func(func() any {
+		return time.Since(start).Seconds()
+	}))
+	expvar.Publish("NumGoroutines", expvar.Func(func() any {
+		return runtime.NumGoroutine()
+	}))
+
+	go statsUpdater()
+
+	logs.Info.Printf("stats: variables exposed at '%s'", path)
+}
+
+func statsRegisterDbStats() {
+	if f := store.Store.DbStats(); f != nil {
+		expvar.Publish("DbStats", expvar.Func(f))
+	}
+}
+
+// Register integer variable. Don't check for initialization.
+func statsRegisterInt(name string) {
+	expvar.Publish(name, new(expvar.Int))
+}
+
+// Register histogram variable. `bounds` specifies histogram buckets/bins
+// (see comment next to the `histogram` struct definition).
+func statsRegisterHistogram(name string, bounds []float64) {
+	numBuckets := len(bounds) + 1
+	expvar.Publish(name, &histogram{
+		CountPerBucket: make([]int64, numBuckets),
+		Bounds:         bounds,
+	})
+}
+
+// Async publish int variable.
+func statsSet(name string, val int64) {
+	if globals.statsUpdate != nil {
+		select {
+		case globals.statsUpdate <- &varUpdate{name, val, false}:
+		default:
+		}
+	}
+}
+
+// Async publish an increment (decrement) to int variable.
+func statsInc(name string, val int) {
+	if globals.statsUpdate != nil {
+		select {
+		case globals.statsUpdate <- &varUpdate{name, int64(val), true}:
+		default:
+		}
+	}
+}
+
+// Async publish a value (add a sample) to a histogram variable.
+func statsAddHistSample(name string, val float64) {
+	if globals.statsUpdate != nil {
+		select {
+		case globals.statsUpdate <- &varUpdate{varname: name, value: val}:
+		default:
+		}
+	}
+}
+
+// Stop publishing stats.
+func statsShutdown() {
+	if globals.statsUpdate != nil {
+		globals.statsUpdate <- nil
+	}
+}
+
+// The go routine which actually publishes stats updates.
+func statsUpdater() {
+	for upd := range globals.statsUpdate {
+		if upd == nil {
+			globals.statsUpdate = nil
+			// Dont' care to close the channel.
+			break
+		}
+
+		// Handle var update
+		if ev := expvar.Get(upd.varname); ev != nil {
+			switch v := ev.(type) {
+			case *expvar.Int:
+				count := upd.value.(int64)
+				if upd.inc {
+					v.Add(count)
+				} else {
+					v.Set(count)
+				}
+			case *histogram:
+				val := upd.value.(float64)
+				v.addSample(val)
+			default:
+				logs.Err.Panicf("stats: unsupported expvar type %T", ev)
+			}
+		} else {
+			panic("stats: update to unknown variable " + upd.varname)
+		}
+	}
+
+	logs.Info.Println("stats: shutdown")
+}