From 0ab48694702ec52a866d93c1d0f054c1dc4e1e53 Mon Sep 17 00:00:00 2001
From: Panos Koutsovasilis <panos.koutsovasilis@elastic.co>
Date: Wed, 3 Apr 2024 05:52:36 +0300
Subject: [PATCH] fix(fim/ebpf): utilise OnceValues to declutter the code

---
 libbeat/ebpf/sys/sys.go  | 35 ++++++++++-------------------------
 libbeat/ebpf/sys/time.go | 30 +++++++-----------------------
 2 files changed, 17 insertions(+), 48 deletions(-)

diff --git a/libbeat/ebpf/sys/sys.go b/libbeat/ebpf/sys/sys.go
index ca0351fada63..2d1d101e66b9 100644
--- a/libbeat/ebpf/sys/sys.go
+++ b/libbeat/ebpf/sys/sys.go
@@ -26,47 +26,32 @@ import (
 
 	"github.com/elastic/beats/v7/x-pack/auditbeat/module/system"
 	"github.com/elastic/go-sysinfo"
+	"github.com/elastic/go-sysinfo/types"
 )
 
-type hostID struct {
-	uniqueID string
-	bootTime time.Time
-	err      error
-}
-
 var (
-	hostInfo = sync.OnceValue(func() hostID {
-		info, err := sysinfo.Host()
+	hostInfoOnce = sync.OnceValues(func() (types.HostInfo, error) {
+		host, err := sysinfo.Host()
 
-		if info == nil {
-			return hostID{
-				err: err,
-			}
+		if host == nil {
+			return types.HostInfo{}, err
 		}
 
-		return hostID{
-			uniqueID: info.Info().UniqueID,
-			bootTime: info.Info().BootTime,
-			err:      err,
-		}
+		return host.Info(), err
 	})
 )
 
-func HostInfo() (string, time.Time, error) {
-	hID := hostInfo()
-
-	return hID.uniqueID, hID.bootTime, hID.err
-}
-
 // EntityID creates an ID that uniquely identifies this process across machines.
 func EntityID(pid uint32, start time.Time) (string, error) {
-	hid, _, err := HostInfo()
+	info, err := hostInfoOnce()
 	if err != nil {
 		return "", err
 	}
 
 	h := system.NewEntityHash()
-	h.Write([]byte(hid))
+	if _, err := h.Write([]byte(info.UniqueID)); err != nil {
+		return "", err
+	}
 	if err := binary.Write(h, binary.LittleEndian, int64(pid)); err != nil {
 		return "", err
 	}
diff --git a/libbeat/ebpf/sys/time.go b/libbeat/ebpf/sys/time.go
index 630b0a563178..7dca6454c328 100644
--- a/libbeat/ebpf/sys/time.go
+++ b/libbeat/ebpf/sys/time.go
@@ -26,35 +26,19 @@ import (
 	"github.com/tklauser/go-sysconf"
 )
 
-type ticksPerSecond struct {
-	value uint64
-	err   error
-}
-
 var (
-	tps = sync.OnceValue(func() ticksPerSecond {
+	ticksPerSecondOnce = sync.OnceValues(func() (uint64, error) {
 		ticks, err := sysconf.Sysconf(sysconf.SC_CLK_TCK)
 		if err != nil {
-			return ticksPerSecond{
-				value: 0,
-				err:   err,
-			}
+			return 0, err
 		}
 
-		return ticksPerSecond{
-			value: uint64(ticks),
-			err:   err,
-		}
+		return uint64(ticks), err
 	})
 )
 
-func TicksPerSecond() (uint64, error) {
-	ticks := tps()
-	return ticks.value, ticks.err
-}
-
 func TicksToNs(ticks uint64) (uint64, error) {
-	tps, err := TicksPerSecond()
+	tps, err := ticksPerSecondOnce()
 	if err != nil {
 		return 0, err
 	}
@@ -63,7 +47,7 @@ func TicksToNs(ticks uint64) (uint64, error) {
 }
 
 func TimeFromNsSinceBoot(ns uint64) (time.Time, error) {
-	_, bt, err := HostInfo()
+	info, err := hostInfoOnce()
 	if err != nil {
 		return time.Time{}, err
 	}
@@ -73,7 +57,7 @@ func TimeFromNsSinceBoot(ns uint64) (time.Time, error) {
 		return time.Time{}, err
 	}
 
-	return bt.Add(time.Duration(reduced)), nil
+	return info.BootTime.Add(time.Duration(reduced)), nil
 }
 
 // When generating an `entity_id` in ECS we need to reduce the precision of a
@@ -81,7 +65,7 @@ func TimeFromNsSinceBoot(ns uint64) (time.Time, error) {
 // eBPF (high precision) or other sources. We must reduce them all to the
 // lowest common denominator such that entity ID's generated are always consistent.
 func reduceTimestampPrecision(ns uint64) (uint64, error) {
-	tps, err := TicksPerSecond()
+	tps, err := ticksPerSecondOnce()
 	if err != nil {
 		return 0, err
 	}