[monitoring] - add options for specifying registry (#205)

As of now, we use global namespace to create registry and report process
and system metrics on that. This PR adds option to specify our custom
registry.
It is intended to be used by beat receivers, so that there is a unique
process and system registry under per-beat namespace to avoid conflicts.

Relates: elastic/ingest-dev#5136

Author: VihasMakwana

report/setup.go

@@ -40,14 +40,40 @@ func init() {
 	systemMetrics = monitoring.Default.NewRegistry("system")
 }
 
+type option struct {
+	systemMetrics  *monitoring.Registry
+	processMetrics *monitoring.Registry
+}
+
+type OptionFunc func(o *option)
+
+func WithProcessRegistry(r *monitoring.Registry) OptionFunc {
+	return func(o *option) {
+		o.processMetrics = r
+	}
+}
+
+func WithSystemRegistry(r *monitoring.Registry) OptionFunc {
+	return func(o *option) {
+		o.systemMetrics = r
+	}
+}
+
 // monitoringCgroupsHierarchyOverride is an undocumented environment variable which
 // overrides the cgroups path under /sys/fs/cgroup, which should be set to "/" when running
 // Elastic Agent under Docker.
 const monitoringCgroupsHierarchyOverride = "LIBBEAT_MONITORING_CGROUPS_HIERARCHY_OVERRIDE"
 
 // SetupMetrics creates a basic suite of metrics handlers for monitoring, including build info and system resources
-func SetupMetrics(logger *logp.Logger, name, version string) error {
-	monitoring.NewFunc(systemMetrics, "cpu", ReportSystemCPUUsage, monitoring.Report)
+func SetupMetrics(logger *logp.Logger, name, version string, opts ...OptionFunc) error {
+	opt := &option{
+		systemMetrics:  systemMetrics,
+		processMetrics: processMetrics,
+	}
+	for _, o := range opts {
+		o(opt)
+	}
+	monitoring.NewFunc(opt.systemMetrics, "cpu", ReportSystemCPUUsage, monitoring.Report)
 
 	name = processName(name)
 	processStats = &process.Stats{
@@ -63,12 +89,12 @@ func SetupMetrics(logger *logp.Logger, name, version string) error {
 		return fmt.Errorf("failed to init process stats for agent: %w", err)
 	}
 
-	monitoring.NewFunc(processMetrics, "memstats", MemStatsReporter(logger, processStats), monitoring.Report)
-	monitoring.NewFunc(processMetrics, "cpu", InstanceCPUReporter(logger, processStats), monitoring.Report)
-	monitoring.NewFunc(processMetrics, "runtime", ReportRuntime, monitoring.Report)
-	monitoring.NewFunc(processMetrics, "info", infoReporter(name, version), monitoring.Report)
+	monitoring.NewFunc(opt.processMetrics, "memstats", MemStatsReporter(logger, processStats), monitoring.Report)
+	monitoring.NewFunc(opt.processMetrics, "cpu", InstanceCPUReporter(logger, processStats), monitoring.Report)
+	monitoring.NewFunc(opt.processMetrics, "runtime", ReportRuntime, monitoring.Report)
+	monitoring.NewFunc(opt.processMetrics, "info", infoReporter(name, version), monitoring.Report)
 
-	setupPlatformSpecificMetrics(logger, processStats)
+	setupPlatformSpecificMetrics(logger, processStats, systemMetrics, processMetrics)
 
 	return nil
 }
@@ -111,7 +137,7 @@ func infoReporter(serviceName, version string) func(_ monitoring.Mode, V monitor
 	}
 }
 
-func setupPlatformSpecificMetrics(logger *logp.Logger, processStats *process.Stats) {
+func setupPlatformSpecificMetrics(logger *logp.Logger, processStats *process.Stats, systemMetrics, processMetrics *monitoring.Registry) {
 	if isLinux() {
 		monitoring.NewFunc(processMetrics, "cgroup", InstanceCroupsReporter(logger, monitoringCgroupsHierarchyOverride), monitoring.Report)
 	}