Uninitialized userSet in metricbeatInit causing missing process metrics

[kevinsmithwrs]

• Version: Metricbeat 8.6 (but applicable to 8.2+ I believe)
• Operating System: Linux, k8s + docker
• Steps to Reproduce:
• Enable system module process metricset, set hostfs: /hostfs, do not set --system.hostfs=/hostfs CLI flag.

I think the Initialization of userSet is missing in metricbeatInit in metricbeat/internal/sysinit/init.go. My understanding is we shouldn't need to set the deprecated --system.hostfs=/hostfs parameter when launching metricbeat, in favour of using the hostfs settings in the individual module metricsets (process, linux, etc) in 8.x. If I do this however, we end up missing some process metrics. The cause is the uninitialized userSet bool, (which then defaults to false) . This is incorrect if the hostfs module setting has been set. In a docker/kubernetes environment, the below check in metricbeat/module/system/process/process.go uses this (incorrect) false for sys.IsSet() resulting in the value for LIBBEAT_MONITORING_CGROUPS_HIERARCHY_OVERRIDE being used, which is set to '/' in the elastic metricbeat docker images thereby overriding the cgroup heirarchy.

As a workaround, I can get all process metrics to come out properly by setting the CLI flag, the proper /hostfs settings in the module, and setting LIBBEAT_MONITORING_CGROUPS_HIERARCHY_OVERRIDE to "" when launching the metricbeat container.

metricbeat/module/system/process/process.go:

if !sys.IsSet() {
    override, isset := os.LookupEnv("LIBBEAT_MONITORING_CGROUPS_HIERARCHY_OVERRIDE")
        if isset {
            m.stats.CgroupOpts.CgroupsHierarchyOverride = override
        }
}

Fix needed in metricbeat/internal/sysinit/init.go:

// Deal with the legacy configs available to metricbeat
 func metricbeatInit(base mb.BaseModule, modulePath string, moduleSet bool) (mb.Module, error) {
        var hostfs = modulePath
-       var userSet bool
+       var userSet = moduleSet
        // allow the CLI to override other settings
        if hostfsCLI != nil && *hostfsCLI != "" {
                cfgwarn.Deprecate("8.0.0", "The --system.hostfs flag will be removed in the future and replaced by a config value.")
	once.Do(func() {
		InitModule(hostfs)
	})
	return &Module{BaseModule: base, HostFS: hostfs, UserSetHostFS: userSet}, nil

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[botelastic[bot]]

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