[hosts] Add troubleshooting section with info on hosts detected by APM (

#4276)

* add troublshooting section

* address feedback from @roshan-elastic

* add to serverless docs

* apply suggestions from code review

Co-authored-by: Mike Birnstiehl <[email protected]>

---------

Co-authored-by: Mike Birnstiehl <[email protected]>

docs/en/observability/monitor-infra/analyze-hosts.asciidoc

@@ -256,3 +256,45 @@ to determine if there is an outage or issue.
 
 [role="screenshot"]
 image::images/hosts-dashed-and-missing.png[Screenshot showing dashed lines and missing data]
+
+[discrete]
+[[analyze-hosts-troubleshooting]]
+== Troubleshooting
+
+////
+Troubleshooting topic template:
+
+Title: Brief description of what the user sees/experiences
+Content:
+1. What the user sees/experiences (error message, UI, behavior, etc)
+2. Why it happens
+3. How to fix it
+////
+
+[discrete]
+[[analyze-hosts-troubleshooting-detected-by-apm]]
+===  What does _this host has been detected by APM_ mean?
+
+// What the user sees/experiences (error message, UI, behavior, etc)
+In the Hosts view, you might see a question mark icon (image:images/icons/questionInCircle.svg[Question mark icon])
+before a host name with a tooltip note stating that the host has been detected by APM.
+// Why it happens
+When a host is detected by APM, but is not collecting full metrics
+(for example, through the https://www.elastic.co/docs/current/integrations/system[system integration]),
+it will be listed as a host with the partial metrics collected by APM.
+
+// How to fix it
+// N/A?
+
+[discrete]
+[[analyze-hosts-troubleshooting-fix-host-name]]
+// What the user sees/experiences (error message, UI, behavior, etc)
+=== I don't recognize a host name and I see a question mark icon next to it
+
+// Why it happens
+This could mean that the APM agent has not been configured to use the correct host name.
+Instead, the host name might be the container name or the Kubernetes pod name.
+
+// How to fix it
+To get the correct host name, you need to set some additional configuration options,
+specifically `system.kubernetes.node.name` as described in <<apm-api-kubernetes-data>>.

docs/en/serverless/infra-monitoring/analyze-hosts.mdx

@@ -266,3 +266,38 @@ Similar to the above scenario, you may want to investigate the time period with
 to determine if there is an outage or issue.
 
 ![Screenshot showing dashed lines and missing data](../images/hosts-dashed-and-missing.png)
+
+## Troubleshooting
+
+{/*
+Troubleshooting topic template:
+Title: Brief description of what the user sees/experiences
+Content:
+1. What the user sees/experiences (error message, UI, behavior, etc)
+2. Why it happens
+3. How to fix it
+*/}
+
+### What does _this host has been detected by APM_ mean?
+
+{/* What the user sees/experiences (error message, UI, behavior, etc) */}
+In the Hosts view, you might see a question mark icon (<DocIcon type="questionInCircle" title="Question mark icon" />)
+before a host name with a tooltip note stating that the host has been detected by APM.
+{/* Why it happens */}
+When a host is detected by APM, but is not collecting full metrics
+(for example, through the <DocLink slug="/integrations/system">system integration</DocLink>),
+it will be listed as a host with the partial metrics collected by APM.
+
+{/* How to fix it */}
+{/* N/A? */}
+
+{/* What the user sees/experiences (error message, UI, behavior, etc) */}
+### I don't recognize a host name and I see a question mark icon next to it
+
+{/* Why it happens */}
+This could mean that the APM agent has not been configured to use the correct host name.
+Instead, the host name might be the container name or the Kubernetes pod name.
+
+{/* How to fix it */}
+To get the correct host name, you need to set some additional configuration options,
+specifically `system.kubernetes.node.name` as described in <DocLink slug="/serverless/observability/apm-server-api" section="kubernetes-data">Kubernetes data</DocLink>.