Remove agent.hostname field from libbeat

[andrewkroh]

What does this PR do?

agent.hostname is not part of ECS so this removes the field. Instead the
agent.name field can be used for this purpose and it it part of ECS.
This add an alias pointing from agent.hostname to agent.name. The alias
can be removed once we confirm all the Kibana apps are migrated to agent.name
for 8.0.

This will not be part of 7.x.

Why is it important?

From #16377

Specifically, a new field agent.hostname was introduced - however this field is not an ECS field, and it's continued use and documentation are creating user confusion.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• [ ] I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Related issues

Closes #16377

[elasticmachine]

Pinging @elastic/siem (Team:SIEM)

[elasticmachine]

💚 Build Succeeded

Expand to view the summary

Build stats

• Build Cause: [andrewkroh commented: run tests]

• Start Time: 2020-05-12T13:16:57.670+0000

• Duration: 92 min 22 sec (5541891)

Test stats 🧪

Test	Results
Failed	0
Passed	7769
Skipped	1236
Total	9005

Steps errors

Expand to view the steps failures

• Name: Report to Codecov

  • Description: curl -sSLo codecov https://codecov.io/bash for i in auditbeat filebeat heartbeat libbeat metricbeat packetbeat winlogbeat journalbeat do FILE="${i}/build/coverage/full.cov" if [ -f "${FILE}" ]; then bash codecov -f "${FILE}" fi done

  • Result: FAILURE

  • Duration: 2 min 22 sec

  • Start Time: 2020-05-12T14:25:20.716+0000

  • log

[andrewkroh]

I created #18329 to track removing the old 6.x-to-7.0 migration aliases.

[elasticmachine]

Pinging @elastic/integrations-services (Team:Services)

[exekias]

nice!

[exekias]

I wonder if we want to keep an alias, is this used by any UI?

[andrewkroh]

There is at least one place using agent.hostname in Kibana. There may be more instances. So I'll remove the migration tag so that the alias always exists (at least until we can confirm all of Kibana is updated in 8.0).

I'll ask the uptime team if they can update 8.0 to use agent.name.

https://github.com/elastic/kibana/blob/523926f0a49a5bd951ed0e056610b049482adbca/x-pack/plugins/uptime/common/runtime_types/ping/ping.ts#L58

[exekias]

cc @andrewvc

[exekias]

Thank you for tackling this! PR is looking good to me, just left a question on keeping the alias or not

[andrewkroh]

run tests

[kaiyan-sheng]

We are considering removing agent.hostname from libbeat for 8.0. @simianhacker Do you know if this field is still used by Kibana metrics UI?

[simianhacker]

@kaiyan-sheng We are not using agent.hostname

[kaiyan-sheng]

Thank you!! @simianhacker We will add removing agent.hostname to our todo list for 8.0 then.