[Elastic-Agent] Use internal port for local fleet server #28993

michalpristas · 2021-11-16T08:59:15Z

What does this PR do?

What this PR solves is a problem when agent got unenrolled on heavier load when agent managing fleet server cannot checkin to it's own server so it will fallback to unenroll.

Problem is solved by adding internal endpoint which is used for communication on local network (with agent handling fleet server)
It lets FS to spin up 2 set of handlers, one on public 8220 and one on port defined in config.

Why is it important?

Prevents unwanted un-enrolls of the most important agent in deployment

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.

How to test this PR locally

This needs to be tested with work on fleet-server Link: elastic/fleet-server#880

Start stack
Install agent with FS in a policy
Check ports

sh-3.2# lsof -i -P | grep LISTEN | grep fleet
fleet-ser  7056            root   19u  IPv4 0xba7881a9227099a5      0t0    TCP localhost:{random_port} (LISTEN)
fleet-ser  7056            root   21u  IPv6 0xba7881a91284721d      0t0    TCP *:8220 (LISTEN)

run wireshark, set filter to random port, there should be some comm
set filter to 8220 port, there should be no comm
enroll new agent, from another VM
there should be some comm on both ports

elasticmachine · 2021-11-16T09:52:38Z

Pinging @elastic/elastic-agent-control-plane (Team:Elastic-Agent-Control-Plane)

elasticmachine · 2021-11-16T10:27:52Z

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…endpoint

ruflin

Can you share your thoughts on why you made port and host configurable?

ruflin · 2021-11-17T14:26:27Z

x-pack/elastic-agent/pkg/agent/cmd/enroll.go

@@ -308,6 +311,24 @@ func enroll(streams *cli.IOStreams, cmd *cobra.Command, args []string) error {

 	ctx := handleSignal(context.Background())

+	if localFleetServer := fServer != ""; localFleetServer {


Could you move this to a separate function and then have some unit tests on it to validate the behaviour?

I think that port should be configurable. What if the user is already using that port for any other process running?

Further down a random port is selected that is free. So this conflict should never happen.

This line is really hard to understand. Can you break it up somehow?

i made it configurable to make the option available for configuring port. if user wants to have it on some managed port. i can take it out if that's something not important atm.

ruflin · 2021-11-17T14:27:00Z

x-pack/elastic-agent/pkg/agent/cmd/enroll.go

@@ -308,6 +311,24 @@ func enroll(streams *cli.IOStreams, cmd *cobra.Command, args []string) error {

 	ctx := handleSignal(context.Background())

+	if localFleetServer := fServer != ""; localFleetServer {
+		if fInternalHost == "" {


What is the use case where we would not use localhost? Should we even support something else?

Fleet-server and its own Elastic Agent are always gonna be on the same host aren't they?

It must be on the same host. Elastic Agent starts fleet-server as a process.

Then it will always be a localhost communication. Gotcha.

Should always be on localhost, however making it overridable could be useful for testing.

scunningham · 2021-11-17T14:36:06Z

x-pack/elastic-agent/pkg/agent/cmd/enroll.go

@@ -308,6 +311,24 @@ func enroll(streams *cli.IOStreams, cmd *cobra.Command, args []string) error {

 	ctx := handleSignal(context.Background())

+	if localFleetServer := fServer != ""; localFleetServer {


This line is really hard to understand. Can you break it up somehow?

scunningham · 2021-11-17T14:36:48Z

x-pack/elastic-agent/pkg/agent/cmd/enroll.go

@@ -308,6 +311,24 @@ func enroll(streams *cli.IOStreams, cmd *cobra.Command, args []string) error {

 	ctx := handleSignal(context.Background())

+	if localFleetServer := fServer != ""; localFleetServer {
+		if fInternalHost == "" {


Should always be on localhost, however making it overridable could be useful for testing.

scunningham · 2021-11-17T14:42:34Z

x-pack/elastic-agent/pkg/agent/cmd/enroll.go

@@ -384,3 +407,19 @@ func mapFromEnvList(envList []string) map[string]string {
 	}
 	return m
 }
+
+func getRandomPort() (uint16, error) {


This works on all os's? Seems risky to me. Assuming that the OS will allow a rebind in a short period of time and/or won't decide to be aggressive and reuse port elsewhere.

Can we just default to 8221 or something?

i was thinking also about reversal flow, and if we agree that having this configurable is ok.
8221 is ok as well, seems it's not used by a lot of services. initially i wanted to avoid low ports, but i'm ok with this as well

scunningham · 2021-11-18T16:09:44Z

x-pack/elastic-agent/spec/fleet-server.yml

@@ -32,6 +32,8 @@ rules:
      selectors:
        - fleet.server.host
        - fleet.server.port
+        - fleet.server.internal_host


still need this?

nope, thanks

ruflin

I'm ok with exposing the internal fleet-server port as it can help for testing. But lets make sure we note that it is unsupported in production in our docs and the log files. Users should NOT use this flag.

ruflin · 2021-11-19T08:41:45Z

x-pack/elastic-agent/pkg/agent/cmd/enroll_cmd.go

@@ -401,6 +405,11 @@ func (c *enrollCmd) prepareFleetTLS() error {
 	if c.options.URL == "" {
 		return errors.New("url is required when a certificate is provided")
 	}
+
+	if c.options.FleetServer.InternalPort > 0 {
+		c.options.InternalURL = fmt.Sprintf("%s:%d", defaultFleetServerInternalHost, c.options.FleetServer.InternalPort)


Can we add a long entry here which internal port is used and that this is not "officially" supported?

i can put it there, but as soon as you have something on a machine which binds this port there needs to be official workaround and i think this is it

Lets wait until this happens. Having the log message and user pinging us on it will also help us detect if this might become a common problem and the port we selected is not ideal.

ruflin · 2021-11-19T08:44:46Z

x-pack/elastic-agent/pkg/agent/cmd/enroll_cmd.go

@@ -865,6 +878,9 @@ func createFleetServerBootstrapConfig(
 	if port == 0 {
 		port = defaultFleetServerPort
 	}
+	if internalPort <= 0 {
+		port = defaultFleetServerInternalPort


Shouldn't this be if internalPort > 0 { internalPort = defaultFleetServerInternalPort } ?

your condition sets default for a case when somebody tried to configure it

🤦‍♂️ Yes. Why is it that on line 878 we have == and here <=?

But I think the second part still holds, this should be assigned to internalPort and not port? Maybe I'm blind here too :-D

ruflin · 2021-11-19T08:47:16Z

x-pack/elastic-agent/pkg/agent/cmd/enroll_cmd.go

+	defaultFleetServerHost         = "0.0.0.0"
+	defaultFleetServerPort         = 8220
+	defaultFleetServerInternalHost = "localhost"
+	defaultFleetServerInternalPort = 8221


Lets make sure we document this internal as needed by fleet-server. @jlind23 Can you make sure we follow up on this? We also need to have this in the changelog as if by chance someone uses this port already on the machine, it would break things (hopefully unlikely).

@ruflin Where should it be documented though?

Two ideas:

https://www.elastic.co/guide/en/fleet/current/fleet-faq.html

https://www.elastic.co/guide/en/fleet/master/fleet-troubleshooting.html

@bmorelli25 Where would these internal docs around elastic-agent and fleet-server fit best?

This is @dedemorton's territory. DeDe, can you take a look?

OK, so it sounds like you don't want to document the internal port setting in the main docs (command reference + Fleet Server settings) because users will not set it in a production environment. It also sounds like we're covered for the situation where the port is already in use (the code will select an unused port when there's a conflict).

I'd like to understand specific use cases for this setting, though, because I'm always suspicious of hidden settings that we don't want to document for users. We have a lot of users who are on the support team and might look in the reference first. My preference is to have reference docs that are complete, but to make the usage clear in the description.

Sounds like it also makes sense to cover this setting in the troubleshooting docs, but we need to explain when/why to change this setting during testing.

We could also mention in the Fleet Server docs that Fleet Server uses port 8221 internally, but will look for another port if that one isn't available.

It will not look for antoher port. We might want to use the port for testing purpose or as an escape hatch if indeed a user has a conflict.

There might we 2 things we should document:

Architecture / Internals: What port is used for internal communication -> public

Hidden config to change it -> developer focus, mentioned that not officially supported

ruflin

LGTM. Only comment left is around the log message.

[Elastic-Agent] IUse itnernal port for local fleet server (#28993) (cherry picked from commit 9b154ad)

…ws-on-file-changes * upstream/master: override host on statsd metricset (elastic#29103) Skip config check in autodiscover for duplicated configurations (elastic#29048) Change "filebeat.config.modules.enabled" to "true" (elastic#28769) Remove deprecated spool queue from Beats (elastic#28869) Add `beat` field back to beat.stats (elastic#29094) Revert "Move labels and annotations under kubernetes.namespace. (elastic#27917)" (elastic#29069) heartbeat: remove w2008 in the CI (elastic#29093) Remove deprecated `--template` and `--index-policy` flags (elastic#28870) Fix parsing of apache trace log levels (elastic#28717) [Elastic-Agent] IUse itnernal port for local fleet server (elastic#28993) [Heartbeat] Log error on dupe monitor ID instead of strict req (elastic#29041) Enable pprof for elastic-agent and beats (elastic#28983)

[Elastic-Agent] IUse itnernal port for local fleet server (#28993) (cherry picked from commit 9b154ad)

…29088) [Elastic-Agent] IUse itnernal port for local fleet server (#28993) (cherry picked from commit 9b154ad) Co-authored-by: Michal Pristas <[email protected]>

…29320) [Elastic-Agent] IUse itnernal port for local fleet server (#28993) (cherry picked from commit 9b154ad) Co-authored-by: Michal Pristas <[email protected]>

use itnernal port for local fleet server

f223462

michalpristas added bug backport-v7.16.0 Automated backport with mergify labels Nov 16, 2021

michalpristas self-assigned this Nov 16, 2021

botelastic bot added the needs_team Indicates that the issue/PR needs a Team:* label label Nov 16, 2021

michalpristas mentioned this pull request Nov 16, 2021

Multiple endpoints elastic/fleet-server#880

Merged

5 tasks

jlind23 added the Team:Elastic-Agent-Control-Plane Label for the Agent Control Plane team label Nov 16, 2021

botelastic bot removed the needs_team Indicates that the issue/PR needs a Team:* label label Nov 16, 2021

Merge branch 'master' of github.com:elastic/beats into use-secondary-…

cfcc3f0

…endpoint

jlind23 requested review from ruflin and lykkin November 17, 2021 08:28

ruflin requested review from scunningham and aleksmaus November 17, 2021 14:21

ruflin reviewed Nov 17, 2021

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scunningham suggested changes Nov 17, 2021

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jlind23 added the v8.0.0 label Nov 17, 2021

internal on localhost

f9a3e4b

scunningham approved these changes Nov 18, 2021

View reviewed changes

remove unwanted exports from spec

fa9f592

ruflin reviewed Nov 19, 2021

View reviewed changes

fixed override

3607c83

ruflin approved these changes Nov 19, 2021

View reviewed changes

michalpristas added 2 commits November 19, 2021 14:50

log message

27400e8

log level

778c564

michalpristas merged commit 9b154ad into elastic:master Nov 23, 2021

mergify bot pushed a commit that referenced this pull request Nov 23, 2021

[Elastic-Agent] IUse itnernal port for local fleet server (#28993)

cb859c6

[Elastic-Agent] IUse itnernal port for local fleet server (#28993) (cherry picked from commit 9b154ad)

mergify bot mentioned this pull request Nov 23, 2021

[7.16](backport #28993) [Elastic-Agent] IUse itnernal port for local fleet server #29088

Merged

michalpristas changed the title ~~[Elastic-Agent] IUse itnernal port for local fleet server~~ [Elastic-Agent] Use internal port for local fleet server Dec 7, 2021

michalpristas added the backport-v8.0.0 Automated backport with mergify label Dec 7, 2021

mergify bot pushed a commit that referenced this pull request Dec 7, 2021

[Elastic-Agent] IUse itnernal port for local fleet server (#28993)

2ad47f8

[Elastic-Agent] IUse itnernal port for local fleet server (#28993) (cherry picked from commit 9b154ad)

mergify bot mentioned this pull request Dec 7, 2021

[8.0](backport #28993) [Elastic-Agent] Use internal port for local fleet server #29320

Merged

		@@ -308,6 +311,24 @@ func enroll(streams cli.IOStreams, cmd cobra.Command, args []string) error {

		ctx := handleSignal(context.Background())

		if localFleetServer := fServer != ""; localFleetServer {

[Elastic-Agent] Use internal port for local fleet server #28993

[Elastic-Agent] Use internal port for local fleet server #28993

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michalpristas commented Nov 16, 2021 • edited Loading

What does this PR do?

Why is it important?

Checklist

How to test this PR locally

elasticmachine commented Nov 16, 2021

elasticmachine commented Nov 16, 2021 • edited by jenkins-beats-ci bot Loading

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michalpristas commented Nov 16, 2021 •

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elasticmachine commented Nov 16, 2021 •

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michalpristas Nov 18, 2021 •

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