Implement keepalived load balancer #4344

juanluisvaladas · 2024-04-29T11:57:09Z

Description

For easier review I split the PR in 5 commits:
1- Add API types and autogenerated code
2- Controller changes to make keepalived work
3- Updated inttest
4- Encapsulate keepalived config in a new struct
5- Documentations

I also found a typo so I sneaked in a tiny 1 line commit

This is part of #4181

Type of change

Bug fix (non-breaking change which fixes an issue)
New feature (non-breaking change which adds functionality)
Breaking change (fix or feature that would cause existing functionality to not work as expected)
Documentation update

How Has This Been Tested?

Manual test
Auto test added

Checklist:

jnummelin · 2024-05-02T09:26:23Z

cmd/controller/controller.go

@@ -232,11 +232,16 @@ func (c *command) start(ctx context.Context) error {
 		if c.SingleNode {
 			return errors.New("control plane load balancing cannot be used in a single-node cluster")
 		}
+		if cplb.Type != v1beta1.CPLBTypeKeepalived {


IMO we should do this in config validation already.

Agreed, this is done in a separate commit because rewriting the git history was quite complex...

jnummelin · 2024-05-02T09:27:42Z

docs/cplb.md

@@ -3,17 +3,23 @@
 For clusters that don't have an [externally managed load balancer](high-availability.md#load-balancer) for the k0s
 control plane, there is another option to get a highly available control plane called control plane load balancing (CPLB).

-CPLB allows automatic assigned of predefined IP addresses using VRRP across masters.
+CPLB has two features that often will be combined, but normally will be used together: VRRP Instances, which allows


CPLB has two features that often will be combined, but normally will be used together

This doesn't sound right 😄

It doesn't 😅 . Fixed

jnummelin · 2024-05-02T09:29:34Z

docs/cplb.md

+* If `VirtualServers` are used, the cluster configuration doesn't specify a non-empty
+  [`spec.api.externalAddress`][specapi]. `VRRPInstances` are compatible.


hmm, I don't really get what this means. Could you rephrase this a bit

I rephrased it, please review it again, I think it's better now but I'm not quite convinced to be honest

pkg/apis/k0s/v1beta1/cplb.go

pkg/component/controller/cplb_reconciler.go

jnummelin · 2024-05-02T09:45:14Z

pkg/component/controller/cplb_reconciler.go

+
+func (r *CPLBReconciler) watchAPIServers(ctx context.Context) {
+	// Before starting check that the API is actually responding
+	for {


Maybe we could utilize our internal watch helper here? IMO would be much simpler and that already handles retries etc.

Changed this as a separate commit. Can be squashed.

pkg/component/controller/cplb_reconciler.go

jnummelin · 2024-05-02T09:49:41Z

pkg/component/controller/cplb_unix.go

+		if err := k.configureDummy(); err != nil {
+			return fmt.Errorf("failed to configure dummy interface: %w", err)
+		}
+		if err := k.Config.ValidateVRRPInstances(nil); err != nil {


Again, IMO we need to hook validation to general config validation "phase"

Agreed, it's added as a separate commit because rewriting the git history wasn't easy...

pkg/component/controller/cplb_unix.go

pkg/apis/k0s/v1beta1/cplb.go

juanluisvaladas · 2024-05-02T12:03:22Z

Converting to draft while I address the concerns.

pkg/component/controller/cplb_unix.go

pkg/apis/k0s/v1beta1/cplb.go

pkg/component/controller/cplb_reconciler.go

docs/cplb.md

pkg/component/controller/cplb_unix.go

pkg/supervisor/supervisor.go

pkg/component/controller/cplb_reconciler.go

twz123 · 2024-05-03T10:57:08Z

pkg/component/controller/cplb_unix.go

+	// Wait for the supervisor to start keepalived before
+	// watching for endpoint changes
+	process := k.supervisor.GetProcess()
+	for process == nil {
+		k.log.Info("Waiting for keepalived to start")
+		time.Sleep(5 * time.Second)
+		process = k.supervisor.GetProcess()
+	}


It might work without this loop, if the nil check would be moved into the update loop.

If you feel strongly about it, I will change it, but I prefer it this way.

Even if the process is dead, s.GetProcess won't return nil once keepalived is started the first time, it will just return a process with an invalid PID. Adding it into the loop means we're doing a check that will always return false. Also we don't care if the PID is of an older dead process because the PID is obtained AFTER writing the template which means the new process will be using the new file.

But if you feel very strongly about it I'll move the nil check inside, there aren't big consecuences anyway, maybe faster reloads when the cluster is bootstrapping.

If you feel strongly about it, I will change it, but I prefer it this way.

Currently, the loop cannot be cancelled externally. That's why I figured that we could just inline the nil check below. Would be less code, too. I'm fine with keeping it, as long as it can be cancelled.

it will just return a process with an invalid PID

Right. I'd argue that this is a current shortcoming of Supervisor, though.

@twz123 I accidentally editted your comment with my reply 🤦

The reply is:

I added a limit of 6 times, that's 30 seconds and should be way more than enough time to start keepalived. It gets cancelled eventually, it's not the prettiest but should fix the problem.

Unfortunatelly I deleted your comment saying that it had to be possible to cancel it from the outside.

Unfortunatelly I deleted your comment saying that it had to be possible to cancel it from the outside.

Restored it from the history 🙃

Signed-off-by: Juan-Luis de Sousa-Valadas Castaño <[email protected]>

pkg/apis/k0s/v1beta1/cplb.go

twz123 · 2024-05-07T10:10:40Z

pkg/apis/k0s/v1beta1/cplb.go

+	TUNLBKind KeepalivedLBKind = "TUN"
+)
+
+type RealServer struct {


Are they? Still not able to spot them 🙈

twz123 · 2024-05-07T10:31:50Z

pkg/component/controller/cplb_unix.go

@@ -108,6 +140,10 @@ func (k *Keepalived) Start(_ context.Context) error {
 		DataDir: k.K0sVars.DataDir,
 		UID:     k.uid,
 	}
+
+	if len(k.Config.VirtualServers) > 0 {
+		go k.watchReconcilerUpdates()


I cannot spot it. Can you verify?

twz123 · 2024-05-07T10:41:05Z

pkg/component/controller/cplb_unix.go

+	// Wait for the supervisor to start keepalived before
+	// watching for endpoint changes
+	process := k.supervisor.GetProcess()
+	for process == nil {
+		k.log.Info("Waiting for keepalived to start")
+		time.Sleep(5 * time.Second)
+		process = k.supervisor.GetProcess()
+	}


If you feel strongly about it, I will change it, but I prefer it this way.

Currently, the loop cannot be cancelled externally. That's why I figured that we could just inline the nil check below. Would be less code, too. I'm fine with keeping it, as long as it can be cancelled.

it will just return a process with an invalid PID

Right. I'd argue that this is a current shortcoming of Supervisor, though.

pkg/apis/k0s/v1beta1/cplb.go

pkg/component/controller/cplb_unix.go

juanluisvaladas · 2024-05-07T11:45:55Z

Everything should be addressed now

twz123

One last thing™. I think we can just omit the delay_loop if it's zero.

twz123 · 2024-05-07T12:36:07Z

pkg/component/controller/cplb_unix.go

+{{ if gt (len $RealServers) 0 }}
+{{ range .VirtualServers }}
+virtual_server {{ .IPAddress }} {{ $APIServerPort }} {
+    delay_loop {{ .DelayLoop.Seconds }}


Suggested change

delay_loop {{ .DelayLoop.Seconds }}

{{- if gt .DelayLoop.Seconds 0.0 }}

delay_loop {{ .DelayLoop.Seconds }}

{{- end }}

We can't. In keepalived it defaults to 60. I set it to 0 because I think it doesn't make sense to delay it at all in CPLB because it's added after kubernetes.default.svc is reconciled and hence has passed all the relevant health local health checks.

We can't in keepalived it defaults to 60.

I see. Apparently I found yet another delay_loop in the keepalived codebase 😅

I set it to 0 because I think it doesn't make sense to delay it at all in CPLB because it's added after kubernetes.default.svc is reconciled and hence has passed all the relevant health local health checks.

I don't fully understand the implications, but a delay_loop of 0 is not a thing in keepalived (it will use the default of 60, then):

# /var/lib/k0s/bin/keepalived --dont-fork --use-file /run/k0s/keepalived.conf --no-syslog --log-console --log-detail --dump-conf -t (/run/k0s/keepalived.conf: Line 33) number '0' outside range [0.000001, 18446744073709.551614] (/run/k0s/keepalived.conf: Line 33) virtual server delay loop '0' invalid - ignoring

But letz address this in a subsequent PR 😄

pkg/apis/k0s/v1beta1/cplb.go

docs/configuration.md

pkg/apis/k0s/v1beta1/cplb.go

And move validation to clusterconfig. Signed-off-by: Juan-Luis de Sousa-Valadas Castaño <[email protected]>

Signed-off-by: Juan-Luis de Sousa-Valadas Castaño <[email protected]>

The field wasn't required and didn't serve any actual purpose, so remove it and auto generate it always. Signed-off-by: Juan-Luis de Sousa-Valadas Castaño <[email protected]>

Signed-off-by: Juan-Luis de Sousa-Valadas Castaño <[email protected]>

Co-authored-by: Tom Wieczorek <[email protected]> Signed-off-by: Juan-Luis de Sousa-Valadas Castaño <[email protected]>

juanluisvaladas force-pushed the k0s-lb-2 branch from 62f99f7 to 0d7de41 Compare April 29, 2024 14:06

jnummelin added this to the 1.30 milestone Apr 29, 2024

juanluisvaladas force-pushed the k0s-lb-2 branch 8 times, most recently from 7c5ef55 to 0871a4b Compare April 30, 2024 15:03

juanluisvaladas mentioned this pull request Apr 30, 2024

Keepalived support #4181

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juanluisvaladas force-pushed the k0s-lb-2 branch 2 times, most recently from 7406008 to d5797f1 Compare April 30, 2024 15:29

juanluisvaladas marked this pull request as ready for review April 30, 2024 15:31

juanluisvaladas requested a review from a team as a code owner April 30, 2024 15:31

juanluisvaladas requested review from ncopa and twz123 April 30, 2024 15:31

juanluisvaladas force-pushed the k0s-lb-2 branch from d5797f1 to 6c6c346 Compare May 2, 2024 08:32

jnummelin reviewed May 2, 2024

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juanluisvaladas marked this pull request as draft May 2, 2024 12:03

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juanluisvaladas force-pushed the k0s-lb-2 branch from 2e89b58 to f103344 Compare May 6, 2024 13:54

Implement CPLB virtualServers and reconciler

c3a0a58

Signed-off-by: Juan-Luis de Sousa-Valadas Castaño <[email protected]>

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juanluisvaladas force-pushed the k0s-lb-2 branch from fb7b554 to 9ca23a5 Compare May 7, 2024 14:18

juanluisvaladas and others added 10 commits May 7, 2024 16:47

Extract keepalived configuration to a subtype

661ef19

And move validation to clusterconfig. Signed-off-by: Juan-Luis de Sousa-Valadas Castaño <[email protected]>

Implement VirtualServers inttest

30966db

Signed-off-by: Juan-Luis de Sousa-Valadas Castaño <[email protected]>

Add VirtualServer docs and fix Keepalived subtype

d61005e

Signed-off-by: Juan-Luis de Sousa-Valadas Castaño <[email protected]>

Automatically add virtualIPs to apiserver SANs

2619364

Signed-off-by: Juan-Luis de Sousa-Valadas Castaño <[email protected]>

Remove VRRPInstances.Name

9175b9f

The field wasn't required and didn't serve any actual purpose, so remove it and auto generate it always. Signed-off-by: Juan-Luis de Sousa-Valadas Castaño <[email protected]>

Remove ControlPlaneLoadBalancing from dynamic conf

8d57249

Signed-off-by: Juan-Luis de Sousa-Valadas Castaño <[email protected]>

Make CPLB.VirtualServers.DelayLoop metav1.Duration

d5d7f1a

Signed-off-by: Juan-Luis de Sousa-Valadas Castaño <[email protected]>

Addess multiple mistakes in code review

0e53299

Signed-off-by: Juan-Luis de Sousa-Valadas Castaño <[email protected]>

Remove unused RealServer struct type

c22cbf3

Signed-off-by: Juan-Luis de Sousa-Valadas Castaño <[email protected]>

Fix documentation for Delayloop

18d3583

Co-authored-by: Tom Wieczorek <[email protected]> Signed-off-by: Juan-Luis de Sousa-Valadas Castaño <[email protected]>

juanluisvaladas force-pushed the k0s-lb-2 branch from 9ca23a5 to 18d3583 Compare May 7, 2024 14:47

twz123 approved these changes May 7, 2024

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juanluisvaladas merged commit bb42d03 into k0sproject:main May 7, 2024
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Implement keepalived load balancer #4344

Implement keepalived load balancer #4344

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		* If `VirtualServers` are used, the cluster configuration doesn't specify a non-empty
		[`spec.api.externalAddress`][specapi]. `VRRPInstances` are compatible.

Implement keepalived load balancer #4344

Implement keepalived load balancer #4344

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juanluisvaladas commented Apr 29, 2024 • edited Loading

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