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HDDS-11618. Enable HA modes for OM and SCM #10

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HDDS-11618. Enable HA modes for OM and SCM #10

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d5a2af0
HDDS-11618. Enable HA modes for OM and SCM
pyttel Nov 2, 2024
8c2606c
fixed namespace issue
pyttel Nov 5, 2024
d7e4322
fixed namespace issue
pyttel Nov 6, 2024
4c27e2d
HDDS-11618. First running version of Helm managed OM HA
pyttel Dec 2, 2024
d60087d
HDDS-11618. Removed unused helm manager settings
pyttel Dec 3, 2024
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48 changes: 48 additions & 0 deletions charts/ozone/templates/_helpers.tpl
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,26 @@ app.kubernetes.io/instance: {{ .Release.Name }}
{{- $pods | join "," }}
{{- end }}

{{/* List of comma separated om ids */}}
{{- define "ozone.om.cluster.ids" -}}
{{- $pods := list }}
{{- $replicas := .Values.om.replicas | int }}
{{- range $i := until $replicas }}
{{- $pods = append $pods (printf "ozone-om-%d" $i) }}
{{- end }}
{{- $pods | join "," }}
{{- end }}

{{/* List of comma separated om ids */}}
{{- define "ozone.scm.cluster.ids" -}}
{{- $pods := list }}
{{- $replicas := .Values.scm.replicas | int }}
{{- range $i := until $replicas }}
{{- $pods = append $pods (printf "ozone-scm-%d" $i) }}
{{- end }}
{{- $pods | join "," }}
{{- end }}

{{/* Common configuration environment variables */}}
{{- define "ozone.configuration.env" -}}
- name: OZONE-SITE.XML_hdds.datanode.dir
Expand All @@ -59,14 +79,42 @@ app.kubernetes.io/instance: {{ .Release.Name }}
value: /data
- name: OZONE-SITE.XML_ozone.metadata.dirs
value: /data/metadata
{{- if gt (int .Values.scm.replicas) 1 }}
- name: OZONE-SITE.XML_ozone.scm.ratis.enable
value: "true"
- name: OZONE-SITE.XML_ozone.scm.service.ids
value: cluster1
- name: OZONE-SITE.XML_ozone.scm.nodes.cluster1
value: {{ include "ozone.scm.cluster.ids" . }}
{{- range $i, $val := until ( .Values.scm.replicas | int ) }}
- name: {{ printf "OZONE-SITE.XML_ozone.scm.address.cluster1.ozone-scm-%d" $i }}
value: {{ printf "%s-scm-%d.%s-scm-headless.%s.svc.cluster.local" $.Release.Name $i $.Release.Name $.Release.Namespace }}
{{- end }}
- name: OZONE-SITE.XML_ozone.scm.primordial.node.id
value: "ozone-scm-0"
{{- else }}
- name: OZONE-SITE.XML_ozone.scm.block.client.address
value: {{ include "ozone.scm.pods" . }}
- name: OZONE-SITE.XML_ozone.scm.client.address
value: {{ include "ozone.scm.pods" . }}
- name: OZONE-SITE.XML_ozone.scm.names
value: {{ include "ozone.scm.pods" . }}
{{- end}}
{{- if gt (int .Values.om.replicas) 1 }}
- name: OZONE-SITE.XML_ozone.om.ratis.enable
value: "true"
- name: OZONE-SITE.XML_ozone.om.service.ids
value: cluster1
- name: OZONE-SITE.XML_ozone.om.nodes.cluster1
value: {{ include "ozone.om.cluster.ids" . }}
{{- range $i, $val := until ( .Values.om.replicas | int ) }}
- name: {{ printf "OZONE-SITE.XML_ozone.om.address.cluster1.ozone-om-%d" $i }}
value: {{ printf "%s-om-%d.%s-om-headless.%s.svc.cluster.local" $.Release.Name $i $.Release.Name $.Release.Namespace }}
{{- end }}
{{- else }}
- name: OZONE-SITE.XML_ozone.om.address
value: {{ include "ozone.om.pods" . }}
{{- end}}
- name: OZONE-SITE.XML_hdds.scm.safemode.min.datanode
value: "3"
- name: OZONE-SITE.XML_ozone.datanode.pipeline.limit
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4 changes: 4 additions & 0 deletions charts/ozone/templates/datanode/datanode-service-headless.yaml
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Expand Up @@ -28,6 +28,10 @@ spec:
ports:
- name: ui
port: {{ .Values.datanode.service.port }}
- name: ratis-ipc
port: 9858
- name: ipc
port: 9859
Comment on lines +31 to +34
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@ptlrs ptlrs Nov 7, 2024 •
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Can the port numbers in all the services and statefulsets be referenced from the values.yaml file? We would like to avoid hardcoding them.

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Yes definitely! I just proposed this. This was also my personal question ^^

selector:
{{- include "ozone.selectorLabels" . | nindent 4 }}
app.kubernetes.io/component: datanode
4 changes: 4 additions & 0 deletions charts/ozone/templates/datanode/datanode-statefulset.yaml
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Expand Up @@ -65,6 +65,10 @@ spec:
ports:
- name: ui
containerPort: {{ .Values.datanode.service.port }}
- name: ratis-ipc
containerPort: 9858
- name: ipc
containerPort: 9859
livenessProbe:
httpGet:
path: /
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4 changes: 4 additions & 0 deletions charts/ozone/templates/om/om-service-headless.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,10 @@ spec:
ports:
- name: ui
port: {{ .Values.om.service.port }}
{{- if gt (int .Values.om.replicas) 1 }}
- name: ratis
port: 9872
{{- end }}
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Is this port being exposed for one Ozone Manager(OM) to communicate with another OM when they form a Ratis ring?
My understanding is that the current selector will match this service with all OM pods. Consequently, the messages sent to this service will be forwarded to a random OM pod instead of a specific OM pod.

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If the number of OM pods are manually modified by kubectl scale then this port will perhaps never be exposed. We should think if there is a downside to always exposing the port.

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As per OM documentation

This logical name is called serviceId and can be configured in the ozone-site.xml
The defined serviceId can be used instead of a single OM host using client interfaces

Perhaps there should be a different service which maps and groups pods as per the serviceId.

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Is this port being exposed for one Ozone Manager(OM) to communicate with another OM when they form a Ratis ring?

yes this was my reason

My understanding is that the current selector will match this service with all OM pods. Consequently, the messages sent to this service will be forwarded to a random OM pod instead of a specific OM pod.

ok if this is the case maybe we can remove this export. I found and used the following Ticket for the port configuration: https://issues.apache.org/jira/browse/HDDS-4677. I'm not really familiar with the architecture. If we can remove it I will do so :)

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If the number of OM pods are manually modified by kubectl scale then this port will perhaps never be exposed. We should think if there is a downside to always exposing the port.

Great point! I hadn't considered that scenario. What could be the downside of exposing the port within an internal Kubernetes network? Perhaps we can use a Helm lookup mechanism to check the current replica count as an alternative, but the simplest approach is to always expose the port.

selector:
{{- include "ozone.selectorLabels" . | nindent 4 }}
app.kubernetes.io/component: om
5 changes: 5 additions & 0 deletions charts/ozone/templates/om/om-statefulset.yaml
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Expand Up @@ -31,6 +31,7 @@ metadata:
app.kubernetes.io/component: om
spec:
replicas: {{ .Values.om.replicas }}
podManagementPolicy: Parallel
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As per OM documentation

To convert a non-HA OM to be HA or to add new OM nodes to existing HA OM ring, new OM node(s) need to be bootstrapped.

Shouldn't there be an init container which calls --bootstrap for OM?

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Yes, I think you are right.

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At this point, I get stuck in the bootstrap init container. I believe this step is only necessary for new cluster nodes. Thus, the problem reoccurs when we scale (once again, the scaling issue).

serviceName: {{ .Release.Name }}-om-headless
selector:
matchLabels:
Expand Down Expand Up @@ -71,6 +72,10 @@ spec:
containerPort: 9862
- name: ui
containerPort: {{ .Values.om.service.port }}
{{- if gt (int .Values.om.replicas) 1 }}
- name: ratis
containerPort: 9872
{{- end }}
livenessProbe:
httpGet:
path: /
Expand Down
12 changes: 12 additions & 0 deletions charts/ozone/templates/scm/scm-service-headless.yaml
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Expand Up @@ -28,6 +28,18 @@ spec:
ports:
- name: ui
port: {{ .Values.scm.service.port }}
- name: rpc-datanode
port: 9861
- name: block-client
port: 9863
- name: rpc-client
port: 9860
{{- if gt (int .Values.scm.replicas) 1 }}
- name: ratis
port: 9894
- name: grpc
port: 9895
{{- end }}
selector:
{{- include "ozone.selectorLabels" . | nindent 4 }}
app.kubernetes.io/component: scm
27 changes: 27 additions & 0 deletions charts/ozone/templates/scm/scm-statefulset.yaml
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Expand Up @@ -31,6 +31,7 @@ metadata:
app.kubernetes.io/component: scm
spec:
replicas: {{ .Values.scm.replicas }}
podManagementPolicy: Parallel
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Is a Parallel policy disruptive when we use kubectl scale up/down.
It would be interesting to see if the Ratis rings are disrupted. Perhaps a PreStop hook for graceful shutdown of OM/SCM/Datanodes is required in a new Jira.

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I see a different problem: If we use kubectl scale the configuration from helpers of cluster ids and so on is also not correct. Puhhh no idea how to solve this at the moment...

serviceName: {{ .Release.Name }}-scm-headless
selector:
matchLabels:
Expand Down Expand Up @@ -61,6 +62,24 @@ spec:
mountPath: {{ .Values.configuration.dir }}
- name: {{ .Release.Name }}-scm
mountPath: {{ .Values.scm.persistence.path }}
{{- if gt (int .Values.scm.replicas) 1 }}
- name: bootstrap
image: "{{ .Values.image.repository }}:{{ .Values.image.tag | default .Chart.AppVersion }}"
args: ["ozone", "scm", "--bootstrap"]
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From the SCM HA docs:

The initialization of the first SCM-HA node is the same as a non-HA SCM:
ozone scm --init
Second and third nodes should be bootstrapped instead of init
ozone scm --bootstrap

Here, we call init and then bootstrap for every SCM pod (re)start.
We would instead have to perform pod-id specific actions.

It is not clear from the documentation whether init and bootstrap should only be performed once during the lifetime of the pod or upon every pod restart.

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It appears from the documentation that init on pod-1 needs to complete before bootstrap on pod-x. This would perhaps require changing podManagementPolicy: Parallel to OrderedReady.

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From the SCM HA docs:

The initialization of the first SCM-HA node is the same as a non-HA SCM:
ozone scm --init
Second and third nodes should be bootstrapped instead of init
ozone scm --bootstrap

Here, we call init and then bootstrap for every SCM pod (re)start.
We would instead have to perform pod-id specific actions.

It is not clear from the documentation whether init and bootstrap should only be performed once during the lifetime of the pod or upon every pod restart.

I used the following doc:

Auto-bootstrap

In some environments (e.g. Kubernetes) we need to have a common, unified way to initialize SCM HA quorum. As a reminder, the standard initialization flow is the following:

On the first, “primordial” node: ozone scm --init
On second/third nodes: ozone scm --bootstrap

This can be improved: primordial SCM can be configured by setting ozone.scm.primordial.node.id in the config to one of the nodes.

ozone.scm.primordial.node.id scm1

With this configuration both scm --init and scm --bootstrap can be safely executed on all SCM nodes. Each node will only perform the action applicable to it based on the ozone.scm.primordial.node.id and its own node ID.

Note: SCM still needs to be started after the init/bootstrap process.

ozone scm --init
ozone scm --bootstrap
ozone scm --daemon start

For Docker/Kubernetes, use ozone scm to start it in the foreground.

This can be found in the Auto-bootstrap section here. I understood that we can run this commands on every instance and it will automatically detect what to do if ozone.scm.primordial.node.id is set correctly

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It appears from the documentation that init on pod-1 needs to complete before bootstrap on pod-x. This would perhaps require changing podManagementPolicy: Parallel to OrderedReady.

I used this because of the ratis ring. The problem with the other configuration is that the hosts of unstated nodes from the headless service cannot be resolved. So the first SCM node cannot start because it depends on the resolution of the other ones, which again cannot start because they start only if first node has finished successfully

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It appears from the documentation that init on pod-1 needs to complete before bootstrap on pod-x. This would perhaps require changing podManagementPolicy: Parallel to OrderedReady.

I used this because of the ratis ring. The problem with the other configuration is that the hosts of unstated nodes from the headless service cannot be resolved. So the first SCM node cannot start because it depends on the resolution of the other ones, which again cannot start because they start only if first node has finished successfully

However, this is only relevant for the bootstrap process. So, you might be right. We probably only need the bootstrap once in persistent mode. Maybe someone from the Ozone contributors can provide a definitive answer to this question.

env:
{{- include "ozone.configuration.env" . | nindent 12 }}
{{- with $env }}
{{- tpl (toYaml .) $ | nindent 12 }}
{{- end }}
{{- with $envFrom }}
envFrom: {{- tpl (toYaml .) $ | nindent 12 }}
{{- end }}
volumeMounts:
- name: config
mountPath: {{ .Values.configuration.dir }}
- name: {{ .Release.Name }}-scm
mountPath: {{ .Values.scm.persistence.path }}
{{- end }}
containers:
- name: scm
image: "{{ .Values.image.repository }}:{{ .Values.image.tag | default .Chart.AppVersion }}"
Expand All @@ -82,10 +101,18 @@ spec:
ports:
- name: rpc-client
containerPort: 9860
- name: block-client
containerPort: 9863
- name: rpc-datanode
containerPort: 9861
- name: ui
containerPort: {{ .Values.scm.service.port }}
{{- if gt (int .Values.scm.replicas) 1 }}
- name: ratis
containerPort: 9894
- name: grpc
containerPort: 9895
{{- end }}
Comment on lines +110 to +115
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Since we are exposing ports, we should also have a readiness probe to toggle access to these ports in a separate Jira.

livenessProbe:
httpGet:
path: /
Expand Down