Configure Cluster Topology for MongoDB Resources

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Prerequisites

Procedure

You can configure the deployment topology of your MongoDB resources within Kubernetes by defining NodeAffinity and PodAffinity. NodeAffinity and PodAffinity specify where Kubernetes deploys MongoDB custom resources in your Kubernetes cluster.

You can implement node affinity by applying node labels to specific nodes within your Kubernetes cluster and defining labelSelector fields with corrosponding labels in your MongoDB CustomResourceDefinition. When you apply node labels and matching labelSelector values, Kubernetes only deploys a given MongoDB CustomResourceDefinition on the nodes you specify within your Kubernetes cluster. Implementing node affinity rules can be useful when deploying MongoDB resources in heterogeneous node groups, as it allows you to deploy specific resources on specific node varieties.

Similarly, you can implement Pod affinity by applying labels to Pods that are running in your cluster and aligning those label values with labelSelector values defined in your MongoDB CustomResourceDefinition. When you apply labels and matching labelSelector values, Kubernetes colocates MongoDB custom resource-managed Pods with Pods with matching labels applied. By collocating Pods, you can improve system performance and reduce latency between Pods that communicate regularly. You can also define Pod antiaffinity rules which allow you to specify Pods which should not be colocated.

For Standalone and Replica Set deployments, you can apply these affinity rules to the spec.podSpec of your MongoDB CustomResourceDefinition. For Sharded Cluster deployments, you can apply these affinity rules to the spec.configSrvPodSpec, spec.shardPodSpec, and spec.mongosPodSpec sections of your MongoDB CustomResourceDefinition.

You must deploy MonogDB resources, such as mongos, shards, and config servers in the case of a Sharded Cluster deployment, in the same namespace as the MongoDB resource. However, within that namespace, you can configure the nodeAffinity and podAffinity for mongos, shards, and config server resource types in the ShardedCluster CustomResourceDefinition.

Prerequisites

To configure the deployment topology for your MongoDB deployment, you must either have a MongoDB replica set deployed through the MongoDB Kubernetes Operator along with labels applied to the Kubernetes resources that will align with labelSelectors defined in the MongoDB CustomResourceDefinition or meet the following prerequisites:

An Ops Manager instance or a Cloud Manager organization.
The MongoDB Enterprise Kubernetes Operator.
A Kubernetes Operator ConfigMap.
Credentials for the Kubernetes Operator or configure a different secret storage tool.
Labels applied to the Kubernetes resources that will align with labelSelectors defined in the MongoDB CustomResourceDefinition.

Procedure

Update your MongoDB CRD manifest.

Populate the podTemplate.affinity sections of your MongoDB Sharded Cluster definition as shown in the following example:

1 ---
2 apiVersion: mongodb.com/v1
3 kind: MongoDB
4 metadata:
5   name: my-sharded-cluster
6 spec:
7   shardCount: 2
8   mongodsPerShardCount: 3
9   mongosCount: 2
10   configServerCount: 3
11   version: 6.0.0
12   service: my-service
13 
14   opsManager:
15     configMapRef:
16       name: my-project
17   credentials: my-credentials
18   type: ShardedCluster
19 
20   persistent: true
21   configSrvPodSpec:
22     podTemplate:
23       spec:
24         affinity:
25           podAffinity:
26             requiredDuringSchedulingIgnoredDuringExecution:
27               - labelSelector:
28                   matchExpressions:
29                     - key: security
30                       operator: In
31                       values:
32                         - S1
33                 topologyKey: failure-domain.beta.kubernetes.io/zone
34           nodeAffinity:
35             requiredDuringSchedulingIgnoredDuringExecution:
36               nodeSelectorTerms:
37                 - matchExpressions:
38                     - key: kubernetes.io/e2e-az-name
39                       operator: In
40                       values:
41                         - e2e-az1
42                         - e2e-az2
43           podAntiAffinity:
44             requiredDuringSchedulingIgnoredDuringExecution:
45             - podAffinityTerm:
46                 topologyKey: nodeId
47   mongosPodSpec:
48     podTemplate:
49       spec:
50         affinity:
51           podAffinity:
52             requiredDuringSchedulingIgnoredDuringExecution:
53               - labelSelector:
54                   matchExpressions:
55                     - key: security
56                       operator: In
57                       values:
58                         - S1
59                 topologyKey: failure-domain.beta.kubernetes.io/zone
60           nodeAffinity:
61             requiredDuringSchedulingIgnoredDuringExecution:
62               nodeSelectorTerms:
63                 - matchExpressions:
64                     - key: kubernetes.io/e2e-az-name
65                       operator: In
66                       values:
67                         - e2e-az1
68                         - e2e-az2
69           podAntiAffinity:
70             requiredDuringSchedulingIgnoredDuringExecution:
71             - podAffinityTerm:
72                 topologyKey: nodeId
73   shardPodSpec:
74     podTemplate:
75       spec:
76         affinity:
77           podAffinity:
78             requiredDuringSchedulingIgnoredDuringExecution:
79               - labelSelector:
80                   matchExpressions:
81                     - key: security
82                       operator: In
83                       values:
84                         - S1
85                 topologyKey: failure-domain.beta.kubernetes.io/zone
86           nodeAffinity:
87             requiredDuringSchedulingIgnoredDuringExecution:
88               nodeSelectorTerms:
89                 - matchExpressions:
90                     - key: kubernetes.io/e2e-az-name
91                       operator: In
92                       values:
93                         - e2e-az1
94                         - e2e-az2
95           podAntiAffinity:
96             requiredDuringSchedulingIgnoredDuringExecution:
97             - podAffinityTerm:
98                 topologyKey: nodeId
99 ...

Apply your changes.

kubectl apply -f mongodb-crd.yaml

Back

Configure MongoDB Database Backups

Configure Storage Options for MongoDB Resources

1	---
2	apiVersion: mongodb.com/v1
3	kind: MongoDB
4	metadata:
5	name: my-sharded-cluster
6	spec:
7	shardCount: 2
8	mongodsPerShardCount: 3
9	mongosCount: 2
10	configServerCount: 3
11	version: 6.0.0
12	service: my-service
13
14	opsManager:
15	configMapRef:
16	name: my-project
17	credentials: my-credentials
18	type: ShardedCluster
19
20	persistent: true
21	configSrvPodSpec:
22	podTemplate:
23	spec:
24	affinity:
25	podAffinity:
26	requiredDuringSchedulingIgnoredDuringExecution:
27	- labelSelector:
28	matchExpressions:
29	- key: security
30	operator: In
31	values:
32	- S1
33	topologyKey: failure-domain.beta.kubernetes.io/zone
34	nodeAffinity:
35	requiredDuringSchedulingIgnoredDuringExecution:
36	nodeSelectorTerms:
37	- matchExpressions:
38	- key: kubernetes.io/e2e-az-name
39	operator: In
40	values:
41	- e2e-az1
42	- e2e-az2
43	podAntiAffinity:
44	requiredDuringSchedulingIgnoredDuringExecution:
45	- podAffinityTerm:
46	topologyKey: nodeId
47	mongosPodSpec:
48	podTemplate:
49	spec:
50	affinity:
51	podAffinity:
52	requiredDuringSchedulingIgnoredDuringExecution:
53	- labelSelector:
54	matchExpressions:
55	- key: security
56	operator: In
57	values:
58	- S1
59	topologyKey: failure-domain.beta.kubernetes.io/zone
60	nodeAffinity:
61	requiredDuringSchedulingIgnoredDuringExecution:
62	nodeSelectorTerms:
63	- matchExpressions:
64	- key: kubernetes.io/e2e-az-name
65	operator: In
66	values:
67	- e2e-az1
68	- e2e-az2
69	podAntiAffinity:
70	requiredDuringSchedulingIgnoredDuringExecution:
71	- podAffinityTerm:
72	topologyKey: nodeId
73	shardPodSpec:
74	podTemplate:
75	spec:
76	affinity:
77	podAffinity:
78	requiredDuringSchedulingIgnoredDuringExecution:
79	- labelSelector:
80	matchExpressions:
81	- key: security
82	operator: In
83	values:
84	- S1
85	topologyKey: failure-domain.beta.kubernetes.io/zone
86	nodeAffinity:
87	requiredDuringSchedulingIgnoredDuringExecution:
88	nodeSelectorTerms:
89	- matchExpressions:
90	- key: kubernetes.io/e2e-az-name
91	operator: In
92	values:
93	- e2e-az1
94	- e2e-az2
95	podAntiAffinity:
96	requiredDuringSchedulingIgnoredDuringExecution:
97	- podAffinityTerm:
98	topologyKey: nodeId
99	...