Access the Neo4j cluster from inside Kubernetes

By default, client-side routing is used for accessing a Neo4j cluster from inside Kubernetes.

1. Access the Neo4j cluster using a specific member

You run cypher-shell in a new pod and point it directly to one of the core members.

Run cypher-shell in a pod to access, for example, core-3:

kubectl run --rm -it --image "neo4j:4.4.8-enterprise" cypher-shell \
     -- cypher-shell -a "neo4j://core-3.default.svc.cluster.local:7687" -u neo4j -p "my-password"

If you don't see a command prompt, try pressing enter.


Connected to Neo4j using Bolt protocol version 4.4 at neo4j://core-3.default.svc.cluster.local:7687 as user neo4j.
Type :help for a list of available commands or :exit to exit the shell.
Note that Cypher queries must end with a semicolon.

Run the Cypher command SHOW DATABASES to verify that all cluster members are online:

SHOW DATABASES;

+----------------------------------------------------------------------------------------------------------------------------------------------------------+
| name     | aliases | access       | address                                 | role           | requestedStatus | currentStatus | error | default | home  |
+----------------------------------------------------------------------------------------------------------------------------------------------------------+
| "neo4j"  | []      | "read-write" | "core-1.default.svc.cluster.local:7687" | "follower"     | "online"        | "online"      | ""    | TRUE    | TRUE  |
| "neo4j"  | []      | "read-write" | "core-3.default.svc.cluster.local:7687" | "follower"     | "online"        | "online"      | ""    | TRUE    | TRUE  |
| "neo4j"  | []      | "read-write" | "core-2.default.svc.cluster.local:7687" | "leader"       | "online"        | "online"      | ""    | TRUE    | TRUE  |
| "neo4j"  | []      | "read-write" | "rr-1.default.svc.cluster.local:7687"   | "read_replica" | "online"        | "online"      | ""    | TRUE    | TRUE  |
| "system" | []      | "read-write" | "core-1.default.svc.cluster.local:7687" | "leader"       | "online"        | "online"      | ""    | FALSE   | FALSE |
| "system" | []      | "read-write" | "core-3.default.svc.cluster.local:7687" | "follower"     | "online"        | "online"      | ""    | FALSE   | FALSE |
| "system" | []      | "read-write" | "core-2.default.svc.cluster.local:7687" | "follower"     | "online"        | "online"      | ""    | FALSE   | FALSE |
| "system" | []      | "read-write" | "rr-1.default.svc.cluster.local:7687"   | "read_replica" | "online"        | "online"      | ""    | FALSE   | FALSE |
+----------------------------------------------------------------------------------------------------------------------------------------------------------+

8 rows
ready to start consuming query after 27 ms, results consumed after another 243 ms

Exit cypher-shell. Exiting cypher-shell automatically deletes the pod created to run it.

:exit;

Bye!
Session ended, resume using 'kubectl attach cypher-shell -c cypher-shell -i -t' command when the pod is running
pod "cypher-shell" deleted

2. Access the Neo4j cluster using headless service

To allow for an application running inside Kubernetes to access the Neo4j cluster without using a specific core for bootstrapping, you need to install the neo4j-cluster-headless-service Helm Chart. This will create a K8s Service with a DNS entry that includes all the Neo4j cores. You can use the created DNS entry to bootstrap drivers connecting to the cluster as shown in the image:

dns resolution

The headless service is a Kubernetes term for a service that has no ClusterIP. For more information, see the Kubernetes official documentation.

Install the headless service using the release name headless, neo4j/neo4j-cluster-headless-service Helm Chart, and the name of your cluster as a value of the neo4j.name parameter.

Alternatively, you can create a values.yaml file with all the configurations for the service. To see what options are configurable on the neo4j/neo4j-cluster-headless-service Helm Chart, use helm show values neo4j/neo4j-cluster-headless-service.

helm install headless neo4j/neo4j-cluster-headless-service --set neo4j.name=my-cluster

NAME: headless
LAST DEPLOYED: Fri Nov  5 16:58:54 2021
NAMESPACE: default
STATUS: deployed
REVISION: 1
TEST SUITE: None
NOTES:
Thank you for installing neo4j-cluster-headless-service.

Your release "headless" has been installed in namespace "default".

Once rollout is complete you can connect to your Neo4j cluster using "neo4j://headless-neo4j.default.svc.cluster.local:7687". Try:

  $ kubectl run --rm -it --image "neo4j:4.4.8-enterprise" cypher-shell \
     -- cypher-shell -a "neo4j://headless-neo4j.default.svc.cluster.local:7687"

Graphs are everywhere!

Check that the headless service is available:

kubectl get services | grep head

NAME               TYPE           CLUSTER-IP      EXTERNAL-IP     PORT(S)                                                                   AGE
headless-neo4j     ClusterIP      None            <none>          7474/TCP,7473/TCP,7687/TCP                                                3m22s

Use kubectl describe service to see the service details:

kubectl describe service headless-neo4j

Name:              headless-neo4j
Namespace:         default
Labels:            app=my-cluster
                   app.kubernetes.io/managed-by=Helm
                   helm.neo4j.com/neo4j.name=my-cluster
                   helm.neo4j.com/service=neo4j
Annotations:       cloud.google.com/neg: {"ingress":true}
                   meta.helm.sh/release-name: headless
                   meta.helm.sh/release-namespace: default
Selector:          app=my-cluster,helm.neo4j.com/dbms.mode=CORE,helm.neo4j.com/neo4j.loadbalancer=include,helm.neo4j.com/neo4j.name=my-cluster
Type:              ClusterIP
IP Families:       
IP:                None
IPs:               None
Port:              http  7474/TCP
TargetPort:        7474/TCP
Endpoints:         10.108.1.19:7474,10.108.2.14:7474,10.108.4.37:7474
Port:              https  7473/TCP
TargetPort:        7473/TCP
Endpoints:         10.108.1.19:7473,10.108.2.14:7473,10.108.4.37:7473
Port:              tcp-bolt  7687/TCP
TargetPort:        7687/TCP
Endpoints:         10.108.1.19:7687,10.108.2.14:7687,10.108.4.37:7687
Session Affinity:  None
Events:

You should see three “endpoints” for each port in the service — these are the IP addresses of the three Neo4j cores servers. These endpoints are contacted to bootstrap the drivers used by applications running in Kubernetes. The drivers will use them to obtain the initial routing table.

Run cypher-shell in another pod and connect to the cluster nodes via the headless service:

kubectl run --rm -it --image "neo4j:4.4.8-enterprise" cypher-shell \
     -- cypher-shell -a "neo4j://headless-neo4j.default.svc.cluster.local:7687" -u neo4j -p "my-password"

If you don't see a command prompt, try pressing enter.
Connected to Neo4j using Bolt protocol version 4.4 at neo4j://headless-neo4j.default.svc.cluster.local:7687 as user neo4j.
Type :help for a list of available commands or :exit to exit the shell.
Note that Cypher queries must end with a semicolon.

Run the Cypher command SHOW DATABASES to verify that all cluster members are online.

SHOW DATABASES;

+----------------------------------------------------------------------------------------------------------------------------------------------------------+
| name     | aliases | access       | address                                 | role           | requestedStatus | currentStatus | error | default | home  |
+----------------------------------------------------------------------------------------------------------------------------------------------------------+
| "neo4j"  | []      | "read-write" | "core-1.default.svc.cluster.local:7687" | "follower"     | "online"        | "online"      | ""    | TRUE    | TRUE  |
| "neo4j"  | []      | "read-write" | "core-3.default.svc.cluster.local:7687" | "follower"     | "online"        | "online"      | ""    | TRUE    | TRUE  |
| "neo4j"  | []      | "read-write" | "core-2.default.svc.cluster.local:7687" | "leader"       | "online"        | "online"      | ""    | TRUE    | TRUE  |
| "neo4j"  | []      | "read-write" | "rr-1.default.svc.cluster.local:7687"   | "read_replica" | "online"        | "online"      | ""    | TRUE    | TRUE  |
| "system" | []      | "read-write" | "core-1.default.svc.cluster.local:7687" | "leader"       | "online"        | "online"      | ""    | FALSE   | FALSE |
| "system" | []      | "read-write" | "core-3.default.svc.cluster.local:7687" | "follower"     | "online"        | "online"      | ""    | FALSE   | FALSE |
| "system" | []      | "read-write" | "core-2.default.svc.cluster.local:7687" | "follower"     | "online"        | "online"      | ""    | FALSE   | FALSE |
| "system" | []      | "read-write" | "rr-1.default.svc.cluster.local:7687"   | "read_replica" | "online"        | "online"      | ""    | FALSE   | FALSE |
+----------------------------------------------------------------------------------------------------------------------------------------------------------+

8 rows
ready to start consuming query after 4 ms, results consumed after another 42 ms

Exit cypher-shell. Exiting cypher-shell automatically deletes the pod created to run it.

:exit;

Bye!
Session ended, resume using 'kubectl attach cypher-shell -c cypher-shell -i -t' command when the pod is running
pod "cypher-shell" deleted

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