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ClickHouse TLS/SSL Encryption

Prerequisite : To configure TLS/SSL in ClickHouse, KubeDB uses cert-manager to issue certificates. So first you have to make sure that the cluster has cert-manager installed. To install cert-manager in your cluster following steps here.

To issue a certificate, the following crd of cert-manager is used:

• Issuer/ClusterIssuer: Issuers, and ClusterIssuers represent certificate authorities (CAs) that are able to generate signed certificates by honoring certificate signing requests. All cert-manager certificates require a referenced issuer that is in a ready condition to attempt to honor the request. You can learn more details here.

• Certificate: cert-manager has the concept of Certificates that define a desired x509 certificate which will be renewed and kept up to date. You can learn more details here.

ClickHouse CRD Specification :

KubeDB uses following crd fields to enable SSL/TLS encryption in ClickHouse.

• spec:
  • tls:
    • issuerRef
    • certificates

Read about the fields in details from clickhouse concept,

KubeDB uses the issuer or clusterIssuer referenced in the tls.issuerRef field, and the certificate specs provided in tls.certificate to generate certificate secrets using Issuer/ClusterIssuers specification. These certificates secrets including ca.crt, tls.crt and tls.key etc. are used to configure clickhouse server and clients.

How TLS/SSL configures in ClickHouse

The following figure shows how KubeDB enterprise used to configure TLS/SSL in ClickHouse. Open the image in a new tab to see the enlarged version.

Deploying ClickHouse with TLS/SSL configuration process consists of the following steps:

1. At first, a user creates a Issuer/ClusterIssuer cr.

2. Then the user creates a ClickHouse CR which refers to the Issuer/ClusterIssuer CR that the user created in the previous step.

3. KubeDB Provisioner operator watches for the ClickHouse cr.

4. When it finds one, it creates Secret, Service, etc. for the ClickHouse cluster.

5. KubeDB Ops-manager operator watches for ClickHouse(5c), Issuer/ClusterIssuer(5b), Secret and Service(5a).

6. When it finds all the resources(ClickHouse, Issuer/ClusterIssuer, Secret, Service), it creates Certificates by using tls.issuerRef and tls.certificates field specification from ClickHouse cr.

7. cert-manager watches for certificates.

8. When it finds one, it creates certificate secrets tls-secrets(server, client, exporter secrets etc.) that holds the actual certificate signed by the CA.

9. KubeDB Provisioner operator watches for the Certificate secrets tls-secrets.

10. When it finds all the tls-secret, it creates the related PetSets so that ClickHouse database can be configured with TLS/SSL.

In the next doc, we are going to show a step-by-step guide on how to configure a ClickHouse cluster with TLS/SSL.