In Cloudera deployments on public cloud, one of many key configuration components is the DNS. Get it fallacious and your deployment could turn out to be wholly unusable with customers unable to entry and use the Cloudera information providers. If the DNS is ready up much less splendid than it may very well be, connectivity and efficiency points could come up. On this weblog, we’ll take you thru our tried and examined greatest practices for establishing your DNS to be used with Cloudera on Azure.
To get began and offer you a really feel for the dependencies for the DNS, in an Azure deployment for Cloudera, these are the Azure managed providers getting used:
- AKS cluster: information warehouse, information engineering, machine studying, and Information movement
- MySQL database: information engineering
- Storage account: all providers
- Azure database for PostgreSQL DB: information lake and information hub clusters
- Key vault: all providers
Typical buyer governance restrictions and the affect
Most Azure customers use personal networks with a firewall as egress management. Most customers have restrictions on firewalls for wildcard guidelines. Cloudera assets are created on the fly, which suggests wildcard guidelines could also be declined by the safety crew.
Most Azure customers use hub-spoke community topology. DNS servers are often deployed within the hub digital community or an on-prem information middle as a substitute of within the Cloudera VNET. Meaning if DNS isn’t configured appropriately, the deployment will fail.
Most Cloudera clients deploying on Azure permit using service endpoints; there’s a smaller set of organizations that don’t permit using service endpoints. Service endpoint is a less complicated implementation to permit assets on a personal community to entry managed providers on Azure Cloud. If service endpoints are usually not allowed, firewall and personal endpoints would be the different two choices. Most cloud customers don’t like opening firewall guidelines as a result of that may introduce the chance of exposing personal information on the web. That leaves personal endpoints the one possibility, which will even introduce further DNS configuration for the personal endpoints.
Connectivity from personal community to Azure managed providers
Firewall to Web
Route from firewall to Azure managed service endpoint on the web straight.
Service endpoint
Azure gives service endpoints for assets on personal networks to entry the managed providers on the web with out going by means of the firewall. That may be configured at a subnet degree. Since Cloudera assets are deployed in several subnets, this configuration have to be enabled on all subnets.
The DNS data of the managed providers utilizing service endpoints will probably be on the web and managed by Microsoft. The IP handle of this service will probably be a public IP, and routable from the subnet. Please discuss with the Microsoft documentation for element.
Not all managed providers help providers endpoint. In a Cloudera deployment state of affairs, solely storage accounts, PostgreSQL DB, and Key Vault help service endpoints.
Fortuitously, most customers permit service endpoints. If a buyer doesn’t permit service endpoints, they need to go together with a personal endpoint, which is analogous to what must be configured within the following content material.
Personal Endpoint
There’s a community interface with a personal IP handle created with a personal endpoint, and there’s a personal hyperlink service related to a particular community interface, in order that different assets within the personal community can entry this service by means of the personal community IP handle.
The important thing right here is for the personal assets to discover a DNS resolve for that non-public IP handle. There are two choices to retailer the DNS file:
- Azure managed public DNS zones will all the time be there, however they retailer various kinds of IP addresses for the personal endpoint. For instance:
- Storage account personal endpoint—the general public DNS zone shops the general public IP handle of that service.
- AKS API server personal endpoint—the general public DNS zone shops the personal IP of that service.
- Azure Personal DNS zone: The DNS data will probably be synchronized to the Azure Default DNS of LINKED VNET.
Personal endpoint is eligible to all Azure managed providers which are utilized in Cloudera deployments.
As a consequence, for storage accounts, customers both use service endpoints or personal endpoints. As a result of the general public DNS zone will all the time return a public IP, the personal DNS zone turns into a compulsory configuration.
For AKS, these two DNS options are each appropriate. The challenges of personal DNS zones will probably be mentioned subsequent.
Challenges of personal DNS zone on Azure personal community
Essential Assumptions
As talked about above for the standard state of affairs, most Azure customers are utilizing a hub-and-spoke community structure, and deploy customized personal DNS on hub VNET.
The DNS data will probably be synchronized to Azure default DNS of linked VNET.
Easy Structure Use Circumstances
One VNET state of affairs with personal DNS zone:
When a personal endpoint is created, Cloudera on Azure will register the personal endpoint to the personal DNS zone. The DNS file will probably be synchronized to Azure Default DNS of linked VNET.
If customers use customized personal DNS, they’ll configure conditional ahead to Azure Default DNS for the area suffix of the FQDN.
Hub-and-spoke VNET with Azure default DNS:
With hub-spoke VNET and Azure default DNS, that’s nonetheless acceptable. The one drawback is that the assets on the un-linked VNET won’t be able to entry the AKS. However since AKS is utilized by Cloudera, that doesn’t pose any main points.
The Problem Half
The preferred community structure amongst Azure customers is hub-spoke community with customized personal DNS servers deployed both on hub-VNET or on-premises community.
Since DNS data are usually not synchronized to the Azure Default DNS of the hub VNET, the customized personal DNS server can not discover the DNS file for the personal endpoint. And since the Cloudera VNET is utilizing the customized personal DNS server on hub VNET, the Cloudera assets on Cloudera VNET will go to a customized personal DNS server for DNS decision of the FQDN of the personal endpoint. The provisioning will fail.
With the DNS server deployed within the on-prem community, there isn’t Azure default DNS related to the on-prem community, so the DNS server couldn’t discover the DNS file of the FQDN of the personal endpoint.
Configuration greatest practices
Towards the background
Possibility 1: Disable Personal DNS Zone
Use Azure managed public DNS zone as a substitute of a personal DNS zone.
- For information warehouse: create information warehouses by means of the Cloudera command line interface with the parameter “privateDNSZoneAKS”: set to”None.”
- For Liftie-based information providers: the entitlement “LIFTIE_AKS_DISABLE_PRIVATE_DNS_ZONE” have to be set. Clients can request this entitlement to be set both by means of a JIRA ticket or have their Cloudera answer engineer to make the request on their behalf.
The only real disadvantage of this feature is that it doesn’t apply to information engineering, since that information service will create and use a MySQL personal DNS zone on the fly. There may be at current no choice to disable personal DNS zones for information engineering.
Possibility 2: Pre-create Personal DNS Zones
Pre-create personal DNS zones and hyperlink each Cloudera and hub VNETs to them.
The benefit of this strategy is that each information warehouse and Liftie-based information providers help pre-created personal DNS zones. There are nevertheless additionally a number of drawbacks:
- For Liftie, the personal DNS zone must be configured when registering the setting. As soon as previous the setting registration stage, it can’t be configured.
- DE will want a personal DNS zone for MySQL and it doesn’t help pre-configured personal DNS zones.
- On-premises networks can’t be linked to a personal DNS zone. If the DNS server is on an on-prem community, there are not any workable options.
Possibility 3: Create DNS Server as a Forwarder.
Create a few DNS servers (for HA consideration) with load balancer in Cloudera VNET, and configure conditional ahead to Azure Default DNS of the Cloudera VNET. Configure conditional ahead from the corporate customized personal DNS server to the DNS server within the Cloudera subnet.
The downside of this feature is that further DNS servers are required, which ends up in further administration overhead for the DNS crew.
Possibility 4: Azure-Managed DNS Resolve
Create a devoted /28 subnet in Cloudera VNET for Azure personal DNS resolver inbound endpoint. Configure conditional ahead from customized personal DNS to the Azure personal DNS resolver inbound endpoint.
Abstract
Bringing all issues collectively, take into account these greatest practices for establishing your DNS with Cloudera on Azure:
- For the storage account, key vault, postgres DB
- Use service endpoints as the primary selection.
- If service endpoint isn’t allowed, pre-create personal DNS zones and hyperlink to the VNET the place the DNS server is deployed. Configure conditional forwards from customized personal DNS to Azure default DNS.
- If the customized personal DNS is deployed within the on-premises community, use Azure DNS resolver or one other DNS server as DNS forwarder on the Cloudera VNET. Conditional ahead the DNS lookup from the personal DNS to the resolver endpoint.
- For the information warehouse, DataFlow, or machine studying information providers
- Disable the personal DNS zone and use the general public DNS zone as a substitute.
- For the information engineering information service
- Configure the Azure DNS resolver or one other DNS server as a DNS forwarder on the Cloudera VNET. Conditional ahead the DNS lookup from the personal DNS to the resolver endpoint. Please discuss with Microsoft documentation for the small print of establishing an Azure DNS Personal Resolver.
For extra background studying on community and DNS specifics for Azure, take a look at our documentation for the assorted information providers: DataFlow, Information Engineering, Information Warehouse, and Machine Studying. We’re additionally completely satisfied to debate your particular wants; in that case please attain out to your Cloudera account supervisor or get in contact.