Key DuploCloud concepts

Key concepts for using DuploCloud with Docker and Azure

While deploying Dockerized applications, familiarize yourself with some key concepts and terminologies.

See Use Cases for a description of DuploCloud Infrastructures and Tenants.

Hosts

These are virtual machines. In AKS deployments, they are also called Worker nodes. By default, apps within a Tenant are pinned to VMs in the same Tenant.

Service

Service is a DuploCloud term. DuploCloud Services are not Kubernetes Services. Services are microservices that are defined by a Name, DockerImage, and number of replicas in addition to many other optional parameters. Behind the scenes, a DuploCloud Service maps 1:1 either to a Kubernetes deployment set or to a StatefulSet depending on whether the microservice has stateful volumes or not. There are many optional configurations associated with a DuploCloud Service that represent various ways Docker containers can be run. A few of these are:

• Environment variables

• Host Network Mode

• Volume mounts

• Entrypoint or command overrides

• Resource caps

• Health Checks

Allocation Tags

If a service needs to be pinned to run only a specific set of Hosts, set an Allocation Tag on the Hosts as well as on the Service. The Allocation Tag is a case-insensitive substring match. For example, an Allocation Tag specified on a Service is usually a substring of the tag specified on the Host. If a Host is tagged HighCpu;HighMem, a Service tagged highcpu can be allocated on it. However, if the Service is tagged highcpu;gpu then it won't be allocated; it would need a Host tagged highcpu;gpu. If a Service does not have any tag set, it can be placed on any Host.

If the Host is tagged with a specific value and you have Services with the same tag, the Host is available for any Service that has no tags. If you want the exclusive assignment of a Host to a set of Services, ensure that every Service in the Tenant is tagged with some value.

In the case of Kubernetes deployments, the concept of Allocation Tags maps to labels on nodes, and on node selectors on the deployment set or StatefulSet.

• Host Networking: By default, Docker containers have their own network addresses. you may want these containers to use the same network interface as the VM. This is called Host Network Mode.

• Load Balancer: If a service must be accessed by other services, it needs to be exposed using a Load Balancer. Supported Load Balancers include:

  • A Network Load Balancer (NLB). An NLB distributes traffic across several servers by using the TCP/IP networking protocol. By combining two or more computers that are running applications into a single virtual cluster, NLB provides reliability and performance for web servers and other mission-critical servers.

  • An Application Load Balancer (ALB). An ALB provides outbound connections to cluster nodes inside the AKS virtual network, translating the private IP address to a public IP address as part of its Outbound Pool.