Single Service instance per host

Context

You have applied the [[Microservice architecture]] pattern and architected your system as a set of services. Each service is deployed as a set of service instances for throughput and availability.

Problem

How are services packaged and deployed?

Forces

• Services are written using a variety of languages, frameworks, and framework versions

• Each service consists of multiple service instances for throughput and availability

• Service must be independently deployable and scalable

• Service instances need to be isolated from one another

• You need to be able to quickly build and deploy a service

• You need to be able to constrain the resources (CPU and memory) consumed by a service

• You need to monitor the behavior of each service instance

• You want deployment to reliable

• You must deploy the application as cost-effectively as possible

Solution

Deploy each single service instance on its own host

Examples

Resulting context

The benefits of this approach include:

• Services instances are isolated from one another

• There is no possibility of conflicting resource requirements or dependency versions

• A service instance can only consume at most the resources of a single host

• Its straightforward to monitor, manage, and redeploy each service instance

The drawbacks of this approach include:

• Potentially less efficient resource utilization compared to [[Multiple Services per Host]] because there are more hosts

Related patterns

• The [[Multiple Service Instances per Host]] pattern is an alternative solution

• The [[Service Instance per VM]] pattern is a refinement of this pattern

• The [[Service Instance per Container]] pattern is a refinement of this pattern

• The [[Serverless deployment]] pattern is an alternative solution.