Pattern: Single Service Instance per Host

pattern   deployment  

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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.