148422597X Kubernetes Management Design Patterns [Vohra 2017-01-29] {E559F6BB}

CHAPTER 12
Using Resource Quotas
In Chapter 10 we introduced a resource consumption model based on requests and limits, using which
resources (CPU and memory) are allocated to a pod’s containers.
Problem
Although we discussed allocating resources to a pod’s containers, we did not take some other factors into
consideration. The resource requirements vary from one development team to another. If one development
team were to use all or most of the resources on a node, another team would not be able to run any
application on the same node. Second, the resource requirements vary across the different phases of
application development. Application development would have different resource usage than application
testing and application in-production work. The resource allocation pattern discussed in Chapter 10 does
not provide a solution for any of these factors.
Solution
Kubernetes provides a management design pattern for elastic quotas. Elastic quotas are not completely
elastic, and a fixed upper limit that is flexible to some extent based on the scope (discussed later in this
chapter) is imposed. Resource quotas are a specification for limiting the use of certain resources in a
particular namespace. The quota is not on a particular object, such as a pod or a replication controller, but
on the aggregate use within a namespace. The objective is to provide a fair share of resources to different
teams, with each team assigned a namespace with quotas. Another application of quotas is creating different
namespaces for production, development, and testing; different phases of application development have
different resource requirements. Creating or updating a resource should not exceed the quota restraint,
failing which the resource is not created or updated, and an error message is generated. Quotas could be
set on compute resources (CPU and memory), which were discussed in chapter 10, and object counts (such
as pods, replication controllers, services, load balancers, and ConfigMaps, to list a few). When a quota is
set for compute resources, requests or limits must be specified for those resources. Quotas are enabled by
default. The total cluster capacity, which could vary if nodes are added or removed, is not a limiting factor
when setting quotas. The total of the quotas of namespaces could exceed the cluster capacity, and resource
contention will be resolved on a first-come-first-served basis. Resource contention is resolved before a
resource is created and does not affect resources already created. Once a resource has been created, any
changes to the quota setting do not affect the resource.
© Deepak Vohra 2017
D. Vohra, Kubernetes Management Design Patterns, DOI 10.1007/978-1-4842-2598-1_12
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