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

Chapter 8 ■ Using Rolling Updates
Table 8-1. Fields for Rolling Update to a Deployment
Field Description Example
maxUnavailable
maxSurge
The maximum number of pods
that may become unavailable
during the update. The value may
be an absolute number, such as 3,
or a percentage, for example 30%.
Default value is 1. The value cannot
be 0 if maxSurge is 0.
The maximum number of pods
that may be running above
the configured or desired level
specified as a number or a
percentage. Default value is 1.
Cannot be 0 if maxUnavailable is 0.
If set to 20% the maximum number of pods that
may be unavailable cannot exceed 20%, and 80%
of the pods must always be available. When the
update starts, the old RC is scaled down to 80%
immediately and new pods started for the new
RC. As new pods are started old RC pods are
stopped, so that the number of pods available is
always 80% of the configured replication level.
If set to 10% the new RC may surge to 110%
of the configured or desired number of pods
immediately when the update is started, but not
more than 110% of the configured replication
level. As old RC pods are stopped more new RC
pods are started, but at any given time the total
number of pods must not exceed 110%.
The Deployment spec provides two fields (Table 8-2) for the rolling update rollback. Neither of these
fields are required.
Table 8-2. Fields for Rolling Update Rollback
Field
rollbackTo
revisionHistoryLimit
Description
The config the deployment is rolled back to in a rollback. The RollbackConfig
provides a field revision to specify the revision to roll back to. If set to 0 rolls
back to the last revision.
The number of old replica sets to retain to allow a rollback.
Next, we shall demonstrate rolling update of a deployment. Create a deployment file mysqldeployment.yaml:
sudo vi mysql-deployment.yaml
Copy the following listing to the definition file:
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: mysql-deployment
spec:
replicas: 5
template:
metadata:
labels:
app: mysql
187