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121 lines
4.6 KiB
121 lines
4.6 KiB
# Guestbook Example
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Welcome to the Guestbook example. It shows you how to build and reuse
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parameterized templates.
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## Prerequisites
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First, make sure DM is installed in your Kubernetes cluster and that the
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Guestbook example is deployed by following the instructions in the top level
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[README.md](../../README.md).
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## Understanding the Guestbook example template
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Let's take a closer look at the template used by the Guestbook example.
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### Replicated services
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The typical design pattern for microservices in Kubernetes is to create a
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replication controller and a service with the same selector, so that the service
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exposes ports from the pods managed by the replication controller.
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We have created a parameterized type for this kind of replicated service called
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[Replicated Service](../../types/replicatedservice/v1), and we use it three times in this
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example.
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Note that the type is defined by a
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[python script](../../types/replicatedservice/v1/replicatedservice.py). It also has a
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[schema](../../types/replicatedservice/v1/replicatedservice.py.schema). Schemas are
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optional. If present in the type definition, they are used to validate uses of the
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type that appear in DM templates.
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For more information about types and templates, see the [design document](../../docs/design/design.md).
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### The Guestbook application
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The Guestbook application consists of 2 microservices: a front end and a Redis cluster.
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#### The front end
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The front end is a replicated service with 3 replicas:
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```
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- name: frontend
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type: https://raw.githubusercontent.com/kubernetes/deployment-manager/master/examples/replicatedservice/replicatedservice.py
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properties:
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service_port: 80
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container_port: 80
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external_service: true
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replicas: 3
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image: gcr.io/google_containers/example-guestbook-php-redis:v3
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```
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(Note that we use the URL for the type replicatedservice.py, not just the type name.)
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#### The Redis cluster
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The Redis cluster consists of two replicated services: a master with a single replica
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and the slaves with 2 replicas. It's defined by [this composite type](../../types/redis/v1/redis.jinja),
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which is a [Jinja](http://jinja.pocoo.org/) template with a [schema](../../types/redis/v1/redis.jinja.schema).
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```
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{% set REDIS_PORT = 6379 %}
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{% set WORKERS = properties['workers'] or 2 %}
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resources:
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- name: redis-master
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type: https://raw.githubusercontent.com/kubernetes/deployment-manager/master/examples/replicatedservice/replicatedservice.py
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properties:
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# This has to be overwritten since service names are hard coded in the code
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service_name: redis-master
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service_port: {{ REDIS_PORT }}
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target_port: {{ REDIS_PORT }}
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container_port: {{ REDIS_PORT }}
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replicas: 1
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container_name: master
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image: redis
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- name: redis-slave
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type: https://raw.githubusercontent.com/kubernetes/deployment-manager/master/examples/replicatedservice/replicatedservice.py
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properties:
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# This has to be overwritten since service names are hard coded in the code
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service_name: redis-slave
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service_port: {{ REDIS_PORT }}
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container_port: {{ REDIS_PORT }}
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replicas: {{ WORKERS }}
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container_name: worker
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image: kubernetes/redis-slave:v2
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# An example of how to specify env variables.
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env:
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- name: GET_HOSTS_FROM
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value: env
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- name: REDIS_MASTER_SERVICE_HOST
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value: redis-master
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```
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### Displaying types
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You can see the types you deployed to the cluster using the `deployed-types` command:
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```
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dm deployed-types
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["Service","ReplicationController","redis.jinja","https://raw.githubusercontent.com/kubernetes/deployment-manager/master/examples/replicatedservice/replicatedservice.py"]
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```
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This output shows 2 primitive types (Service and ReplicationController), and 2
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composite types (redis.jinja and one imported from github (replicatedservice.py)).
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You can also see where a specific type is being used with the `deployed-instances` command:
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```
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dm deployed-instances Service
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[{"name":"frontend-service","type":"Service","deployment":"guestbook4","manifest":"manifest-1446682551242763329","path":"$.resources[0].resources[0]"},{"name":"redis-master","type":"Service","deployment":"guestbook4","manifest":"manifest-1446682551242763329","path":"$.resources[1].resources[0].resources[0]"},{"name":"redis-slave","type":"Service","deployment":"guestbook4","manifest":"manifest-1446682551242763329","path":"$.resources[1].resources[1].resources[0]"}]
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```
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This output describes the deployment and manifest, as well as the JSON paths to
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the instances of the type within the layout.
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For more information about deployments, manifests and layouts, see the [design document](../../docs/design/design.md).
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