Aws-integrator charm

This charm acts as a proxy to AWS and provides an interface to apply a certain set of changes via IAM roles, profiles, and tags to the instances of the applications that are related to this charm.

Usage

When on AWS, this charm can be deployed, granted trust via Juju to access AWS, and then related to an application that supports the interface. The set of permissions that the related application could request is documented in the interface’s Requires API documentation.

For example, Charmed Kubernetes has support for this, and can be deployed with the following bundle overlay:

applications:
  aws-integrator:
    charm: cs:~containers/aws-integrator
    num_units: 1
    trust: true
relations:
  - ['aws-integrator', 'kubernetes-master']
  - ['aws-integrator', 'kubernetes-worker']

Then deploy Charmed Kubernetes using this overlay:

juju deploy cs:charmed-kubernetes --overlay ./k8s-aws-overlay.yaml --trust

RDS

In addition to the integrator relation, this charm also provides a proxy to the AWS Relational Database Service (RDS) for charms using the mysql interface. Charms attached to the rds-mysql relation endpoint will have an RDS MySQL database instance created for them and access information provided via the relation.

For example, if this was deployed alongside the Mediawiki charm, it could provide the database for backing the wiki:

applications:
  aws-integrator:
    charm: cs:~containers/aws-integrator
    num_units: 1
    trust: true
  mediawiki:
    charm: cs:mediawiki
    num_units; 1
relations:
  - ['aws-integrator:rds-mysql', 'mediawiki:db']

Permissions Requirements

The credentials given to the charm must include the following access rights:

Note that these may be different from the permissions that Juju requires to operate.

Resource Usage Note

By relating to this charm, other charms can directly allocate resources, such as EBS volumes and ELBs, which could lead to cloud charges and count against quotas. Because these resources are not managed by Juju, they will not be automatically deleted when the models or applications are destroyed, nor will they show up in Juju’s status or GUI. It is therefore up to the operator to manually delete these resources when they are no longer needed, using the AWS console or API.

Examples

Following are some examples using AWS integration with Charmed Kubernetes.

Creating a pod with an EBS-backed volume

This script creates a busybox pod with a persistent volume claim backed by AWS’s Elastic Block Storage.

#!/bin/bash

# create a storage class using the `kubernetes.io/aws-ebs` provisioner
kubectl create -f - <<EOY
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: ebs-1
provisioner: kubernetes.io/aws-ebs
parameters:
  type: gp2
EOY

# create a persistent volume claim using that storage class
kubectl create -f - <<EOY
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: testclaim
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 100Mi
  storageClassName: ebs-1
EOY

# create the busybox pod with a volume using that PVC:
kubectl create -f - <<EOY
apiVersion: v1
kind: Pod
metadata:
  name: busybox
  namespace: default
spec:
  containers:
    - image: busybox
      command:
        - sleep
        - "3600"
      imagePullPolicy: IfNotPresent
      name: busybox
      volumeMounts:
        - mountPath: "/pv"
          name: testvolume
  restartPolicy: Always
  volumes:
    - name: testvolume
      persistentVolumeClaim:
        claimName: testclaim
EOY

Creating a service with an AWS load-balancer

The following script starts the hello-world pod behind an AWS Elastic Load Balancer.

kubectl create deployment hello-world --image=gcr.io/google-samples/node-hello:1.0
kubectl scale deployment hello-world --replicas=5
kubectl expose deployment hello-world --type=LoadBalancer --name=hello --port=8080
watch kubectl get svc hello -o wide

Configuration

credentials

Description:

The base64-encoded contents of an AWS credentials file, which must include both ‘aws_access_key_id’ and ‘aws_secret_access_key’ fields.

This can be used from bundles with ‘include-base64://’ (see https://discourse.charmhub.io/t/bundle-reference/1158), or from the command-line with ‘juju config aws credentials=”$(base64 /path/to/file)”’.

It is strongly recommended that you use ‘juju trust’ instead, if available. This will take precedence over the ‘access-key’ / ‘secret-key’ config options.

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snapd_refresh

Description:

How often snapd handles updates for installed snaps. The default (an empty string) is 4x per day. Set to “max” to check once per month based on the charm deployment date. You may also set a custom string as described in the ‘refresh.timer’ section here: https://forum.snapcraft.io/t/system-options/87

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