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Interact with the service registry

This guide will show you how you can interact with etcd and create example objects on the service registry.

Requirements

Before going further, make sure you have a working etcd cluster: if you don't have one, you can follow the Cluster Setup guide.

We will suppose that your cluster has the following:

  • etcd has at least endpoint 10.10.10.10:2379
  • authentication mode is enabled
  • service registry prefix is /service-registry
  • user cnwan-operator exists
  • role cnwan-operator-role exists and has readwrite access to prefix /service-registry
  • user cnwan-operator has role cnwan-operator

Add resources

We will interact with etcd with etcdctl to add service registry objects into it.

In case you have installed etcd without Docker, its path will be /tmp/etcd-download-test/etcdctl. Otherwise it will be docker exec etcd-gcr-v<version> /bin/sh -c "/usr/local/bin/etcdctl <command>". For shortness, in this document we will use the former: please adapt the commands for Docker usage in case you are running etcd with Docker.

Let's create an alias, so we can make all commands shorter - edit <password> with the correct value:

alias etcdctl="/tmp/etcd-download-test/etcdctl --endpoints http://10.10.10.10:2379 --user cnwan-operator:<password>"

Now, try to do

etcdctl get /service-registry --prefix

And you should see an empty response because the service registry is currently empty. --prefix tells etcd to get all objects that a key starting with the provided key.

Create a namespace

Create the following file on your machine and call it production.yaml, which represents a very simple namespace:

name: production
metadata:
    env: production

Now, since this is a namespace, its key will be /namespaces/production.

Remember though that we want prefix /service-registry to be there for all service registry objects: therefore its full key will be /service-registry/namespaces/production. If you haven't already, please read the service registry keys section for more information.

Now, let's insert it on etcd:

cat production.yaml | etcdctl put /service-registry/namespaces/production

OK should be displayed.

Let's now try to retrieve it:

etcdctl get /service-registry/namespaces/production

and you will see the same object we just put a few minutes ago. Let's move on and create a service.

Create a service

We will actually create two services here: payroll and training, and they both belong to production namespace.

payroll has the following definition:

name: payroll
namespaceName: production
metadata:
    traffic-profile: standard
    version: v1.3.1
    status: stable
    hash-commit: hu2gd1c127

and this is training:

name: training
namespaceName: production
metadata:
    traffic-profile: standard
    version: v3.4.0
    status: stable
    hash-commit: hu2gd1c127

It doesn't really matter what you put under metadata for this example, but please keep traffic-profile there as we will use this later.

For the same reasons we said on the previous section, the two keys will be:

  • /service-registry/namespaces/production/services/payroll for payroll
  • /service-registry/namespaces/production/services/training for training

Create the two service on etcd:

# Create payroll
cat payroll.yaml | etcdctl put /service-registry/namespaces/production/services/payroll

# Create training
cat training.yaml | etcdctl put /service-registry/namespaces/production/services/training

or even:

# Create payroll
cat << EOF | etcdctl put /service-registry/namespaces/production/services/payroll
name: payroll
namespaceName: production
metadata:
    traffic-profile: standard
    version: v1.3.1
    status: stable
    hash-commit: hu2gd1c127
EOF

# Create training
cat << EOF | etcdctl put /service-registry/namespaces/production/services/training
name: training
namespaceName: production
metadata:
    traffic-profile: standard
    version: v3.4.0
    status: stable
    hash-commit: n5f3yjhc9o
EOF

Try to read them from etcd with:

# Read payroll
etcdctl get /service-registry/namespaces/production/services/payroll

# Read training
etcdctl get /service-registry/namespaces/production/services/training

You can also just get /service-registry/namespaces/production with --prefix, which tells etcd to get all keys that start with that key:

etcdctl get /service-registry/namespaces/production/ --prefix

and you will see everything under production namespace.

Create Endpoints

Create the following endpoints:

# Create an endpoint for payroll
cat << EOF | etcdctl put /service-registry/namespaces/production/services/payroll/endpoints/payroll-1
name: payroll-1
namespaceName: production
serviceName: payroll
address: 10.11.12.13
port: 80
metadata:
    protocol: TCP
EOF

# Create an endpoint for training
cat << EOF | etcdctl put /service-registry/namespaces/production/services/training/endpoints/training-1
name: training-1
namespaceName: production
serviceName: training
address: 10.21.22.23
port: 8080
metadata:
    protocol: TCP
EOF

Please take a look at previous sections for considerations about keys and how to read them from etcd.

Watch for chages

Now that you have data there, let's try something different: open a new terminal window and put it side by side with the one you used until now.

You will probably need to set an alias again on the new terminal window. For your convenience:

alias etcdctl="/tmp/etcd-download-test/etcdctl --endpoints http://10.10.10.10:2379 --user cnwan-operator:<password>"

On the new terminal, execute the following command, which will watch for changes in etcd but only for keys that start with /service-registry/ (--prefix does this):

etcdctl watch /service-registry/ --prefix

Now, leave that window there and switch to the previous one again. You just realized that the training service contains video training session: standard is probably not a good traffic profile choice there. Let's change it to video:

cat << EOF | etcdctl put /service-registry/namespaces/production/services/training
name: training
namespaceName: production
metadata:
    traffic-profile: video
    version: v3.4.0
    status: stable
    hash-commit: n5f3yjhc9o
EOF

Press enter and the other window will show you the /service-registry/namespaces/production/services/training key along with the new object data.

Next steps

Congratulations: you just performed tasks that the CN-WAN Operator and Reader perform automatically for you. So why don't you take a step further and set up the CN-WAN Operator to do this for you? We'll see you there :)