instance discovery

Automatic

One key benefit to a service mesh is the dynamic handling of ephemeral service nodes. These nodes have neither consistent IP addresses nor consistent numbers of instances as services are spun up and down. The gm-control-api server, in conjunction with Grey Matter Control, can handle these ephemeral services automatically.‌

The ability to automatically populate instances of a particular microservice comes from the cluster object. In particular, the name field in the cluster object determines which nodes will be pulled out of the mesh and populated in the instances array. In the example below, the name is catalog. This means that all services that announce as catalog in service discovery, will be found and populated into the instances array after creation.‌

Create the following object:

{
  "zone_key": "default-zone",
  "cluster_key": "catalog-proxy",
  "name": "catalog",
  "instances": [],
  "circuit_breakers": {
    "max_connections": 500,
    "max_requests": 500
  },
  "outlier_detection": null,
  "health_checks": []
}

It will be populated in the mesh as:

{
    "cluster_key": "catalog-proxy",
    "zone_key": "default-zone",
    "name": "catalog",
    "secret": {
        "secret_key": "",
        "secret_name": "",
        "secret_validation_name": "",
        "subject_names": null,
        "ecdh_curves": null,
        "set_current_client_cert_details": { "uri": false },
        "checksum": ""
    },
    "instances": [
        {
            "host": "10.128.2.183",
            "port": 9080,
            "metadata": [
                {
                    "key": "pod-template-hash",
                    "value": "2000163809"
                },
                {
                    "key": "gm_k8s_host_ip",
                    "value": "10.0.2.132"
                },
                {
                    "key": "gm_k8s_node_name",
                    "value": "ip-10-0-2-132.ec2.internal"
                }
            ]
        },
        {
            "host": "10.128.2.140",
            "port": 9080,
            "metadata": [
                {
                    "key": "pod-template-hash",
                    "value": "475497808"
                },
                {
                    "key": "gm_k8s_host_ip",
                    "value": "10.0.2.82"
                },
                {
                    "key": "gm_k8s_node_name",
                    "value": "ip-10-0-2-82.ec2.internal"
                }
            ]
        }
    ],
    "circuit_breakers": {
        "max_connections": 500,
        "max_pending_requests": null,
        "max_retries": null,
        "max_requests": 500
        },
    "outlier_detection": null,
    "health_checks": [],
    "checksum": "2b6d2a8a6886eb30574f16480b0f99b90e11484d9ddb10fb7970c3ce37d945ab"}

‌ Even though the object was created with no instances, they were discovered from the mesh and populated. Now any service that needs to talk to catalog, can link to this cluster and address all live instances.‌