Update Instance ID documentation

Author: scottmelhop

docs/scaling.md

@@ -108,11 +108,9 @@ Rather than running a single installation in your cluster, run one per namespace
 
 ### Instance ID
 
-Within a cluster can use instance ID to run N Argo instances within a cluster.
+Within a cluster you can use instance ID to run many Argo instances within a cluster. You can run each instance in separate, or the same namespace.
 
-Create one namespace for each Argo, e.g. `argo-i1`, `argo-i2`:.
-
-Edit [`workflow-controller-configmap.yaml`](workflow-controller-configmap.yaml) for each namespace to set an instance ID.
+For each instance, edit the [`workflow-controller-configmap.yaml`](workflow-controller-configmap.yaml) to set an `instanceID`.
 
 ```yaml
 apiVersion: v1
@@ -123,13 +121,42 @@ data:
     instanceID: i1
 ```
 
-You may need to pass the instance ID to the CLI:
+#### CLI Usage
+
+When you are using the CLI, set the `--instanceid` to interact with a specific instance. For example, to submit a Workflow defined in `my-wf.yaml`:
 
 ```bash
 argo --instanceid i1 submit my-wf.yaml
 ```
 
-You do not need to have one instance ID per namespace, you could have many or few.
+#### Declarative Usage
+
+You can also declare which instance to use in the each of the Custom Resources. For example, on a `Workflow`:
+
+```yaml
+apiVersion: argoproj.io/v1alpha1
+kind: Workflow
+metadata:
+    labels:
+        workflows.argoproj.io/controller-instanceid: i1
+```
+
+It can also be useful, when defining a `WorkflowTemplate` to use `templateDefaults`
+
+```yaml
+apiVersion: argoproj.io/v1alpha1
+kind: WorkflowTemplate
+metadata:
+    labels:
+        workflows.argoproj.io/controller-instanceid: i1
+    name: example
+spec:
+    templateDefaults:
+        metadata:
+            labels:
+                workflows.argoproj.io/controller-instanceid: i1
+```
+
 
 ### Maximum Recursion Depth
 

docs/workflow-controller-configmap.md

@@ -76,7 +76,7 @@ Config contains the root of the configuration settings for the workflow controll
 | `KubeConfig`               | [`KubeConfig`](#kubeconfig)                                                                                 | KubeConfig specifies a kube config file for the wait & init containers                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
 | `ArtifactRepository`       | [`wfv1.ArtifactRepository`](fields.md#artifactrepository)                                                   | ArtifactRepository contains the default location of an artifact repository for container artifacts                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
 | `Namespace`                | `string`                                                                                                    | Namespace is a label selector filter to limit the controller's watch to a specific namespace                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
-| `InstanceID`               | `string`                                                                                                    | InstanceID is a label selector to limit the controller's watch to a specific instance. It contains an arbitrary value that is carried forward into its pod labels, under the key workflows.argoproj.io/controller-instanceid, for the purposes of workflow segregation. This enables a controller to only receive workflow and pod events that it is interested about, in order to support multiple controllers in a single cluster, and ultimately allows the controller itself to be bundled as part of a higher level application. If omitted, the controller watches workflows and pods that *are not* labeled with an instance id. |
+| `InstanceID`               | `string`                                                                                                    | InstanceID is a label selector to limit the controller's watch to a specific instance. It contains an arbitrary value that is carried forward into its pod labels, under the key workflows.argoproj.io/controller-instanceid, for the purposes of workflow segregation. This enables a controller to only receive workflow and pod events that it is interested about, in order to support multiple controllers in a single cluster, and ultimately allows the controller itself to be bundled as part of a higher level application. If omitted, the controller watches workflows and pods that *are not* labeled with an instance id. See [Scaling - Instance ID](scaling.md#instance-id) for more details. |
 | `MetricsConfig`            | [`MetricsConfig`](#metricsconfig)                                                                           | MetricsConfig specifies configuration for metrics emission. Metrics are enabled and emitted on localhost:9090/metrics by default.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
 | `TelemetryConfig`          | [`MetricsConfig`](#metricsconfig)                                                                           | TelemetryConfig specifies configuration for telemetry emission. Telemetry is enabled and emitted in the same endpoint as metrics by default, but can be overridden using this config.                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
 | `Parallelism`              | `int`                                                                                                       | Parallelism limits the max total parallel workflows that can execute at the same time                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |