Track variable usage in telemetry (#2593)

## Why
This gives us insight into usage patterns of variables by customers.
Like how popular are lookup variables or complex variables overall
compared to just default variables.

Potential followup: track lookup variable usage per resource type. 

## Tests
Acceptance tests.

Author: shreyas-goenka

acceptance/bundle/telemetry/deploy-variable-count/databricks.yml

@@ -0,0 +1,32 @@
+bundle:
+  name: chicken
+
+variables:
+  v1:
+    description: var 1
+    default: 1
+
+  v2:
+    description: var 2
+    default: 2
+
+  v3:
+    description: var 3
+    default: 3
+
+  lv1:
+    description: lookup var 1
+    lookup:
+      cluster: cluster_one
+
+  lv2:
+    description: lookup var 2
+    lookup:
+      cluster: cluster_two
+
+  c1:
+    description: complex 1
+    type: complex
+    default:
+      a: 1
+      b: 2

acceptance/bundle/telemetry/deploy-variable-count/output.txt

@@ -0,0 +1,39 @@
+
+>>> [CLI] bundle deploy
+Uploading bundle files to /Workspace/Users/[USERNAME]/.bundle/chicken/default/files...
+Deploying resources...
+Deployment complete!
+
+>>> cat out.requests.txt
+{
+  "bundle_uuid": "[UUID]",
+  "deployment_id": "[UUID]",
+  "resource_count": 0,
+  "resource_job_count": 0,
+  "resource_pipeline_count": 0,
+  "resource_model_count": 0,
+  "resource_experiment_count": 0,
+  "resource_model_serving_endpoint_count": 0,
+  "resource_registered_model_count": 0,
+  "resource_quality_monitor_count": 0,
+  "resource_schema_count": 0,
+  "resource_volume_count": 0,
+  "resource_cluster_count": 0,
+  "resource_dashboard_count": 0,
+  "resource_app_count": 0,
+  "experimental": {
+    "configuration_file_count": 1,
+    "variable_count": 6,
+    "complex_variable_count": 1,
+    "lookup_variable_count": 2,
+    "target_count": 1,
+    "bool_values": [
+      {
+        "key": "python_wheel_wrapper_is_set",
+        "value": false
+      }
+    ],
+    "bundle_mode": "TYPE_UNSPECIFIED",
+    "workspace_artifact_path_type": "WORKSPACE_FILE_SYSTEM"
+  }
+}

acceptance/bundle/telemetry/deploy-variable-count/script

@@ -0,0 +1,5 @@
+trace $CLI bundle deploy
+
+trace cat out.requests.txt | jq 'select(has("path") and .path == "/telemetry-ext") | .body.protoLogs.[] | fromjson | .entry.databricks_cli_log.bundle_deploy_event'
+
+rm out.requests.txt

acceptance/bundle/telemetry/deploy-variable-count/test.toml

@@ -0,0 +1,16 @@
+[[Server]]
+Pattern = "GET /api/2.1/clusters/list"
+Response.Body = '''
+{
+  "clusters": [
+    {
+      "cluster_id": "cls-1",
+      "cluster_name": "cluster_one"
+    },
+    {
+      "cluster_id": "cls-2",
+      "cluster_name": "cluster_two"
+    }
+  ]
+}
+'''

acceptance/bundle/telemetry/deploy-whl-artifacts/output.txt

@@ -32,7 +32,7 @@ Deployment complete!
   "resource_app_count": 0,
   "experimental": {
     "configuration_file_count": 1,
-    "variable_count": 0,
+    "variable_count": 1,
     "complex_variable_count": 0,
     "lookup_variable_count": 0,
     "target_count": 2,
@@ -72,7 +72,7 @@ Deployment complete!
   "resource_app_count": 0,
   "experimental": {
     "configuration_file_count": 1,
-    "variable_count": 0,
+    "variable_count": 1,
     "complex_variable_count": 0,
     "lookup_variable_count": 0,
     "target_count": 2,

bundle/config/variable/variable.go

@@ -1,7 +1,6 @@
 package variable
 
 import (
-	"errors"
 	"fmt"
 	"reflect"
 )
@@ -66,19 +65,25 @@ func (v *Variable) Set(val VariableValue) error {
 		return fmt.Errorf("variable has already been assigned value: %s", v.Value)
 	}
 
-	rv := reflect.ValueOf(val)
-	switch rv.Kind() {
-	case reflect.Struct, reflect.Array, reflect.Slice, reflect.Map:
-		if v.Type != VariableTypeComplex {
-			return errors.New("variable type is not complex")
-		}
+	if v.IsComplexValued() && v.Type != VariableTypeComplex {
+		return fmt.Errorf("variable type is not complex: %s", v.Type)
 	}
 
 	v.Value = val
 
 	return nil
 }
 
+func (v *Variable) IsComplexValued() bool {
+	rv := reflect.ValueOf(v.Value)
+	switch rv.Kind() {
+	case reflect.Struct, reflect.Array, reflect.Slice, reflect.Map:
+		return true
+	default:
+		return false
+	}
+}
+
 func (v *Variable) IsComplex() bool {
 	return v.Type == VariableTypeComplex
 }

bundle/config/variable/variable_test.go

@@ -0,0 +1,52 @@
+package variable
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestVariable_IsComplexValued(t *testing.T) {
+	tests := []struct {
+		name string
+		v    *Variable
+		want bool
+	}{
+		{
+			name: "map",
+			v: &Variable{
+				Value: map[string]any{
+					"foo": "bar",
+				},
+			},
+			want: true,
+		},
+		{
+			name: "slice",
+			v: &Variable{
+				Value: []any{1, 2, 3},
+			},
+			want: true,
+		},
+		{
+			name: "struct",
+			v: &Variable{
+				Value: struct{ Foo string }{Foo: "bar"},
+			},
+			want: true,
+		},
+		{
+			name: "non-complex valued",
+			v: &Variable{
+				Value: "foo",
+			},
+			want: false,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			assert.Equal(t, test.want, test.v.IsComplexValued())
+		})
+	}
+}

bundle/phases/deploy.go

@@ -319,6 +319,22 @@ func logTelemetry(ctx context.Context, b *bundle.Bundle) {
 		bundleUuid = b.Config.Bundle.Uuid
 	}
 
+	variableCount := len(b.Config.Variables)
+	complexVariableCount := int64(0)
+	lookupVariableCount := int64(0)
+	for _, v := range b.Config.Variables {
+		// If the resolved value of the variable is a complex type, we count it as a complex variable.
+		// We can't rely on the "type: complex" annotation because the annotation is optional in some contexts
+		// like bundle YAML files.
+		if v.IsComplexValued() {
+			complexVariableCount++
+		}
+
+		if v.Lookup != nil {
+			lookupVariableCount++
+		}
+	}
+
 	artifactPathType := protos.BundleDeployArtifactPathTypeUnspecified
 	if libraries.IsVolumesPath(b.Config.Workspace.ArtifactPath) {
 		artifactPathType = protos.BundleDeployArtifactPathTypeVolume
@@ -372,6 +388,9 @@ func logTelemetry(ctx context.Context, b *bundle.Bundle) {
 				PythonUpdatedResourcesCount: b.Metrics.PythonUpdatedResourcesCount,
 				PythonResourceLoadersCount:  int64(len(experimentalConfig.Python.Resources)),
 				PythonResourceMutatorsCount: int64(len(experimentalConfig.Python.Mutators)),
+				VariableCount:               int64(variableCount),
+				ComplexVariableCount:        complexVariableCount,
+				LookupVariableCount:         lookupVariableCount,
 			},
 		},
 	})