feat: add tracing

pkg/commands/scan/command.go

@@ -17,5 +17,6 @@ func Command() *cobra.Command {
 	cmd.Flags().StringVar(&command.payload, "payload", "", "Path to payload (json or yaml file)")
 	cmd.Flags().StringSliceVar(&command.preprocessors, "pre-process", nil, "JmesPath expression used to pre process payload")
 	cmd.Flags().StringSliceVar(&command.policies, "policy", nil, "Path to kyverno-json policies")
+	cmd.Flags().BoolVar(&command.trace, "trace", false, "Enable tracing")
 	return cmd
 }

pkg/commands/scan/options.go

@@ -9,6 +9,8 @@ import (
 	jsonengine "github.com/kyverno/kyverno-json/pkg/json-engine"
 	"github.com/kyverno/kyverno-json/pkg/payload"
 	"github.com/kyverno/kyverno-json/pkg/policy"
+	"github.com/kyverno/kyverno-json/pkg/tracing"
+	"github.com/kyverno/kyverno-json/pkg/tracing/tracer"
 	"github.com/kyverno/kyverno/cmd/cli/kubectl-kyverno/output/pluralize"
 	"github.com/spf13/cobra"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
@@ -18,9 +20,12 @@ type options struct {
 	payload       string
 	preprocessors []string
 	policies      []string
+	trace         bool
 }
 
 func (c *options) run(cmd *cobra.Command, _ []string) error {
+	var tracer tracer.Tracer
+	ctx := tracing.WithTracer(context.Background(), &tracer)
 	out := cmd.OutOrStdout()
 	fmt.Fprintln(out, "Loading policies ...")
 	policies, err := policy.Load(c.policies...)
@@ -37,7 +42,7 @@ func (c *options) run(cmd *cobra.Command, _ []string) error {
 	}
 	fmt.Fprintln(out, "Pre processing ...")
 	for _, preprocessor := range c.preprocessors {
-		result, err := template.Execute(context.Background(), preprocessor, payload, nil)
+		result, err := template.Execute(ctx, preprocessor, payload, nil)
 		if err != nil {
 			return err
 		}
@@ -54,7 +59,7 @@ func (c *options) run(cmd *cobra.Command, _ []string) error {
 	}
 	fmt.Fprintln(out, "Running", "(", "evaluating", len(resources), pluralize.Pluralize(len(resources), "resource", "resources"), "against", len(policies), pluralize.Pluralize(len(policies), "policy", "policies"), ")", "...")
 	e := jsonengine.New()
-	responses := e.Run(context.Background(), jsonengine.JsonEngineRequest{
+	responses := e.Run(ctx, jsonengine.JsonEngineRequest{
 		Resources: resources,
 		Policies:  policies,
 	})

pkg/json-engine/engine.go

@@ -12,6 +12,7 @@ import (
 	"github.com/kyverno/kyverno-json/pkg/engine/blocks/loop"
 	"github.com/kyverno/kyverno-json/pkg/engine/builder"
 	"github.com/kyverno/kyverno-json/pkg/engine/template"
+	"github.com/kyverno/kyverno-json/pkg/tracing"
 )
 
 type JsonEngineRequest struct {
@@ -75,15 +76,38 @@ func New() engine.Engine[JsonEngineRequest, JsonEngineResponse] {
 			return response
 		}).
 		Predicate(func(ctx context.Context, r request) bool {
+			if r.rule.Exclude == nil {
+				tracing.Tracef(ctx, "No exclude statement, will never exclude")
+				return true
+			}
 			errs, err := assert.Match(ctx, nil, r.rule.Exclude, r.value, r.bindings)
-			return err == nil && len(errs) != 0
+			if err != nil {
+				tracing.Tracef(ctx, "An error occurred while matching exclude: %s", err)
+				return false
+			} else if len(errs) == 0 {
+				tracing.Trace(ctx, "Exclude statement matched the resource")
+				return false
+			} else {
+				tracing.Tracef(ctx, "Exclude statement didn't match the resource: %s", errs.ToAggregate())
+				return true
+			}
 		}).
 		Predicate(func(ctx context.Context, r request) bool {
 			if r.rule.Match == nil {
+				tracing.Tracef(ctx, "No match statement, will always match")
 				return true
 			}
 			errs, err := assert.Match(ctx, nil, r.rule.Match, r.value, r.bindings)
-			return err == nil && len(errs) == 0
+			if err != nil {
+				tracing.Tracef(ctx, "An error occurred while matching: %s", err)
+				return false
+			} else if len(errs) == 0 {
+				tracing.Trace(ctx, "Match statement matched the resource")
+				return true
+			} else {
+				tracing.Tracef(ctx, "Match statement didn't match the resource: %s", errs.ToAggregate())
+				return false
+			}
 		})
 	// TODO: we can't use the builder package for loops :(
 	return loop.New(inner, looper)

pkg/tracing/tracer/tracer.go

@@ -0,0 +1,13 @@
+package tracer
+
+type Tracer struct {
+	traces []string
+}
+
+func (t *Tracer) Trace(trace string) {
+	t.traces = append(t.traces, trace)
+}
+
+func (t *Tracer) Traces() []string {
+	return t.traces
+}

pkg/tracing/tracing.go

@@ -0,0 +1,34 @@
+package tracing
+
+import (
+	"context"
+	"fmt"
+)
+
+type Tracer interface {
+	Trace(string)
+}
+
+type contextKey struct{}
+
+func WithTracer(ctx context.Context, tracer Tracer) context.Context {
+	return context.WithValue(ctx, contextKey{}, tracer)
+}
+
+func Trace(ctx context.Context, a ...any) {
+	value := ctx.Value(contextKey{})
+	if value != nil {
+		if tracer, ok := value.(Tracer); ok {
+			tracer.Trace(fmt.Sprint(a...))
+		}
+	}
+}
+
+func Tracef(ctx context.Context, format string, a ...any) {
+	value := ctx.Value(contextKey{})
+	if value != nil {
+		if tracer, ok := value.(Tracer); ok {
+			tracer.Trace(fmt.Sprintf(format, a...))
+		}
+	}
+}