Generate decision ID using flowid generator (#2926)

* OPA: Use flowId for decision ID.

Signed-off-by: Pushpalanka Jayawardhana <pushpalanka.jayawardhana@zalando.de>

filters/openpolicyagent/evaluation.go

@@ -16,17 +16,24 @@ import (
 )
 
 func (opa *OpenPolicyAgentInstance) Eval(ctx context.Context, req *ext_authz_v3.CheckRequest) (*envoyauth.EvalResult, error) {
-	result, stopeval, err := envoyauth.NewEvalResult()
-	span := opentracing.SpanFromContext(ctx)
-	if span != nil {
-		span.SetTag("opa.decision_id", result.DecisionID)
-	}
 
+	decisionId, err := opa.idGenerator.Generate()
 	if err != nil {
 		opa.Logger().WithFields(map[string]interface{}{"err": err}).Error("Unable to generate decision ID.")
 		return nil, err
 	}
 
+	result, stopeval, err := envoyauth.NewEvalResult(withDecisionID(decisionId))
+	if err != nil {
+		opa.Logger().WithFields(map[string]interface{}{"err": err}).Error("Unable to generate new result with decision ID.")
+		return nil, err
+	}
+
+	span := opentracing.SpanFromContext(ctx)
+	if span != nil {
+		span.SetTag("opa.decision_id", result.DecisionID)
+	}
+
 	var input map[string]interface{}
 	defer func() {
 		stopeval()
@@ -71,3 +78,9 @@ func (opa *OpenPolicyAgentInstance) logDecision(ctx context.Context, input inter
 
 	return decisionlog.LogDecision(ctx, opa.manager, info, result, err)
 }
+
+func withDecisionID(decisionID string) func(*envoyauth.EvalResult) {
+	return func(result *envoyauth.EvalResult) {
+		result.DecisionID = decisionID
+	}
+}

filters/openpolicyagent/openpolicyagent.go

@@ -32,6 +32,7 @@ import (
 	"google.golang.org/protobuf/encoding/protojson"
 
 	"github.com/zalando/skipper/filters"
+	"github.com/zalando/skipper/filters/flowid"
 	"github.com/zalando/skipper/filters/openpolicyagent/internal/envoy"
 	"github.com/zalando/skipper/routing"
 	"github.com/zalando/skipper/tracing"
@@ -360,6 +361,8 @@ type OpenPolicyAgentInstance struct {
 
 	maxBodyBytes       int64
 	bodyReadBufferSize int64
+
+	idGenerator flowid.Generator
 }
 
 func envVariablesMap() map[string]string {
@@ -395,6 +398,11 @@ func interpolateConfigTemplate(configTemplate []byte, bundleName string) ([]byte
 // new returns a new OPA object.
 func (registry *OpenPolicyAgentRegistry) new(store storage.Store, configBytes []byte, instanceConfig OpenPolicyAgentInstanceConfig, filterName string, bundleName string, maxBodyBytes int64, bodyReadBufferSize int64) (*OpenPolicyAgentInstance, error) {
 	id := uuid.New().String()
+	uniqueIDGenerator, err := flowid.NewStandardGenerator(32)
+	if err != nil {
+		return nil, err
+	}
+
 	opaConfig, err := config.ParseConfig(configBytes, id)
 	if err != nil {
 		return nil, err
@@ -428,6 +436,8 @@ func (registry *OpenPolicyAgentRegistry) new(store storage.Store, configBytes []
 
 		preparedQueryDoOnce:    new(sync.Once),
 		interQueryBuiltinCache: iCache.NewInterQueryCache(manager.InterQueryBuiltinCacheConfig()),
+
+		idGenerator: uniqueIDGenerator,
 	}
 
 	manager.RegisterCompilerTrigger(opa.compilerUpdated)